Physiological and Biochemical Basis of Stress Tolerance in Soybean

Abstract

Soybean is considered as a species sensitive to several abiotic stresses, such as drought, salinity, and waterlogging, when compared with other legumes, and these abiotic stresses have a negative effect on soybean plants’ growth and crop productivity. Clearing the conception on the physiological and biochemical responses to drought is essential for an overall understanding of the mechanism of plant resistance to water-restricted conditions and for developing drought resistance screening techniques that can be used for plant breeding. Plants can adapt in response to water scarcity situations by altering cell metabolism and activating various defense mechanisms. Higher salt tolerance in resistant soybean genotypes was associated with better water relation, salt dilution by juiciness, and better osmotic adaptation with an accumulation of more amino acids, sugars, and proline. In addition, less damaging chlorophylls, higher photosynthetic efficiency and cell membrane stability, and higher calcium content contributed to the higher salt tolerance of soybean genotypes. Plants adapted to flooded conditions have mechanisms to cope with this stress. Aerenchyma formation increased availability of soluble carbohydrates, greater activity of glycolytic pathways and fermenting enzymes, and involvement of antioxidant defense mechanisms to cope with post-hypoxic/post-anoxic oxidative stress. Ethylene, a gaseous plant hormone, plays an important role in altering a plant’s response to oxygen deficiency.