Acclimation strategy and plasticity of different soybean genotypes in intercropping

Abstract

In response to shading, plant leaves acclimate through a range of morphological, physiological and biochemical changes. Plants produce a myriad of structurally and functionally diverse metabolites that play many important roles in plant response to continually changing environmental conditions as well as abiotic and biotic stresses. To develop a clearer understanding of the effects of shade on soybeans at different growth stages, a comprehensive, three-year, stage-wise study was conducted. Leaf area, leaf thickness, stem diameter, chlorophyll contents, photosynthetic characteristics and other morphological and physiological features were measured along with biochemical assays for antioxidants such as superoxide dismutase, peroxidase and caralase and yield attributes of different soybean genotypes (Guixia 2, Nandou12, Nandong Kang-22, E61 and C103) under shading nets with 50% light transmittance. It was observed that early shading (VER1 and VER2) significantly decreased main stem length and main stem length/stem diameter. Later shading (R1R8 and R2R8) had significant effects on morphological characters such as branch number and pod height. In Nandou 12, the protein contents in plants shaded at R1R8, R2R8 and R5R8 were 9.20, 8.98 and 6.23% higher than in plants grown under normal light levels (CK), respectively, and the crude fat content was 9.31, 10.74 and 4.28% lower. The influence of shading in the later period on anatomy was greater than that in the earlier period. Shading reduced the light saturation point (LSP), the light compensation point (LCP) and the maximum photosynthetic rate (Pnmax), and increased the apparent quantum yield (AQ). Shading also increased the antioxidant enzyme activity in the plants, and this increase was greater with early shading than late. The variability in the chlorophyll (a + b) content and the chlorophyll a/b ratio in R2 stage plants was less than in R5 stage (VER5) plants. Similarly, the activity of antioxidant enzymes in R2 after returning the plants to normal light levels (VER2) was lower than in R5 after relighting (VER5). Compared with later shading, the early shading had a greater effect on the photosynthetic and related characteristics. The longer the shading time, the greater the adverse effects and the less able the plants’ were to recover. The data collected in this study contribute to an understanding of the physiological mechanisms underlying the early and late growth stage acclimation strategies in different soybean genotypes subjected to shade stress.

Shade-Tolerant Soybean Reduces Yield Loss by Regulating Its Canopy Structure and Stem Characteristics in the Maize–Soybean Strip Intercropping System

“…Intercropping of maize ( Zea mays L.) and soybean ( Glycine max L.) has been practiced on a large scale in the world, especially in China ( Du et al, 2018 ; Iqbal et al, 2019 ). This planting pattern can harvest an extra-season of soybean seeds without reducing the yield or slightly reducing the yield of maize ( Hussain et al, 2020a ). However, soybean plants suffer severe shading stress from maize during the intergrowth in maize–soybean intercropping systems ( Zhou et al, 2019a , b ; Hussain et al, 2020b ), which reduces the red-to-far-red ratio of light inside the soybean canopy ( Yang et al, 2014 , 2020 ; Fan et al, 2018 ).…”

Response characteristics of highland barley under freeze-thaw, drought and artemisinin stresses

“…Compared with the CK group, the decrease of the net photosynthetic rate of the A group was due to the allelopathy of artemisinin which inhibited photosynthesis, and the reason may be that artemisinin inhibited the synthesis of chlorophyll in highland barley [ 24 ]. The net photosynthetic rate of the D and D + A groups was lower than the CK group’s, and it was probably because that the drought stress decreased the contents of the chlorophyll a, b, and total chlorophyll [ 25 , 26 ]. The FT1 ~ 3 groups decreased by 61, 72, and 65%, respectively, indicating that low temperature had a stronger effect on plant photosynthesis, especially sub-zero temperature.…”

Effect of simultaneous shade and drought stress on morphology, leaf gas exchange, and yield parameters of different soybean cultivars

“…Plants alter their photosynthetic characteristics to acclimate to various environmental conditions (Hussain et al 2020c). Drought stress is reported to negatively affect the leaf gas-exchange parameters under full light as well as shade conditions (Chaves et al 2009, Duan et al 2009, Li et al 2011.…”