Saponin biopriming positively stimulates antioxidants defense, osmolytes metabolism and ionic status to confer salt stress tolerance in soybean

Salinity is a deleterious factor that hinders plant production across the globe. Salinity reduces irrigation water quality. Plant tolerance to salinity stress requires sophisticated adaptation at the physiological level and in metabolic pathways. Experiments were set up to investigate saponin priming impact on the antioxidant metabolism and growth of soybean cultivated under salt stress. Two concentrations of saponin, i.e., 5 and 10% were used for priming the seeds. Seed priming at 5% effectively mitigated salinity stress mediating decline in growth and chlorophyll synthesis. Saponin (5%) improved chlorophyll and carotenoid synthesis significantly and ameliorated the adverse effects of NaCl. Soybean seedlings primed with 5% saponin exhibited the greater antioxidant enzyme activities and the biosynthesis of glutathione and ascorbic acid. Increased antioxidant metabolism of primed seedlings accompanied by the reduced rate of lipid peroxidation and increased membrane stability index. Additionally, saponin priming effectively augmented the relative water content of salt-stressed seedlings by improving the biosynthesis of proline, sugars, and glycine betaine. In conclusion, saponin priming (5%) proved beneficial through modulation of the antioxidant system, osmolytes metabolism, and the significant reduction in sodium-ion accumulation.