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.

Soybean production under maize–soybean relay-intercropping system (MSICS) is vulnerable to shading. A study was initiated to investigate the effects of three sowing-times: ST₁, 90; ST₂, 70; and ST₃, 50 days of co-growth period and two phosphorus-rates: P₀, 0; and P₆₀, 60 kg P ha⁻¹ on soybean under MSICS. Results revealed that ST₃ significantly increased the photosynthetically active radiations, leaf area index, and photosynthetic rate by 72% and 58%, and 61% and 38%, and 6% and 8%, respectively, at full-flowering and full-pod stage of soybean than ST₁. Treatment ST₃, increased the total dry-matter (TDM) and the highest TDM was reached at full-seed (R₆) stage. Similarly, ST₃ considerably increased the dry-matter partitioning to pods and seeds, relative to ST₁, soybean under ST₃ at R₆ had 35% and 30% higher pod and seed dry-matter, respectively. Moreover, ST₃ exhibited the maximum seed-yield (mean 1829.5 kg ha⁻¹) for both years of this study. Soybean under ST₃ with P₆₀ accumulated 38% higher P, and increased the P content in pods and seeds by 36% and 33%, respectively at R₆ than ST₁. These results imply that by selecting the appropriate sowing-time and phosphorus-rate for soybean, we can increase the TDM and seed-yield of soybean under MSICS.

Oilseeds yield response to sulphur (S) has been well investigated but the dynamics of total biomass accumulation (TBA) and partitioning by sesame plants in response to S are not well understood. This study was initiated to investigate the effects of S on sesame, in which four sesame varieties V_1, SG-27; V_2, SG-30; V_3, SG-36; V_4, SG-51 and four S treatments T₁, 20; T₂, 30; T₃, 40; T₄, 50 kg ha⁻¹ were used. Results revealed that the leaf area index and photosynthetic rate of sesame varieties were significantly higher under T₃ with V₃. Similarly, S fertilization considerably increased the TBA and maximum TBA was reached at late-flowering with V₃ in T₃. Relative to T₁, plants in T₃ had 33 and 23% higher capsule and seed biomass, respectively. Furthermore, total S accumulation and distribution in different plant organs changed with growth stage, at pre-flowering and mid-flowering stage maximum S was found in the stem, whereas at late-flowering and full-maturity stage highest S was recorded in reproductive parts. These results implied that S fertilizers should be applied to agricultural fields to improve oilseed production and by selecting the appropriate and area-specific genotype we can increase sesame seed yield under rainfed conditions.

Salinity is a major abiotic stress which limits crop production, especially under rainfed conditions. Selenium (Se), as an important micronutrient, plays a vital role in mitigating detrimental effects of different abiotic stresses. The objective of this research was to examine the effect of Se fertilization on black gram (Vigna mungo) under salt stress. Our results showed that salt stress (100 mM NaCl) in leaves significantly induced oxidative damage and caused a decline in relative water content, chlorophyll (Chl), stomatal conductance (gs), photochemical efficiency (Fv/Fm), sucrose, and reducing sugars. A low dose of Se (1.5 ppm) significantly reduced hydrogen peroxide content, malondialdehyde formation, cell membrane damage, and also improved antioxidative enzyme activities, including superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione peroxidase under salt stress. Se-treated plants exhibited higher Chl, gs, Fv/Fm, sucrose, and reducing sugars than untreated plants in response to salt stress. In addition, Se application enhanced Se uptake and reduced Na⁺ uptake, but Cl⁻ remained unaffected. Our results indicated that a low dose of Se effectively alleviated salt damage via inhibition of Na⁺ uptake and enhanced antioxidant defense resulting in a significant decrease in oxidative damage, and maintained gaseous exchange and PS II function for sucrose and reducing sugars accumulation in black gram.