Physiological and Morphological Responses of Soybean to Water Stress and Rehydration: Implications for Growth, Seed Yield and Quality

ABSTRACT Rapid stomatal regulation is an early response associated with improved maintenance of leaf water status and post‐stress recovery in soybean, but it cannot fully offset the detrimental effects of severe drought on seed production. This study evaluated the physiological and morphological responses of soybean genotypes to progressive water stress and subsequent rehydration imposed at different growth stages under controlled‐environment conditions. Water stress rapidly reduced stomatal conductance, which was associated with improved maintenance of leaf water content and partial recovery following rehydration. Rehydration after severe water stress, except when imposed at pod set, partially compensated for yield losses by prolonging vegetative and reproductive growth and delaying maturity. However, severe drought during flowering and pod set caused substantial reductions in seed yield, with losses of up to 82% relative to the control. The soybean genotypes did not accelerate seed filling under water stress, indicating limited drought‐escape capacity. These findings demonstrate that drought timing is a major determinant of recovery and yield loss, highlighting the importance of traits associated with stomatal regulation, recovery following rehydration and yield stability for improving drought resilience in soybean breeding.