Submergence stress in plants: molecular mechanisms, physiological changes, and adaptive responses

Among abiotic stresses faced by plants, submergence or flooding is a significant factor that limits plant growth and yield. The partial or complete submergence leads to hypoxic conditions that severely restrict the growth of the plants. To survive under the stress, plants employ adaptive strategies like the escape mechanism, where they grow rapidly to rise above the water, or the quiescent strategy, conserving resources until stress conditions improve. The plant undergoes numerous biochemical, molecular, and morphological changes under submergence stress, including alterations in photosynthesis, nutrient uptake, ionic balance, and gene expression, particularly in the group of hypoxia-responsive genes. The plant responds to this stress by modulating a variety of biochemical pathways, including the N-degron pathway, trehalose synthesis pathways, and carbohydrate sensing. The state-of-the-art genetic engineering techniques (GE) can be the way out from this stress, but due to the multigenic reaction from the plant towards the stress, the direct pathway that makes plant submergence tolerant is still unknown and needs to be explored. Moreover, the review considers the known molecular changes that can enhance submergence tolerance in economically important crops, which could help improve agricultural resilience in flood-prone regions.