Seed growth and nitrogen partitioning of soybean under water stress.

摘要

The purpose of this study was to investigate seed growth of soybean [ Glycine max (L.) Merr.] Plant Introduction 416937 (PI) and the relationship of nitrogen accumulation and drought adaptation of PI during pod-filling stage under moderate-to-severe water stress. This objective was achieved under both the field condition and the phytotron controlled condition, using analysis of variance, longitudinal data analysis, and nonlinear regression technique.; PI had a relatively lower yield under well-watered condition in contrast to the cultivar Holladay, but higher yield under moderate-to-severe water-stressed condition. PI produced larger biomass, and partitioned more biomass to leaves and roots under both water conditions. PI had a lower specific leaf area, which might be a mechanism for stress adaptation, in addition to the strong root system and nodule function of PI under water-stressed condition.; Pod wall mass accumulation continued to mid-R5, and decreased after late R5 under water stress. PI had relatively larger proportion of pod wall mass, in contrast to Holladay. Since water stress had little effect on pod wall, pod number, and seed number during pod-filling stage, yield stress reduction was primarily through the effect of the stress on individual seed mass. Individual seed growth of PI was less sensitive to the stress than that of Holladay. PI had significantly larger maximum seed growth, larger relative growth rate, and a longer growth period under water stress. Genotypic difference for leaf stomatal resistance was found with much lower resistance for PI under water stress.; PI accumulated more N in whole plants, leaves, and seed, especially for plants pretreated with high N solution during the early vegetative growth, during the entire season. Among the N accumulated in seed, both a smaller amount and lesser proportion was derived from N remobilization from PI leaves than from Holladay leaves, especially for plants pretreated with high N solution and under water stress. The remobilized N from PI leaves to seed also accounted for lesser proportion of N accumulation in leaves at the beginning R5.; PI adaptation of water stress undoubtedly is related to a mix of morphological and physiological features. This study strongly suggests that PI stress adaptation be related to high N accumulated in leaves before R5 and a reduced capacity of N remobilization from leaves to seed during R5 under water stress. As a result, PI can maintain stronger leaf function and lower stomatal resistance and fix more nitrogen for seed formation. Thus, PI has a higher growth rate and a longer growth period under water stress.