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We examined the effects of leaf herbivory by the dorcas gazelle, Gazella dorcas, on the compensatory growth of the geophyte Pancratium sickenbergeri (Amaryllidaceae) in the Negev desert, Israel. In three populations exposed to different levels of herbivory, we removed different
amounts of photosynthetic leaf area from plants in five clipping treatm...
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... was a significant difference among the clipping treatments in the growth response of the leaves. The analysis of covariance for log 10 RGR, with log 10 leaf width as a covariate, showed a significant effect of population, treatment, and a significant interaction between these two factors ( Table 1). In the popula- tion with the lowest level of herbivory (Makhtesh Katan), RGR was lowest, and the plants overcom- pensated only at the lowest level of clipping (25%) (Fig. 1). ...
Similar publications
We investigated the effects of herbivory by the dorcas gazelle, Gazella dorcas, on the production of a second inflorescence in a desert lily, Pancratium sickenbergeri (Amaryllidaceae), after the first inflorescence was eaten. In three populations exposed to different levels of herbivory, we conducted an inflorescence-clipping experiment in the flow...
Citations
... This regenerative ability is crucial because S. grandis survival requires the rapid restoration of active photosynthesis and growth [58]. After grazing, the remaining or newly developed organs can undergo physiological changes that enhance photosynthesis, which can further increase the photosynthetic capacity of the grazed plants [55,59]. Under LG and MG conditions, when plant diversity is relatively high, livestock will selectively graze on the highly palatable vegetation, such as L. chinensis, Cleistogenes squarrosa, and Chenopodium glaucum, resulting in minimal damage to S. grandis [60]. ...
Organisms have evolved effective and distinct adaptive strategies to survive. Stipa grandis is a representative species for studying the grazing effect on typical steppe plants in the Inner Mongolia Plateau. Although phenotypic (morphological and physiological) variations in S. grandis in response to long-term grazing have been identified, the molecular mechanisms underlying adaptations and plastic responses remain largely unknown. Here, we performed a transcriptomic analysis to investigate changes in gene expression of S. grandis under four different grazing intensities. As a result, a total of 2357 differentially expressed genes (DEGs) were identified among the tested grazing intensities, suggesting long-term grazing resulted in gene expression plasticity that affected diverse biological processes and metabolic pathways in S. grandis. DEGs were identified in RNA-Seq and qRT-PCR analyses that indicated the modulation of the Calvin–Benson cycle and photorespiration metabolic pathways. The key gene expression profiles encoding various proteins (e.g., ribulose-1,5-bisphosphate carboxylase/oxygenase, fructose-1,6-bisphosphate aldolase, glycolate oxidase, etc.) involved in these pathways suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of S. grandis. Our findings provide scientific clues for improving grassland use and protection and identifying important questions to address in future transcriptome studies.
... This regenerative ability is crucial because S. grandis survival requires the rapid restoration of active photosynthesis and growth [58]. After grazing, the remaining or newly developed organs can undergo physiological changes that enhance photosynthesis, which can further increase the photosynthetic capacity of the grazed plants [55,59]. Under LG and MG conditions, when plant diversity is relatively high, livestock will selectively graze on the highly palatable vegetation, such as L. chinensis, Cleistogenes squarrosa, and Chenopodium glaucum, resulting in minimal damage to S. grandis [60]. ...
Organisms have evolved effective and distinct adaptive strategies to survive. Stipa grandis is one of the widespread dominant species on the typical steppe of the Inner Mongolian Plateau, and is regarded as a suitable species for studying the effects of grazing in this region. Although phenotypic (morphological and physiological) variations in S. grandis in response to long-term grazing have been identified, the molecular mechanisms underlying adaptations and plastic responses remain largely unknown. Accordingly, we performed a transcriptomic analysis to investigate changes in gene expression of S. grandis under four different grazing intensities. A total of 2,357 differentially expressed genes (DEGs) were identified among the tested grazing intensities, suggesting long-term grazing resulted in gene expression plasticity that affected diverse biological processes and metabolic pathways in S. grandis . DEGs were identified that indicated modulation of Calvin–Benson cycle and photorespiration metabolic pathways. The key gene´expression profiles encoding various proteins (e.g., Ribulose-1,5-bisphosphate carboxylase/oxygenase, fructose-1,6-bisphosphate aldolase, glycolate oxidase etc.) involved in these pathways suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of S. grandis . Our findings provide scientific clues for improving grassland use and protection, and identify important questions to address in future transcriptome studies.
... Nevertheless, herbivores have to face complex plant defense syndromes consisting of a variety of combinations of Communicated by Eleonora Egidi. defensive features (Futuyma and Agrawal 2009;Rasmann and Agrawal 2009), which may comprise nutritional quality, regrowth capacity (i.e., tolerance), physical, chemical, and phenological traits (Coley and Barone 1996;Ruiz et al. 2008;Lamarre et al. 2014). Traits may serve two or more functions and are considered as defense mechanisms even if this is not their primary purpose (Strauss and Agrawal 1999). ...
Vascular plants exhibit defense syndromes, a variety of interdependent defensive traits against herbivores, which may considerably differ between plant groups. Although ferns are an abundant component of tropical forest understories, studies of fern–herbivore interactions are scarce, and none has focused on the underlying defense syndromes. To examine the potential defense syndromes of 34 species of tropical ferns of Brazilian forests, we measured ten leaf traits and examined their correlation with parallelly assessed leaf damages. The first three components of categorical PCA were related (1) with SLA, water content, nitrogen, and phosphorus (33.2% of variance); (2) with tannins and saponins, but negatively with trichome density (22.5%); and (3) with phenol concentrations (16.1%). We identified three groups of fern species with similar leaf damages but different defense syndromes: (I) 14 species were of high nutritional quality (= high SLA, N and water content), but a variable trichome density; (II) 4 species were of low nutritional quality, but had high phenol concentrations, and often a high trichome density; and (III) 16 species were of intermediate nutritional quality and had a low trichome density or were glabrous. Most species (groups I and III) including tree ferns used chemical defenses to protect their highly valuable, nutritious leaves. Group II, exemplified by bracken fern, combined however a low nutritional quality with a powerful chemical defense, including high phenol concentrations, and many trichomes. Because leaf damages did not differ significantly among groups, we conclude that each defense syndrome provides species with a similar resistance against their herbivores.
... At the same time, the steadily decreasing plant height and internode length with increasing grazing intensity produced plants with more of a dwarf phenotype, which may represent a grazing avoidance strategy that protects the plants. On the other hand, the increase in tiller number with increasing grazing intensity would promote regrowth of the plants, and could also represent a grazing tolerance mechanism [65]. At the heavy grazing intensity, roots of L. chinensis absorbed more nutrients rapidly from the soil to grow complementally, which also reduced the soil nutrient in the heavy grazing plots [76]. ...
Background:
Grazing is an important land use in northern China. In general, different grazing intensities had a different impact on the morphological and physiological traits of plants, and especially their photosynthetic capacity. We investigated the responses of Leymus chinensis to light, medium, and heavy grazing intensities in comparison with a grazing exclusion control.
Results:
With light grazing, L. chinensis showed decreased photosynthetic capacity. The low chlorophyll and carotenoid contents constrained light energy transformation and dissipation, and Rubisco activity was also low, restricting the carboxylation efficiency. In addition, the damaged photosynthetic apparatus accumulated reactive oxygen species (ROS). With medium grazing, more energy was used for thermal dissipation, with high carotene content and high non-photochemical quenching, whereas photosynthetic electron transport was lowest. Significantly decreased photosynthesis decreased leaf C contents. Plants decreased the risk caused by ROS through increased energy dissipation. With high grazing intensity, plants changed their strategy to improve survival through photosynthetic compensation. More energy was allocated to photosynthetic electron transport. Though heavy grazing damaged the chloroplast ultrastructure, adjustment of internal mechanisms increased compensatory photosynthesis, and an increased tiller number facilitated regrowth after grazing.
Conclusions:
Overall, the plants adopted different strategies by adjusting their metabolism and growth in response to their changing environment.
... Similarly, numerous researchers have concluded that partially removing leaves is a practical agronomic approach to change the maize canopy structure, which significantly maximizes the seed yield of maize plants (Zhu et al. 2004;Gambí n et al. 2006;Ma et al. 2008). However, the seed yield response to leaf defoliation treatments differs significantly (Liu et al. 2014a) while the impact (positive or negative) of leaf defoliation levels on the maize growth and seed yield depends on the intensity and timing of leaf defoliation (Ruiz-r et al. 2008;Liu et al. 2015a). Alteration in source (leaves) size at the reproductive stage often increases the stem weight because the photosynthates are stored in this part temporarily, which then fulfils the demand of carbohydrates by sinks (seeds) (Tollenaar 1977;Tollenaar and Daynard 1978;Uhart and Andrade 1995). ...
Intercropping is the growing of two or more crops simultaneously in the same field, while in relay-intercropping, two crops are planted in the same field in alternating strips of the two species, whereby the growing periods overlap for a limited period of co-growth. Intercropping legumes with cereals are the most common type of relay-intercropping in China, amongst which maize-soybean relay-intercropping system is the most prevalent relay-intercropping system, especially where the growing season is too short for double cropping. In the maize-soybean relay-intercropping system, soybean is sown sixty-five days after the sowing of maize, and the taller maize plants shade the soybeans, especially during their co-growth phase from germination to flowering, which substantially decreases the final yield of soybean plants under this system. Moreover, there exists leaf redundancy for maize in intercropping systems, and the top canopy leaves shade more competent leaves at the middle strata leaves of maize plants, which significantly reduce the maize seed yield under this system. However, judicious defoliation of maize plants in MSR could help to alleviate this problem to improve the growth, dry matter production, nutrient uptake and yields of intercrop species (maize and soybean) under this system.
Therefore, this study was initiated to elucidate the effects of leaf defoliation treatments from the top of maize plants in maize-soybean relay-intercropping system to fully clarify the needs and balance of light environment of intercrop species in maize-soybean relay-intercropping system under the field conditions. This field study employed six treatments: two sole crops viz. sole soybean (SS) and sole maize (SM), and four-leaf defoliation treatments viz. no defoliation from maize plants (R0), defoliation of two leaves from maize top (R2), defoliation of four leaves from maize top (R4), and defoliation of six leaves from maize top (R6). Defoliation treatments were applied to maize at the silking stage (86 days after sowing) when soybean was at the first trifoliate stage (21 days after sowing) by cutting different number leaves from the top of maize plant in maize-soybean relay-intercropping system to improve the light environment of intercrop species. This thesis aims to explain and quantify the defoliation effects on maize and soybean growth and development in MSR and to develop the new agronomic practice for increasing maize and soybean yields under this system, especially under the low sunlight regions such as Sichuan.
Results showed that as compared to R0, treatment R6 increased the photosynthetically active radiation-transmittance (PART) and red to far-red ratio (R: FR) of soybean canopy by 77% and 37%, 70% and 34%, and 41% and 36% at 20, 40, and 60 days after sowing (DAS), respectively. This improved light environment in R6 considerably enhanced the chlorophyll content and photosynthetic rate of soybean plants, especially during the co-growth period. Relative to control (R0), at 90 DAS, defoliation treatment R6 increased the leaf area index (by 37%), stem diameter (by 36%) and stem breaking strength (by 53%) but decreased the plant height (by 20%) and lodging rate (by 83%). Our findings implied that by maintaining the optimum level of PART (from 60% to 80%) and R: FR ratio (0.9 to 1.1), we could improve morphological and photosynthetic characteristics of soybean plants in maize-soybean relay-intercropping system.
Besides, defoliation treatments are beneficial to increase the flower-number and the pod-number in the maize-soybean relay-intercropping system. Furthermore, in this study, we reveal that leaf-defoliation from maize-canopy improves the PART and dry-matter production of soybean (especially during the co-growth phase). At 90 DAS, the dry-matter of pods and seeds was increased by 25% and 32%, respectively, under R6 than R0. Importantly, enhanced PART and dry-matter production (DMP) under R6 enabled soybean to initiate a greater number of flowers 182.2 plant-1 compared to 142.7 plant-1 under R0, and it also decreased the flower-abscission (by 13%, from 54.9% under R0 to 47.6% under R6). These positive responses increased the pod-number by 49% and seed-number by 28% under R6 than R0.
Moreover, defoliation treatments are beneficial to improve the uptake and distribution of major nutrients in various crop organs in the maize-soybean relay-intercropping system. In this study, R2 defoliation-treatment was the only treatment that increased the nutrient uptake in both maize and soybean under maize-soybean relay-intercropping system. At maturity, compared to R0, treatment R2 improved the uptake of nitrogen (N), phosphorus (P), and potassium (K) in each plant part of maize by 23, 12, and 11 % (grain), 22, 19, and 13 % (straw), and 28, 14, and 18 % (root), respectively, and it also enhanced the uptake of N, P, and K in each plant part of soybean by 5, 5, and 10 % (grain), 10, 17, and 13 % (straw), and 14, 11, and 11% (root), respectively. On average, over two years, under R2, relay-cropped maize obtained 107% of the sole-yield, and relay-cropped soybean obtained 65% of the sole-yield. The R2 defoliation treatment also achieved the highest land equivalent ratio of 1.69 and 1.77, with a net profit of 1301.6 $ ha-1 and 1293.4 $ ha-1 in 2017 and 2018, respectively. In conclusion, following the optimum defoliation treatment of maize in maize-soybean intercrops, i.e., defoliation of the topmost two-leaves, the photosynthesis, dry matter production and seed yields of intercrop species can be increased, and the nutrient uptake and its partitioning over plant organs be better balanced.
Optimum defoliation, therefore, enhances the productivity of the maize-soybean intercropping system, especially in low sunlight conditions. Furthermore, the effects of four-leaf defoliation treatments on light interception, leaf area index (LAI), photosynthetic characteristics, total biomass accumulation at blistering stage (BS), dough stage (DS), and physiological maturity (PM), and seed yield of maize were investigated through field experiments for two-years under maize-soybean relay-intercropping system and sole cropping system. This study aimed to determine the optimum leaf area of maize plants under maize-soybean relay-intercropping system and SM. Results showed that, under MSR and SM, as compared to control (R0), optimum defoliation of leaves (R2) from the top of maize plants significantly improved the light interception (by 25%, 18%, and 16% at BS, DS, and PM, respectively) to lower strata leaves and accelerated the biomass partitioning to maize seeds (by 13% and 12% at DS, and PM, respectively). Importantly, plants under R2 exhibited higher green leaf area than control, i.e., defoliation the top two leaves led to an increase in LAI at PM by 10%, suggesting that leaf senescence under R2 was delayed which enhanced the photosynthetic rate at PM by 7% in 2017 and 6% in 2018. Relative to R0, maize under R2 produced 19% and 13% higher maize yield under maize-soybean relay-intercropping system and sole maize, respectively, and relay-cropped maize had 90% of sole maize seed yield.
Overall, these results suggest that by manipulating the canopy structure of maize plants, we can enhance the biomass accumulation and seed yield of maize crops under the MSR and sole cropping system. Overall, this thesis studied the effects of leaf defoliation treatments from maize top on the growth and productivity of maize-soybean relay-intercropping at organ, plant, and cropping system level, and also assessed its contribution to grain production and sustainability. The findings suggest that optimum defoliation of leaves from maize top provides opportunities to increase maize and soybean seed yields under maize-soybean relay-intercropping system, especially under the low sunlight regions, i.e., Sichuan. Furthermore, our results provide a new insight to breeders to develop maize varieties with smaller top leaves. And they also inform farmers to adopt this new agronomic practice to increase their maize yield and income by manipulating crop canopies; for instance, chemicals can be developed to optimize plant growth at the appropriate time.
Finally, the historic component of this dissertation heightens the need for studying the effects of different light conditions on maize and soybean growth and development in maize-soybean relay-intercropping system. Future studies are needed to improve the light environment of intercrop species for the sustainability of this system, especially under the low sunlight regions.
... Partly removing leaves is a practical agronomic approach to change the maize canopy structure, which significantly improves the nutrient uptake and maximise the grain yield of maize plants (Zhu et al., 2004;Gambín et al., 2006;Ma et al., 2008;Raza et al., 2019d). However, the grain yield response to leaf defoliation treatments differs significantly between two, four and six-leaf removal treatments while the impact (positive or negative) of leaf defoliation levels on the crop growth and grain yield, depends on the intensity and timing of leaf defoliation (Ruiz-r et al., 2008). Optimum defoliation of the upper leaves of the maize plant (defoliation of two leaves) can improve the light environment within the maize canopy (Jun et al., 2017), delay the leaf senescence and increase the net photosynthetic rate of the flag leaves (Hao et al., 2010). ...
Upper canopy leaves of maize decrease the light-transmittance at middle-strata-leaves of maize and soybean canopy in maize-soybean relay-intercropping systems (MS). This affects the uptake of nutrients and distribution patterns in various plant organs of intercrop species in MS. Judicious defoliation of maize plants in MS could help to alleviate this problem and improve nutrient uptake and intercrop yields. In a two-year field experiment with MS, including the measurements of biomass production, nutrients uptake, and distribution at the organ level, and grain yields of intercrop species, maize plants were subjected to four-leaf defoliation treatments to improve the light-transmittance of maize and soybean plants. Defoliation of the topmost two-leaves (T 2), four-leaves (T 4), six-leaves (T 6) was compared to no defoliation (T 0). Compared to T 0 , treatment T 2 improved the uptake of nitrogen (N), phosphorus (P), and potassium (K) in each plant part of maize by 23, 12, and 11% (grain), 22, 19, and 13% (straw), and 28, 14, and 18% (root), respectively. Defoliation also enhanced the uptake of N, P, and K in each plant part of soybean by 5, 5, and 10% (grain), 10, 17, and 13% (straw), and 14, 11, and 11% (root), respectively. The improved nutrient uptake in T 2 increased the total biomass and its distribution in the root, straw, and grain of soybean and maize by 15 and 13%, and 21 and 15%, 20 and 14%, 7 and 10%, respectively compared to T 0. On average, over two years, under T 2 , relay-cropped maize obtained 107% of the sole-yield, and relay-cropped soybean obtained 65% of the sole-yield. The T 2 defoliation treatment also achieved the highest land equivalent ratio of 1.69 and 1.77, with a net profit of 1301.6 $ ha −1 and 1293.4 $ ha −1 in 2017 and 2018, respectively. Following the optimum defoliation treatment of maize in maize-soybean intercrops, i.e., defoliation of the topmost two-leaves, the nutrient uptake can be increased, and the nutrient partitioning over plant organs be better balanced. Optimum defoliation, therefore, enhances the productivity of maize-soybean intercropping systems.
... where in formula (1) subscript x represents ramet height (H) or aboveground biomass of ramet (AB), and T refers to the number of days after clipping in mid-June until the end of August. In formula (2) (Ruiz-R, Ward, & Saltz, 2008), the remaining height of ramet in unclipped treatment was the actual height measured in June because it was not clipped in that time (i.e., the removal height is equal to zero). ...
Plants' pattern of compensatory growth is often used to intuitively estimate their grazing tolerance. However, this tolerance is sometimes measured by the overall grazing tolerance index (overall GTI), which assumes that tolerance is a multivariate linear function of various underlying mechanisms. Because the interaction among mechanisms is not independent, the grazing tolerance expression based on overall GTI may be inconsistent with that based on compensatory growth. Through a manipulative field experiment from 2007 to 2012, we measured the responses of 12 traits of Elymus nutans to clipping under different resource availabilities in an alpine meadow and explored the compensatory aboveground biomass and the overall GTI to assess the possible differences between the two expressions of tolerance. Our results showed that these two expressions of tolerance were completely opposite. The expression based on overall GTI was over‐compensatory and did not vary with clipping and resource availability, while the expression based on compensatory aboveground biomass was under‐compensatory and altered to over‐compensation after fertilization. The over‐expression of highly variable traits with extremely high negative mean GTI to defoliation damage, the influence of random errors contained in traits considered, and the doubling weight of functional redundant traits greatly inflated the overall GTI, which leads to the inconsistency of the two tolerance expressions. This inconsistency is also associated with the different determining mechanisms of the two tolerance expressions. Our data suggest that plants' grazing tolerance is not a multivariate linear function of traits or mechanisms that determine grazing tolerance; the overall GTI is only a measure of traits' variability to defoliation damage. Our findings highlight that the tolerance of E. nutans mainly depends on the response of traits with lower variability to defoliation, and the overall GTI is not an ideal predictor for describing a single‐species tolerance to grazing.
... In addition to resource availability, plant defense strategies against herbivores can respond to different consumption levels. Indeed, herbivore intensity and duration modify plant defense responses, with some traits only being induced under high herbivory (e.g., secondary metabolites, mineral crystals; Vergés et al. 2008;Dostálek et al. 2016;Hartley et al. 2016), while others tend to be induced under moderate herbivory (e.g., compensatory growth; Ruiz-R et al. 2008;Vergés et al. 2008;Sanmartí et al. 2014). Therefore, increased resource availability (when limiting resources are considered) could minimize the costs of defense under different levels of herbivory pressure. ...
Numerous hypotheses have been posited to explain the observed variation in plant defense strategies against herbivory. Under resource-rich environments, plants are predicted to increase their tolerance (limiting resource model; LRM) and, while the resource availability hypothesis (RAH) predicts a decrease in constitutive resistance in plant species growing in resource-rich environments, at the intraspecific level, plants are predicted to follow an opposite pattern (intraspecific RAH). Furthermore, the effect of multiple factors in modulating plant defense strategies has been scarcely explored and is more difficult to predict. Our aim was to understand how plant defense traits respond to herbivory, resource availability and their interactions, and to assess the effects on plant palatability. To this end, we performed an in situ factorial experiment at two sites simulating three herbivory levels and two nutrient availability conditions with the seagrass Posidonia oceanica. Additionally, we performed a series of feeding experiments with its two main herbivores. While plants decreased their constitutive resistance under nutrient fertilization (contrary to intraspecific RAH but in accordance to the RAH), and did not increase allocation to tolerance (likely due to resource limitation, LRM), simulated herbivory induced resistance traits. However, we found no interactive effects of nutrient fertilization and herbivory simulation on plant defense. Both herbivores responded similarly to changes in plant palatability, strongly preferring nutrient-enriched plants and non-clipped plants. This work highlights the need to better understand the drivers of plant defense intraspecific variability in response to resources, particularly in habitat-forming species where changes in plant traits and abundance will cascade onto associated species.
... When plants are injured after artificial defoliation, eaten by animals or pests, the leaf area decrease thereafter [13,14], however residual organs have a compensating effect when the photosynthetic organs injured above a certain threshold level [15,16]. The effect (negative, positive, or zero) of source-reducing on plants growth depends on the frequency and intensity of defoliation [17]. Liu et al. [12] has demonstrated that defoliation above the cob decreased leaf area index significantly, whereas it markedly improved light condition within the canopy. ...
... In our study, S 2 enhanced the light transmission rate of both ear and bottom layers (Fig. 1), which enabled the leaves in lower canopy to obtain more light energy and achieve a higher grain yield ultimately [31]. Although LAI decreased (Table 2), Chl content and net photosynthetic rate of ear leaf were enhanced after two leaves removal [12], which may account to the positive compensatory effect of plants [17]. On the contrary, a higher amount of leaf removal (S 4 ) resulted in a significant decrease in grain yield compared to the control, which might be due to the insufficient sources to favor the formation of assimilates after four leaves removal. ...
Background
Under high plant density, intensifying competition among individual plants led to overconsumption of energy and nutrients and resulted in an almost dark condition in the lower strata of the canopy, which suppressed the photosynthetic potential of the shaded leaves. Leaf removal could help to ameliorate this problem and increase crop yields. To reveal the mechanism of leaf removal in maize, tandem mass tags label-based quantitative analysis coupled with liquid chromatography–tandem mass spectrometry were used to capture the differential protein expression profiles of maize subjected to the removal of the two uppermost leaves (S2), the four uppermost leaves (S4), and with no leaf removal as control (S0).
Results
Excising leaves strengthened the light transmission rate of the canopy and increased the content of malondialdehyde, whereas decreased the activities of superoxide dismutase and peroxidase. Two leaves removal increased the photosynthetic capacity of ear leaves and the grain yield significantly, whereas S4 decreased the yield markedly. Besides, 239 up-accumulated proteins and 99 down-accumulated proteins were identified between S2 and S0, which were strongly enriched into 30 and 23 functional groups; 71 increased proteins and 42 decreased proteins were identified between S4 and S0, which were strongly enriched into 22 and 23 functional groups, for increased and decreased proteins, respectively.
Conclusions
Different defoliation levels had contrastive effects on maize. The canopy light transmission rate was strengthened and proteins related to photosynthetic electron-transfer reaction were up-regulated significantly for treatment S2, which improved the leaf photosynthetic capacity, and obtained a higher grain yield consequently. In contrast, S4 decreased the grain yield and increased the expressions of proteins and genes associated with fatty acid metabolism. Besides, both S2 and S4 exaggerated the defensive response of maize in physiological and proteomic level. Although further studies are required, the results in our study provide new insights to the further improvement in maize grain yield by leaf removal.
Electronic supplementary material
The online version of this article (10.1186/s12870-018-1607-8) contains supplementary material, which is available to authorized users.
... Previous studies widely approved that the compensatory growth occurred only in resourcerich environments [43][44][45][46][47][48]. A few studies have reported that defoliation duration plays a much more important role than resources in modulating compensatory growth at a relatively low intensity of defoliation; however, at high defoliation intensities resource availability does more [48,49]. ...
Fertilizer with different ratios of nitrogen (N) to phosphorus (P) can influence crop plant performance and defense against herbivores. Spodoptera exigua is an important agricultural pest that has caused serious economic loss, especially in recent decades. In the present study, we explored effects of different intensities and durations of S. exigua herbivory on host plant biomass and on S. exigua enzyme activities in response to five fertilizer treatments with different N: P ratios of 1: 5, 1: 3, 1: 1, 3: 1 and 5: 1. The results showed that fertilizer type can significantly influence interactions between caterpillars and its hosts. Compensatory growth of leaf biomass was detected under fertilizer with N: P = 3: 1. Fertilizer with a higher proportion of N appears to maintain stem biomass in defoliated seedlings similar to controls that are not exposed to herbivory. There was no significant difference in root biomass under most conditions. High proportion of N also enhanced the activity of two antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD) in low density of beet armyworm. However, with increased herbivorous intensity, a higher proportion of P played a more important role in increasing the activities of CAT and SOD. Higher P likely enhanced acetylcholine esterase (AChE) activity at lower degrees of defoliation, but a higher N proportion resulted in higher AChE activity at higher degrees of defoliation. Higher N proportion contributed to reduced carboxylesterase (CarE) activity at high intensity, short-term defoliation. However, when defoliation intensity increased, the difference in CarE activity between fertilizer categories was little. The study explored the interaction between the damage of S. exigua and the biomass accumulation of its host plant Brassica rapa, and the influence of the N/P ratio in plant fertilizer on this interaction. Systematic analysis was provided on the biomass of B. rapa and the activity of metabolic enzymes of S. exigua under different treatments.
