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Influence of Soil Water Supply on the Plant Water Balance of Four Tropical Grain Legumes
Abstract
The water balance of soybean (Glycine max), cowpea (Vigna unguiculata), black gram (Vigna mungo), and pigeonpea (Cajanus cajan) grown in pots was studied during a soil drying cycle. The response of the plants was analysed for three distinct stages of dehydration. In stage I, the rate of transpiration remained constant and equal to that of well watered plants even though soil water status fell by more than 50%. Stage II began when the rate of soil water supply to the plant was less than potential transpiration and stomates closed resultingjn the maintenance of plant water balance. When soil water content was expressed as a fraction of transpirable soil water, all species showed a transition from stage I to stage II at a fraction of transpirable soil water of about 0.3 to 0.2. As the soil water declined further, all species had a similar decrease in relative transpiration rate. Consequently, the responses of the four species in stages I and II were essentially identical, except that pigeonpea extracted a slightly greater amount of soil water.
Stage III occurred once stomates had reached minimum conductance and water loss was then a function of the epidermal conductance and the environment around the leaf. Substantial differences were found among the four grain legumes in epidermal conductance. Soybean had the highest conductance, followed by black gram, cowpea and pigeonpea. Substantial variation in dehydration tolerance among the four grain legumes was also found: the ranking of dehydration tolerance based on the relative water content was pigeonpea > cowpea > mungbean > soybean. Differences among the four grain legume species in the duration of stage III which finished when plants died, were consistent with differences in epidermal conductance and in dehydration tolerance of leaves.
... Moreover, water deficit is currently the primary limiting factor for soybean yield for most soybean farmers worldwide Merlos et al. 2015). In Brazil, the yield gap resulting from drought can restrict soybean yield potential in certain regions by up to 50% (Sentelhas et al. 2015;Tagliapietra et al. 2021;Winck et al. 2023 (Sinclair and Ludlow 1986;Riar et al. 2018), a decrease in net photosynthesis (Guo et al. 2018;Streck 2004;Fuganti-Pagliarini et al. 2017;Martignago et al. 2020), and reduced growth (Souza et al. 2014;Becker et al. 2021). ...
... The experimental design was completely randomized. The experiments were conducted under two soil water conditions: T1 (replacement of 100% of transpired water) and T2 (no replacement of transpired water), following the approach by Sinclair and Ludlow (1986). Further details of the experimental setup can be found in Table 1. ...
... The response of soybean plants to water deficit was assessed using the fraction of transpirable soil water (FTSW) approach proposed by Sinclair and Ludlow (1986). This approach considers two stages of water deficit. ...
The objectives of this study were (i) to identify growth and physiological changes in soybean resulting from the insertion of the TF AtAREB1, both in the original 1Ea2939 event and in an improved genotype derived from the cross between 1Ea2939 and the elite cultivar BMX Desafio RR; (ii) to determine the ecophysiological traits contributing to drought tolerance in soybean with the TF AtAREB1, compared to commercial cultivars, using the fraction of transpirable soil water (FTSW) approach; and (iii) to evaluate the field performance of AtAREB1 genotypes in comparison to their parents. Greenhouse experiments were conducted to evaluate leaf transpiration rates, leaf growth, dry matter accumulation, gas exchange, and water use efficiency (WUE) in four commercial cultivars, as well as in the AtAREB1 genotypes 1Ea2939 and BRT18-0280. Additionally, a field experiment was carried out to assess grain yield and water use efficiency in AtAREB1 genotypes. The “AtAREB1” genotypes exhibited reduced daily transpiration rates in both irrigated and dry environments compared to the commercial cultivars. The higher drought tolerance can be attributed to a lower FTSW threshold for leaf transpiration rate, a higher root/shoot ratio, and prolonged survival during drought conditions.The “BRT18-0280” genotype showed a higher yield and water use efficiency under field conditions. This study indicates that soybean with TF AtAREB1 is an alternative to increase soybean tolerance to water deficit in regions where drought is a limiting factor for high yields.
... The point at which the transpiration rate of WS plant was 10% less than WW plants the experiment was terminated and the plant samples were collected for biomass calculation. As at this point the theoretical NTR value will be 0.1 (Sinclair & Ludlow, 1986), and the plant no longer sustains the stress situation. During the soil drying process, NTR was often expressed as a function of FTSW. ...
... Second normalization aims at avoiding differences due to plant size, calculated by dividing each TR value with an average TR value of the first 3 days when there was no water limitation. Detailed description on importance and application of NTR-FTSW was previously mentioned by various authors (Sinclair & Ludlow, 1986;Devi et al., 2009). ...
... Genotypes with higher threshold values for FTSW often restrict the amount of water loss via transpiration. FTSW threshold for genotype A-1: 0.79 (R 2 = 0.99), followed by Bhima: 0.74, (R 2 = 0.98), CO-1: 0.71 (R 2 = 0.91), and GMU-2347: 0.71, (R 2 = 0.92) had high threshold values as well as TE, strengthening the theoretical fact (Sinclair & Ludlow, 1986) (Table 1 and Fig. 2). Devi & Reddy (2020) from their experiments on maize genotypes revealed that at higher VPD (vapour pressure deficit) genotypes limited their transpiration rate exhibiting high FTSW threshold values. ...
Oilseeds with high productivity and tolerance to various environmental stresses are in high demand in the food and industrial sectors. Safflower, grown under residual moisture in the semi-arid tropics, is adapted to moisture stress at certain levels. However, a substantial reduction in soil moisture has a significant impact on its productivity. Therefore, assessing genetic variation for water use efficiency traits like transpiration efficiency (TE), water uptake, and canopy temperature depression (CTD) is essential for enhancing crop adaptation to drought. The response of safflower genotypes (n = 12) to progressive soil moisture depletion was studied in terms of water uptake, TE, and CTD under a series of pot and field experiments. The normalised transpiration rate (NTR) in relation to the fraction of transpirable soil water (FTSW) varied significantly among genotypes. The genotypes A-1, Bhima, GMU-2347, and CO-1 had higher NTR-FTSW threshold values of 0.79 (R2 = 0.92), 0.74 (R2 = 0.96), 0.71 (R2 = 0.96), and 0.71 (R2 = 0.91), respectively, whereas GMU-2644 had the lowest 0.38 (R2 = 0.93). TE was high in genotype GMU-2347, indicating that it could produce maximum biomass per unit of water transpired. At both the vegetative and reproductive stages, significant positive relationships between TE, SPAD chlorophyll metre reading (SCMR) (p < 0.01) and CTD (p < 0.01) were observed under field conditions by linear regression. The genotypes with high FTSW-NTR thresholds, high SCMR, and low CTD may be useful clues in identifying a genotype’s ability to adapt to moisture stress. The findings showed that the safflower genotypes A-1, Bhima, GMU-2347, and CO-1 exhibited an early decline and regulated water uptake by conserving it for later growth stages under progressive soil water depletion
... The gradual imposition of water deficit is essential for the plant's activation of drought tolerance mechanisms, allowing better discrimination of genotypic tolerance to drought. In the work of [6], identifying the three stages of dehydration (Figure 1), the plants were grown in plastic bags, 0.13 m in diameter and 2.3 m high, covered with plastic, to avoid direct water evaporation from the soil to the atmosphere. In this case, cowpea and pigeon pea, which are water deficit tolerant species (Table 1), took 31 and 43 days, respectively, to reach the lethal ᴪ a,l as in (Figure 1), thus having a gradual imposition of the stress, as would occur with the plants in the field [6]. ...
... In the work of [6], identifying the three stages of dehydration (Figure 1), the plants were grown in plastic bags, 0.13 m in diameter and 2.3 m high, covered with plastic, to avoid direct water evaporation from the soil to the atmosphere. In this case, cowpea and pigeon pea, which are water deficit tolerant species (Table 1), took 31 and 43 days, respectively, to reach the lethal ᴪ a,l as in (Figure 1), thus having a gradual imposition of the stress, as would occur with the plants in the field [6]. For some time, a single test was sought to indicate drought tolerance to discriminate genotypes of the same species as for leaf proline content [5]. ...
... For some time, a single test was sought to indicate drought tolerance to discriminate genotypes of the same species as for leaf proline content [5]. Today, it is known that this is impossible due to the diversity of physiological events in different plant organs, which confer the adaptation to the lack of water, which is, thus, considered a multigenic characteristic [2,5,6]. Among the many different responses of plants to water deficiency (Table 2), there are some harmful to plants (such as a metabolic imbalance in the plant with increased production of reactive oxygen species [ROS], which can lead to plant death. ...
... Before starting the dry-down cycle, 23-33 days after planting, all pots were in a wellwatered condition for normal crop growth [30,[39][40][41]. Similar plants with 9-12 leaves were selected [41], watered to saturation, attaining field capacity after one day. ...
... According to [40], response of the plants to soil drying occurs at three stages. In stage I, TR remains constant and transpiration of WS plants does not differ from that of WW plants (TR ≈ 1.0). ...
... Stage III starts at very low TR (TR < 0.1), when stomata have a minimum conductance. We conducted our experiment until the WS plants reached a NTR < 0.1, i.e., 10% of the reference transpiration [40,41,45]. The biomass accumulated during this dry down period can be considered as a function of water transpired [24]. ...
Potato (Solanum tuberosum L.) is the third most consumed food crop after rice and wheat in the world. It is a short-duration crop, suitable for growing in a wide range of environments, but abiotic factors can limit potato production, and drought is the main one. Therefore, managing drought stress is of utmost importance under climate change conditions. Potato as a drought-sensitive crop needs choice of suitable genotypes for dry environments. In this study, transpiration efficiency (TE), soil water conservation and drought tolerance were analysed for potato genotypes from different origins. Three glasshouse experiments under different Vapor Pressure Deficit (VPD) conditions with water-stressed (WS) and well-watered (WW) plants resulted in significantly different total amounts of transpiration among the genotypes and water supply levels. Transpiration in WS plants was the same as with WW plants up to a specific threshold “Fraction of Transpirable Soil Water” (FTSW) and then sharply decreased in response to soil drying. Genotypes showed a substantial variation in FTSW thresholds (0.19 to 0.36 FTSW) under low VPD condition, which narrowed down (0.19 to 0.29) when air humidity was lower. Furthermore, we observed hardly any relationships between TE and FTSW threshold (r = 0.125) or TE and water saving (r = 0.031). Our results provide insights into genotypic interactions with VPD on FTSW threshold and TE under dry-down conditions in potato.
... Photosynthesis (Pn) and stomatal conductance (G s ) were recorded each day, as the soil dried, to reflect the 'drought kinetic' of the Moricandia species ( Figure 6). The fraction of transpirable soil water (FTSW) technique serves as a relative scale based upon the start/end point G s and the pot weight as the soil dries [29], allowing for a comparison of plants of differing sizes, species and pot sizes (e.g., [30,31]). It is noteworthy that the G s values of Msu (the C2 species with strong C2-physiology on the basis of the CO 2 compensation point and estimated photorespiration; Figure 2) were broadly lower than those of C2 Mav and C3 Mmo ( Figure 6A). ...
... The fraction of transpirable soil water (FTSW) method [29] was used to gauge the kinetics of the soil drying of the Moricandia species with different photosynthetic physiologies. Thirty-five plants of equivalent sizes were selected for each species. ...
... The opening of the bags for approximately 20 min each day enabled the exchange of gases between the soil and the atmosphere and prevented the soil from becoming anoxic. When the G s declined to 10% of the starting G s value in the water deficit treatment or the pot weight remained constant for three days, it was considered that all water within the soil available for transpiration had been exhausted (i.e., 0% FTSW), and the FTSW was calculated as [29]: ...
Citation: Pinheiro, C.; Emiliani, G.; Marino, G.; Fortunato, A.S.; Haworth, M.; De Carlo, A.; Chaves, M.M.; Loreto, F.; Centritto, M. Metabolic Background, Not Photosynthetic Physiology, Determines Drought and Drought Recovery Responses in C3 and C2 Moricandias. Int. J. Mol. Sci. 2023, 24, 4094. https://doi. Abstract: Distinct photosynthetic physiologies are found within the Moricandia genus, both C3-type and C2-type representatives being known. As C2-physiology is an adaptation to drier environments, a study of physiology, biochemistry and transcriptomics was conducted to investigate whether plants with C2-physiology are more tolerant of low water availability and recover better from drought. Our data on Moricandia moricandioides (Mmo, C3), M. arvensis (Mav, C2) and M. suffruticosa (Msu, C2) show that C3 and C2-type Moricandias are metabolically distinct under all conditions tested (well-watered, severe drought, early drought recovery). Photosynthetic activity was found to be largely dependent upon the stomatal opening. The C2-type M. arvensis was able to secure 25-50% of photosynthesis under severe drought as compared to the C3-type M. moricandioides. Nevertheless, the C2-physiology does not seem to play a central role in M. arvensis drought responses and drought recovery. Instead, our biochemical data indicated metabolic differences in carbon and redox-related metabolism under the examined conditions. The cell wall dynamics and glucosinolate metabolism regulations were found to be major discriminators between M. arvensis and M. moricandioides at the transcription level.
... The fraction of transpirable soil water (FTSW) methodology was the concept that most closely indicated the amount of water extracted by plants by transpiration (Sinclair & Ludlow, 1986;Lago et al., 2011Lago et al., , 2012Souza et al., 2014;Kelling et al., 2015). By using FTSW, it is possible to control the availability of water to plants and the stage of the plant cycle at which one wishes to impose the water deficit to examine the plants' response. ...
... By using FTSW, it is possible to control the availability of water to plants and the stage of the plant cycle at which one wishes to impose the water deficit to examine the plants' response. Studies using this methodology have also been conducted in soybean, but in trials outside Brazil and considering genotypes, growth habits, and relative maturity groups different from those of cultivars currently sown in Brazil (Sinclair & Ludlow, 1986;Bagherzadi et al., 2017). ...
... Water deficit in T1 began on 01/03/2019, when the plants were between stages V7 and V9; in T2, on 02/02/2019, when they were between V6 and V8; and in T3 on 11/19/2019, between V6 and V7, according to the scale described by Fehr and Cavines (1977). The plants were exposed to water deficit following the methodology proposed by Sinclair and Ludlow (1986), whereby the FTSW considers that the soil water content absorbed by the plant and released by transpiration varies between maximum transpiration, under field capacity, to 10% of maximum transpiration. ...
The influence of water deficit on plant physiological and biochemical responses as measured by the fraction of transpirable soil water (FTSW) has not been investigated in cultivars developed by the world's largest soybean producer. This information can help obtain plants with improved tolerance to the abiotic stress that most affects soybean production in Brazil, enabling adaptation to edaphoclimatic conditions to enhance the crop's yield potential. We aim to determine the FTSW threshold for transpiration and evaluate changes in the growth, physiological activities, and biochemical and antioxidant responses of soybean cultivars. Three trials were sown on 11/19/2018 (T1), 12/28/2018 (T2), and 9/9/2019 (T3), representing almost the entire soybean sowing window in Brazil. The estimated FTSW threshold values were 0.33, 0.29, and 0.31 in T1; 0.35, 0.41, and 0.43 in T2; and 0.31, 0.49, and 0.45 in T3 for cultivars BMX GARRA IPRO, DM 66I68 RSF IPRO, and NA 5909 RG, respectively. In the three trials, NA 5909 RG showed the greatest height. The POD enzyme was activated in non-irrigated plants in T2 only in cvs. DM 66I68 RSF IPRO and NA 5909 RG. We conclude that cvs. DM 66I68 RSF IPRO and NA 5909 RG showed a more efficient stomatal control, conserving soil water for a longer time, which indicates greater tolerance to water deficit.
... The point of reduction in transpiration under WD was calculated by the relationship between the relative transpiration rate (RT) and the fraction of transpirable substrate water (FTSW) (Sinclair and Ludlow 1986). The transpiration rate corresponds to the daily amount of transpired water under WD, divided by the average daily transpiration of the WW plants for each species. ...
... The fraction of transpirable substrate water corresponds to the fraction of water inside the container that plants can use to transpire. The RT of each plant was divided by the respective mean RT of plants under WW conditions for each species during the period when the soil was still well-watered to normalize the initial values (Sinclair and Ludlow 1986). Then, RT was adjusted to a logistic equation as in Eq. 2: ...
To compare water stress tolerance traits between different fruit tree species under the same experimental conditions can provide valuable information for understanding the mechanisms underlying water stress tolerance in a broader sense. This work aimed to determine and compare the water stress tolerance of six fruit tree species typically cultivated in Mediterranean regions, i.e., pomegranate, fig, mandarin, avocado, and two Prunus species ('R40' and 'R20') and evaluate its association with water use and growth under water deficit. Iso-anisohydric behavior (low to high water stress tolerance) was assessed through a multi-trait approach and associated with growth and water use under well-watered and water deficit conditions. Avocado and mandarin were classified as species with stricter stomatal control over water potential, while pomegranate, fig, and Prunus spp. showed a lesser stomatal control. This classification was supported by the multi-traits analysis, which showed that avocado and mandarin, in contrast to the rest of the species, were characterized by more sensitive gas-exchange thresholds. A more isohydric behavior was associated with lower soil water use capacity, but higher root hydraulic conductivity, and a lower growth capacity. Some traits, such as the fraction of transpirable soil water thresholds, root hydraulic conductivity, and residual soil water content, provide valuable information to discriminate between species or genotypes that are better adapted to water deficit conditions. These traits explain the position of the species in the iso-anisohydric spectrum and allow us to understand and develop better strategies for water management in agricultural systems.
... The soil moisture content was monitored daily (at 6 am and 6 pm) using a TDR device (Time Domain Reflectometry), with water replacement of the control plants carried out up to field capacity (FC), based on TDR readings. The Fraction of Transpirable Soil Water (FTSW) was calculated by the methodology according to Sinclair and Ludlow (1986) [18]: FTSW = ydayÀ yFinal yinitialÀ yFinal . Leaf gas exchange analysis was carried out in mature leaves -third leaf, between 9:00-10:00am, throughout the experiment using a portable photosynthesis meter ADC BioScientific (model LCpro-SD, Ltd., UK). ...
... The soil moisture content was monitored daily (at 6 am and 6 pm) using a TDR device (Time Domain Reflectometry), with water replacement of the control plants carried out up to field capacity (FC), based on TDR readings. The Fraction of Transpirable Soil Water (FTSW) was calculated by the methodology according to Sinclair and Ludlow (1986) [18]: FTSW = ydayÀ yFinal yinitialÀ yFinal . Leaf gas exchange analysis was carried out in mature leaves -third leaf, between 9:00-10:00am, throughout the experiment using a portable photosynthesis meter ADC BioScientific (model LCpro-SD, Ltd., UK). ...
DNA methylation plays a key role in the development and plant responses to biotic and abiotic stresses. This work aimed to evaluate the DNA methylation in contrasting cassava genotypes for water deficit tolerance. The varieties BRS Formosa (bitter) and BRS Dourada (sweet) were grown under greenhouse conditions for 50 days, and afterwards, irrigation was suspended. The stressed (water deficit) and non-stressed plants (negative control) consisted the treatments with five plants per variety. The DNA samples of each variety and treatment provided 12 MethylRAD-Seq libraries (two cassava varieties, two treatments, and three replicates). The sequenced data revealed methylated sites covering 18 to 21% of the Manihot esculenta Crantz genome, depending on the variety and the treatment. The CCGG methylated sites mapped mostly in intergenic regions, exons, and introns, while the CCNGG sites mapped mostly intergenic, upstream, introns, and exons regions. In both cases, methylated sites in UTRs were less detected. The differentially methylated sites analysis indicated distinct methylation profiles since only 12% of the sites (CCGG and CCNGG) were methylated in both varieties. Enriched gene ontology terms highlighted the immediate response of the bitter variety to stress, while the sweet variety appears to suffer more potential stress-damages. The predicted protein-protein interaction networks reinforced such profiles. Additionally, the genomes of the BRS varieties uncovered SNPs/INDELs events covering genes stood out by the interactomes. Our data can be useful in deciphering the roles of DNA methylation in cassava drought-tolerance responses and adaptation to abiotic stresses.
... The fraction of transpirable soil water (FTSW) was calculated by equation proposed by Sinclair and Ludlow (1986) as follows: ...
... where, DTR a is the mean of DTR of the five pots under WW conditions to each plant combination. To normalize the TR (NTR) and centred around 1.0, since plants under water deficit may vary the size, the DTR of each plant was divided by the mean DTR of four days while the plants were under WW condition (Sinclair and Ludlow, 1986). The fraction of transpirable soil water threshold (FTSW threshold ) was calculated at the point when the NTR began to decline in an 80%. ...
Sweet cherry is mainly cultivated in arid and semi-arid areas. In the last decade, these areas have experienced a dramatic reduction in rainfall, which has resulted in water shortage for sweet cherry. The use of specific root-stock and scion combinations could help improve the tolerance of plants to water shortage events. This study reports on the influence of rootstocks on whole-plant performance under water deficit as detected by hydraulic sensitivity, root hydraulic conductivity (L p), water use efficiency and sugar content. Four Prunus rootstocks/scion combinations-'Bing/Colt', 'Lapins/Colt', 'Bing/Mx60', 'Lapins/Mx60', and two self-rooted rootstocks Colt and Maxma 60-were acclimated for 30 days and then exposed to well-watered (WW) and water deficit (WD) conditions for 36 days. Whole-plant transpiration and growth were both influenced by WD, and two groups were identified based on responses: 'Bing/Colt', 'Bing/Mx60' and 'Mx60' had an early reduction (conservative strategy), whereas 'Lapins/Mx60', 'Lapins/Colt' and 'Colt' had late reduction (productive strategy) in transpi-ration as WD increased. Among the combinations, 'Lapins/Colt' and 'Colt' showed a remarkable growth response to the WD being less affected in shoot and root biomass. The 'Colt' rootstock maintained a higher Ψ gs50 (near-isohydric behavior) than combinations using the 'Mx60' rootstock (near anisohydric behavior). The relationship between L p and the variation of Ψ pre-dawn-Ψ midday showed differences among rootstock/scion combinations, and under WD condition the reduction in L p induced by WD affected the whole-plant WUE of combinations differently. Sucrose and sorbitol content in leaves and roots of WD-tolerant combinations such as 'Colt' and 'Lapins/ Colt', showed a remarkable increase under WD condition. Our finding highlights the importance of the specific interaction between rootstock and scion, suggesting that combinations characterized by a higher water uptake capacity under conditions of lower water availability would be sustainable under minimal to moderate water deficit.
... Further details of the climate data can be found in Table 1. The ratio between the Available Soil Water at a given time (ASW) and the Total Transpirable Soil Water (TTSW) of a certain crop in a given soil is called the Fraction of Transpirable Soil Water (FTSW) [48]. The ability of the crop to absorb moisture from the soil is usually less than the theoretical volume of soil water calculated by the field capacity minus the permanent wilting point. ...
... Similar to Colinas do Douro, the difference between the soil water content at field capacity and the minimum soil water content was used to determine the TTSW for each access tube, and the amount of ASW was calculated as the difference between the soil water content on the day of measurements and the minimum soil water content. The ratio of the ASW to the TTSW was used to calculate the FTSW [48]. Figure 5 show the FTSW calculated from the soil water content data for Quinta de Pancas. ...
As agriculture has an increasing impact on the environment, new techniques can help meet future food needs while maintaining or reducing the environmental footprint. Those techniques must incorporate a range of sensing, communication, and data analysis technologies to make informed management decisions, such as those related to the use of water, fertilizer, pesticides, seeds, fuel, labor, etc., to help increase crop production and reduce water and nutrient losses, as well as negative environmental impacts. In this study, a Bidirectional Long Short-Term Memory (BiLSTM) model was trained on real data from Internet of Things sensors in a vineyard located in the Douro wine-growing region, from 2018–2021, to evaluate the ability of this model to predict the Fraction of Transpirable Soil Water (FTSW). The model uses historical data, including reference evapotranspiration, relative humidity, vapor pressure deficit, and rainfall, and outputs the FTSW for periods of one, three, five, and seven days. The model achieved an RMSE between 8.3% and 16.6% and an R2-score between 0.75 and 0.93. The model was validated on an independent dataset collected in 2002–2004 from a different vineyard located in the Lisbon wine-growing region, Portugal, and achieved an R2-score of 87% and an RMSE of 10.36%. Finally, the performance of the FTSW in the vineyard prediction model was compared with that of the Random Forest model, support vector regression, and linear regression. The results showed that BiLSTM performed better than the RF model on the unseen data, and the BiLSTM model can be considered a suitable model for the accurate prediction of the FTSW.
... Soil water content (θ) is important for plant growth [1][2][3]. Plant growth will be inhibited if soil water is deficient [4,5]. There is a threshold θ value (θTHR) for plant growth and physiological processes [6][7][8]. ...
... The threshold FPAW (FPAWTHR) and threshold FTSW (FTSWTHR) are defined as the values of FPAW and FTSW at θ equal to θTHR. θPWP is estimated as θ, corresponding to 15,000 cm soil water suction [14,15] or to θ at the plant transpiration rate in drying soil less than 10% of that in fully watered soil [4,7,12]. It is time consuming to measure θPWP. ...
It is important to obtain the soil water content threshold (θTHR) for agricultural water management. However, the measurement of θTHR is time consuming and needs specialized and expensive equipment. The accuracy of the empirical estimates is often low. Therefore, the development of a simple, rapid, and accurate prediction method for θTHR is the focus of the present study. The value of θTHRis regarded as the soil water content at the capillary break capacity (θCB). A formula based on field capacity (θFC) and soil bulk density (Db) is proposed to calculate θCB, expressed as . Six soils from six published studies on the response of tree physiological processes to water deficit were used to calculate θCB using this formula. The calculated θCB values were compared with the measured θTHR. The results showed that the calculated θCB values were nearly equal to the measured θTHR. A highly significant (adj R2 = 0.9826, p < 0.001) linear relationship with a slope of 0.9506 and a y intercept of 0.0072 was found between the calculated θCB and measured θTHR. The formula proposed in this study provides a novel approach for estimating the θTHR of trees in the semi-arid regions on the Loess Plateau.
... Rice yield was adversely affected by drought and salinity. Many studies have shown that drought and salinity stimulated the transcription of antioxidant genes in plants [14,20,21]. However, the study on the local cultivar of Indonesian rice has not been reported. ...
... Drought stress was imposed by initiating a soil dry-down protocol starting 12 d after sowing. The dry-down process continued until the pot reached the target fraction of transpirable soil water (FTSW) [21]. The weight of each pot was determined every day during the dry-down process to estimate the transpiration of soil water. ...
The development of self-oxidative defense is a crucial mechanism of crops to survive in an unfavorable
condition such as drought and salinity. The possible involvement of the antioxidant gene(s) in such defense under drought and salinity stresses was studied in leaves of rice (Oryza sativa L.) Cv Cempo Ireng seedling. Fifteen days old seedlings were subjected to 0.2 (extreme), 0.5 (mild) and 1.0 (control) FTSW (fraction of transpirable soil water as representative to drought stress) levels, and 0 mM (control) 125 mM (mild) and 250 mM (extreme) NaCl as representative to salinity stress levels for 6 d. The transcription levels of cCuZnSod1, cCuZnSod2, MnSod1, cApx1, cApx2, chl-tApx, Cat1, Cat2, Cat3, Gr1, Gr2 and Gr3 were analyzed using semi-quantitative RT-PCR technique. The antioxidant genes in seedling treated to drought showed a difference of transcription levels to seedling treated to salinity. The number
of antioxidant genes increasing in transcription was lower in rice seedling under drought (cCuZnSod1, cCuZnSod2, cApx2, cApx3, Cat1, Cat2 , Gr2 and Gr3) as compared to that in seedling under salinity (cCuZnSod1, cCuZnSod2, MnSod1, cApx2, cApx3, Cat2, Cat3, Gr1, Gr2 and Gr3 ). The present concluded that dismutation of superdioxide radical and biosynthesis of reduced ascorbic acid in gluthationine-ascorbate cycle within cells were less in seedling under drought stress so that the oxidative damage of seedling under drought was higher than that under salinity
... The fraction of transpirable soil water (FTSW) was calculated according to Sinclair and Ludlow [77] as follows: ...
Disease severity and drought due to climate change present significant challenges to orchard productivity. This study examines the effects of spring inoculation with Pseudomonas syringae pv. syringae (Pss) on sweet cherry plants, cvs. Bing and Santina with varying defense responses, assessing plant growth, physiological variables (water potential, gas exchange, and plant hydraulic conductance), and the levels of abscisic acid (ABA) and salicylic acid (SA) under two summer irrigation levels. Pss inoculation elicited a more pronounced response in ‘Santina’ compared to ‘Bing’ at 14 days post-inoculation (dpi), and those plants inoculated with Pss exhibited a slower leaf growth and reduced transpiration compared to control plants during 60 dpi. During differential irrigations, leaf area was reduced 14% and 44% in Pss inoculated plants of ‘Bing’ and ‘Santina’ respectively, under well-watered (WW) conditions, without changes in plant water status or gas exchange. Conversely, water-deficit (WD) conditions led to gas exchange limitations and a 43% decrease in plant biomass compared to that under WW conditions, with no differences between inoculation treatments. ABA levels were lower under WW than under WD at 90 dpi, while SA levels were significantly higher in Pss-inoculated plants under WW conditions. These findings underscore the influence on plant growth during summer in sweet cherry cultivars that showed a differential response to Pss inoculations and how the relationship between ABA and SA changes in plant drought level responses.
... Given that Ca 2+ plays a pivotal role in determining a plant's salt sensitivity and the associated ratio reflects the plant's ability to survive osmotic stress [33], these findings highlight the robustness of CE in adverse conditions. Relative water content serves as a valuable indicator of a plant's water status, offering insights into leaf survival and metabolic activity, making it a key parameter for comparing plants' sensitivity and tolerance to salinity stress [34]. In this study, it was observed that MM and SP exhibited increased RWC only under low salinity levels, suggesting the activation of specific pathways geared towards enhancing salinity stress tolerance ( Figure 3). ...
Salinity stress impairs growth and physiological performance in tomato, which is one of the most economically important vegetables and is widely cultivated in arid and semi-arid areas of the world. Plant landraces, which are heterogeneous, local adaptations of domesticated species, offer a unique opportunity to valorize available germplasm, underpinning the productivity, resilience, and adaptive capacity of staple crops in vulnerable environments. Here, we investigated the response of fully mature tomato plants from a commercial variety, an ancestral wild relative, and a landrace under short-term salinity exposure, as well as their ability to recover upon cessation of stress. The heterogeneous panel evaluated in this study revealed different adaptative strategies to cope the stress. Our data highlighted the ability of the tomato clade to handle low and intermediate salinity stress for short-term exposure time, as well as its capacity to recover after the cessation of stress, although inter- and intraspecific variations in morphological and physiological responses to salinity were observed. Overall, the landrace and the wild type performed similarly to control conditions under low salinity, demonstrating an improved ability to maintain ionic balance. In contrast, the commercial genotype showed susceptibility and severe symptoms even under low salinity, with pronounced reductions in K+/Na+ ratio, PSII photochemical efficiency, and photosynthetic pigments. This research confirmed that improved salt tolerant genotypes can lead to substantial, positive impacts on horticultural production. While the salt tolerance mechanism of domesticated tomato was efficient under mild stress conditions, it failed at higher salinity levels.
... Transgenic tobacco lines overexpressing SbbZIP17 genes showed enhanced hydration status, antioxidant activities, reduced chlorophyll loss, and membrane damage under heat stress conditions (Fig. 5) The RWC is regarded as an index of dehydration tolerance which points out the metabolic activities and measured the status of water in plant cells (Sinclair and Ludlow 1986). Abiotic stresses such as heat or cold can negatively affect Chl biosynthesis and lead to its degradation, therefore Chl content is considered as a parameter of thermo-tolerance (Rossi et al. 2017). ...
Basic leucine zipper (bZIP) TF family is key regulator of diverse biological functions, including heat stress tolerance. However, its role in response to heat stress is unexplored in Sorghum bicolor, an abiotic stress-tolerant cereal plant. Bio-prospecting of genes for abiotic stress tolerance from elite natural stress-tolerant species is a promising approach for development of abiotic stress-tolerant crops. Therefore, qRT-PCR analysed for heat stress induced bZIP17 gene from S. bicolor, showed 14.7 and 17.3-fold expression at 4 h and 6 h of heat stress respectively at one-month old seedling stage. Further its cDNA sequence was cloned (named as SbbZIP17) for further functional validation in model plant system. In silico analysis showed SbbZIP17 encodes for bZIP polypeptide, an endoplasmic reticulum (ER) type II membrane-tethered transcription factor (type II MMTF), highly conserved, having a single ligand-binding site, interacting with heat stress-responsive proteins (HSP70, NF-Ys), expressed in different tissues and organs. Over-expression of SbbZIP17 in independent events of transgenic tobacco (Nicotiana tabacum) lines (T1) is responsible for activation of genes involved in unfolded protein response (UPR) pathway under heat stress. Transgenic tobacco lines showed enhancement in hydration status, antioxidant activity, reduction in chlorophyll loss, and membrane damage. Our analysis demonstrated that SbbZIP17 plays an important role in regulating heat stress tolerance in plants.
... The model is based on the model of [16] with some extensions introduced by [20]. The soil water is represented by a reservoir characterized by its total transpirable soil water (T T SW ), representing the difference between maximum and minimum (extractable) water content, the transpirable soil water (T SW ) and the fraction of transpirable soil water (F T SW = T SW/T T SW ) remaining at any time during the season [15], [21]. The reservoir incorporates two subreservoirs, one for cover crops and one for bare soil, while sub-reservoirs are used to calculate individual water balance routines for cover crops and bare soil in order to separate the actual evapotranspiration fluxes between cover crops, bare soil, and grapevines [20]. ...
This paper presents and evaluates a plot-specific grapevine drought stress simulation model fed with weather and plant physiological data and forecasts, enabling accurate
drought stress prediction in viticulture that is directly applicable to evapotranspiration or irrigation management.
... The point of reduction in transpiration under WD was calculated by the relationship between the relative transpiration rate (RT) and the fraction of transpirable substrate water (FTSW) (Sinclair and Ludlow, 1986). The transpiration rate corresponds to the daily amount of transpired water under WD, divided by the average daily transpiration of the WW plants for each species. ...
Compare water stress tolerance traits between different fruit tree species under the same experimental conditions can provide valuable information for understanding the mechanisms underlying water stress tolerance. This work aimed to determine and compare the water stress tolerance of six fruit tree species typically cultivated in Mediterranean regions and evaluate its association with water use and growth under water deficit. Six fruit tree species were used in this study: pomegranate, fig, mandarin, avocado, and two Prunus species ('R40' and 'R20'). Iso-anisohydric behavior (low to high water stress tolerance) was assessed through a multi-trait approach and associated with growth and water use under well-watered and water deficit conditions. Avocado and mandarin were classified as species with more strict stomatal control over water potential, while pomegranate, fig, and Prunus spp. showed less stomatal control. This classification was supported by the multi-traits analysis, which showed that avocado and mandarin, in contrast to the rest of the species, were characterized by higher gas-exchange thresholds (more sensitive). A more isohydric behavior was associated with lower water, but higher root hydraulic conductivity, and a lower growth capacity. Some traits, such as the FTSW threshold to the drop of relative transpiration, root hydraulic conductivity, and residual soil water content, provide valuable information to discriminate between species or genotypes that are better adapted to water deficits. These traits explain the position of the species in the iso-anisohydric spectrum and allow us to understand and develop better strategies for water management in agricultural systems.
... The normalization of the transpiration (TRS) was achieved by dividing the transpiration of each plant in the WD regime (WD transpiration ; mL) by the mean transpiration of the WW plants (WW transpiration.average ; mL). For comparing the transpiration between plants, a second normalization was done so that the normalized transpiration rate (NTR) of each plant was defined as 1.0 when the soil water content in each pot was at field capacity (Sinclair and Ludlow 1986). The available soil water or the fraction of transpirable soil water (FTSW), for each pot, was calculated by dividing the pot weight (g) minus the final pot weight by the transpirable soil water of that pot, using the following formula: ...
Drought stress is a significant constraint that affects the yield of almost all major crops. Its impact is expected to worsen due to global climate change and human population expansion. Potato (Solanum tuberosum L.) is the third most important food crop worldwide, but it is highly susceptible to drought stress. In order to understand the effects of drought stress on yield and identify traits for selecting drought-tolerant potato genotypes, we evaluated the response of a range of agronomic and physiological traits in 15 potato genotypes under well-watered (WW) and water deficit (WD) conditions. The harvest index (HI) was found to have a high plot-based heritability (0.98), indicating that it can be used for the indirect selection of drought-tolerant genotypes. In contrast, SPAD was sensitive to detecting early drought stress in potatoes. Drought-tolerant genotypes, including CIP392797.22 (UNICA), CIP397077.16, CIP398190.89, CIP398208.219, and CIP398208.620, were able to allocate limited water towards tuber production rather than biomass. These genotypes showed high tuber production under WW conditions and increased photosynthetic activity and water use efficiency under WD conditions.
... Measurements were taken every 10 cm. The total water stock at 1.60 m depth was used to compute the fraction of total soil transpirable water (FTSW) [23], as per equation (1): ...
Cereal-legume intercropping has been traditionally practiced across West Africa by farmers and provides resilience of agriculture to climate variability. Intensification of these extensive intercropping systems in order to meet future food demand is critical. This study aims at evaluating the agronomic performance of the intensification of millet-cowpea intercropping with low cowpea density, and its variation with climate variability, using an on-station experiment in Bambey, Senegal. Two trials (irrigated vs rainfed) were set up to compare millet sole- and inter-cropping with a grain and a fodder variety of cowpea, in 2018 and 2019. Two levels of fertilization were tested: 0 kg(N) ha−1 and 69 kg(N) ha−1. The two cropping years were contrasting and water stress around flowering and/or during grain filling (indicated by the Fraction of Transpirable Soil Water) was higher in 2019 than in 2018 in the rainfed experiment. In both experiment and for all treatments, land equivalent ratio (LER) in the intercropping was 1.6 and 1.4 for grain and biomass respectively. Millet aboveground biomass was significantly higher in intercropping than in sole cropping in the irrigated experiment but not in the rainfed experiment. In the rainfed experiment, the interaction between cropping system and year was significant, so that millet aboveground biomass was greater in intercropping than in sole cropping in 2018 (year of lower water stress) but not in 2019 (year of higher water stress). The effect of fertilization on millet aboveground biomass did not significantly interact with cropping system (sole vs intercrop). For grain yield, fertilization interacted significantly with the cropping system in the irrigated trial: the benefits of intercropping on millet grain yield were greater with 69 kg(N) ha−1 than with 0 kg(N) ha−1. This significant interaction could not be observed in the rainfed trial, potentially due to water stress. These results show that the level of water stress (related here to the year and to the rainfed or irrigated experiment) and that of fertilization modulate the performance of millet-cowpea intercropping in the semi-arid context of Senegal. Overall, fertilization had a stronger effect on millet grain yield than intercropping. The two strategies (intercropping and mineral fertilization) can be complementary to achieve sustainable intensification of cropping system in semi-arid areas of West Africa.
... Kays and Nottingham (2008) reported that the optimum air temperature for most JA genotypes ranges between 6 -26 o C in temperate zones. Leaf relative water content is an important indicator of plant water status and metabolic activity (Sinclair and Ludlow, 1986). Our results revealed that the value of RWC for W1 was significantly higher than W2, and W2 was significantly higher than W3 for all plant ages (Table 2), indicating that the control of water supply for all water regimes was reasonably good, and different levels of plant water stress were clearly separated by water treatment. ...
Genetic diversity plays a critical role in crop improvement, but information on genetic diversity for chlorophyll fluorescence is rare regarding the Jerusalem artichoke (JA). This study aimed to investigate genetic variations for chlorophyll fluorescence in JA accessions and to identify superior genotypes under different water gradient conditions. A field experiment was conducted in a strip plot design with four replications. A horizontal factor was three different water regimes (W1= 100% of the crop water requirement, W2 = 50%, and W3=25% of the crop water requirement) and a vertical factor consisted of forty JA genotypes. Chlorophyll fluorescence and relative water content were recorded at 40, 60, and 70 days after transplanting (DAT). Results indicated that there were significant genetic variations in chlorophyll fluorescence and there was no significant interaction between genotypes and water regimes for this trait. The genotypes CN52867, JA70, HEL257, JA125, and JA92 showed significantly higher F'v/F'm than the other genotypes at all plant ages, whereas the CN52867 genotype showed the highest Fv/Fm at all plant ages. These genotypes would be profitable genetic resources for improving the efficiency of the photosystem of JA in the future.
... Different biochemical assays were performed after 6, 9, and 12-day intervals and statical analysis was done on 12 th day data. The pot weight was measured at 0, 3, 6, 9 and 12 day intervals once a day to calculate fraction transpirable soil water (FTSW) as recommended by Sinclair and Ludlow (1986). ...
Citrus plants face various abiotic stresses like drought during their life span which significantly affect their active growth and development. Tetraploid (4×) plants are more adaptable to environmental constraints than diploid (2×) plants by inducing critical physiological and biochemical processes. In this study, tetraploid and their corresponding diploid sour orange rootstocks were subjected to drought stress for 12 days. Results revealed that drought stress significantly affected plant physiology by reducing photosynthesis rate, stomatal conductance, transpiration rate, and leaf colour, which was prominent in diploid plants compared to tetra-ploid plants. In diploid plants, phenotypic differences (i.e. wilting and rolling of leaves) were also significant. Diploids with more accumulation of malondialdehyde and hydrogen peroxide in their leaves and roots exhibited more oxidative damage. It was observed that tetraploid plants had higher activities of peroxidase and catalase enzymes, while lower superoxide dismutase was recorded in the leaves and roots of plants. Higher glycine betaine, proline, total soluble protein, total phenolic content, and antioxidant activities were also observed in the leaves and roots of tetraploids. Overall, results suggest that tetraploids in citrus can have better defence mechanisms that help them to sustain under water deficit scenarios.
... The relative water content (RWC) is a measure of the plant water status, giving an overview of the metabolic activity in plant tissues. It is used mainly as an index to identify the plant's adaptability to support dehydration tolerance [41]. However, the MSI (%) showed a high sensitivity while decreasing depending on the soil's ionic charge [34]. ...
In the context of intensive and sustainable agriculture, limiting soil degradation and the loss of organic matter has become an obligation to maintain food security. The use of organo-mineral fertilizer (OMF) products is an innovative technology that may solve the different challenges raised. This study aimed to evaluate the effect of various organo-mineral fertilizer (OMF) formulations on Zea mays agro-physiological traits, phosphorus (P)-related parameters, and water conservation during a 90-day pot experiment. The OMF formulations consisted of blending several doses of a stable OMWS compost (10 t /ha(OMF1), 50 t/ha (OMF2), or 100 t/ha (OMF3)) with different sources of mineral P, namely diammonium phosphate (DAP), rock phosphate (RP), or phosphate washing sludge (PWS), compared with separate applications. The results indicated that the effect of an OMF on the soil and plants was strongly dependent on the source of P used and the dose of OMWS compost. The best agronomic performance was attributed to OMF1-based DAP, which resulted in a significant improvement in the shoot and root biomass dry weight by more than 260% and 40%, respectively. However, using an OMF2 formulation was more optimal when using RP and PWS as mineral P sources. Independently of the type of P fertilizer, the addition of stable OM systematically improved multiple soil properties, including water availability, and the nutrient concentrations, such as the available P, exchangeable potassium, and magnesium. Furthermore, the plant's respiration , photosynthetic activity, and nutrient assimilations were positively affected by the OMF formulations. Overall, our results demonstrate that organo-mineral fertilization is a promising solution for increasing the efficiency of low-P and high-P mineral fertilizers in alkaline soils through direct and indirect mechanisms involving improved soil properties and higher P solubilization.
... Water stress in the field was monitored by measuring the volumetric soil moisture (Diviner 2000, Sentek Pty Ltd) once a week during the irrigated period and twice a week during the stress period to assess the fraction of transpirable soil water (FTSW) (Debieu et al., 2018;Sinclair & Ludlow, 1986). ...
Sorghum is a staple food for many in the Sahel. However, it often faces early-stage water deficit resulting in production decrease. Research is focusing on developing early drought tolerant varieties. This study assessed the effects of early drought stress on 10 elite varieties of West African sorghum collection tested over 2 years (2018-2019) in Bambey (Senegal). Water stress was applied by withholding irrigation 25 days after sowing for one month, followed by optimal irrigation until maturity. Soil moisture and agro-physio-morphological traits were monitored. Results showed highly significant effects of early drought stress on sorghum plants growth. The combined analysis of variance revealed highly significant differences (P ≤ 0.01) between varieties in the different environments for most traits studied. Under water deficit, the genotypic adaptation was linked to the capacity of varieties to increase the dead leaves weight and the roots length density and to reduce photosynthesis rate, stomata conductance, and leaf transpiration. The analysis of spectral indices across water treatments revealed significant variation. However, the differential responses between varieties remained the same. Fadda (V1), Nieleni (V2), Soumba (V8) and 621B (V9) showed promising behavior under drought stress and could be suitable for further use in West Africa.
... To start the research, water deficit levels treatment was given once the leaves reached the maximum size with dark green color (two months old leaves). The FTSW for water deficit levels determination was calculated by plotting the NTR (normalized transpiration rate) value in the NTR and FTSW relation curve with the formula [43]: ...
It is predicted that drought will be more frequent and sustained in the future, which may affect the decline of rubber tree production. Therefore, it is critical to research some of the variables related to the drought-resistance mechanism of the rubber tree. As a result, it can be used to guide the selection of new rubber drought-resistance clones. The goal of this study was to identify drought-resistance mechanisms in rubber clones from the high drought factor index (DFI) group using ecophysiological and biochemical variables. The treatments consist of two factors, namely water deficit and contrasting clones based on the DFI variable. The first factor consisted of three levels, namely normal (fraction of transpirable soil water (FTSW) > 0.75), severe water deficit (0.1 < FTSW < 0.20), and recovery condition (FTSW > 0.75 after rewatering). The second factor consisted of seven clones, namely clones G239, GT1 (low DFI), G127, SP 217, PB 260 (moderate DFI), as well as G206 and RRIM 600 (high DFI). RRIM 600 had the highest DFI among the other clones as a drought-tolerance mechanism characteristic. Furthermore, clones RRIM 600, GT1, and G127 had lower stomatal conductance and transpiration rate than drought-sensitive clone PB 260. As a result, as drought avoidance mechanisms, clones RRIM 600, GT1, and G127 consume less water than clone PB 260. These findings indicated that clone RRIM 600 was a drought-resistant clone with drought tolerance and avoidance mechanisms.
... The irrigation conditions were imposed using the fraction of transpirable soil water (FATS) method at R5 (Fernández et al., 1986) for all cultivars in the first experiment and for Triunfo and Garapiá in experiment 2, whereas FC104 in the last experiment was subjected to water deficit at the V4 vegetative stage (Fernández et al., 1986). Plants under water deficit were not irrigated until they showed 10% of the transpiration of the irrigated plants, which had their amount of transpired water replenished daily, according to the method proposed by Sinclair & Ludlow (1986). ...
O uso de métodos estatísticos para avaliar o crescimento e produção das plantas é crucial para o avanço tecnológico do feijoeiro. A pesquisa teve por objetivo dimensionar a amostra para a estimação da média de caracteres avaliados em diferentes cultivares e condições hídricas. Os dados foram coletados quinzenalmente a partir de dois experimentos fatoriais 3 x 2 (3 cultivares: Triunfo, Garapiá e FC104; 2 regimes hídricos: irrigado, não irrigado). Foram coletados dezoito caracteres (estatura, diâmetro da haste, número de nós, comprimento da raiz, massa fresca e seca da parte aérea e raízes, temperatura foliar, área foliar, número de nódulos, massa fresca e seca dos nódulos, número de vagens, comprimento das vagens, grãos por vagem, grãos por planta e massa seca dos grãos). O tamanho da amostra foi determinado através do método de reamostragem boodstrap a partir de de 2.000 reamostragens, e foi definido pelo número de plantas a partir das quais o intervalo de confiança de 95% foi de 10% a 40% da estimativa média. Como resultado, o tamanho da amostra é diferente entre os caracteres e entre as cultivares e condições hídricas utilizadas. No intervalo de confiança de 95% com erro padrão de 40% da estimativa da média, para avaliar todos os caracteres analisados são necessárias 44 plantas dos caracteres de parte aérea, 132 plantas para os caracteres de raiz e 12 plantas nos caracteres produtivos. Para analisar os dezoito caracteres estudados são necessárias 132 plantas.
... Based on such models and on the experimental findings of Sinclair and Ludlow (1986), and Sinclair et al. (2005), we hypothesize that as the soil dries below θ LP (the onset of drought stress and source-limited transpiration), stomata closure will proceed, and canopy water vapor conductance will decrease until reaching a minimum value slightly greater than zero resulting from imperfect stomata closure and/or cuticular transpiration. It corresponds to a residual transpiration rate equal to T p⋅ f WP , where f WP is the ratio between the minimum and the maximum (potential) canopy water vapor conductance. ...
Plant available water (PAW) is an important indicator of soil suitability for crop growth and biomass production. Total available water (TAW) is defined as the difference between the water content at field capacity (FC) and at wilting point (WP). The readily available water (RAW) is a fraction of TAW defined as the water content between FC and the limiting point (LP). The challenge in determining TAW and RAW lies in the correct determination of FC, WP, and LP. We propose a process-based approach to address the issue, referenced as flux-based method (FBM). Five scenarios were used to assess the FBM: (1) generic soil-plant-atmosphere conditions, from which sensitivity analyses were performed; (2) a maize crop on several soils to compare the predictions of the FBM and the traditional FAO method; (3) mean plant-atmosphere conditions to map PAW from soil texture using the FBM and the FAO method; (4) a field experiment with a fully irrigated soybean crop; and (5) a field experiment with a common bean crop under water deficit. Resulting flux-based TAW and RAW showed high sensitivity to root length density and soil hydraulic parameters. The FBM tended to predict higher water contents at FC than the FAO method for maize crop scenarios. Texture triangles to predict TAW and RAW showed that the differences between the predictions of FBM and FAO are mostly due to the distinct values for FC, and for the LP, respectively. For both observed scenarios of soybean and common bean crops, the predictions of the FBM were plausible with time series of observed data. The FBM allows predicting PAW in Van Genuchten-Mualem type soils for different FC flux criteria, soil depths, root densities, and dynamic potential transpiration rates.
... Drought treatments were based on the fraction of transpirable soil water (FTSW) (Sinclair and Ludlow, 1986) with three replications. Drought stress was imposed by initiating a soil dry-down protocol starting three days before anthesis. ...
... RLWC is a good indicator of the quantity of water a plant has in its tissues as it measures the quantity of H 2 O in the plant's tissues. Plants' photosynthetic potential improves as RLWC levels rise, and this, in turn, results in increased yield [27]. Thus, complementary differences in dehydration tolerance genotypes are the most valuable indices. ...
Abstract There is an increasing concern over globalwarming, which has changed climate and weather patternsresulting in adverse abiotic situations such as droughtstress to crop plants and the general vegetation area. Thishas posed a threat to food security and ecosystem structure,thus it's needed to identify resistant cultivars that cansurvive the propagation stress. Three (3) varieties (H1, H2,and H3) of Doum palms were subjected to water regimes:sufficiently irrigated, moderate, and severe water shortageconditions for 65 days to assess the drought adaptationability. Findings revealed that the water status of the plantwas noticeably affected by water shortage in all the studiedgenotypes. Drought stress imposed for 65 dayssignificantly reduced (P ≤0.05) the physiological andbiochemical characteristics of the experimental Doumplant, such as relative leaf water content (RLWC),membrane stability index (MSI), starch content, and arelative decrease in chlorophyll content. Water stressinduced a significant (P ≤0.05) increase in leaf proline,total soluble sugar (TSS), total free amino acid (TFAA),and glycine betaine. The findings, therefore, present thefirst step in understanding how doum palms react to harshwater conditions. Physiological and biochemicalcharacteristics such as RLWC, MSI, leaf proline, TSS,TFAA, glycine betaine, and starch content are indicatorswhen prospecting for drought tolerance doum palms.Keywords Doum Palm, Glycine Betaine, Proline,Drought Potential, Starch Content
(21) (PDF) Physiological and Biochemical Evaluations for Identification of Drought Tolerance Potential in Doum Palms (Hyphaene Compressa) under Water Deficit Treatment. Available from: https://www.researchgate.net/publication/364282846_Physiological_and_Biochemical_Evaluations_for_Identification_of_Drought_Tolerance_Potential_in_Doum_Palms_Hyphaene_Compressa_under_Water_Deficit_Treatment#fullTextFileContent [accessed May 28 2024].
... Benefiting from the long-term phenotyping and modeling of Trm,VPD, we discovered that cowpea had the potential to maintain a higher transpiration rate under very severe soil drought (VWC < 0.15). This finding is reminiscent of an earlier study reporting lower lethal RWC values of leaves in cowpea (40%) than in soybean (50%) 26 , and argued that conservation or profligation in water use is a conditional concept. Given the viewpoint that any plant traits to avoid or postpone drought become ineffective under terminal drought or in soils with very low water-holding capacity 2 , we propose that the water regime-dependent conservative/profligate water use behavior in a plant is an adaptive trait to help balance survival and productivity under dynamic environmental changes. ...
Vegetable soybean and cowpea are related warm-season legumes showing contrasting leaf water use behaviors under similar root drought stresses, whose mechanisms are not well understood. Here we conducted an integrative phenomic-transcriptomic study on the two crops grown in a feedback irrigation system that enabled precise control of soil water contents. Continuous transpiration rate monitoring demonstrated that cowpea used water more conservatively under earlier soil drought stages, but tended to maintain higher transpiration under prolonged drought. Interestingly, we observed a soybean-specific transpiration rate increase accompanied by phase shift under moderate soil drought. Time-series transcriptomic analysis suggested a dehydration avoidance mechanism of cowpea at early soil drought stage, in which the VuHAI3 and VuTIP2;3 genes were suggested to be involved. Multifactorial gene clustering analysis revealed different responsiveness of genes to drought, time of day and their interactions between the two crops, which involved species-dependent regulation of the core clock genes. Gene network analysis identified two co-expression modules each associated with transpiration rate in cowpea and soybean, including a pair of negatively-correlated modules between species. Module hub genes, including the ABA-degrading gene GmCYP707A4 and the trehalose-phosphatase/synthase gene VuTPS9 were identified. Inter-modular network analysis revealed putative co-players of the hub genes. Transgenic analyses verified the role of VuTPS9 in regulating transpiration rate under osmotic stresses. These findings propose that species-specific transcriptomic reprograming in leaves of the two crops suffering similar soil drought was not only a result of the different drought resistance level, but a cause of it.
... Section 2.4 based evaluations of water stress risk are interesting tools that could help monitor irrigation (Gaudin and Gary, 2012). For example, the fraction of transpirable soil water (FTSW) appears to be well correlated to plant water stress (Sinclair and Ludlow, 1986) and models such as Wa-LIS , validated in several situations (Delpuech et al., 2010), can be used by professionals to predict water deficit zones at the vineyard scale and to monitor irrigation (Dufourcq et al., 2013). Robust indicators of service crop development are also needed for service crop management. ...
Les systèmes viticoles font face à des enjeux environnementaux liés à l'érosion des sols, la perte de matière organique des sols, la pression phytosanitaire et ses effets sur la santé et la biodiversité, dans un contexte de changement climatique. L'utilisation d’enherbements dans les vignobles représente un ensemble de pratiques agroécologiques crédibles permettant à la fois de satisfaire les objectifs de production et de répondre aux différents enjeux environnementaux en viticulture. L'atteinte de ces objectifs et la réponse aux enjeux dépendent des fonctions des espèces dans les systèmes viticoles, de leur diversité dans les enherbements, et des relations entre cette diversité et les services écosystémiques. Comment décrire la diversité des communautés végétales dans les enherbements viticoles ? Comment évaluer le lien entre cette diversité végétale et les services écosystémiques fournis par les communautés ? Peut-on piloter la fourniture de services écosystémiques dans les agrosystèmes ?Pour répondre à ces questions, deux expérimentations au champ ont été réalisées dans une vigne expérimentale entre 2015 et 2018 : i) une expérimentation permettant de tester la pertinence de l’approche fonctionnelle pour la description de la diversité des enherbements viticoles et l’évaluation des services écosystémiques fournis par les communautés végétales, mesurés par des indicateurs, et ii) une expérimentation destinée à évaluer l’effet de la date de tonte d’un engrais vert sur la fourniture de services en viticulture. Les résultats obtenus ont confirmé la pertinence et la généricité de l’approche fonctionnelle pour décrire la diversité des espèces végétales composant les enherbements en lien avec la fourniture de services, sur la base de marqueurs fonctionnels de communautés composées d'espèces semées et spontanées. Les résultats présentés dans cette thèse ont ainsi confirmé l’existence de relations entre les propriétés fonctionnelles des communautés végétales et les services écosystémiques qu’elles fournissent dans un système viticole enherbé. La qualité des relations mises en évidence a montré la capacité des marqueurs fonctionnels à décrire les fonctions des espèces à l’échelle des communautés, et à expliquer des parts de variation importantes des indicateurs de services. Cette thèse a également confirmé l'importance du pilotage des cultures de services par des interventions techniques (e.g. date de tonte) afin d'optimiser la fourniture de services écosystémiques et éviter les dysservices. La mise en œuvre de l'approche fonctionnelle dans des contextes pédoclimatiques variés pourrait conduire à l'élaboration de règles générales de fonctionnement des communautés végétales pour la fourniture de services écosystémiques dans les agrosystèmes.
Cloud forests are unique biomes that thrive in foggy environments for a substantial part of the season. Fog in cloud forests plays two critical roles: it reduces incoming radiation and creates a humid environment, leading to the wetting of the canopy. This paper aims to investigate the combined effect of both radiation and wetness on Myrica faya -a cloud forest species present in subtropical regions- both directly in plants and through simulations. Experiments consisted of a controlled environment with two levels of radiation and leaf wetness: low radiation/wet conditions, and high radiation/no-wetness; and three treatments: continuous low radiation and wetness (CLR), continuous high radiation and no wetness (CHR), and alternate high low radiation and alternate wetness (AHLR). The results revealed that a combination of low radiation and leaf wetness significantly improves leaf stomata conductance and increases the specific leaf area (SLA). Changes in SLA were driven by leaf size changes. However, the minimum leaf conductance (gmin) did not respond to any of the treatments. The simulations focused on exploring the impact of radiation and canopy wetness on transpiration efficiency (TE), i.e. the ratio between photosynthesis (An) and transpiration (Tc), i.e. TE = An/Tc. The simulations demonstrated that TE increased exponentially as the canopy was gradually wetted, regardless of the radiation environment. This increase in TE results from Tc approaching zero while An maintains positive values. Overall, this study provides an integrated understanding of how fog alters M. faya functioning and, potentially, other cloud forest tree species.
O Stylosanthes spp cv. Campo Grande possui grande potencial adaptativo aos solos pobres, presentes em grande parte do semiárido brasileiro, além de ser resistente a elevadas temperaturas e umidade ao longo do ano vem sendo utilizada como uma importante ferramenta para minimizar a degradação de pastagens em virtude de sua característica de fixação do nitrogênio no solo. No entanto, as informações fisiológicas dessa espécie ainda estão sendo iniciadas, possuindo poucas pesquisas nessa ótica. Assim, o objetivo do trabalho foi avaliar os aspectos fisiológicos e produtivos de Stylosanthes spp. cv Campo Grande no semiárido brasileiro sob diferentes condições nutricionais. O delineamento utilizado foi em blocos casualizados, sendo composto de 5 tratamentos (T1 - sem adubação, T2 - adubação orgânica, T3 - adubação mineral, T4 - pó de rocha e T5 - pó de rocha + adubação orgânica) e 4 repetições, onde foram avaliadas o teor relativo de clorofila, taxa de assimilação líquida de CO2 (A),, condutância estomática (gs), taxa de transpiração (E), concentração interna de CO2 (Ci), temperatura da folha (Tleaf), eficiência do uso da água (EUA), eficiência de carboxilação (EC) e percentual de matéria seca (MS). Das variáveis analisadas, apenas a concentração interna de CO2 (Ci) na aplicação de adubação orgânica apresentou resultado significativo.
Drought is a serious constraint to crop growth and production of important staple crops such as maize. Improved understanding of the responses of crops to drought can be incorporated into cropping system models to support crop breeding, varietal selection and management decisions for minimizing negative impacts. We investigate the impacts of different soil types (stony and silty) and water regimes (irrigated and rainfed) on hydraulic linkages between soil and plant, as well as root: shoot growth characteristics. Our analysis is based on a comprehensive dataset measured along the soil-plant-atmosphere pathway at field scale in two growing seasons (2017, 2018) with contrasting climatic conditions (low and high VPD). Roots were observed mostly in the topsoil (10–20 cm) of the stony soil while more roots were found in the subsoil (60–80 cm) of the silty soil. The difference in root length was pronounced at silking and harvest between the soil types. Total root length was 2.5–6 times higher in the silty soil compared to the stony soil with the same water treatment. At silking time, the ratios of root length to shoot biomass in the rainfed plot of the silty soil (F2P2) were 3 times higher than those in the irrigated silty soil (F2P3) while the ratio was similar for two water treatments in the stony soil. With the same water treatment, the ratios of root length to shoot biomass of silty soil was higher than stony soil. The observed minimum leaf water potential (ψleaf) varied from around -1.5 MPa in the rainfed plot in 2017 to around -2.5 MPa in the same plot of the stony soil in 2018. In the rainfed plot, the mimimum ψleaf in the stony soil was lower than in silty soil from -2 to -1.5 MPa in 2017, respectively while these were from -2.5 to -2 MPa in 2018, respectively. Leaf water potential, water potential gradients from soil to plant roots, plant hydraulic conductance (Ksoil_plant), stomatal conductance, transpiration, and photosynthesis were considerably modulated by the soil water content and the conductivity of the rhizosphere. When the stony soil and silt soil are compared, the higher 'stress' due to the lower water availability in the stony soil resulted in less roots with a higher root tissue conductance in the soil with more stress. When comparing the rainfed with the irrigated plot in the silty soil, the higher stress in the rainfed soil resulted in more roots with a lower root tissue conductance in the treatment with more stress. This illustrates that the 'response' to stress can be completely opposite depending on conditions or treatments that lead to the differences in stress that are compared. To respond to water deficit, maize had higher water uptake rate per unit root length and higher root segment conductance in the stony soil than in the silty soil, while the crop reduced transpired water via reduced aboveground plant size. Future improvements of soil-crop models in simulating gas exchange and crop growth should further emphasize the role of soil textures on stomatal function, dynamic root growth, and plant hydraulic system together with aboveground leaf area adjustments.
Plant physiological status is the interaction between the plant genome and the prevailing growth conditions. Accurate characterization of plant physiology is, therefore, fundamental to effective plant phenotyping studies; particularly those focused on identifying traits associated with improved yield, lower input requirements, and climate resilience. Here, we outline the approaches used to assess plant physiology and how these techniques of direct empirical observations of processes such as photosynthetic CO2 assimilation, stomatal conductance, photosystem II electron transport, or the effectiveness of protective energy dissipation mechanisms are unsuited to high-throughput phenotyping applications. Novel optical sensors, remote/proximal sensing (multi- and hyperspectral reflectance, infrared thermography, sun-induced fluorescence), LiDAR, and automated analyses of below-ground development offer the possibility to infer plant physiological status and growth. However, there are limitations to such ‘indirect’ approaches to gauging plant physiology. These methodologies that are appropriate for the rapid high temporal screening of a number of crop varieties over a wide spatial scale do still require ‘calibration’ or ‘validation’ with direct empirical measurement of plant physiological status. The use of deep-learning and artificial intelligence approaches may enable the effective synthesis of large multivariate datasets to more accurately quantify physiological characters rapidly in high numbers of replicate plants. Advances in automated data collection and subsequent data processing represent an opportunity for plant phenotyping efforts to fully integrate fundamental physiological data into vital efforts to ensure food and agro-economic sustainability.
Desert algae are important components of the desert soil crust and play an essential role in desert soil ecosystem development. Owing to their special habitat, desert algae are often exposed to harsh environments, among which drought represents the most common stress. Green algae are considered to have drought tolerance potential; however, only a few studies have investigated this. In this study, we selected the green alga Chlorella sp., which was isolated from desert soil, and studied its physiological response to polyethylene glycol (PEG) 6000‐induced drought stress. The results showed that drought stress can affect the photosynthetic efficiency of Chlorella sp., reduce its water retention ability, and destroy its ultrastructure. However, Chlorella sp. can cope with drought stress through a series of physiological regulatory strategies. Protective strategies include quick recovery of photosynthetic efficiency and increased chlorophyll content. In addition, induced synthesis of soluble proteins, lipids, and extracellular polysaccharide (EPS), and accumulation of osmotic regulatory substances, such as sucrose and trehalose, also contribute to improving drought tolerance in Chlorella sp. This study provides insights into the physiological responses of Chlorella sp. to drought stress, which may be valuable for understanding the underlying drought adaptation mechanisms of desert green algae.
Drought stress is a significant environmental concern affecting crop growth, development, and yield. A laboratory experiment was conducted to examine the germination characteristics of four maize genotypes under varying levels of osmotic stress (0%, 2.5%, 5%, 7.5%, 10%) using polyethylene glycol (PEG) 6000 as an osmoticum. The experiment followed a factorial design within a Completely Randomized Design (CRD) framework with three replications. Varying concentrations of PEG influenced the germination and early growth of plants. An interesting finding was that as the concentration of PEG increased, there was a noticeable decrease in plant growth, indicating a negative correlation between the two. The findings indicated that subjecting maize plants to water stress treatments significantly affected various growth parameters (with a statistical significance level of P<0.05). Furthermore, with the increase in PEG concentration, there was a gradual decline in both respiration and transpiration rates, resulting in a decrease in protein concentration. There is a significant decrease in relative water content (RWC) in both shoot and root by 28.65% and 11.13%, respectively, compared with the control. When maize seedlings were subjected to water deficit by treating them with 2.5 to 10% PEG, there was a significant decrease (by 60.05%) in the level of chlorophyll 'b' while the decrease (by 33.25%) in chlorophyll 'a' content was comparatively less pronounced.
Sorghum [ Sorghum bicolor (L.) Moench] yield loss due to terminal drought stress is common in semiarid regions. Stay‐green is a drought adaptation trait, and a deeper understanding of stay‐green associated traits is necessary for sorghum breeding. We hypothesize that the stay‐green trait in sorghum may be associated with root architecture and transpiration rate under drought stress. The objectives were to (i) identify the relationship among stay‐green associated traits, compare the root system architecture and transpiration rate of stay‐green (B35 and 296B) and senescent (BTx623 and R16) genotypes under drought stress, and (ii) quantify the impacts of reproductive stage drought stress on gas exchange and grain yield of stay‐green and senescent genotypes. A series of drought experiments were conducted with these genotypes. Under drought stress, the stay‐green genotypes had an increased total root length in the top 30–60 cm (18%) and 60–90 cm of soil (45%) than the senescent genotypes. In contrast, under progressive soil drying, stay‐green genotypes had a decreased transpiration rate (9%) than senescent genotypes by an early (∼1h) partial closure of stomata under high vapor pressure deficit conditions. The increased seed yield (43%) in stay‐green genotypes is through an increased photosynthetic rate (30%) and individual seed size (35%) than senescent genotypes. Overall, it is concluded that stay‐green phenotype had two distinct drought adaptive mechanisms (i) increased root length for increased soil exploration for water; and (ii) an early decrease in transpiration rate to conserve soil moisture. Identifying genomic markers for these traits would accelerate drought‐tolerant sorghum breeding.
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Rice is more vulnerable to drought than maize, wheat, and sorghum because its water requirements remain high throughout the rice life cycle. The effects of drought vary depending on the timing, intensity, and duration of the events, as well as on the rice genotype and developmental stage. It can affect all levels of organization, from genes to the cells, tissues, and/or organs. In this study, a moderate water deficit was applied to two contrasting rice genotypes, IAC 25 and CIRAD 409, during their reproductive stage. Multi‐level transcriptomic, metabolomic, physiological, and morphological analyses were performed to investigate the complex traits involved in their response to drought. Weighted gene network correlation analysis was used to identify the specific molecular mechanisms regulated by each genotype, and the correlations between gene networks and phenotypic traits. A holistic analysis of all the data provided a deeper understanding of the specific mechanisms regulated by each genotype, and enabled the identification of gene markers. Under non‐limiting water conditions, CIRAD 409 had a denser shoot, but shoot growth was slower despite better photosynthetic performance. Under water deficit, CIRAD 409 was weakly affected regardless of the plant level analyzed. In contrast, IAC 25 had reduced growth and reproductive development. It regulated transcriptomic and metabolic activities at a high level, and activated a complex gene regulatory network involved in growth‐limiting processes. By comparing two contrasting genotypes, the present study identified the regulation of some fundamental processes and gene markers, that drive rice development, and influence its response to water deficit, in particular, the importance of the biosynthetic and regulatory pathways for cell wall metabolism. These key processes determine the biological and mechanical properties of the cell wall and thus influence plant development, organ expansion, and turgor maintenance under water deficit. Our results also question the genericity of the antagonism between morphogenesis and organogenesis observed in the two genotypes.
Climate change is responsible for the increasing frequency and intensity of abiotic stresses generating water
scarcity conditions. There is a need to breed plants adapted to future environmental conditions and resistant to
water stress. This study presents a High-Throughput Screening (HTS) system for continuously and simultaneously
monitoring plant stress response to drought in a semi-controlled environment. The HTS system combines a
gravimetric weighing system with soil moisture and atmospheric sensors. In operative terms, the system was
tested on the Sage (Salvia officinalis L.) under two soil water deficit treatments managed according to a feedback
control irrigation scheduling.
The system was able to model the sage water stress function following the root water uptake macroscopic
approach. The threshold of soil water status below which crop water stress occurred was also identified. The
gravimetric-based daily evapotranspiration (ETa) and the time domain reflectometry (TDR)-based root wateruptake (RWU) rates showed a high correlation during the drying when the evaporation flux is minimal. Moreover, the effects of soil bulk density on the root density and the plant biomass were evaluated, indicating the
importance of carrying out a homogeneous procedure of the pot-filling process
Climate change and the widespread intensive agriculture are responsible for the increasing frequency and intensity of abiotic stresses consequent to water scarcity. At present, there is the need to select and release, in short time, plants adaptable to the current environmental conditions and resistant to biotic and/or abiotic stress. In this work we designed and validated a High-Throughput Screening (HTS) system for the continuous and simultaneous monitoring of plant drought stress response in a semi-controlled environment. Structurally, the HTS-system consists of three hardware segments for high-frequency detection of the agrometeorological forcing variables (i.e., atmometry), the weights (i.e., gravimetry), and the soil water content, SWC, (i.e., time domain reflectometry, TDR) of sixteen pots in which the medicinal crop Salvia officinalis L (sage) was grown.Two irrigation treatments, which were based on soil water deficit conditions, were applied and an automated micro-irrigation system was designed to manage water by following a feedback control irrigation scheduling protocol.The system was able to model the sage water stress function following the root water uptake macroscopic approach. The threshold of soil water status below which crop water stress occurred was also identified. The gravimetric-based daily evapotranspiration (ETa) and the time domain reflectometry (TDR) -based root water-uptake (RWU) rates showed a high correlation, which allowed validating RWU indicators based on soil moisture sensors to estimate the ETa fluxes.KeywordsAgro-hydrological modelingHigh-throughput systemsRoot water uptakeSageWater stress function
The water deficit experienced by crops is a function of atmospheric water demand (vapor pressure deficit, VPD) and soil water supply over the whole crop cycle. We summarize typical transpiration response patterns to soil and atmospheric drying and the sensitivity to plant hydraulic traits. We explain the transpiration response patterns using a soil-plant hydraulic framework. In both cases of drying, stomatal closure is triggered by limitations in soil-plant hydraulic conductance. However, traits impacting the transpiration response differ between the two drying processes and act at different time scales. A low plant hydraulic conductance triggers an earlier restriction in transpiration during increasing VPD. During soil drying, the impact of the plant hydraulic conductance is less obvious. It is rather a decrease in the belowground hydraulic conductance (related to soil hydraulic properties and root length density) that is involved in transpiration downregulation. The transpiration response to increasing VPD has a daily time scale. In the case of soil drying, it acts on a seasonal scale. Varieties that are conservative in water use on a daily scale may not be conservative over larger time scales (e.g. during soil drying). This potential independency of strategies needs to be considered in environmental-specific breeding for yield-based drought tolerance.
Impervious surfaces create large volumes of stormwater which degrades receiving waterways. Incorporating trees into biofilters can increase evapotranspiration and therefore reduce stormwater runoff. Tree species with i) high water use, ii) drought tolerance and iii) rapid and full recovery after drought have been suggested for biofilters to maximise runoff reduction while minimising drought stress. Moisture availability fluctuates greatly in biofilter substrates and trees growing in biofilters will likely experience multiple, extended drought events that increase trade-offs between these traits. Providing an internal water storage has the potential to reduce tree drought stress and increase evapotranspiration. Two urban tree species (Agonis flexuosa and Callistemon viminalis) were grown in plastic drums with biofilter profiles. Three irrigation treatments were used: well-watered, drought with an internal water storage and drought without an internal water storage. Transpiration, leaf water potential and biomass were measured to determine the effect of biofilter internal water storage and repeated drought events on tree water use, drought stress and growth. Biofilter internal water storage improved water use and reduced drought stress for A. flexuosa, whereas C. viminalis reduced leaf loss but saw no change in water use or drought stress. A. flexuosa with biofilter internal water storage was able to recover transpiration to well-watered levels after repeated droughts, while C. viminalis experienced reduced recovery ability. It is recommended all biofilters planted with trees should have internal water storage. In systems with lower moisture availability a species with more stomatal control, such as A. flexuosa, is recommended. If selecting a species with less stomatal control, such as C. viminalis, the internal water storage volume needs to be increased to avoid drought stress.
Black gram (Vigna mungo) is one of the major pulse crops cultivated in more areas almost all over the world, particularly in India. This pulse crop is cultivated in both kharif and rabi seasons. Recent statistical data revealed that black gram yields are depleting drastically year by year in both India and the rest of the world. Drought stress is one of the primary causes for this yield reduction, and this stress happens due to lack of sufficient and improper distribution of rainfall. Black gram is extremely sensitive to drought, especially in both vegetative and reproductive stages, and witnesses 20–30% yield reduction. Drought stress is the reason for improper germination, reduced growth, injuring of the photosynthetic machinery, and declining of net photosynthesis and nutrient uptake, thereby causing yield reduction in black gram. Since stress sensing, signal transduction, and various adoption mechanisms are highly complex networks, to understand more about this network system, one should know more about physiological, biochemical, and molecular level changes that occurred in the plant system during stress and stress-responding mechanisms. Advance molecular technologies can be used to limelight the different gene regulation patterns and adoptive mechanisms concerning drought resistance, and this will be useful to develop drought stress-tolerant or -resistant black gram variety with higher yield potential under water-stress conditions. This chapter mainly concentrates on the impact of drought, morphological and physiochemical changes, stress-adaptive mechanisms, important drought-resistant traits, and physiological and molecular methods to manage drought stress in black gram.
Damask rose is one of the oldest and most valuable rose varieties that to some extent, tolerates water deficiency.
However, the selection and identification of genotypes that are more tolerant to drought stress will be effective in
development of cultivation of the plant. In this case, an experiment was performed under in vitro conditions using
polyethylene glycol at five levels (0, 25, 50, 75 and 100 g L-1) on four genotypes of Damask rose (Maragheh, Urmia,
Pakdasht and Kashan) and the tolerance of genotypes to drought stress was measured based on water relations traits of
the plant via response surface method (RSM). Results showed that as the severity of drought stress increased, the
percentage of dry matter was increased in genotypes of Maragheh, Urmia and Kashan compared to the control. At
concentration of 100 g L-1 PEG, Maragheh genotype had the highest fresh and dry weight, total chlorophyll, chl a and
chl b and the lowest leaf number and height compared to the other genotypes. Carotenoid contents in Urmia and
Maragheh genotypes were higher in 100 g L-1 PEG than other genotypes. As water deficiency increased, leaf water
content in Maragheh, Kashan and Urmia genotypes decreased. Maragheh genotype with high values of relative leaf
water content, on the other hand, with a decrease in water moisture reduction, relative water loss and saturated water
deficiency, showed a better protection mechanism against drought stress than the other three genotypes. After
Maragheh genotype, Pakdasht genotype was partially resistance to drought stress up to 75 g L-1 polyethylene glycol.
Vegetable soybean and cowpea are related warm-season legumes showing contrasting leaf water use behaviors under similar root drought stresses, whose mechanisms are not well understood. Here we conducted an integrative phenomic-transcriptomic study on the two crops grown in a feedback irrigation system that enabled precise control of soil water contents. Continuous transpiration rate monitoring demonstrated that cowpea used water more conservatively under earlier soil drought stages, but tended to maintain higher transpiration under prolonged drought. Interestingly, we observed a soybean-specific transpiration rate increase accompanied by phase shift under moderate soil drought. Time-series transcriptomic analysis suggested a dehydration avoidance mechanism of cowpea at early soil drought stage, in which the VuHAI3 and VuTIP2;3 genes were suggested to be involved. Multifactorial gene clustering analysis revealed different responsiveness of genes to drought, time of day and their interactions between the two crops, which involved species-dependent regulation of the circadian clock genes. Gene network analysis identified two co-expression modules each associated with transpiration rate in cowpea and soybean, including a pair of negatively-correlated modules between species. Module hub genes, including the ABA-degrading gene GmCYP707A4 and the trehalose-phosphatase/synthase gene VuTPS9 were identified. Inter-modular network analysis revealed putative co-players of the hub genes. Transgenic analyses verified the role of VuTPS9 in regulating transpiration rate under osmotic stresses. These findings propose that species-specific transcriptomic reprograming in leaves of the two crops suffering similar soil drought was not only a result of the different drought resistance level, but a cause of it.
Although soil water deficit is the primary constraint on transpiration globally, the mechanisms by which soil drying and soil properties impact transpiration and stomatal regulation remain elusive. This work aimed to investigate how soil textures and vapor pressure deficit (VPD) impact the relationship between transpiration rate, canopy conductance, and leaf water potential of maize (Zea mays L.) during soil drying. We hypothesize that the decrease in soil–plant hydraulic conductance (Ksp) triggers stomatal closure and the latter is soil specific.
Plants were grown in two contrasting soil textures (sand and loam) and exposed to two consecutive VPD levels (1.8 and 2.8 kPa). We measured transpiration rate, canopy conductance, soil and leaf water potentials during soil drying.
Transpiration rate decreased at higher soil matric potential in sand than in loam at both VPD levels. In sand, high VPD generated a steeper drop in canopy conductance with decreasing leaf water potential. The decrease in canopy conductance was well correlated with the drop in Ksp, which was significantly affected by soil texture.
Our results demonstrated that variations in canopy conductance were not simply a function of leaf water potential but largely affected by soil hydraulics. These results reinforce a model of stomatal closure driven by a loss in soil hydraulic conductivity. Further studies will determine if soil-specific stomatal regulation exists among species.
In predicting evaporation rates for field crops, it is important to consider the influence of soil water status on the actual evaporation rate relative to the potential rate. This study was conducted to determine actual evaporation rates of corn (Zea mays L.) as influenced by soil water status and potential evaporation rate. Actual evaporation rates were measured during the 1972 growing season with a weighing lysimeter. Evaporation rates were found to be practically independent of the soil water status for all existing conditions of potential evaporation. During the season more than 20 cm of soil water was removed from the 120-cm deep profile.
Leaf diffusion resistance and leaf water potential measurements indicated that at least 80% of the extractable soil water was freely available to plant roots. These findings differ from those of Denmead and Shaw (Agron J. 54:385–390, 1962) who found that evaporation reduction in container grown corn plants started when about 20% of the extractable water was removed from the soil for potential evaporation rates above 6 mm/day. The difference between the results from the experiment reported by Denmead and Shaw and this experiment point out that serious errors are possible when using their results for predicting evaporation from corn plants growing under field conditions.
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The onset of water stress within a crop is defined as the time at which the rate of water loss declines below that of a well watered crop in the same locality. The relation to the onset of water stress and soil water status of several readily measured plant parameters was investigated in crops of wheat and soybeans over three years. Evapotranspiration ET was monitored with weighing lysimeters. A noticeable decline in the rate of ET for both wheat and soybeans was detected once 20% to 30% of the total plant available water PAW remained in the 1 m deep lysimeter soil profile. Extension growth of wheat declined when PAW was 33% and 34% in two years of measurement. In soybeans, the decline in the rate of leaf extension coincided with the decline in the rate of ET. Midmorning measurement of exposed leaf water potential L, covered leaf water potential CL and covered plant leaf water potential CP yielded similar results for both wheat and soybeans. Day-to-day variability was least in CP and most in L. Values of CP, L and CL decreased rapidly with PAW < 30%.="" daily="" values="" of="" leaf="" diffusive="" conductance="" were="" variable="" but="" there="" was="" a="" general="" decline="" in="" conductance="" with="" paw="">< 30%.="" it="" is="" suggested="" that="">CL may be the easiest and most reliable parameter to monitor as a means of detecting the onset of stress. The results indicated that PAW levels in the root zone of 50% for wheat and 30% for soybean probably do not affect extension growth or plant water status parameters and can thus be used as criteria for irrigation scheduling.
The responses of leaf conductance, leaf water potential and rates of transpiration and net photosynthesis at different vapour pressure deficits ranging from 10 to 30 Pa kPa-1 were followed in the sclerophyllous woody shrub Nerium oleander L. as the extractable soil water content decreased. When the vapour pressure deficit around a plant was kept constant at 25 Pa kPa-1 as the soil water content decreased, the leaf conductance and transpiration rate showed a marked closing response to leaf water potential at-1.1 to-1.2 MPa, whereas when the vapour pressure deficit around the plant was kept constant at 10 Pa kPa-1, leaf conductance decreased almost linearly from-0.4 to-1.1 MPa. Increasing the vapour pressure deficit from 10 to 30 Pa kPa-1 in 5 Pa kPa-1 steps, decreased leaf conductance at all exchangeable soil water contents. Changing the leaf water potential in a single leaf by exposing the remainder of the plant to a high rate of transpiration decreased the water potential of that leaf, but did not influence leaf conductance when the soil water content was high. As the soil water content was decreased, leaf conductances and photosynthetic rates were higher at equal levels of water potential when the decrease in potential was caused by short-term increases in transpiration than when the potential was decreased by soil drying.
As the soil dried and the stomata closed, the rate of photosynthesis decreased with a decrease in the internal carbon dioxide partial pressure, but neither the net photosynthetic rate nor the internal CO2 partial pressure were affected by low water potentials resulting from short-term increases in the rate of transpiration. Leaf conductance, transpiration rate and net photosynthetic rate showed no unique relationship to leaf water potential, but in all experiments the leaf gas exchange decreased when about one half of the extractable soil water had been utilized. We conclude that soil water status rather than leaf water status controls leaf gas exchange in N. oleander.
The relative turgidity technique consists in comparing the initial and turgid water contents, on a percentage basis, of disks punched from leaves, the turgid water content being obtained by floating the disks on water.
The effects of soil water depletion on crop evaporation and root absorption of water were studied in soybean and sorghum crops. Sorghum did not deplete the maximum soil water store by more than 100 mm, whereas rainfed crops of soybeans, cvv. Ruse and Bragg, depleted the soil water store by 130 and 170 mm, respectively. This was sufficient to reduce soybean yields by 35% and hasten maturity in both cultivars when compared with irrigated crops. The post-flowering efficiency of water use by rainfed crops of soybeans was about one-third that of sorghum.
The root distribution of Ruse and its pattern of soil water extraction indicated that during bean- fill it was unable to exploit water from much below 80 cm depth, but this effect was offset by its reaching maturity before yield was severely affected by water stress. As Ruse approached maturity, its root densities decreased in soil layers below 10 cm depth, whereas Bragg, which matured 2 weeks later than Ruse, maintained a deep root system and continued to deplete water down to 120 cm. The contrast in root distribution between soybean cultivars also influenced the level of soil water depletion at which crop evaporation fell below the potential rate. Soil and root resistances to water absorption were used to interpret the effects of root density and soil water depletion on water uptake.
The regional implications of the results were examined using a water balance model to analyse historical rainfall records. It was concluded that similar soil moisture conditions could be expected about 1 year in 5, indicating that these results have a ready application for irrigation scheduling in this area.
Growth responses, water relations, leaf conductance, and gas exchange of V.unguiculata were studied under conditions of drought in both the aerial and the soil environment. Dry air caused a significant reduction in whole plant biomass and all its components despite a plant water status which was not different from plants in humid air. Stomata closed in dry air and water loss per plant was lower in dry than in humid air because of both lower leaf conductances and a smaller total leaf area.
Dry soil also caused decreases in biomass growth, but leaf growth continued at the soil water status at which stomata began to close (45% depletion of plant available water). Relative leaf expansion rate started to decline below the rate of control plants when 60% (humid air) or 65% (dry air) of plant available water was depleted. Therefore, in V. unguiculata, stomata appear to be more sensitive to soil drought than growth of leaves. Leaf relative water content and osmotic potential remained at the level of control plants when stomata started to close and decreased only slightly below the level of control plants even under severe water stress. A trend of decreasing osmotic potentials at 55-60% depletion of plant available water was observed, but leaf growth ceased only when 90% of plant available water was depleted. Leaf conductance decreased more rapidly than CO2 assimilation during development of soil drought.
Growth and water use of soybean (Glycine max), black gram (Vigna mungo), green gram (V. radiata) and cowpea (V. unguiculata) in response to water stress were evaluated in the field at Dalby in southeast Queensland. Differing strategies of growth and water use which reflected the differential expression of dehydration avoidance and developmental plasticity in response to stress were identified among species. The primary difference between strategies related to differences in dehydration avoidance. Soil water extraction during the initial phases of drought was faster, and leaf area development and plant growth were relatively less affected, in soybean than in the Vigna spp. Where adequate soil water existed, these differences were sustained during the drought period but were reversed where soil water was limited. Soil water extraction by soybean occurred to greater depths, and to lower potentials, than in the Vigna spp. Developmental plasticity influenced growth pattern in the Vigna spp. to varying degrees. Drought periods invariably curtailed growth and hastened maturity in green gram and black gram, but rain prior to maturity induced renewed growth in black gram. Moderate stress curtailed growth and hastened maturity in cowpea, which also responded to late rains with renewed growth. Severe stress inhibited growth and delayed development in cowpea indefinitely.
The response of soybean (Glycine max CPI 26671), black gram (Vigna mungo cv. Regur), green gram ( V , radiata cv. Berken) and cowpea (V. unguiculta CPI 28215) to water stress was evaluated in the field at Dalby in south-east Queensland. Three stress response mechanisms were identified in each species but the degree of expression varied substantially. The Vigna spp. cultivars exhibited a measure of escape through faster development in response to stress, particularly in the flowering to maturity phase. Black gram and cowpea revealed additional developmental plasticity in terms of the ability to produce new flushes of flowering when stress was relieved late in the life cycle. Variation in phenology of the soybean cultivar in response to stress was small. Two mechanisms served to avoid dehydration through reduced water loss, viz. (i) stomatal closure in response to falling leaf water potential, and (ii) paraheliotropic leaf movement. Stomatal closure occurred at higher leaf water potentials and the expression of paraheliotropy under stress was strongest in Vigna spp. cultivars. Reduced leaf conductances were associated with higher leaf temperatures, particularly in soybean where paraheliotropy under stress was small. The inter-relationships between stress mechanisms, and some implications of cultivar differences for acclimatization to drought, are discussed.
Differences in the proportion of radiation intercepted at solar noon (F), leaf canopy development and leaf conductance (g1) of soybean (Glycine max cvs. Buchanan and Durack), green gram (Vigna radiata cvs. Berken and CES-ID-21), black gram (Vigna mungo cv. Regur), cowpea (Vigna unguiculata cv. Red Caloona), lablab bean (Lablab purpureus cv. Highworth) and pigeon pea (Cajanus cajan cvs. Royes and insensitive ICP 7179) grown under different soil water regimes were analysed. When water deficits developed immediately following seedling establishment and were unrelieved to maturity the reduction in F was attributed to reduced leaf area development and more vertical leaf orientation, but no leaf loss occurred until near maturity. These reductions in F occurred in all grain legumes before any decreases in g1 measured at solar noon were observed. In contrast, when water deficits developed from 6 weeks after sowing after an appreciable canopy had developed, F decreased immediately primarily due to leaf loss but did not fall as low as the maximum value of F in the regime where irrigation was terminated at seedling establishment. This indicates that leaf loss is not as sensitive to water deficits as leaf area development. Also, there were immediate reductions in g1 as well as F when irrigation was terminated 6 weeks after sowing.There were differences among grain legumes in the degree of reduction in F in response to water deficits. Since the measurement of F is simpler and more rapid than the measurement of g1, and since F is a much more sensitive indicator of the time of onset of water deficits, it is suggested that F be used as an index to quantify the development of water deficits in these crops.
Seedlings of Zea mays L. (John Innes hybrid) were grown with roots divided between two containers such that part of the root system could reduce
the water potential of the soil in its immediate vicinity while the rest of the root system was well supplied with water.
When compared to plants rooted in two pots of moist soil, drying of part of the root system resulted in partial closure of
stomata, even though leaf water potential, turgor and abscisic acid (ABA) content remained unaffected. When leaf pieces were
removed from the two groups of plants and incubated under conditions favourable for stomatal opening, stomata of the ‘half-watered’
plants still showed restricted apertures. Incubation in kinetin (10 mmol m−3) or zeatin (100 mmol m−3) reversed the closure of stomata stimulated by soil drying. These results suggest that a continuous supply of cytokinin from
roots may be necessary to sustain maximal stomatal opening and an interruption of this supply due to soil drying may act as
an indicator of inhibited root activity, resulting in restricted stomatal opening and thereby restricted water use.
Dry matter production, yield and water use efficiency of soybean (Glycine max), black gram (Vigna mungo), green gram (V. radiata) and cowpea (V. unguiculata) under irrigated, rain-fed fallowed and rain-fed double-cropped culture were evaluated at Dalby in south-east Queensland. Differential species responses to cultural treatments were related to strategies of growth and water use in response to water stress. The major effect of differences between strategies related to differences in the short term rate of soil water use, which together with the seasonal pattern of water availability influenced both the total, and seasonal pattern of water use. Regardless of strategy adopted, dry matter production was primarily a function of water use. However, seed yield and water use efficiency for seed yield depended on the seasonal pattern of water use. The relative agronomic success of the various strategies therefore depended on the seasonal profiles of water availability. Some implications of the differences in stress response strategy for adaptation of these species to agricultural environments are discussed.
Six dryland crops (mungbean, cow pea, soya bean, groundnut, maize and sorghum) and two rice cultivars (C·171·136 and IR 36) were grown under rainfed and irrigated conditions on a dryland site with a clay loam soil at the International Rice Research Institute, Philippines. After the first 30 days of growth there was no effective rain, and the rainfed crops encountered different water deficits. Crop productivity, leaf area, plant water status, root distribution, and soil water use were measured.
Neither rice cultivar yielded seed under rainfed conditions, but all other crops did. With mungbean and cow pea there was little difference between the yields under rainfed and irrigated conditions, but groundnut, soya bean, sorghum and maize gave higher yields under irrigation.
The rainfed crops extracted different amounts of stored soil water, ranging from 100 mm for IR 36 to 250 mm for groundnut. The different amounts were associated with different growth durations, rooting depths and rates of soil water depletion from within the root zone. Biological productivity of the six rainfed crops with the C 3 photosynthetic pathway was linearly related to transpiration, which was estimated from soil water extraction and soil evaporation. Biological productivity per unit of transpiration for the two crops with the C 4 pathway was 2·2 times higher than for those with the C 3 pathway. The different seed yields of the rainfed crops were due to differences in harvest index and the chemical composition of seeds, as well as to biological productivity.
The results are discussed in relation to the potential for growing dryland crops after rice in rice-based cropping systems.
Abstract Water-stressed pigeonpea leaves have high levels of osmotic adjustment at low leaf water potentials. The possible contribution of this adjustment of dehydration tolerance of leaves was examined in plants grown in a controlled environment. Osmotic adjustment was varied by withholding water from plants growing in differing amounts of soil, which resulted in different rates of decline of leaf water potential.The level of osmotic adjustment was inversely related to leaf water potential in all treatments. In addition, at any particular water potential, plants that had experienced a rapid development of stress exhibited less osmotic adjustment than plants that experienced a slower development of stress. Leaves with different levels of osmotic adjustment died at water potentials between –3.4 and –6.3 MPa, but all leaves died at a similar relative water content (32%). Consequently, leaves died when relative water content reached a lethal value, rather than when a lethal leaf water potential was reached. Osmotic adjustment delayed the time and lowered the leaf water potential when the lethal relative water content occurred, because it helped maintain higher relative water contents at low leaf water potentials. The consequences of osmotic adjustment for leaf survival in water-stressed pigeonpea are discussed.
The water use of two soybean cultivars (Bragg and Ruse) was measured for three seasons for a range of irrigation treatments. The seasonal totals of plant and soil evaporation ranged from 450 to 750 mm or from 36 to 64% of class A pan evaporation for the same period. Both cultivars extracted approximately 60% of the total extractable soil water in the top 1.2 m of soil before actual evaporation (Ea) dropped below potential evaporation (Eo). Up to this point the ratio between Ea and class A pan evaporation averaged 0.8. Ruse used water at a faster rate than Bragg but Ruse was not as effective in extracting the deep (below 1.0 m) soil water as Bragg. Water use efficiency (kg seed ha–1 mm–1 water) showed a small but general increase with decreasing irrigation water application. Runoff losses varied from zero for non-irrigated Ruse in 1977/78 to 352 mm for frequently-irrigated Bragg in 1976/77, generally increasing with the number of irrigations.
It has previously been reported that canopy water loss by cowpea (Vigna unguiculata) decreases with small depletions in soil water. In these studies, under field conditions, it was demonstrated that with small changes in soil water status leaf conductance of cowpea decreases in a manner which is consistent with the sensitive regulation of canopy water loss.
However, treatments which differed in leaf conductance, and presumably stomatal aperture, had similar leaf water potentials. It is hypothesized that the stomatal closure which results from soil water depletion is mediated by changes in root water status through effects on the flow of information from root to shoot. An efficient mechanism of this type could be partially responsible for the extreme drought avoidance exhibited by this plant.
The development of plant water deficits in soybean (Glycine max cvs. Buchanan and Durack), green gram (Vigna radiata cvs. Berken and CES-ID-21), black gram (V. mungo cv. Regur), cowpea (V. unguiculata cv. Red Caloona), lablab bean (Lablab purpureus cv. Highworth) and pigeon pea (Cajanus cajan cvs. Royes and insensitive ICP 7179) were compared using measurements of leaf conductance (g1) and leaf water potential (ψ1) taken around solar noon at weekly intervals from seedling emergence until maturity on irrigated and unirrigated crops grown in a semi-arid tropical environment. In all grain legumes g1 fluctuated over time in a manner unrelated to soil water availability. Rather, g1 was influenced more by the saturation deficit of the air (δe) in all grain legumes except pigeon pea. In green gram, black gram, cowpea, and lablab bean, ψ1 was maintained at relatively high levels throughout the season independent of soil water content. Fluctuations in g1, and the maintenance of high ψ1, over time prevent the use of g1 and ψ1 as parameters to characterize the development of water deficits in these crops.Diurnal trends were also quantified. There was little recovery in g1 or ψ1 later in the afternoon as the photon flux density (PFD) decreased since δe remained at peak values until dusk. Consequently the correlation between g1 and δe observed in all grain legumes except pigeon pea indicates the importance of early morning photosynthesis to total daily assimilation under both irrigated and unirrigated conditions, although the relative effect of δe on g1 decreased as the availability of soil water declined.The extent of osmotic adjustment was assessed at two stages of growth. Osmotic adjustment was least in black gram and cowpea and greatest in soybean. This information together with trends in g1 and ψ1 were used to examine the physiological responses of different grain legumes to environmental water deficits.
The comparative responses of phenology, and seed yield and its components to prolonged water deficits in soybean (Glycine max cvs. Buchanan and Durack), green gram (Vigna radiata cvs. Berken and CES-ID 21), black gram (V. mungo cv. Regur), cowpea (V. unguiculata cv. Red Caloona), labaab bean (Lablab purpureus cv. Highworth) and pigeon pea (Cajanus cajan cvs. Royes and insensitive ICP7179) was examined during the dry season in semi-arid tropical Australia. In general, water deficits had little effect on the date of flowering, but the duration of flowering and pod-filling was reduced and the time to maturity was markedly shortened. Under well-watered conditions, seed yields were similar in green gram, cowpea, soybean and pigeon pea, with slightly higher yields being obtained in black gram and lablab bean. In contrast, green gram, cowpea and lablab bean produced the highest yield under conditions of water deficit. Early-maturing cultivars yielded better than late-maturing cultivars but inter-species variation in seed yield was not necessarily related to phenology. Most of the reduction in yield arose from a decrease in pod numbers although there was some variation in seed size and seeds per pod. In contrast to absolute yield levels, the reduction in yield due to water deficits relative to the well-watered situation was, with the exception of black graam, greater the later the maturity of the grain legume. Thus the relative reduction in yield was least in green gram, followed by cowpea, soybean cv. Buchanan, insensitive pigeon pea, and lablab bean, with black gram, soybean cv. Durack and pigeon pea cv. Royes having the greatest yield reduction due to water deficits.Variation in productivity was also examined in terms of evapotranspiration (ET) and water use efficiency (WUEDM on a net above-ground dry matter basis, and WUEy on a seed yield basis). Under prolonged water deficits, lablab bean, soybean cv. Durack and both pigeon-pea cultivars extracted the most water. These differences in ET were examined in terms of rooting characteristics. WUEDM was unaffected by water deficits in both soybean cultivars, both green grams and cowpea, but tended to decrease in response to water deficits in the remaining grain legumes. WUEy was more responsive to water deficits than WUEDM. Only in the early-maturing green grams and cowpea was WUEy unaffected by water deficits.
The daily (24-hour) carbon balances of whole sorghum plants (Sorghum bicolor L. Moench cv BTX616) were continuously measured throughout 15 days of water stress, followed by rewatering and 4 more days of measurements. The plants were grown under controlled environment conditions typical of warm, humid, sunny days. During the first 12 days, osmotic potentials decreased in parallel with decreased water potentials to maintain pressure potentials near 0.5 kilojoules per kilogram (5 bars). Immediately before rewatering on day 15, the water potential was -3.0 kilojoules per kilogram. Osmotic adjustment at this point was 1.0 kilojoules per kilogram, as measured by the decrease in the water potential at zero turgor from its initial value of -1.4 kilojoules per kilogram.Gross input of carbon was less but the fraction retained was greater because a smaller fraction was lost through respiration in stressed plants than in unstressed plants. This was attributed to a lower rate of biomass synthesis, and conversely a higher rate of storage of photosynthate, due to inhibition of leaf expansion. The reduction in the cost associated with biomass synthesis more than balanced any metabolic cost of osmotic adjustment. The net daily gain of carbon was always positive in the stressed plants.There was a large burst of respiration on rewatering, due to renewed synthesis of biomass from stored photosynthate. Over the next 3 days, osmotic adjustment was lost and the daily carbon balance returned to that typical of nonstressed plants. Thus, osmotic adjustment allowed the stressed plants to accumulate biomass carbon throughout the cycle, with little additional metabolic cost. Carbon stored during stress was immediately available for biomass synthesis on rewatering.
Crop physiology in dryland agriculture
- J D Eastin
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Eastin, J. D., Dickson, T. E., Kreig, D. R., and Maunder, A. B. (1983). Crop physiology in dryland agriculture. In 'Dryland Agriculture'. Agronomy Monograph No. 23, pp. 333-64. [Am. Soc. Agron.: Madison.]
A Factual Key for the Recognition of Australian Soils Epicuticular wax and cuticular resistance in rice
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