No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Towards the Reliable Prediction of Time to Flowering in Six Annual Crops. I. The Development of Simple Models for Fluctuating Field Environments
Abstract
Despite numerous altempts, the development of generalixed models capable of accurate predictions of the times from sowing to flowering (f) of crop plants in field environments has remained elusive. Models which seek to correlate ; with various states of environmental factors such as photoperiod, P, and temperature, T, using formal statistical procedures arc often complex. Here, we describe a family of photothermal responses (involving unambiguous parameters and limits) which quantify the linear, non-interacting effects of P and T not on but on 1/, i.e. on the rate of progress towards flowering. Based on these relations we suggest that the modelling of crop phenology will be simplified, more reliable and more biologically plausible.
... This simplified model, summarized by Lawn et al. (1995) and Summerfield et al. (1991), Summerfield et al. (1997) has also been used with pea (Pisum sativum L.; Alcalde et al., 2000), chickpea (Cicer arietinum L.; Roberts et al., 1985;Ellis et al., 1994b), rice (Oryza sativa; Summerfield et al., 1992), soybean (Glycine max L. ;Summerfield et al., 1993;Upadhyay et al., 1994), cowpea (Vigna unguiculata L., Walp.; Ellis et al., 1994a), mung bean (Vigna spp.; Ellis et al., 1994c) and faba bean (Vicia faba L.; Catt & Paull, 2017;Lizarazo et al., 2017); and has potential utility for predicting days from sowing to flowering and quantifying temperature and photoperiod sensitivity, which could assist breeders in identifying genotypes adapted to a specific environment. In addition, equation 1 can be modified to estimate the "nominal base temperature" (T b ) and "nominal base photoperiod" (P c ): ...
... in Canada (Bush & Lemmen, 2019), South Asia (Mani et al., 2018), and the Mediterranean (Saadi et al., 2015). Increases in temperature are expected to cause a decrease in DTF, up until the top end of the optimal temperature range, after which further increases will delay flowering (Summerfield et al., 1991). Additionally, supraoptimal temperatures can also decrease yield related traits such as the duration of the reproductive period and plant height (Summerfield et al., 1989) and cause flower and/or pod abortion . ...
... These inaccurate predictions suggest that additional factors, besides T and P, are influencing DTF at these sites and that T and P alone may not be sufficient for accurate prediction of DTF. For example, low light quality (Mobini et al., 2016;Yuan et al., 2017) or water stress (Gorim & Vandenberg, 2017) can accelerate flowering, while supraoptimal temperatures will delay and/ or prevent flowering (Saint-Clair, 1972;Summerfield et al., 1991). In the initial evaluation of the model by Summerfield et al. (1985), vernalization of the seed was shown to have a significant impact on flowering and changed the values of the a, b, and c constants. ...
... This simplified model, summarized by Lawn et al. (1995) and Summerfield et al. (1991), Summerfield et al. (1997) has also been used with pea (Pisum sativum L.; Alcalde et al., 2000), chickpea (Cicer arietinum L.; Roberts et al., 1985;Ellis et al., 1994b), rice (Oryza sativa; Summerfield et al., 1992), soybean (Glycine max L. ;Summerfield et al., 1993;Upadhyay et al., 1994), cowpea (Vigna unguiculata L., Walp.; Ellis et al., 1994a), mung bean (Vigna spp.; Ellis et al., 1994c) and faba bean (Vicia faba L.; Catt & Paull, 2017;Lizarazo et al., 2017); and has potential utility for predicting days from sowing to flowering and quantifying temperature and photoperiod sensitivity, which could assist breeders in identifying genotypes adapted to a specific environment. In addition, equation 1 can be modified to estimate the "nominal base temperature" (T b ) and "nominal base photoperiod" (P c ): ...
... in Canada (Bush & Lemmen, 2019), South Asia (Mani et al., 2018), and the Mediterranean (Saadi et al., 2015). Increases in temperature are expected to cause a decrease in DTF, up until the top end of the optimal temperature range, after which further increases will delay flowering (Summerfield et al., 1991). Additionally, supraoptimal temperatures can also decrease yield related traits such as the duration of the reproductive period and plant height (Summerfield et al., 1989) and cause flower and/or pod abortion . ...
... These inaccurate predictions suggest that additional factors, besides T and P, are influencing DTF at these sites and that T and P alone may not be sufficient for accurate prediction of DTF. For example, low light quality (Mobini et al., 2016;Yuan et al., 2017) or water stress (Gorim & Vandenberg, 2017) can accelerate flowering, while supraoptimal temperatures will delay and/ or prevent flowering (Saint-Clair, 1972;Summerfield et al., 1991). In the initial evaluation of the model by Summerfield et al. (1985), vernalization of the seed was shown to have a significant impact on flowering and changed the values of the a, b, and c constants. ...
Societal Impact Statement
Lentil is a staple in many diets around the world and growing in popularity as a quick‐cooking, nutritious, plant‐based source of protein in the human diet. Lentil varieties are usually grown close to where they were bred. Future climate change scenarios will result in increased temperatures and shifts in lentil crop production areas, necessitating expanded breeding efforts. We show how we can use a daylength and temperature model to identify varieties most likely to succeed in these new environments, expand genetic diversity, and give plant breeders additional knowledge and tools to help mitigate these changes for lentil producers.
Summary
Lentil (Lens culinaris Medik.) is cultivated under a wide range of environmental conditions, which has led to diverse phenological adaptations and resulted in a decrease in genetic variability within breeding programs due to reluctance in using genotypes from other environments.
We phenotyped 324 genotypes across nine locations over three years to assess their phenological response to the environment of major lentil production regions and to predict days from sowing to flowering (DTF) using a photothermal model.
DTF was highly influenced by the environment and is sufficient to explain adaptation. We were able to predict DTF reliably in most environments using a simple photothermal model, however, in certain site‐years, results suggest there may be additional environmental factors at play. Hierarchical clustering of principal components revealed the presence of eight groups based on the responses of DTF to contrasting environments. These groups are associated with the coefficients of the photothermal model and revealed differences in temperature and photoperiod sensitivity.
Future climate change scenarios will result in increased temperature and/or shifts in production areas. The ability to use the photothermal model to identify genotypes most likely to succeed in these new environments has important social impacts with respect to traditional cropping systems.
... Accordingly, prediction of time to flowering help select appropriate crop management practices such as optimum sowing and harvesting dates 2,7 which determines plant size and thus affects dry matter production and product yield 8,9 . Simple linear regression models have been proposed to predict the effects of temperature and photoperiod on flowering behaviour of a range of both long-and shortday plants 7 . The developmental rate is defined as the inverse of flowering duration (1/f ) for developing and testing models to predict time to flowering 5 . ...
... The developmental rate is defined as the inverse of flowering duration (1/f ) for developing and testing models to predict time to flowering 5 . Empirical models have been developed by linearly relating the developmental rate to mean photoperiod and/or mean temperature in crops such as soybean 7 , sulla and persion clover 5,6 and pigeonpea 10 . The effects of temperature and photoperiod have proved to be additive 11 . ...
... However, the T b and GDD requirements of PS genotypes need to be validated by evaluating them in environments with temperatures different from that in the present study. Further, dolichos (Table 5) which is comparable to warm season short-day legume crop such as pigeonpea (24°C) 33 and slightly higher in soybean (26-28°C) 5,7 . ...
Prediction of time to flowering of crop plants (especially photoperiod sensitive (PS) ones) help make appropriate crop management decisions such as choosing optimum sowing and harvesting dates which in turn determine plant size and thus affect dry matter production and crop yield. Modelling time to flowering of dolichos bean, a highly PS short-day food legume crop species, indicated greater role of temperature than photoperiod in regulating time to flowering of PS genotypes. The PS and photoperiod insensitive (PIS) genotypes of dolichos bean differed for base (Tb) and optimum temperature requirement for time to flowering. However, they were comparable for critical minimum, maximum and optimum photoperiod requirement for time to flowering. Dolichos bean requires critical minimum, maximum and optimum photoperiods of 11.11, 12.28 and 12.21 h respectively, and critical minimum growing degree days of 372.05°C day⁻¹ and optimum temperature of 23.13°C for time to flowering. Using average daily air temperature, and working backwards in time, it is possible to predict the combination of dolichos bean cultivar and sowing date that will produce ready for harvest crop on a predetermined day when fresh pod quality is optimal.
... Vigna species, where the process could be reversed even well after development of floral buds and in the case of garden balsam (Impatiens balsamina) reversibility of reproductive stage to vegetative growth stage, serves a function in the perenniality of the plant (Summerfield et al., 1991). However, these are exceptional cases and for the vast majority of plants, including Arabidopsis, flowering is an irreversible process once initiated. ...
... In Arabidopsis, the leaf primordia and an inflorescence meristem, which is a floral structure, are produced from the shoot apical meristem until environmental and internal signals cause a change of fate (Komeda, 2004). However, in onion, leaf sheaths swell and produced bladeless bulb scales, which is a storage structure Summerfield, 1991). ...
... Bulb initiation in LD onion at the physiological level is regulated in a similar way to the photoperiodic regulation of flowering in Arabidopsis (Taylor et al., 2010) as described in section 1.7. Both processes are photoperiodically driven and involve a homeotic conversion of leaves, though, in Arabidopsis, floral structures are the result, whereas, in onion it is a storage structure (Summerfield, 1991). Flowering in Arabidopsis has been characterised at the molecular and genetic level and is regulated by 6 major separate pathways viz., photoperiodic, convergent autonomous, sucrose, gibberellin, temperature and light quality pathway (Jack, 2004;Thomas et al., 2006). ...
Genetic studies aimed at onion improvement have been limited because of outcrossing, high heterozygosity and a very large genome size with a high level of repetitive DNA. Onion bulb initiation is photoperiod-dependent, which places a significant barrier to adapting new varieties for growth at different latitudes. In comparison to photoperiodic regulation of flowering, relatively little is known about genetic regulation of the bulbing process. This project aims to test the hypothesis that the genetic regulation of bulb formation in response to daylength is analogous to the daylength regulation of flowering and to identify genes involved in daylength adaptation in onion. A comprehensive set of developmental, diurnal and spatial mRNA and quantitative expression experiments were carried out to investigate the bulbing response.
Bulbing ratios were used to measure the bulbing response of onion plants and the reversibility of the bulbing process under long day (LD) and short day (SD) conditions. RNA-Seq analysis provided a large number of differentially expressed transcripts in onion in response to daylength. Five FT and three COL genes were identified in onion including two novel COL sequences. AcFT1 was expressed in LD, which might induce bulb formation, while AcFT4 was expressed in SD, which might inhibit bulb formation. AcFT5 and AcFT6 were expressed in LD and might also be involved in bulb formation itself. FKF1, GI and COL2 showed good diurnal expression patterns consistent with photoperiod sensing and regulation of FT1. All FT genes exhibited different diurnal expression patterns peaking at different times of the day. FKF1, COL2, COL3, FT1, FT4, LFY and GA3ox1 genes showed distinctive patterns of tissue specific expression in onion. FT genes did not show any variation in expression that would account for the difference in critical daylength between the LD and SD varieties of onion.
... Yin et al. (1997) and Carberry et al. (2001) have challenged the use of mean photoperiod during the preflowering stage. The progress from sowing to flowering calculated as the inverse of the duration from sowing to flowering to the mean preflowering photoperiod and temperature (Summerfield et al., 1991) has been in use for crop models such as the Cropping System Model (CSM) of the Decision Support System for Agrotechnology Transfer (DSSAT; Jones et al., 2003;Hoogenboom et al., 2015), the Agricultural Production Systems Simulator (APSIM; McCown et al., 1996), and Bambara Groundnut Growth (BAMGRO; Karunaratne et al. 2015), which assume that the daily progress towards panicle, flower, and pod initiation is proportional to the ratio between biological temperature and photoperiod (McCown et al., 1996;Jones et al., 1998). However, some of these models are unable to predict the sometimes very long delay of flowering in pigeon pea [Cajanus cajan (L.) Millsp.] ...
... Linnemann and Craufurd (1994) also observed that photoperiod usually has a stronger effect on podding than on flowering in bambara groundnut. According to Summerfield et al. (1991), most crops respond to photoperiod and, in general, short-day plant development is delayed if the photoperiod is longer or shorter than the critical period. Craufurd and Wheeler (2009) further described short-day plants to be quantitative when flowering is delayed but not prevented, that qualitative types will not flower if the photoperiod transgresses a critical threshold, and that most crops are effectively quantitative short-day plants. ...
... Our results further support the findings of Vince-Prue (1975), Summerfield et al. (1991), and Keatinge et al. (1996) that qualitative short-day plants flower only if the photoperiod is shorter than the critical value, and that in quantitative short day plants, flowering and podding are reduced but never prevented. In contrast with the hypothesis of Brink (1997), who found that the sensitivity of pod initiation to photoperiod in bambara groundnut occurred when photoperiod exceeded 12 h, we observed four cardinal points: critical photoperiod (P c ), optimum photoperiod (P opt ), and two photoperiod sensitivities (P s1 and P s2 ). ...
Photoperiod and temperature are important environmental factors that affect the adaptation of bambara groundnut (Vigna subterranea Verdc.) and other crops to hostile climates in the tropics. The use of the accumulation concept, in which the relative rate of progress towards podding sums up to one is a common methodology. However, the lack of quantitative information, has resulted in poor decision making for crop management practices in relation to the time of optimum pod growth rate (Ropt). This study investigated modeling pod growth using an additive and interactive relation between pod growth rate, mean photoperiod, and temperature during the pod inductive phase. The field experiment was conducted at Ekpoma Nigeria. Ten bambara groundnut landraces from three different regions in Nigeria (Anyigba, Otukpo, and Nsukka) were sown on six dates from 15 June to 1 September during the successive growing seasons of 2010 to 2012, thus exposing the landraces to mean natural photoperiods of 12 h 23 min, 12 h 19 min, 12 h 14 min, 12 h 10 min, 12 h 5 min, 12 h, 11 h 55 min, 11 h 51 min, and 11 h 47 min during the pod inductive period. The observed optimum photoperiod and temperature for Ropt were 12 h and 26°C, respectively, for all landraces. Allocation to pod growth began at the critical photoperiod (Pc) of 12 h 19 min for Otukpo landraces, whereas Pc for Nsukka landraces was 12 h 14 min. However, the Pc for Anyigba landraces occurred earlier at 12 h 23 min. The pod growth model that was developed provided good predictions of pod growth for a natural range of photoperiods and temperatures.
... The temperatures in Pringgarata seem already beyond the limit of tolerance adaptation of wheat varieties studied. This made the growth became slower (Summerfield et al., 1991). ...
... In the second week, plant development at the seed growth phase was almost similar (Zadoks Scale / SZ dozen). Summerfield et al. (1991) suggested that the growth of wheat plants when grown in areas with temperatures above the tolerance threshold (supra-optimal temperature) would show a decrease in growth rate. This was also found in long-lived varieties (Cobra and Scout). ...
... Handoko (2007) also reported that the yield of 2 t / ha could be obtained from the crops planted at an elevation of 500 m above sea level. As the low areas plains have high temperature, the low yields at 200 m above sea level is because the temperature of above tolerance limits growth and production of wheat (Summerfield et al. 1991). Table 5 show evidence that there was genetic variation of plant response to high temperature stress. ...
Wheat is not currently grown as a commercial crop in Indonesia, however since the consumption of wheat in Indonesia is steadily increasing and alternative of dry season crops are required for farming system diversification, wheat becomes an important crop to be adapted in dry land areas of Indonesia, one of them is dry land area of Lombok Island. The aims of this experiment is to adapt and screen wheat varieties including national and introduced Australian varieties in lowland Lombok Island. In future, wheat is expected to be an alternative crop for degraded lands. The experimental method used to evaluate growth and yield of 10 wheat varieties to look at the adaptability on the lowland of 200 m asl (Pringgarata) and on higher land of 400 m asl (Aik Bukak). The results showed that at a lower altitude (Pringgarata), wheat growth is slower than in Aik Bukak, which can be caused by the temperature at 200 m asl has exceeded the tolerance limit for grain growth (supra optimal temperature). Wheat can give good yields on 400 m asl, but the yield is decreased at 200 m asl (average 1.68 t/ha vs 0.82 t/ha). This low yield is mainly due to sterility indicated by the low number of grain/spikelet ( 2 t/ha ), higher than other varieties
... In plant science, photoperiod sensitivity is usually analysed as photothermal response, where both photoperiod and temperature effects are considered simultaneously. Quantitative models to predict flowering time are simplified additive linear models with temperature and photoperiod as possible predictors and flowering time as response variable (Keatinge et al., 1998;Summerfield et al., 1991). ...
... Further, the development towards flowering was expressed as development rate -the reciprocal of the duration from sowing to flowering ((1/ f ) = D, d −1 ). The thermal and photothermal response of flowering were described using the triple-plane rate model (Summerfield et al., 1991). ...
... Photoperiodism of Lablab purpureus 9 for daylength between the critical photoperiod (P c ) and ceiling photoperiod (P ce ), where a , b and c are genotypic coefficients (Iannucci et al., 2008;Summerfield et al., 1991). Third, the maximum delay in flowering is reached when the daylength exceeds the ceiling photoperiod (P ce ) in SDP (for daylength below P ce in LDPs) and the development is expressed as ...
Legumes have gained increased importance in smallholder farming systems of sub-Saharan Africa due to their contribution to household nutrition and health and their ability to grow in low fertility soils. With unpredictable and highly variable rainfall characteristics of the semi-arid areas, short-season grain types are seen as a promising option for drought avoidance. Knowledge of phenological development and, in particular, time to flowering is crucial information needed for estimating the possible production success of new accessions to new environments. The photoperiod-sensitivity of 10 promising short-season Lablab purpureus (L.) Sweet accessions (CPI 525313, CPI 52533, CPI 52535, CPI 52535, CPI 52552, CPI 52554, CPI 60795, CPI 81364, CQ 3620, Q 6880B) were evaluated for their response to varying temperature and daylength regimes in field trials in Limpopo province, South Africa and under controlled conditions in growth chamber experiments in Göttingen, Germany. Photoperiod sensitivity was quantified using the triple-plane rate model of flowering response with time to flowering expressed in thermal time (Tt, °Cd). Additionally, piecewise regression analysis was conducted to estimate the critical photoperiod (Pc ) above which time to flowering was delayed significantly. Relatively high variation of time to flowering amongst and within accessions in days after planting (DAP) was observed, ranging from 60 to 120 DAP depending on sowing date or daylength/temperature regime. Furthermore, a clear positive effect of temperature on growth and development of the tested accessions was found and time to flowering expressed as thermal time were consistent for the tested accessions, ranging from 600 to 800 °Cd for daylength <13 h. Only at daylength of ≥13 h and temperatures above 28 °C, development towards flowering was delayed significantly for accessions CPI 52513, CPI 52535, CPI 52554 and CPI 60795 with vegetative growth continuing for >110 DAP. The tested lablab accessions are therefore considered photoperiod insensitive, or weakly photoperiod responsive and are classified as short-day plants (SDP). Since daylength does not exceed 13 h between the latitudes 30 N to 30 S, these lablab accessions are recommended for further testing as short-duration grain legumes.
... The effects of high temperature on growth and development of wheat have been widely reviewed [2]. An increase in average daily temperature above 20-25°C hastens phenological development such as timing of double ridge, terminal spikelet initiation, and duration of spikelet primordial initiation as well time to flowering of wheat [5,6,7], but further increases in temperature can delay development [8]. Heat stress at specific growth stages can reduce yields significantly with the period just prior to and during [5]. ...
... However, the early development of the 2 Indonesian varieties was less sensitive to high temperature as their time to DR and TSI showed no significant difference at 28°/20°C and 32°/23°C. Flowering times spanned 15-20 days among the varieties at each temperature with Axe being the earliest and Dewata the latest ( The rate of plant development increases with high temperature up to an optimum temperature after which development slows with further increases in temperatures [8]. This effect was apparent in the present experimental though there were differences among varieties investigated. ...
The aim of the experiment was to examine how wheat responded to an extended period of high temperatures under controlled conditions to supplement field studies with these varieties on Lombok Island. Two Indonesian wheat varieties (Nias and Dewata) and two Australian varieties (Axe and Gladius) were examined in growth room experiments at 3 different temperature regimes 32/23°C, 28/20°C and 25/15°C day/night with 12 h daylight. Temperature and photoperiod were selected to simulate conditions on Lombok Island, at lowland (32/23°C) and highland (28/20°C) sites. A third temperature (25/15°C) was selected to represent the temperature in a more temperate wheat producing area. The rate of plant development increases with the rise of the temperatures up to an optimum temperature and slower after further increases. Despite being exposed to high temperatures from the establishment, the effect of high temperature was more severe during the reproductive stage as seen by the fact that yield was more affected than dry matter accumulation and yield was most strongly related to grain number. Genetic variability in response to heat stress was evident with the Indonesian varieties being more tolerant to high temperatures than Australian varieties. Nias and Dewataproduced higher yield and biomass.
... 1 RESEARCH P hotoperiod is one of the most important factors that affect soybean [Glycine max (L.) Merr.] flowering (Garner and Allard, 1920;Wang et al., 1956;Shanmugasundaram and Toung, 1979;Wu et al., 2006;Wu et al., 2015), seed setting (He et al., 1993;Han et al., 1998), and yield formation (Yang and Zhou, 1999;Kantolic and Slafer, 2005;Langewisch et al., 2017). Photoperiod sensitivity is a dominant characteristic that determines the ecological adaptability of soybean (Steinberg and Garner, 1936;Major, 1980;Summerfield et al., 1991). Various soybean genotypes exhibit a large difference in photoperiod sensitivity (Wang et al., 1956;Han and Wang., 1996;Jiang et al., 2013). ...
... More importantly, the critical photoperiod obtained in this study will help breeders to synchronize the flowering time of parents from distant geographic origins and break the reproductive isolation among different ecotype cultivars. (Summerfield et al., 1991). In the current study, the second definition is used. ...
Soybean [Glycine max (L.) Merr.] is a photoperiod‐sensitive crop, and the photoperiod response determines the ecological adaptability of soybean genotypes. Critical photoperiod is the dividing daylength between photoperiod sensitivity and photoperiod insensitivity phases and is one of the most important indicators of photoperiod sensitivity. However, the appropriate experimental treatment and calculation method for quantifying the critical photoperiod are poorly documented. To characterize the photoperiod response of genotypes, 72 soybean genotypes belonging to 14 different maturity groups (MG 0000–MG X) were included, and five photoperiod treatments of 12‐, 14‐, 16‐, 18‐, and 20‐h daylength were conducted in the consecutive 3 yr from 2015 to 2017. The piecewise linear regression model based on the median function was used to determine the critical photoperiod. The results showed that the photoperiodic responses of soybean genotypes were significantly different among various MGs. The critical photoperiod of MG 0000 was 16.4 h d⁻¹, whereas those of MG 000 to MG I, MG II to MG III, MG IV, MG V to MG VIII, and MG IX to MG X were 15.7 to 15.8, 15.3, 14.7, 13.4 to 13.7, and ≤12 h d⁻¹, respectively. A significant negative linear relationship between the critical photoperiod and relative maturity group (RMG) was found. It is of particular importance for the quantification of soybean photoperiod response and precise prediction of the developmental process. More importantly, the critical photoperiod obtained in this study will help breeders to synchronize the flowering time of parents from distant geographic origins and break the reproductive isolation among different ecotype cultivars.
... Arabidopsis thaliana and other temperate longday species such as lentils, pea (Pisum sativum L.), chickpea, and barrel medic (Medicago truncatula) (Thomas and Vince-Prue 1996;Weller et al. 2012) flower earlier under long daylengths. By contrast, flowering in other species such as rice (Oryza sativa), cowpea, soybean, and common bean (Phaseolus vulgaris) is promoted by short daylengths (Summerfield et al. 1991;Summerfield et al. 1993;Song et al. 2010). Besides the onset of flowering, several other aspects of reproductive development such as pod and seed yield, and seed filling are influenced by photoperiod, and these are perhaps the most important agronomic traits for agricultural research and policy (Guiamet and Nakayama 1984;Morandi et al. 1988;Bagnall and King 1991a;Harris and Azam-Ali 1993;Linnemann et al. 1995;Brink 1997;Brink 1998;Brink et al. 2000;Nico et al. 2015). ...
... Photoperiod regulation has been reported in most grain legumes, e.g., flowering time and seed production in soybean (Summerfield et al. 1993;Kantolic and Slafer 2005;Kantolic et al. , 2013; flowering time in cowpea (Ellis et al. 1994); flowering response in faba bean (Vicia faba L.) (Ellis et al. 1990;Imrie and Lawn 1990); flowering in common bean (Wallace et al. 1993;Kornegay et al. 1993); flowering and pod set in bambara groundnut (Linnemann et al. 1995;Brink 1997); and flowering and pod number in groundnut (Flohr et al. 1990;Bell et al. 1991;Bagnall and King 1991b). It is generally assumed that both photoperiod and temperature are important in the phenological development of most annual crops, due to the difficulties in uncoupling photothermal effects in fluctuating field environments (Summerfield et al. 1991). The exposure to long photoperiods in indeterminate soybean, for example, lengthened the reproductive period from flowering to maturity leading to increased pod and seed number, and this was associated with increments in the amount of radiation accumulated during the crop cycle Slafer 2005, 2007;Nico et al. 2015). ...
Main conclusion
Bambara groundnut has the potential to be used to contribute more the climate change ready agriculture. The requirement for nitrogen fixing, stress tolerant legumes is clear, particularly in low input agriculture. However, ensuring that existing negative traits are tackled and demand is stimulated through the development of markets and products still represents a challenge to making greater use of this legume.
Abstract
World agriculture is currently based on very limited numbers of crops, representing a significant risk to food supplies, particularly in the face of climate change which is expected to increase the frequency of extreme events. Minor and underutilised crops can help to develop a more resilient and nutritionally dense future agriculture. Bambara groundnut [Vigna subterranea (L.) Verdc.[, as a drought resistant, nitrogen-fixing, legume has a role to play. However, as with most underutilised crops, there are significant gaps in knowledge and also negative traits such as ‘hard-to-cook’ and ‘photoperiod sensitivity to pod filling’ associated with the crop which future breeding programmes and processing methods need to tackle, to allow it to make a significant contribution to the well-being of future generations. The current review assesses these factors and also considers what are the next steps towards realising the potential of this crop.
... In addition to the photoperiodic response of soybean plants, the maturity group and the critical photoperiod can be indicators of plant sensitivity to light. Critical photoperiodis is defined as the dividing daylength between photoperiod sensitivity and photoperiod insensitivity phases and is one of the paramount indicators of photoperiod sensitivity [95]. Soybean varieties with different maturity groups may show different photoperiodic responses and, therefore, adapt to different daylength conditions and have different critical photoperiods. ...
The sharp increase in soybean (Glycine max (L.) Merrill) acreage in the late 20th century and early 21st century is due to the demand for edible oil and feed protein. However, a limiting factor in the extent of soybean cultivation is its high heat requirements and response to photoperiod. Most varieties are short-day plants and are generally the best-yielding genotypes. At higher latitudes (longer day length), there is a delay in the occurrence of subsequent developmental stages and problems with plant maturation before the onset of autumn frost. Global warming allows the cultivation range of warm-season species (including soya) to be shifted; however, periodic droughts and very high temperatures limit crop production. Adverse weather events result in a reduction in soybean seed yield of around 30%. Environmental stresses related to day length, high and low temperatures and water shortage or excess have the greatest impact on soybean yields, as we have no influence on them and can only, to a very limited extent, offset their negative effects. This paper reviews the recent world literature on how soybean responds to these stress factors. The results of our own research were also used.
... In the second year of research, the average June temperature was lower than the first year June temperature, and in the same month was the first development phase that inversely affected the 1000-kernel weight. Summerfield et al. reported that there is a positive linear relationship between plant development after seedling emergence and air temperature [55]. In the second year of our study, there was low air temperature during the first development phase, which was one of the reasons for lower values of grain yield (Tables 2 and 6). ...
Food security is directly coupled with enhanced production under optimized cropping intensity. Intercropping is a diversified and sustainable agricultural technique with optimized cropping intensity. Intercropping is used to obtain a higher yield and more balanced products per unit area. This study was performed at Aidyn Research Institute, Nur Sultan, Kazakhstan, in 2018 and 2019 to identify the effects of different sowing patterns on maize–white bean (Zea mays–Phaseolus vulgaris) sowing systems. The field experiment was arranged in a randomized complete block design with three replications. Göynük-98 was used for white beans, and SY Miami was used for maize, with 20 cm and 40 cm row spaces for maize, and 10 cm and 20 cm row spaces for white bean and sole maize, sole white bean, maize–white bean–maize–white bean, maize–white bean–white bean–maize and white bean–maize–maize–white bean sowing systems. The results showed that wide row spacing was better than narrow row spacing in terms of land equivalent ratio (LER) for both maize and white beans, but grain yield was higher in narrow row spacing. Yield items for both maize and white beans showed higher values in intercropping. Grain yield was higher in sole sowing. The maize–white bean–white bean–maize sowing system for maize and the white bean–maize–maize–white bean sowing system for white beans were determined as the best sowing systems according to the yield components.
... Drastic changes in environmental conditions have been well documented to influence both the physiological and morphological growth of the plants (Summerfield et al. 1985(Summerfield et al. , 1991Erskine et al. 1994). The basic principle behind speed breeding is to accelerate the rate of photosynthesis. ...
Crop improvement in light of the rapidly changing climate and the increasing human population continues to be one of the primary concerns for researchers across the globe. The rate at which current crop improvement programs are progressing is essentially inadequate to meet the food demand. There is an urgent need for redesigning the crops for climate resilience and sustainable yield and nutrition. The rate of crop improvement is largely impeded owing to the long generation time taken by crop plants during the breeding process. As a solution in this direction, speed breeding is now being practiced at a large scale to reduce generation time to accommodate multiple generations of crops per year. To enhance the efficiency of breeding, researchers are now adopting an integrated approach where speed breeding is used along with modern plant breeding and genetic engineering technologies. In the present review, we have summarized the technological aspects, opportunities, and limitations associated with speed breeding. The application of speed breeding such as mapping population development, haplotype-based breeding, transgenic breeding, and genome-edited line advancement has also been discussed. Speed breeding is a promising technology that expedites the goals of food and industrial crop improvement by reducing the breeding cycles for establishing nutritional security and sustainable agriculture.
... Although the mechanism underlying daylengthdependent bulbing in onion is not yet elucidated, there is good reason to use Arabidopsis flowering as a model. In both species, the perception of daylength is in the leaves and the site of response is the apical meristem, which for Arabidopsis is in the shoot apex, whereas the meristem in onion is basal, which is where the bulb forms (Summerfield, Roberts, Ellis, & Lawn, 1991). Both processes therefore require a mobile signal to pass from the leaf to the apex. ...
Onion bulb initiation is photoperiod-dependent. Understanding this is crucial for adapting new varieties for growth at different latitudes as well as aiding germplasm screening for choice of current varieties. This study aims to gain further understanding of the molecular mechanisms involved in onion bulbing process based on the parallels with well characterised functional clock genes in the Arabidopsis flowering pathway. A comprehensive set of diurnal quantitative expression experiments was carried out to investigate the bulbing response in two different onion varieties, namely Renate, a long-day variety and Hojem, a short-day variety under increasing intermediate day-lengths. All onion homologous to Arabidopsis flowering time genes showed clear diurnal expression patterns peaking at different times of the day for both long/short-day onions, indicating their role in daylength dependent bulbing process at molecular level. Under intermediate daylengths, AcFT1 expression level increased with daylengths in both varieties, while AcFT4 was expressed in all daylengths. The two genes showed complementary expression with AcFT4 peaking in the morning and AcFT1 in the evening in longer days. The results indicate that AcFT1 and AcFT4 are negatively co-regulated, but AcFT1 is the predominant regulator of bulb formation in response to day length.
... Similarly the deficiency of nitrogen is evident in the reduction of light interception by decreasing leaf area index, which results in lower grain yield (Hammad et al., 2011). The study of phenology is one most important function that determines the crop growth and development of any crop and is essential to acquire knowledge on the physiological response of the crop under different field conditions (Summerfield et al.,1991). The phenology of the crop is influenced by parameters like the crop genotype, nutrient, biotic, abiotic and weather parameters. ...
A field experiment was conducted during 2014 and 2016 rainy season in Tudun Wada-Kano and Shika-Zaria within the Northern Guinea Savanna of Nigeria in order to study the phenological responses of maize-hybrids under low nitrogen levels. The experiment consisted of two nitrogen levels 0 and 120 N kg ha-1 as main plot and 8 recently developed drought-tolerant maize hybrids:-plot laid out in a randomized split-plot design and replicated three times. Interaction between hybrids and nitrogen was significantly affected at both locations. Based on these results, application of nitrogen significantly decreased the phenological growth indices of maize-hybrids. Recent hybrids showed decreased phenology though, they were better adapted to low nitrogen. The magnitude of decrease in phenology was also higher in 2014 in Zaria because rainfall was higher and better distributed. Hence, the recently released maize-hybrids were more adapted to abiotic stress.
... A thorough understanding of the response of the crop growth and development to environmental factors is thus critical to interpret the crop's performance across environments. The most important environmental factors affecting chickpea growth and development are temperature (Siddique and Sedgley, 1985), photoperiod (Summerfield et al., 1991;Upadhyay et al., 1994;Ellis et al., 1994) and soil moisture (Saxena et al., 1990). ...
The present study investigated if partial reduction of shoot dry matter during early vegetative growth phase of chickpea crop (cv. PBA Seamer) saves sub-soil water for reproductive growth and grain filling of the crop grown at 9 diverse environments. The environments were created by a combination of 3 sites (Emerald, Hermitage and Kingaroy), 3 planting windows (environments 1, 2, 3 at each site) with and without supplementary irrigation. The effects of environments on canopy management (partial reduction in shoot dry matter vs control) and irrigation treatments on the water uptake by roots, crop growth and yield performance and yield components were investigated. Crops in the planting windows (EN 1, 2, 3) experienced variable environments at each site. Days to 50% flowering and crop maturity reduced progressively from EN 1 to EN 3 at the three sites. The environment had significant effect on shoot biomass, yield and HI at the three sites (P < 0.01 or P < 0.0001). Environments had bigger effects on crop that partial reduction in shoot biomass (PRS). The PRS at early vegetative phase resulted in a 25% reduction in radiation intercepted but rapid compensatory growth that followed, resulted in minimal effect on shoot biomass and yield. The HI varied from 0.18 in EN 1 at Kingaroy to > 0.5 in EN 2 at Emerald. There was a trend for an increase in HI from EN 1 to EN 3 at all sites. The response to Irr, computed as the difference in peak shoot biomass and yield between the Irr and RF treatments, was the highest at Hermitage and the least at Emerald site. Vapour pressure deficit during reproductive phase accounted for the majority of variation in shoot biomass response to irrigation (r² = 0.66, P < 0.001) for total dry matter and (r² = 0.46, P < 0.01) for yield. The environments had a significant effect on radiation use efficiency and water use efficiency and the yield components including hundred seed weight.
... Especially in West and Central Africa (WCA), one of the main adaptations of sorghum crop to the unpredictable beginning of rainy season is its sensitivity to photoperiod (PP). Sorghum PP sensitivity allows farmers to sow the crop with the onset of rains (within broad, around 2 months, sowing window with gradually shortening PP) but harvesting crop within relatively narrow window time of the year (Summerfield et al. 1991;Vaksmann et al. 1996;Folliard et al. 2004). Rapid response to PP thus enables the varieties sown within broad sowing window to mature in narrow time window and therefore great flexibility to reduce the damage caused by, for example, grain mold, insects, and birds (Vaksmann et al. 1996;Folliard et al. 2004). ...
This book chapter intends to equip the readers with the basic understanding of what crop models are, answer the common questions which the crop-modelling community usually receives from the other research disciplines, and briefly describe the frequent model misuses which many times hamper broader usage of models in agriculture. We will briefly discuss the diversity of crop models and usage of the appropriate modelling tool to address the questions relevant in crop improvement programs (focus on sorghum/cereals models; APSIM). Furthermore, we will use several examples focusing on sorghum crop of how modelling approaches are currently being deployed to accelerate agricultural/cropping systems production and resilience improvement. Here, we will depict few examples of sorghum model development necessary to reflect agricultural systems in developing countries (e.g., challenges specific to model sorghum crop in Africa). We will point out to emerging directions of model development needed to address some of the global developmental goals and challenges.
... The dry matter production of the faba bean is related to its ability to intercept the incident photosynthetically active radiation (PAR) [7]. In legumes, phenology is mainly regulated by the genetic response to temperature and photoperiod, and the bean is considered a quantitative long day plant, as defined in [8], since it is a species whose flowering begins more quickly in long days, but is not inhibited (qualitative) in short days, only delayed [4]. ...
The Pampas region is characterized by a high complexity in its productive system planning and faces the challenge of satisfying future food demands, as well as reducing the environmental impact of the activity. Climate change affects crops and farmers should use species capable of adapting to the changed climate. Among these species, faba bean (Vicia faba L.) cv. ‘Alameda’ has shown good adaptation to weather variability and, as a winter legume, it can help maintain the sustainability of agricultural systems in the area. The main purpose of this research was to select the models which describe the production characteristics of the ‘Alameda’ bean by using the least number of variables. Experimental and agrometeorological data from the cultivation of the ‘Alameda’ in Azul, Buenos Aires province, Argentina were used to generate mathematical models. Several modelling methodologies have been applied to study the production characteristics of the faba bean. The prediction of the models generated was analyzed by randomly disturbing the experimental data and analyzing the magnitude of the errors produced. The models obtained will be useful for predicting the biomass production of the faba bean cv. ‘Alameda’ grown in the agroclimatic conditions of Azul, Buenos Aires province, Argentina.
... Temperature and to less extent photoperiod have been reported to be the major environmental factors that determine the timing and duration of each of the phenological phases in the physiological development of crops (Roberts et al., 1993). Many models have been developed to explain the phenological phases that take place during growth and development of crops (Alocija andRitchie 1991, Matthews andHunts 1994), while the physiological mechanisms that govern the transition from one phenophase to another are strongly influenced by environmental factors and have been described using photothermal models (Summerfield et al., 1991). ...
... En contraste, en las épocas de baja intensidad de lluvias (época 3), se observó una disminución en el número de vainas por planta, debido a la deficiente oferta hídrica durante el periodo de cultivo; en esta época, se destacan las líneas GRICAND401, GRICAND402 y GRICAND404, con promedios desde 10 a 12,33 vainas por planta. Al respecto, Sañudo Summerfield et al. (1991) concluyeron que, además del genotipo, hay factores ambientales externos, que influyen sobre el crecimiento y el desarrollo de las plantas, como la temperatura, el fotoperiodo y la disponibilidad de agua y nutrientes. ...
La arveja arbustiva tiene características potenciales para la agroindustria y comercio en fresco y puede ser una alternativa para la zona cerealista de Nariño. La presente investigación, se realizó en dos municipios (Yacuanquer y Guaitarilla), pertenecientes a la zona cerealista de Nariño, durante tres épocas de siembra, en el 2017. La combinación de localidades por épocas constituyeron los seis ambientes estudiados. Se evaluaron ocho líneas de arveja arbustiva por número de vainas por planta, adaptabilidad y estabilidad fenotípica, para rendimiento en vaina verde y reacción a enfermedades foliares. En número de vainas sobresalieron GRICAND404 y GRICAND402. El análisis de adaptabilidad y de estabilidad fenotípica permitió identificar, como ambientes favorables, a Yacuanquer abril, Guaitarilla abril y Yacuanquer marzo; GRICAND405, con un rendimiento promedio de 9,27t.ha-1, se consideró una línea adaptable y predecible en los seis ambientes evaluados y GRICAND406, con 9,07t.ha-1, fue predecible y mostró mejor adaptación a los ambientes más favorables. En reacción a las enfermedades evaluadas, todas las líneas fueron susceptibles al ataque del complejo Ascochyta y el porcentaje de infestación de la enfermedad, se evidenció mayor en épocas muy lluviosas, como la época 1 (siembra de marzo) y disminuyó en épocas secas, como la época 3 (siembra de mayo); el ataque de Oídio, se evidenció mayormente en la época de menor precipitación (época 3), siendo resistente la línea GRICAND402.
... Arabidopsis flowering and onion bulbing are both photoperiodically-controlled developmental events [190] that are induced by long days; signal insight lies in the leaf and response is at the top. Sepals, petals, stamens, and anthers are formed as the end produce in Arabidopsis, whereas storage-scale leaves are formed as the end produce in bulbs [191]. Arabidopsis flowering and onion bulbing can be linked via the phytochrome, and both developments are promoted by far-red light through PHYA [192]. ...
The photoperiod marks a varied set of behaviors in plants, including bulbing. Bulbing is controlled by inner signals, which can be stimulated or subdued by the ecological environment. It had been broadly stated that phytohormones control the plant development, and they are considered to play a significant part in the bulb formation. The past decade has witnessed significant progress in understanding and advancement about the photoperiodic initiation of bulbing in plants. A noticeable query is to what degree the mechanisms discovered in bulb crops are also shared by other species and what other qualities are also dependent on photoperiod. The FLOWERING LOCUS T (FT) protein has a role in flowering; however, the FT genes were afterward reported to play further functions in other biological developments (e.g., bulbing). This is predominantly applicable in photoperiodic regulation, where the FT genes seem to have experienced significant development at the practical level and play a novel part in the switch of bulb formation in Alliums. The neofunctionalization of FT homologs in the photoperiodic environments detects these proteins as a new class of primary signaling mechanisms that control the growth and organogenesis in these agronomic-related species. In the present review, we report the underlying mechanisms regulating the photoperiodic-mediated bulb enlargement in Allium species. Therefore, the present review aims to systematically review the published literature on the bulbing mechanism of Allium crops in response to photoperiod. We also provide evidence showing that the bulbing transitions are controlled by phytohormones signaling and FT-like paralogues that respond to independent environmental cues (photoperiod), and we also show that an autorelay mechanism involving FT modulates the expression of the bulbing-control gene. Although a large number of studies have been conducted, several limitations and research gaps have been identified that need to be addressed in future studies.
... Arabidopsis flowering and onion bulb formation are both photoperiodically driven processes , induced by LD, signal perception is in the leaf and response is at the apex. Sepals, petals, stamens and anthers are produced as the end product in Arabidopsis, whereas, a storage scale leaves are produced as the end product in onion (Summerfield et al., 1991). Arabidopsis flowering and onion bulb formation can be compared in terms of the involvement of phytochrome, and both processes are promoted by far-red light, through PHYA (Brewster et al., 1977). ...
Bulb initiation in long-day onion is regulated at the physiological level in a similar way to the photoperiodic regulation of flowering in Arabidopsis. This study establishes in onion, the diurnal time-course expression, in onion, of key genes particularly linked to circadian regulation in Arabidopsis. The long-day onion variety 'Renate' and the short-day (SD) onion variety 'Hojem' were used for these experiments. Onion plants were grown under natural LD conditions in the Phytobiology Glasshouse and immediately after bulbing they were transferred to two SANYO 2279 controlled environment cabinets for 10 d providing constant LD (16 h photoperiod including 8 h fluorescent followed by 8 h incandescent light) and constant short days (8 h photoperiod with fluorescent light). Five FLOWERING LOCUS T (FT) and three CONSTANS-LIKE (COL) genes were identified in onion, including two novel COL sequences through RNA-Seq analysis. The new AcCOL2 shows a diurnal pattern of expression similar to Arabidopsis CONSTANS (CO). Allium cepa FLAVIN-BINDING, KELCH REPEAT, F-BOX PROTEIN 1 (AcFKF1), Allium cepa GIGANTEA (AcGI) and AcCOL2 showed good diurnal expression patterns consistent with photoperiod sensing and regulation of AcFT1. All FT genes exhibited different diurnal expression patterns peaking at different times of the day. Notably, AcFT1 was expressed in the later part of the day which is very similar to the expression of Arabidopsis FT, while AcFT4 was expressed late in the night and the early morning in both Renate and Hojem varieties of onion, with the caveat that, AcFT4 is under less stringent day-length control in Hojem than in Renate. The timing of the peaks and expression pattern in both Renate F1 and Hojem suggest that AcFT5 may be under circadian or diurnal regulation under LD conditions and AcFT6 might not be circadian or diurnally regulated. These findings will help to understand the basis of the difference between responses of onions adapted to different latitudes, which is important for developing new varieties.
... Two approaches are being used to produce three generations per year: (1) Changes in environmental conditions strongly influence plant morphological growth and reproductive behavior. The effect of temperature and photoperiod on flowering time in grain legumes has been well documented [14][15][16]. Photoperiod altered developmental activities such as germination, shoot growth, leaf expansion, and flowering [17,18]. In most coolseason legume crops including chickpea, long days promote flowering. ...
This study was aimed at developing a protocol for increasing the number of generation cycles per year in chickpea (Cicer arietinum L.). Six accessions, two each from early (JG 11 and JG 14), medium (ICCV 10 and JG 16), and late (CDC-Frontier and C 235) maturity groups, were used. The experiment was conducted for two years under glasshouse conditions. The photoperiod was extended to induce early flowering and immature seeds were germinated to further reduce generation cycle time. Compared to control, artificial light caused a reduction in flowering time by respectively 8–19, 7–16, and 11–27 days in early-, medium-, and late-maturing accessions. The earliest stage of immature seed able to germinate was 20–23 days after anthesis in accessions of different maturity groups. The time period between germination and the earliest stage of immature seed suitable for germination was considered one generation cycle and spanned respectively 43–60, 44–64, and 52–79 days in early-, medium-, and late-maturing accessions. However, the late-maturing accession CDC-Frontier could not be advanced further after three generation cycles owing to the strong influence of photoperiod and temperature. The mean total number of generations produced per year were respectively 7, 6.2, and 6 in early-, medium-, and late-maturing accessions. These results have encouraging implications for breeding programs: rapid progression toward homozygosity, development of mapping populations, and reduction in time, space and resources in cultivar development (speed breeding).
... However, it is important to note that there is not a single function to fit all the experimental data and that different researchers developed or modified functions to fit better their data best. The simplest function that is used to describe the rate of biological processes within a limited range of temperatures is the linear one (Summerfield et al. 1991;Marshall and Squire 1996;Vigil et al. 1997): ...
Accurate quantification of biological processes (e.g. germination) response to temperature was and still is of particular interest to many disciplines. Our objective was to develop and compare a new function (modified segmented function) with existing non-linear functions in fitting experimental data that cover both sub- and supra-optimum temperature ranges. We utilized diverse experimental and literature data on various crops such as safflower, maize, sorghum to test the functions which were: a modified segmented (derived in this paper), segmented and beta growth function. The datasets covered different plant biological processes, such as seed germination, leaf elongation. The new function fitted various experimental data with a root mean square deviation (RMSD) from 0.011 to 0.082. In 6 out of the 11 datasets, the new function performed better than the beta and segmented function according to various statistics. However, the performance of the segmented and beta function was better that our function in 4 and 1 out of the 11 datasets, respectively. The new function is interesting because all parameters have biological interpretation, it offers advanced flexibility in fitting complex datasets as compared to the two other functions and its response curve parts can be varied from linear to nonlinear based on thermal sensitivity parameter. We concluded that the new function is a good alternative to beta and segmented functions. Lastly our study confirms that there is no best function that can fit different data of temperature response.
... Temperature and to less extent photoperiod have been reported to be major environmental factors that determine the timing and duration of each of the phenological phases in the physiological development of crops [8]. Many models have been developed to explain the phenological phases that take place during growth and development of crops [9,10], while the physiological mechanisms that govern the transition from one phenophase to another are strongly influenced by environmental factors and have been described using photothermal models [11]. ...
Seven canola genotypes selected from early and mid-maturing groups of canola genotypes presently planted in the Western Cape canola production area were grown in 3 litre plastic bags filled with a mixture of sand and compost at ratio of 1:1 and irrigated with fully balanced nutrient solution at EC=2.0 in two glasshouses at night/day temperature regimes of 10/15˚C and 15/20˚C. Plant heights were measured at 14 days interval from 28 to 84 days after planting (DAP). Plants were sampled for leaf area (LA) and above ground dry mass (DM) at budding, flowering and seed physiological maturity stages. Plant growth rates (PGR) from planting to budding, from budding to flowering and from flowering to physiological maturity growth stages were calculated. Relative growth rates (RGR) and net assimilation rates (NAR) from budding to flowering and from flowering to physiological maturity stages were also calculated. Days after planting, GDD and PTU at budding, flowering and physiological maturity were correlated with leaf area, dry mass, number of pods plant-1 and pod dry mass plant-1 at budding, flowering and physiological maturity stages to determine whether there were relationships between the variables. The study showed that by increasing night/day temperature from 10/15˚C to 15/20˚C plant height, number of leaves plant-1 at budding stage, leaf area at budding , plant growth rate (PGR) from planting to budding stage and relative growth rate (RGR) from budding to flowering stage were increased. However, PGR from budding to physiological maturity, RGR from flowering to physiological maturity, net assimilation rate (NAR) from budding to flowering stage, leaf area at flowering and physiological maturity stages, as well as number of flower stems, number of pods plant-1, above ground total dry mass at flowering and physiological maturity stages were decreased. Pod dry mass at physiological maturity decreased by 22.24% to 40.35% for different genotypes which clearly demonstrated the variations in sensitivity of canola genotypes to increasing night/day temperatures and also indicates that canola crop can be genetically improved for heat tolerance.
... Where f is the number of days from sowing to flowering (Tasseling, Anthesis and Silikng) which resulted into three models for each equation, T is mean daily temperature, P is the mean daily photoperiod (day length) in hours, H is heat units calculated from the daily minimum and maximum temperature using this formula: [22] P and H are calculated from mean photoperiod and heat units from planting to flowering for each variety per replication. The coefficients a, b, a', c', a'', d'', a''', b''', c''', a'''', b'''' and d'''' are genotypic constants (regression coefficients) [23]. These five regression models were developed for individual varieties evaluated during the 2007 late cropping season using all the flowering traits [14]. ...
... Several studies have reported that day length after flowering may affect seed-set, embryo development and seed development in numerous annual crops (Thomas and Raper, 1976;Cure et al., 1982;Summerfield et al., 1991;Linnemann, 1993;Lobell et al., 2000;Lagercrantz, 2009). For example, in soybean the seed dry weight and seed number increased under a 15 h day length regime (Cure et al., 1982). ...
The objective of this study was to evaluate the effect of day length after flowering on pollen tube elongation, embryo formation and seed development. The quinoa varieties used in this study were Amarilla de Marangani (valley type) and NL-6 (sea-level type). After sowing, the quinoa plants were cultivated in growth cabinets. From sowing to flowering, plants were exposed to a 15 h day length regime. After flowering, the plants were grown under either a 15 h or 11 h day length regime. The elongation of the pollen tube and the formation of the early embryo were not inhibited in either Amarilla de Marangani or NL-6 under the 11 or 15 h day length regimes. Although growth of the embryo in NL-6 was not inhibited by the 15 h day length regime after flowering, the same was not observed in the case for Amarilla de Marangani. In Amarilla de Marangani, seed diameter at 8 and 14 days after flowering under the 11 h day length regime was larger than that of seeds grown under the 15 h day length regime. Thus, the decrease in the number of seeds in Amarilla de Marangani grown under the 15 h day length regime may be caused by the suspension of embryo growth after fertilization.
... The results showed that higher GDD and EDD would significantly accelerate the leaf senescence and shorten the RGD at both station scale (Fig. 5a-c) and regional scale (Fig. 5d-f). These results are supported by previous controlled experiments showing that the growth duration of winter wheat was closely related to the climate conditions during reproductive growing stages (Summerfield et al., 1991;Asseng et al., 2011;Tao et al., 2012a,b). High temperature, especially during critical periods of development, would accelerate the crop senescence and consequently shorten the duration (Al-Khatib and Paulsen, 1984;Dias and Lidon, 2009;Talukder et al., 2014). ...
Impact of high temperature stress on crop growth and productivity is one key concern with respect to crop production and food security under climate change. Due to the complexity and diversity of crop characteristics and farmers’ management practices, as well as the difficulties in quantifying those agronomic management practices at reasonable temporal and spatial scales, crop responses to heat stress at a regional scale have not been properly assessed yet. In this study, we used remote-sensing data to investigate the responses of growth duration and leaf area index (LAI) of winter wheat to extreme high temperature during reproductive growing stage in the North China Plain from 2001 to 2008. Growing degree days above 0 °C (GDD) from heading to maturity was used to represent average temperature of growing environment, and the extreme temperature (>34 °C) degree days (EDD) was used as an indicator for heat stress. We detected statistically significant shortening of reproductive growing duration due to increase in GDD and EDD at both site and regional scales. We also found acceleration of leaf senescence under warmer environment, as well as considerable damages to leaf area by extremely high temperatures according to LAI values from remote-sensing data. Our results present the explicit patterns of crop responses to heat stress at different spatial scales and periods, indicating the complexity of the impacts of extreme events. Moreover, we highlighted that exposure, vulnerability and adaptation all should be considered in evaluating the impacts of extreme events. In addition, our findings suggest great potential for improving regional crop growth monitoring and yield prediction through assimilating remote-sensing data into mechanistic crop simulation models.
... Para elaborar un modelo para la papa, es importante conocer su fenología (Jefferies y Lawson, 1991). Summerfield et al. (1991) proponen que el modelado de la fenología de los cultivos debe ser simple, confiable y plausible desde el punto de vista biológico; según Arazi et al. (1993), estos modelos generalmente se basan en las unidades calor para predecir las fases fenológicas de la planta. ...
El objetivo del presente estudio fue evaluar tres métodos para predecir la fenología en el cultivo de papa (Solanum tuberosum L.) mediante tiempo térmico, para lo cual se trabajó con un total de 15 parcelas a nivel comercial sembradas con la variedad 'Alpha' en el norte de Sinaloa, México. Los métodos comparados fueron: temperatura media, grados día (°D) y días fenológicos de papa (P-days), los tres calculados con los datos obtenidos mediante el monitoreo en campo de cada fase fenológica durante los ciclos agrícolas otoño-invierno 2005-2006 y 2006-2007. Los resultados indicaron que el mejor método para predecir la fenología de esta variedad de papa con base en el tiempo térmico fue el P-days, porque presentó los menores valores de coeficiente de variación con 0.07 y de desviación estándar con 18.03 para todas las etapas fenológicas analizadas. Al comparar los errores encontrados para cada método en el grupo de parcelas en las que se determinaron las necesidades térmicas más un grupo de otras parcelas usadas para validar dichas necesidades, se confirmó que el método P-days tuvo menores errores, pues los valores encontrados fueron 3.6 y 3.2 % para la raíz cuadrada del cuadrado medio del error RMSE y el error medio absoluto MAE, respectivamente.
... The photothermal model of progress towards flowering, developed in the 1980s for faba bean (Ellis et al. 1988a,b,c;Ellis et al., 1990), has been applied to soya bean (Glycine max L.) (Hadley, Roberts, Summerfield, & Minchin, 1984;Upadhyay et al., 1994), several annual field crops (Summerfield, Roberts, Ellis, & Lawn, 1991) and forage legumes (Iannucci et al., 2008), but it is limited by its restriction to temperature and photoperiod. Thus, it works well in controlled conditions and is informative about genetic differences in photoperiod and temperature sensitivity, but our results show that it is not sufficiently predictive in field conditions. ...
Predicting and understanding the progress towards flowering in faba bean are important to achieve the adaptation and high productivity of the crop under varying environmental conditions. Traditional controlled-environment experiments showed that the rate of progress towards flowering was dependent mainly on photoperiod and temperature. Here, we highlight the need to include measures of solar radiation and water deficit in order to achieve an adequate model for field conditions. The improved model was assessed in two steps: first with a “basic” model across all 20 cultivars and then with an “extended” model that included terms to fit exceptional cultivars. The two new parameters were necessary to achieve an acceptable fit of progress towards flowering and clearly separated two cultivars, “Kontu” and “Witkiem Manita,” that were significantly quicker to flower than the other 18, which fit a single line. As the regression coefficients of the two exceptional cultivars differed only in intercept, not slope, we conclude that flowering responses to day length, temperature, solar radiation and drought stresses were consistent in this set of germplasm and that the two cultivars differed in earliness “per se.” Growth-chamber experiments added information about differing ceiling temperatures for progress to flowering in four cultivars and different sensitivities to supraoptimal temperatures.
... The influence of photoperiod and temperature on the rate of progress towards flowering has been well studied in the grain legumes and can be evaluated using linear models that describe the flowering behavior in response to these factors (Summerfield et al. 1985(Summerfield et al. , 1991Erskine et al. 1994). Light quality also plays a key role in the regulation of time to flowering in plants (Weller et al. 2001); however, its effect is still unclear but exploitable. ...
Understanding the role light quality plays on floral initiation is key to a range of pre-breeding tools, such as accelerated single-seed-descent. We have elucidated the effect of light quality on early flowering onset in cool-season grain legumes and developed predictive models for time to flowering under the optimised light conditions. Early and late flowering genotypes of pea, chickpea, faba bean, lentil and lupin were grown in controlled environments under different light spectra (blue and far red-enriched LED lights and metal halide). All species and genotypes showed a positive response to a decreasing red to far-red ratio (R:FR). In general, ratios above 3.5 resulted in the longest time to flowering. In environments with R:FR below 3.5, light with the highest intensity in the FR region was the most inductive. We demonstrate the importance of considering both relative (R:FR) and absolute (FR photons) light values for flower induction in grain legumes. Greater response to light spectra was observed in the later flowering genotypes, enabling a drastic compression of time to flowering between phenologically diverse genotypes. A novel protocol for robust in vitro germination of immature seeds was developed for lupin, a species known for its recalcitrance to in vitro manipulation. We show how combining this protocol with growth under conditions optimized for early flowering drastically speeds generation turnover. The improved understanding of the effect of light on flowering regulation and the development of robust in vitro culture protocols will assist the development and exploitation of biotechnological tools for legume breeding.
... Two approaches have been used to model temperature and photoperiod effects on soybean phenology. One approach is to sum over separate temperature and photoperiod functions [18][19][20][21][22] with a convenient coefficient for quantifying genetic differences for photoperiod sensitivity. Unfortunately, simple addition doesn't account for temperature effects on photoperiod sensitivity as shown by Cober et al. [14] who added a function to account for temperature-photoperiod interactions. ...
Soybean isolines with different combinations of photoperiod sensitivity alleles were planted in a greenhouse at different times during the year resulting in natural variation in daily incident irradiance and duration. The time from planting to first flower were observed. Mathematical models, using additive and multiplicative modes, were developed to quantify the effect of photoperiod, temperature, photoperiod-temperature interactions, rate of photoperiod change, and daily solar irradiance on flowering time. Observed flowering times correlated with predicted times (R2 = 0.92, Standard Error of the Estimate (SSE) = 2.84 d, multiplicative mode; R2 = 0.91, SSE = 2.88 d, additive mode). The addition of a rate of photoperiod change function and an irradiance function to the temperature and photoperiod functions improved the accuracy of flowering time prediction. The addition of a modified photoperiod function, which allowed for photoperiod sensitivity at shorter photoperiods, improved prediction of flowering time. Both increasing and decreasing rate of photoperiod change, as well as low levels of daily irradiance delayed flowering in soybean. The complete model, which included terms for the rate of photoperiod change, photoperiod, temperature and irradiance, predicted time to first flower in soybean across a range of environmental conditions with an SEE of 3.6 days when tested with independent data.
Temperature and photoperiod are two major environmental determinants that affect the rate of development towards flowering. Quantifying the interactive effect of temperature and photoperiod on flowering of pigeonpea genotypes is essential in selecting photoperiod insensitive lines. The coefficients derived from non-linear broken stick model can be used as a proxy for photoperiod sensitivity.
Sorghum production system in the semi-arid region of Africa is characterized by low yields which are generally attributed to high rainfall variability, poor soil fertility, and biotic factors. Production constraints must be well understood and quantified to design effective sorghum-system improvements. This study uses the state-of-the-art in silico methods and focuses on characterizing the sorghum production regions in Mali for drought occurrence and its effects on sorghum productivity. For this purpose, we adapted the APSIM-sorghum module to reproduce two cultivated photoperiod-sensitive sorghum types across a latitude of major sorghum production regions in Western Africa. We used the simulation outputs to characterize drought stress scenarios. We identified three main drought scenarios: (i) no-stress; (ii) early pre-flowering drought stress; and (iii) drought stress onset around flowering. The frequency of drought stress scenarios experienced by the two sorghum types across rainfall zones and soil types differed. As expected, the early pre-flowering and flowering drought stress occurred more frequently in isohyets < 600 mm, for the photoperiod-sensitive, late-flowering sorghum type. In isohyets above 600 mm, the frequency of drought stress was very low for both cultivars. We quantified the consequences of these drought scenarios on grain and biomass productivity. The yields of the highly-photoperiod-sensitive sorghum type were quite stable across the higher rainfall zones > 600 mm, but was affected by the drought stress in the lower rainfall zones < 600 mm. Comparatively, the less photoperiod-sensitive cultivar had notable yield gain in the driest regions < 600 mm. The results suggest that, at least for the tested crop types, drought stress might not be the major constraint to sorghum production in isohyets > 600 mm. The findings from this study provide the entry point for further quantitative testing of the Genotype × Environment × Management options required to optimize sorghum production in Mali.
Supplementary Information
The online version contains supplementary material available at 10.1007/s13593-023-00909-5.
A principal objective in agriculture is to maximise food production; this is particularly relevant with the added demands of an ever increasing population, coupled with the unpredictability that climate change brings. Further improvements in productivity can only be achieved with an increased understanding of plant and crop processes. In this respect, mathematical modelling of plants and crops plays an important role. In this paper we present a two-scale mathematical model of crop yield that accounts for plant growth and canopy interactions. A system of nonlinear ordinary differential equations (ODEs) is formulated to describe the growth of each individual plant, where equations are coupled via a term that describes plant competition via canopy-canopy interactions. A crop of greenhouse plants is then modelled via an agent based modelling approach in which the growth of each plant is described via our system of ODEs. The model is formulated for the African drought tolerant legume bambara groundnut (Vigna subterranea), which is currently being investigated as a food source in light of climate change and food insecurity challenges. Our model allows us to account for plant diversity and also investigate the effect of individual plant traits (e.g. plant canopy size and planting distance) on the yield of the overall crop. Informed with greenhouse data, model results show that plant positioning relative to other plants has a large impact on individual plant yield. Variation in physiological plant traits from genetic diversity and the environmental effects lead to experimentally observed variations in crop yield. These traits include plant height, plant carrying capacity, leaf accumulation rate and canopy spread. Of these traits plant height and ground cover growth rates are found to have the greatest impact on crop yield. We also consider a range of different planting arrangements (uniform grid, staggered grid, circular rings and random allocation) and find that the staggered grid leads to the greatest crop yield (6% more compared to uniform grid). Whilst formulated specifically for bambara groundnut, the generic formulation of our model means that with changes to certain parameter’s, it may be extended to other crop species that form a canopy.
‘Rocha’ pear culture demonstrated to have high yield potencial and when submited to new production models has combined it with the production of high quality fruits. It was demonstrated the need to increase tree density, coupled with changes in training systems to increase light interception. We proposed alternating axes tilt angles, which allow average yields increases of 24.4% and 15.2% in medium and high density orchards respectively.
High density production means adjust technical operations to light microclimate in order to maintain high photosynthetic efficiency inside all the points of the canopy and enhance fruit growth, increasing harvest index. Intensive and precision pruning helped this balance, allowing better light distribuition and stimulating new production organs formation, more efficient and better able to produce quality fruits.
Submodels were calibrated and validated for simulations of development, radiation interception and fruit growth, including in a robust generic model that simulates generic processes of pear ‘Rocha’ development, growth and yield. Modeling helped to clarify interactions between cultural management and conversion and assimilates partitioning, providing important analytical tools and indicators for decision support strategies.
‘Rocha’ pear culture demonstrated to have high yield potencial and when submited to new production models has combined it with the production of high quality fruits. It was demonstrated the need to increase tree density, coupled with changes in training systems to increase light interception. We proposed alternating axes tilt angles, which allow average yields increases of 24.4% and 15.2% in medium and high density orchards respectively.
High density production means adjust technical operations to light microclimate in order to maintain high photosynthetic efficiency inside all the points of the canopy and enhance fruit growth, increasing harvest index. Intensive and precision pruning helped this balance, allowing better light distribuition and stimulating new production organs formation, more efficient and better able to produce quality fruits.
Submodels were calibrated and validated for simulations of development, radiation interception and fruit growth, including in a robust generic model that simulates generic processes of pear ‘Rocha’ development, growth and yield. Modeling helped to clarify interactions between cultural management and conversion and assimilates partitioning, providing important analytical tools and indicators for decision support strategies.
Extended abstract
Introduction: Since the maximum percentage and rate of germination of rapeseed occur at a certain temperature, finding these temperatures can play an important role in determining the appropriate time and place for the cultivation of different cultivars. Also, light can affect the germination percentage of rapeseed at different temperatures, but the response of rapeseed to light, especially at lower and higher temperatures, has not been studied. Therefore, this study aimed to investigate the changes in the germination of rapeseed cultivars at different temperatures and determine cardinal germination temperatures based on germination percentage and rate under both the presence and absence of light conditions.
Materials and methods: In this study, germination tests were carried out at 5, 10, 15, 20, 25, 30, 35, 37, and 40°C temperatures in two light conditions (12 h light / 12 h dark) and darkness on nine spring cultivars (Traper, Agamax, Hayola-50, Hayola-420, RGS, Mahtab, Hayola-61, Zafar, and Zarfam) and one winter cultivar (Garo). The four-parameter Hill model was used to describe germination changes over time and the dent model was used to calculate cardinal temperatures. Seed viability at lower and higher temperatures was evaluated by the tetrazolium test.
Results: The evaluation of the trend of cumulative germination percentage over time in different cultivars showed that all cultivars were in the temperature range between 15-30 °C, some in the temperature range of 10-30 °C (Hyola-61) and others even in the temperature range of 5-30 °C (RGS, Mahtab, Garo, Zafar, and Zarfam) had the highest germination percentage. The highest germination rate in all cultivars was observed at the temperature range of 22-35 °C. Light only had an effect on the germination percentage of the seeds at sub and super optimal temperatures. At these temperatures, light increased the germination percentage. The remaining seed of 5, 10, 35, 37, and 40 °C temperature after transfer to 20 °C did not germinate, whereas most of them were viable based on the tetrazolium test.
Conclusion: The difference in the optimum temperature range for germination percentage and rate showed that to optimize seed performance, the optimal temperature range between the germination percentage and germination rate consider as the optimum temperature for germination. In sub and supra optimal temperatures, light leads to improved germination in some cultivars. The effect of light on germination in supra optimal temperatures was far higher than that of sub-optimal ones. Survival of the remaining seeds at the sub and supra optimal temperatures in some cultivars provided evidence of thermo-dormancy in these cultivars, this issue needs further investigation in the future.
Keywords: Cardinal temperatures, Germination rate, Germination percentage, Survival, Tetrazolium
Highlights:
1- The cardinal temperatures were studied based on both the percentage and rate of germination and the effect of light on them.
2- Some new varieties such as Traper and Agamax that don't have much information about their characteristics were examined.
3- In this study, the reason for the lack of germination of rapeseed at the sub and supra optimal temperatures especially in the darkness has been mentioned.
The identification of genes that affect plant growth and development has played a prominent role in modern plant research. Mathematical modeling can be a useful tool in this process of quantifying the effects of individual genes. In soybean [ Glycine max (L.) Merr.], seven loci ( E1 to E7) have been identified that condition time to flowering and maturity and photoperiod sensitivity. Twenty‐nine near‐isogenic lines with different combinations of alleles at six of these loci in either ‘Clark’ or ‘Harosoy’ background were used in this study. Days from planting to first flower were observed in these lines over 2 yr at two locations (Ottawa, ON, Canada, and Urbana, IL, USA) under natural daylength and a 20‐h photoperiod. A mathematical model was developed to simulate the effect of average daily temperature, photoperiod, and the temperature × photoperiod interaction. A photoperiod coefficient was calculated for each isoline, which resulted in an R ² of 0.93 when calculations of times to first flower were correlated with observations. A submodel was developed to calculate photoperiod coefficients by adding contributions from each locus with dominant alleles. This reduced the 29 isoline coefficients to seven coefficients (one for each locus plus an additional value for unknown genes) but with a reduction of the R ² of from 0.93 to 0.89. The E1 coefficient was approximately twice the size of the other five allele coefficients. Time from planting to first flower can be calculated from the average daily temperatures and latitude of a given location using the gene model if the genetic makeup of the line is known.
Simulation models have the potential of greatly enhancing decision‐making by farmers and researchers in Nigeria. These models however, need to be adapted before use. This study was conducted to test the phenology module of CERES‐Maize model version 3.5 under varying N rates as a step toward adapting the model in the Southern Guinea Savanna of Nigeria. Data on seven late‐maturing cultivars of maize ( Zea mays L.) grown under 0, 30, 60, 90, and 120 kg N ha ⁻¹ in the field for two seasons were used for running the model. There was a linear relationship between N rates and days to silking and maturity with R ² values of > 0.70 for most of the cultivars, indicating that N strongly influenced phenology. Predictions of days to silking at high N rates (90 and 120 kg N ha ⁻¹ ) were close, with most prediction errors of <2 d. The highest deviations in the calibration results were 4 and 2 d for 90 and 120 kg N ha ⁻¹ , respectively, while in the validation results, they were 1 and 2 d. Similarly, days to maturity were closely predicted by the model at high N rates with <2‐d deviations for most predictions. At low N rates, however, there were greater deviations in model predictions. This shows that the CERES‐Maize model can be reliably used for predicting maize phenology only under nonlimiting N conditions. Thus, a N stress factor needs to be incorporated into the model for more accurate phenology prediction in low‐N tropical soils.
Climate change is a pernicious and irrefutable reality. The objective of this work was to analyze trends in extreme temperature indices in Aguascalientes. With RClimdex 1.0 and data on daily maximum (T max) and minimum temperature (T min), 16 temperature indices were calculated. The trend in indices was determined with the non-parametric Mann-Kendall test (p ≤ 0.05), while the rate of change was obtained with Theil-Sen's trend estimator. Significant positive trends were observed in 72 time series of indices associated with T max and in 39 time series of indices associated with T min. Significant negative trends were observed in 22 time series of indices associated with T max , and in 45 time series of indices associated with T min. In some regions of Aguascalientes, diurnal warming is occurring; in others, warmer or less cold nights prevail. The changes in extreme temperature indices might have severe implications in the use of irrigation water, cause physiological stress in crops, promote respiratory and cardiac diseases, and improve the reproduction cycles and populations of insects. Also, the fruit production, such as guava, could be affected under the reduction of minimum temperature, and the increase in warm days where other fruit trees are cultivated can intensify the use of chemical compensators of cold. These results are of significance for long-term economic planning and design of strategies of adaptation/mitigation to climate change. In Aguascalientes, the changes observed in extreme temperature indices could be due to climate change of a bigger scale, either regional or at the watershed level.
Although the model described here was developed from research in controlled environments, there is now considerable evidence that in can be applied to a very wide range of natural environments in several species. Multi-locational trials augmented by successional sowing and, if considered necessary, supplementary illumination in the field to increase daylength, can be used to estimate the values of the model coefficients: (1) to characterize germplasm collections and so predict flowering behaviour elsewhere; (2) for interpreting and understanding crop adaptation; and (3) for genetic analysis of photoperiod sensitivity. We do not yet know whether the model has any contribution to make to the understanding of the biochemical mechanisms of photoperiod and temperature responses, but at the very least, it should provide the basis for indicating the most appropriate environmental conditions, genotypes and physiological stage of the plants most suitable for such investigations.
Bambara groundnut (Vigna subterranea (L) Verdc.) is an underutilized legume native to sub-Saharan Africa, where it is grown at low levels by many farmers as a component of household food and nutritional security. It is generally regarded as drought tolerant and fills the same agroecological niche as peanut (Arachis hypogaea L). Molecular research in this crop really began only in the early 2000s but has gathered pace and the recent publication of the first genome draft as part of the AOCC drive to sequence 101 African crop species marks an important milestone towards the application of genome-enabled breeding. This crop has potential to contribute to the climate-smart agriculture of the future. The current article traces the progress made in recent years and highlights the challenges that still remain.
Shallot is one of the major vegetable crops used for seasoning local cuisines in Ethiopia. It is propagated vegetatively using bulbs as planting material. However, the use of bulbs as planting material is not advisable, because bulbs are expensive, bulky to transport, transmit diseases from one generation to the next, and have short shelf life. As a result, production of shallot decreased considerably in favor of the seed propagated onions. To reverse the trend, a study was undertaken to develop shallot varieties that can be propagated through seed. In the first phase of the development, sixty nine shallot accessions, that could bolt and produce seeds, were identified. Three accessions (DZSHT-91-2B, DZSHT-193-1A and DZSHT-157-1B), which had desirable bulb characteristics were developed through recurrent positive selection from 2008 to 2014. Then the three varieties were compared with an onion variety Bombay Red, a vegetatively propagated shallot variety Minjar and an introduced seed propagated shallot variety Vethalan. The trials were lied out in Randomized Complete Block Design with three replications at three different agro-ecological locations. The results of the study showed that the three varieties, in addition to mitigating the aforementioned problems, had 44–86% higher bulb yield and higher proportion of big and medium size bulbs as compared to shallot variety Minjar. The yield and total soluble solids (TSS) of the varieties were comparable with Bombay Red and Vethalan varieties. The three selected seed producing cultivars also produced seed yield of 6.0–10.4 g per plant. Therefore, the varieties will benefit shallot bulb and seed producers, transporters and traders.
The phenological development of crops from emergence to flowering time is largely controlled by temperature and photoperiod. Flowering time is a critical phenological stage for subsequent reproductive phase. Lotus tenuis management in grasslands, pastures and seed production systems is through defoliation and sowing date; however, yet little is known about their effects on flowering time. The data presented in this study were obtained from experiments conducted with L. tenuis during the years 1989 to 2016 under field conditions. Our objectives were to determine if flowering time (a) is affected by sowing date; (b) can be predicted through equations using temperature and photoperiod and (c) is affected by defoliation applied at vegetative stage. Two defoliation intensities were applied, low (LDI) crop height reduced by 54% compared to pre-defoliation crop height and high (HDI), crop height reduced by 75%. The rate of progress from seedling emergence to flowering time (inverse of time from emergence to first flowering, 1/f) was modulated by temperature, photoperiod and photothermal functions. When L. tenuis sowing was delayed from autumn to spring, time from seedling emergence to first flowering decreased from 260 to 100 days. 1/f was linearly related to average temperature ( R ²=0.75) and photoperiod ( R ²=0.85) and both variables ( R ²=0.92). Defoliation retarded flowering time. Flower and pod growth periods were shorter under defoliation than in control one. Defoliation did not cause abortion of flowers and pods. Flower production was fitted to quadratic function of photoperiod. Flowering peak was approximately within 15.2 h. The prediction of flowering time using thermal, photoperiod and photothermal models can provide information about crop management decisions, such as optimal environmental regimes for crop growth through sowing date.
Investigations of the“physiology of yield” in the cool season food legumes have often measured only the end-products of physiological and phenological processes at reproductive maturity. Information on these“static” components-of-yield provides little understanding of why economic yield or any particular component of it varies; neither does it contribute much understanding of the processes by which components of yield are determined, nor how they relate to plant growth or the environment.
Four types of dynamic processes — development (phenology), expansion (e.g., of leaf area and root length), and the assimilation and partition of dry matter — combine to determine economic yield. Environmental factors and agronomic variables have considerable effect on each of these processes, and there can be substantial quantitative differences between genotypes, too. Experience suggests and experiments increasingly confirm that the first category of processes, i.e., phenological events, are of fundamental importance in relation to the capture by crops of environmental resources, notably of solar radiation, water, and nutrients. The first step towards maximizing yield by management or breeding is therefore to ensure that the phenology of the crop is well matched to the resources and constraints of the production environment. Hitherto, empirical approaches to screening germplasm for phenological events such as times to flowering have predominated in food legume breeding programs. These“evaluation descriptors” are often specific to location and season and so are of limited value. However, it is now clear that analyses of the responsiveness of flowering to photothermal conditions are more reliable and more informative when based not on times to flowering (f) but on rates of progress towards flowering (1/f). Furthermore, the approach now advocated provides“genetic descriptors” which are independent of environment, but which are capable of predicting flowering responses in any environment, and so are of widespread value.
Plant breeders have modified plant architecture to fit crop production systems, particularly for mechanical harvesting, but have given inadequate attention to the effects of architecture on yield. The development of high yielding dwarf wheat, rice and determinate tomato cultivars have emphasized the relation of plant architecture to crop yield. Delayed flowering of photoperiod sensitive dry beans ( Phaseolus vulgaris L.) under long days produced more fruiting nodes per plant and increased yield 50 to 70%. The contributions of plant architecture components to yield and quality have been investigated with near-isogenic lines of various crops. Modifications of plant architecture have been adopted to alleviate heat and moisture stress, to confer insect resistance, and to avoid disease.
The times from sowing to first flowering (f) of 231 accessions of lentil (Lens culinaris Medik.), comprising germ plasm from eight countries and breeding lines from ICARDA in Syria, were recorded in four glasshouse environments; two photoperiods (16 and 13 h/day) combined with warmer (24°/13°C) and cooler (18°/9°C) day/night temperatures. The linear model 1/f=a+bT + cP (where T is mean diurnal temperature and P is photoperiod) provided an average fit over the 231 accessions of r
2=0.852. Since there is no interaction term in this linear model, the flowering responses of an accession to temperature and photoperiod are independent. The values of the constants b and c indicate relative responsiveness of rate of progress towards flowering (1/f) to temperature and photoperiod, respectively. Comparison among the 231 accessions showed a weak, but significant, negative correlation between the values of b and c (r=-0.291, P<0.01). Since the proportion of the variance of b not attributed to its linear regression on c was >0.91, we conclude that these phenological responses are under separate control and that there is considerable scope for selection of any combination of sensitivities to temperature and photoperiod in lentil. Just as a large proportion of the variation among accessions in mean time to first flowering was attributed to country of origin, so also was variability in the values of the constants a, b, and c. In particular, sensitivity to photoperiod (i.e., the value of constant c) was dependent upon latitude of origin. Breeding lines from ICARDA were equally variable in a, b, and c as were germ plasm accessions from elsewhere, while the mean values were similar to those of accessions from neighboring Jordan. A single accession of wild lentil (L. culinaris subsp. orientalis) from Turkey showed flowering responses to T and P similar to the mean value of accessions of cultivated lentil from that country. Results from diverse environments for the Argentinian cv Precoz show that the use of this linear model facilitates predictions of time to flowering in any environment (within wide limits) of known mean temperature and photoperiod. The model, then, minimizes the need for multisite evaluations of phenology, since predictions of pre-flowering duration in any environment, and characterization of flowering responses to photoperiod and temperature, can now be achieved by screening germ plasm in a few, carefully selected locations.
The flowering response of two cultivars of wheat, oats, rye, Polish rape, Argentine rape, flax, sorghum, and soybeans to photoperiods between 12 and 24 h at 1-h intervals was studied in controlled environment cabinets. The results indicated that in long-day species, the relationship between time to heading or first flower and photoperiod was linear and decreased as photoperiod increased to the minimum optimal photoperiod (MOP). Within the range of optimal photoperiods, the number of days to heading or flowering was constant and provided a measure of the length of the basic vegetative phase (BVP). The slope of the response line obtained in non-optimal photoperiods provided an estimate of photoperiod sensitivity. The three characteristics, MOP, BVP, and photoperiod sensitivity, were equally valid for the short-day species except that as daylength increased, there was a linear increase in time to flowering as daylength increased above a maximum optimal photoperiod (MOP). For three of four short-day cultivars, there was also a critical photoperiod above which flowering occurred in a constant number of days. Data suggest separate genetic controls for each of the response characteristics.
The pulse of life with the seasons is a classic theme of biology, equally cap turing every man's curiosity about early and late milestones of every year's cycle and the critical physiologist's inquiry into life's subtle signals and responses. Natural historians of ancient and renaissance time as well as today have charted the commonsense facts behind inspired traditions of poetry and practical rules for growing food and fiber. This volume brings together several ways of organizing the basic principles of phenology. These find order in the otherwise overwhelming mass of detail that captures our fleeting attention, like the daily newspaper, and then tends to fade into the overstuffed archives of history. Is this order so obvious and understandable that there is no longer any scien tific challenge to "phenology" as a tradition? Or does apparent simplicity mask a complex and ultimately baffling obstacle to the understanding of seasonality in even those few indicator plants and animals we know best, not to men tion the less known species or races making up the rest of each major land scape unit or ecosystem? Denying both these hasty opinions, we think that this volume well illustrates a range of questions and answers-from soundly established (but not trivial) doctrine to exciting inquiry about how ecosystems are organized.
Two cultivars of lentils, Laird and Precoz, were subjected to 18 potentially vernalizing treatments, comprising constant temperatures of 1, 5 or 9 °C in factorial combination with photoperiods of 8 or 16 h for 10, 30 or 60 d. These seeds or seedlings, together with non-vernalized seeds (as controls), were then transferred to four different growing regimes ('day'/'night' temperatures of 18/5 °C or 24/13 °C, factorially combined with photoperiods of 11 or 16 h). Variation in the number of days from sowing to first flower (f) in the growing regimes for the controls conformed to the equation I/f = a+b+cP, where is mean temperature (°C), P is photoperiod (h) and a, b and c are genotype-specific constants. Accordingly, when the environment varies during development, the photothermal time required to flower in day-degrees (°C d) is given by 1/b above a base temperature defined as -(a+cP)/b. Most variation in time to flower could be accounted for by the photothermal time accumulated in the two successive environments. Therefore, there was no evidence of a specific low-temperature vernalization response in either cultivar. Neither was there evidence of 'short-day' vernalization, i.e. advancement of flowering resulting from preliminary short-day treatments. A potential error inherent in the predictive model described arises because it ignores the presence of a pre-inductive, photoperiod-insensitive phase; but agro-ecological considerations suggest that this error may not be important in practice.
Various cool treatments of imbibing seeds reduced the subsequent times taken to flower in two genotypes of chickpea (Cicer arietinum L.). These reductions were greater in the kabuli cv. Rabat than in the desi accession ICC 5810. Nevertheless, in both genotypes, the hastening of flowering was entirely accounted for by the photothermal time accumulated during each cool temperature pretreatment, provided it was recognized that the ceiling photoperiods were approximately 10 and 8 h d -1, respectively; i.e. neither genotype shows a true vernalization response. A thorough reevaluation of ' responsiveness to vernalization' in the chickpea germplasm might now be prudent.
Reanalyses of extensive results from three separate controlled environment studies show that the rate of progress towards flowering in plants of the Sudanese faba bean (Vicia faba L.) land-race Zeidab Local responds consistently and without interaction to photoperiod and sub-optimal temperatures across all investigations, with no specific low-temperature vernalization response. Moreover, the additive model developed to describe the photothermal response is sufficiently robust to show that the range between the two boundary photoperiods is substantial, and so covers most agricultural environments: the critical photoperiod, below which flowering is delayed, is ≥ 18 h d -1; and the ceiling photoperiod, i.e. the longest photoperiod which gives the maximum delay in flowering, is ≈ 7·5 h d -1 Despite their different origins, Zeidab Local and the UK cv. Maris Bead show a similar sensitivity of rate of progress towards flowering to temperature and also to photoperiod. Differences in the base and optimum temperatures are, however, substantial. Data for other diverse genotypes of faba bean also provide no evidence of any significant variation in the sensitivity of rate of progress towards flowering to temperature, but sensitivity to photoperiod varies greatly. A simple method of characterizing the sensitivity of time to flower to fluctuating field environments in the faba bean germplasm is proposed.
Factorial combinations of three photoperiods (10, 13 and 16 h), two day temperatures (18 and 28 °C) and two night temperatures (5 and 13 °C) were imposed on nodulated plants of six diverse genotypes (cultivars and land-races) of lentil (Lens culinaris Medic.) grown in pots in growth cabinets from vernalized (1.5 ± 0.5 °C for 30 d) or non-vernalized seeds (i.e. 144 'treatment' combinations). The times from sowing to the appearance of first open flowers were recorded. Vernalization, long days and warm temperatures hastened flowering but genotypes differed in relative sensitivity to each of these factors and in time to flowering in the same most-inductive environment. Rates of progress towards flowering (i.e. 1 f, the reciprocals of the times to first flower, f) in all genotypes, vernalized or not, were linear functions of both mean temperature, t ̄, and photoperiod, p, with no interaction between the two terms. So, over a wide range of conditions (covering the photo-thermal regimes experienced by lentil crops world-wide), time to flowering can be described by the equation: 1 f= a + b t ̄ + cp, where a, b and c are constants which differ between genotypes and the values of which provide a sound basis for screening germplasm for sensitivity to temperature and photoperiod. Although these two environmental factors affect the same phonological event (i.e. time to flowering) our data suggest the responses are under separate genetic control. Seed vernalization consistently increased the values of both a and b in all genotypes. The implications of these collective findings for the screening of lentil germplasm are discussed.
Plants of six contrasting genotypes of barley were raised from vernalized (imbibed at 1 °C for 30 d) or non-vernalized seeds and grown in 12 different controlled environments comprising factorial combinations of three photoperiods (10, 13 and 16 h d -1), two day temperatures (18 and 28 °C) and two night temperatures (5 and 13 °C). Except at longer days for Athenais or Arabi Abiad, the 28 °C day temperature was generally supra-optimal and delayed awn emergence. At lower temperatures and in photoperiods shorter than the critical value, P C, which delay awn emergence, the time from sowing to awn emergence for five of the genotypes conformed to the equation 1/f=a +bT-+cP where f is the time to awn emergence (d), T- is mean diurnal temperature (°C), P is photoperiod (h d -1) and a, b and c are genotype-specific constants. In Arabi Abiad, however, significant responses to temperature were not detected. The low temperature pre-treatment of the seeds reduced the subsequent time to awn emergence in Athenais and the autumn-sown genotypes Ager, Arabi Abiad and Gerbel B, especially in longer days, but either had no effect or tended to delay awn emergence in the spring-sown types Emir and Mona. In the spring-sown types P C was outside the range investigated (i.e. > 16 h d -1), but in Ager it was approx. 13 h d -1 and in Gerbel B just over 13 h d -1. For plants of Arabi Abiad grown from vernalized seeds P c was almost 15 h, but ≤ 13 h in plants from non-vernalized seeds. In Athenais, whether or not the seeds had been vernalized, P C varied with mean diurnal temperature, from about 12·5 h d -1 at 10 °C to about 15 h d -1 at 20 °C. These results are discussed in relation to field predictions and the development of simple procedures for screening germplasm for sensitivity to temperature and photoperiod.
Barley plants were grown at a mean diurnal temperature of 15 °C and reciprocally transferred between different photoperiods (from 16 h d⁻¹ to 8, 10 or 13 h d⁻¹ or vice versa at 4, 8, 16 or 32 d after germination). Ten contrasting genotypes were examined, including seven spring-sown types-Mona, BGS T16-2, Athenais, Emir, Funza, USDA-016525 and S-37, and three autumn-sown types-Gerbel B, Arabi Abiad and Ager. In the latter two all treatments were repeated on plants grown from seeds which had been vernalized at 2 °C for 42 d.
The results suggest that, between the critical photoperiod (below which there is a delay in flowering) and the ceiling photoperiod (below which there is no further delay), there is a linear relation between photoperiod and the reciprocal of the time taken to flower (awn emergence). In all genotypes the ceiling photoperiod was ≲, 10 hdd⁻¹; the critical photoperiod was always > 13 hdd⁻¹ often > 14 hdd⁻¹, and sometimes > 16 hdd⁻¹.
All genotypes were initially insensitive to long days. At 15 °C this pre-inductive phase typically lasted for 8–10 d after germination in spring-sown types and in vernalized autumn-sown types, but continued for more than 32 d in non-vernalized autumn-sown types. It was followed by an inductive phase, the duration of which depended on photoperiod, being longer in shorter days. Finally, there was a photoperiod-insensitive, post-inductive phase, which probably began about 2 weeks before awn emergence.
The low-temperature seed-vernalization treatment considerably hastened awn emergence in Arabi Abiad and in Ager; in Arabi Abiad low-temperature vernalization could be partly replaced by treating young plants with short days (8 or 10 h dd⁻¹). Both low-temperature and short-day vernalization advanced flowering by advancing ear initiation (reducing the duration of the pre-inductive phase), whereas long days stimulated the rate of development following ear initiation.
Times from sowing to emergence and to the appearance of first open flowers were recorded for six diverse genotypes of faba bean (Vicia faba L.) grown in 18 h daylengths at seven different constant temperatures between 15 and 30 °C. The optimum temperatures for the mean rate of seedling emergence and the rate of progress towards flowering varied amongst genotypes within the ranges 19·9-26·5 °C and 19·9-25·4 °C, respectively. There was no significant correlation between the optimum temperatures for emergence and flowering amongst the six genotypes tested (r = 0·514, P > 0·25). For both seedling emergence and flowering, positive linear relations were found between rate of development and sub-optimal temperatures, and negative linear relations between rate of development and supra-optimal temperatures. Despite absolute differences in the rate of progress towards flowering, the response to sub-optimal temperatures did not differ significantly amongst the six genotypes (P > 0·25). This was confirmed by re-analysis of earlier data. In contrast, the response to supra-optimal temperatures differed significantly (P < 0·005) amongst the six genotypes. They could be classified into two discrete groups which accorded with differences in optimum temperatures. Genotypes BPL 1722, Zeidab Local and Giza-4 had warmer optimum temperatures and greater sensitivity to supra-optimal temperatures than Aquadulce, Maris Bead and Syrian Local Large.
Factorial combinations of two photoperiods (12 and 15 h), three day temperatures (20, 25 and 30 °C) and three night temperatures (10, 15 and 20 °C) were imposed on nodulated plants of nine chickpea genotypes (Cicer arietinum L.) grown in pots in growth cabinets. The times to first appearance of open flowers were recorded. For all genotypes, the rates of progress towards flowering (the reciprocals of the times taken to flower) were linear functions of mean temperature. There were no interactions between mean temperature and photoperiod but the longer photoperiod increased the rate of progress towards flowering. These effects were independent of both radiation integral (the product of irradiance and photoperiod) and the vegetative stature of the plant. Taken in conjunction with evidence from work on other long-day species, it is suggested that the photo-thermal response of flowering in chickpeas, over the range of environments normally experienced by the crop, may be described by the equation: 1/f = a+bi+cp in which f is the number of days from sowing to first flower, i is mean temperature and p is photoperiod. The values of the constants a, b and c vary between genotypes and provide the basis for screening genotypes for sensitivity to temperature and photoperiod.
The agricultural phenologist studies the impact of climate and soil conditions on the timing of biological events in plants of commercial and ornamental importance. The studies may include forests and pastures, as well as food crops. Phenophases observed include economic elements like harvesting and marketing of commercial plants; and in this respect his interests are broader than those of purely biological phenologists.
The fascination of the unfolding blossom or the emerging chrysalis cannot be doubted; it is the compensation of the countless volunteers who man phenological networks. In addition to fascination, however, one can ask if phenology and models of seasonality have utility. This paper, therefore, first provides some prerequisites for utility and then cites some examples.
Three genotypes of barley were subjected to 18 potentially vernalizing pre-treatments, comprising constant temperatures of 1, 5 or 9 °C in factorial combination with photoperiods of 8 or 16 h d -1 for 10, 30 or 60 d -1. These pre-treated seeds or seedlings, together with non-pre-treated seeds as controls, were then transferred to each of four growing-on regimes, namely day/night temperatures of 18/5 °C or 24/3 °C in factorial combination with photoperiods of 11 or 16 h d -1. The times from sowing to awn emergence were recorded. The warmer growing-on regime (mean 19 °C) was not supra-optimal in long days, but in short days it considerably delayed awn emergence in all three genotypes. In cv. Athenais there was no specific response to the potentially vernalizing pre-trcatments: the rate of progress towards awn emergence could be treated as a linear function of the integrated responses to temperature and photoperiod acting independently throughout development. In addition to these responses, cv. Gerbel B and the land-race Arabi Abiad also responded to low-temperature vernalization and the response became saturated during the longer-duration pre-treatments. In Arabi Abiad, the rate at which vernalization occurred, and the period required to saturate the response, were not greatly influenced by difference in pre-treatment temperature between 1 and 9 °C. In contrast, in Gerbel B the cooler the temperature of pre-treatment the greater the saturated response to vernalization, the greater the effect of each day of pre-treatment, and the shorter the period required to saturate the response. Models of the photothennal and vernalization responses were combined in a single entity which described the influence of environment on rate of development. Simple germplasm-screening techniques are proposed for genotype characterization so that the phenotypic flowering response can be estimated for any environment
Six pea varieties, early to late flowering, were grown in 16 environments made up of all combinations of four mean daily temperatures (6, 12, 18 or 24°C) and four photoperiods (8, 12, 16 or 24 h). For the earliest variety, days from sowing to first flower was inversely proportional to temperature, and independent of photoperiod. Sensitivity to photoperiod in the other five varieties was temperature-dependent. At 24°C, all were photoperiod-sensitive, but at 6°C only the latest three varieties were sensitive. Flowering was most rapid at 24°C in 24-h photoperiod. However, the lowest node of first flower occurred in 24 h photoperiod, irrespective of temperature. The duration of the period from floral initiation to first flower was independent of variety and photoperiod. Thus, any differences in flowering between varieties arose prior to floral initiation.
These differences are explained by three factors: different times to floral initiation in 24 h photoperiod, a photoperiod response in low temperature, and a photoperiod-temperature interaction. These factors are related to the flowering genes Lf, Sn and Hr and the 'units of maturity genotype'. The likely genotypes of the varieties are deduced from the reported action of these genes. Vernalization is interpreted in terms of high-temperature inhibition of flowering in short photoperiods. The effect of temperature on the relationship between node of first flower and days from sowing to floral initiation, and the influence of genotype and growing season on flowering time, are also discussed.
Two experiments involving the testing of a number of soya bean varieties under a range of different photoperiods showed that all varieties were capable of flowering under all photoperiods tested, and appeared to be facultative short-day genotypes. Differential varietal responses were not obtained for flowering time at photoperiods of less than 12 hr per day, but the tropical varieties Mamloxi and Avoyelles differed markedly from the temperate variety Bienville in the flowering pattern under longer photoperiods. Other plant characters responded similarly to flowering time. Possible relationships of such responses to latitude of introduction, field adaptation in southeastern Queensland, and screening of varietal accessions are discussed. Uniform frequency distributions of an F2 population were obtained for most characters and photoperiods, which indicated a relatively complex form of inheritance. Skewness of some distributions, particularly in the longer photoperiods, suggested that the spectrum of action of genes determining these traits varied with photoperiod. Deviations from mid-parent values indicated dominance of low number of days to flowering, short node length, and high node number. Plant height approached that of the low parent in short photoperiods and the high parent in longer photoperiods. Transgressive segregation occurred for most traits, particularly in the longer photoperiods, and evidence of substantial genetic control of differences in photoperiodic response between varieties was found.
The responses of 3 soybean cultivars to sowing date during the wet season in the Ord Imgation Area (OIA) in northern Western Australia are described. The cultivars, Buchanan, Ross and Durack, are classified as early, medium and late maturity respectively, when grown during the wet season in the OIA. The cultivars were grown 10 times between 22 December and 18 April during 2 wet seasons and we investigated the patterns of phenology, growth and seed production. Sowing date had no significant effect (P> 0.05) on the time to flowering (26-36 days) with cv. Buchanan, but the duration of flowering was curtaiied so that the period from sowing to maturity declined from 120 to 95 days as sowing was delayed from December to April. In contrast the time to flowering of cv. Durack declined in response to photoperiod from about 70 to 40 days and the time from sowing to maturity declined from about 160 to 100 days. The responses of cv. Ross were intermediate between those of Buchanan and Durack. The phenological responses to sowing date were consistent with responses to photoperiod rather than to temperature. Sowing date also affected plant morphology and yields and quality of seed. Delay in sowing after December led to declines in above-ground dry matter yields at flowering, in number of nodes on the main stem at flowering, crop height at maturity and seed yields. Mean individual seed weights increased with delay in sowing. Oil concentrations in the seed declined (from 23 to 17%) and protein concentrations increased (from 32 to 45%) as the period of pod development occurred later in the season. Phenology is a major determinant of the suitability of a cultivar for specific cropping systems. The early maturing cultivar, Buchanan, most closely meets the requirements for a system of double cropping in which the wet season soybean crop is followed by a May sown dry season crop. The late maturing cultivar, Durack, is suitable for a system involving a single wet-season crop.
The phenology of mung beans is extremely plastic; responsiveness to both photoperiod and temperature is known to modulate flowering. A previous conclusion, perpetuated uncritically now for almost forty years, has been that both (quantitative) short- and long-day flowering responses exist in the mung bean germplasm. However, our re-analysis of the original data leads us to an alternative conclusion: that genotypes of mung bean are quantitative short-day plants with different optimum mean diurnal temperatures for flowering. This alternative interpretation (which is plausible biologically and in evolutionary terms) is discussed.(Accepted April 02 1987)
Genotypes of mung bean commence flowering at very different times depending on sowing date and location, but relatively little is known about the modulation of flowering by environmental factors. Previous and frequently cited conclusions have been that: (a) genotype, photo-period and temperature all interact to determine relative earliness to flower, and that (b) the genetic control of these photothermal responses is seemingly complex. However, our reanalyses of original data in terms of rates of progress towards flowering, 1/f, rather than the traditional approach based on days from sowing to flowering, f, show that the photothermal modulation of flowering in mung bean can be described by a series of simple, linear models, and that interaction terms involving photoperiod and temperature are often insignificant. The merits and implications of this alternative analysis and interpretation of original data are discussed.
Although daylength has a major effect on flowering and several other aspects of plant development, the actual environmental time signals for the beginning and the end of day are obscure. An intensive spectroradiometric study was carried out in three contrasting environments: namely, unshaded sites, a mature oak woodland and a sugar beet crop. Spectral photon distributions were obtained describing numerous twilight phases and intervening photoperiods throughout the year. From each, absolute photon fluence rates, photon fluence rate ratios and phytochrome photoequilibria were calculated. Although substantial changes in spectral composition occurred during twilight, they were less capable of providing reliable and accurate time signals than the absolute fluence rate; this was especially apparent beneath the canopies. Thus, spectral changes are unlikely to be valuable in photoperiodic perception. The results are discussed in relation to the possible involvement of the known plant photoreceptors in photoperiodism.
A critical duration of darkness must be exceeded for the photoperiodic induction of flowering in short‐day plants. This requires detection of the light/dark transition at dusk and the coupling of this information to a time‐measuring system.
Lowering the P fr /P tot , ratio photochemically at the end of the day did not accelerate the onset of dark timing in Pharbitis nil Choisy cv. Violet. Time‐measurement was initiated when, with no change in spectral quality, the irradiance fell below a threshold value. Thus, if the light/dark transition at dusk is sensed by a reduction in P fr , this reduction can be achieved as rapidly through thermal reactions as through photochemical ones. When given at hourly intervals during a 6‐h extension of a 24‐h main light period in white light, pulses of red light were as effective as continuous red light in delaying the onset of timing; pulses every 2 or 3 h were less effective. The effectiveness of intermittent red light indicates that phytochrome is the photoreceptor and the requirement for frequent exposures suggests that P fr is lost rapidly in the dark. However, the red light pulses could not be reversed by far‐red light, which argues against this hypothesis. An alternative explanation is that the perception of light as being continuous occurs only when “new” P fr is regenerated sufficiently frequently.
The nature of the coupling of the dusk signal to the time‐measuring system is discussed and it is suggested that the effect of each red light pulse is to delay the phase of the photoperiodic rhythm by 1–3 h.
Factorial combinations of four photoperiods (10 h, 11 h 40 min, 13 h 20 min and 15 h) and three night temperatures (14, 19 and 24 °C) combined with a single day temperature (30 °C) were imposed on nodulated plants of 11 cowpea accessions [ Vigna unguiculata (L) Walp.] grown in pots in growth cabinets. The times to first appearance of flower buds, open flowers and mature pods were recorded. Linear relationships were established between the reciprocal of the times taken to flower and both mean diurnal temperature and photoperiod. When the equations describing these two responses are solved, the time to flower in any given photothermal regime is predicted by whichever solution calls for the greater delay in flowering. Thus in different circumstances flowering is controlled exclusively by either mean temperature or photoperiod. The value of the critical photoperiod is temperature-dependent and a further equation, derived from the first two, predicts this relationship. Considered together as a quantitative model these relationships suggest simple field methods for screening genotypes to determine photo-thermal response surfaces.
Factorial combinations of five photoperiods (8 h 20 min, 10 h, 11 h 40 min, 13 h 20 min and 15 h) and three night temperatures (14, 19 and 24 �C) combined with a single day temperature (30 �C) were imposed on nodulated plants of nine soya bean genotypes [ Glycine max (L.) Merrill] grown in pots in growth cabinets. The times to first appearance of open flowers were recorded. For a photoperiod-insensitive cultivar, and for the remaining eight photoperiod-sensitive genotypes in photoperiods shorter than the critical daylength, the rates of progress towards flowering (the reciprocals of the times taken to flower) were linear functions of mean diurnal temperature. For all photoperiod-sensitive genotypes, times to flowering in photoperiods longer than the critical daylength increased as inverse functions of both increasing photoperiod and decreasing temperature. A consequence of these two relations is that the critical daylength becomes longer with higher mean temperatures. In the five photoperiod-sensitive genotypes which flowered in all environments before the experiment was terminated (after 150 d) the delays in flowering due to low temperatures or long photoperiods were limited by a maximum period to flowering specific for each genotype. These results are discussed in relation to the development of a simple technique for the large-scale screening of soya bean germplasm to determine photo-thermal response surfaces for flowering.
The durations from emergence to the appearance of first flower buds and to first open flowers were recorded in three genotypes of lentil ( Lens culinaris Medic.) when plants were transferred from short days (either 8 or 10 h) to long days (16 h), or vice versa , after various times from emergence. These results were compared with those of control treatments in which plants remained in either short or long days throughout. Four developmental phases were identified: pre-emergence, pre-inductive, inductive and post-inductive. The first two phases and the last are insensitive to photoperiod, but are probably sensitive to temperature. The duration of the inductive phase, which has to be completed before flowering can occur at the end of the post-inductive phase, can be predicted by assuming that its reciprocal is a linear function of both photoperiod and temperature. It follows that the critical photoperiod decreases with increase in temperature and that the duration of the inductive phase can be calculated from a summation of the amounts by which successive daylengths exceed the critical photoperiod until a value (‘the photoperiodic sum’) characteristic of the genotype is reached. The implications of these findings for predictive field models of time to flowering in lentils are discussed.
The effects of photoperiod on plants are often extensive and profound (Fig. 3.1), so much so that we wonder why they were not appreciated until Garner and Allard’s paper published in 1920. (Earlier suggestions and observations had foreshadowed this paper.) Photoperiodism, Garner and Allard’s term, is the response of plants or animals to the relative lengths of day and/or night. Perhaps it seemed incredible to pre-1920 biologists that organisms would be capable of accurately measuring the duration of light and/or darkness, although it was well appreciated that organisms could respond to the quantity and even the quality (wavelength) of light (especially in vision, but also, since the late 1700s, in photosynthesis). In this overview, I examine several important areas of photoperiodism research: the diversity of plant manifestations caused by photoperiod, the diversity of response types (e.g., long-day, short-day), and a few current ideas about how plants detect light and darkness in photoperiodism, measure time, and alter their hormonal status as a prelude to the observed plant responses. Several of these topics have horticultural implications.