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Effects of consecutive drought stress during adjacent growth stages on soybean morpho-physiological traits and yield
Abstract
Consecutive drought events spanning adjacent soybean growth stages compound physiological stress and intensify yield penalties. The experimental design involved applying varying drought intensities to two adjacent growth stages, achieved by employing pairwise combinations of the stages seedling (S1), branching (S2), flowering-podding (S3), and seed filling (S4), to assess their impact on soybean morphology and physiology. The results demonstrated that drought stress significantly reduced all parameters in treated groups compared to the normal irrigation group, with losses increasing with severity. Under drought stress, soybean exhibited maximal reductions in plant height (PH, 25.70%) and tap root length (TRL, 24.45%) at S1-S2, while the S2-S3 stage saw greatest decreases in primary branch number (PBN, 75.00%), root dry weight (RDW, 44.16%), and stem dry weight (SDW, 33.89%). The most severe impacts occurred at S3-S4, with grain yield (GY, 67.19%), total pod number (TPN, 49.82%), total seed number (TSN, 58.94%), and pod wall weight (PWW, 64.82%) showing maximal reductions, accompanied by the highest empty pod rate (EPR, 18.68%). Notably, GY showed strong positive correlations with RDW and pod traits (TPN, TSN, PWW), but negative correlation with EPR (p≤0.001). 63.2% of the total variance in soybean drought response traits was collectively captured by these parameters within the first principal component (PC1). Thus, targeted irrigation during the S3-S4 stage is essential for mitigating drought-induced yield losses in soybean
