Molecular and Physiological Mechanisms Underlying Submerged Germination in Rice

Submergence during germination (SG) is a major constraint during sowing, severely limiting the promotion and application of direct-seeded rice. Recent studies have revealed the adaptive mechanisms by which rice responds to SG. At the physiological level, flood-tolerant varieties effectively maintain energy supply and cellular homeostasis by enhancing amylase activity, improving glycolysis and ethanolic fermentation efficiency, promoting embryo sheath elongation, and activating antioxidant enzyme systems; at the molecular level, multiple key genes and signalling pathways have been identified, including SUB1A, OsTPP7, OsGF14h, etc., participating in hypoxia perception, metabolic reprogramming, and hormone signal integration to regulate SG under flooding. In addition, the interactions among plant hormones, such as ethylene, gibberellin, abscisic acid, and cytokinin, also play key roles in the SG process. Future research should prioritize breeding strategies that pyramid multiple genes by integrating gene editing, whole-genome selection, and high-throughput phenotyping to improve seed germination under flood stress.