Synergistic effects of low IAA and GA concentrations promote dehiscence-zone separation in vegetable soybean

Pod dehiscence, also known as pod shattering, is the process by which mature pods open and release their seeds at physiological maturity. In vegetable soybean (Glycine max L.), premature seed release from mature pods is a major cause of yield loss during seed production. As pod dehiscence occurs within the dehiscence zone, understanding the physiological mechanisms governing its formation and degradation is essential. To investigate these mechanisms, we compared the activities of pectinase, polygalacturonase (PG), cellulase, indole-3-acetic acid (IAA), gibberellin (GA), abscisic acid (ABA) and zeatin (ZA) in the pod ventral sutures of dehiscent vegetable soybean and indehiscent grain soybeans. The ventral sutures of dehiscent vegetable soybean exhibited significantly higher activities of pectinase, polygalacturonase, and cellulase, but lower concentrations of IAA and GA than those of indehiscent grain soybean. Reduced levels of IAA and GA in the dehiscence zone were associated with increased activities of cellulase, pectinase, and polygalacturonase activities, which may accelerate cell wall degradation and promote lignification, thereby promoting pod dehiscence.