Improving amino acid composition of soybean under salt stress by salicylic acid and jasmonic acid

A greenhouse experiment with factorial arrangement based on randomized complete block design with four replications was conducted in 2015 to investigate the effects of salicylic acid (SA) (1 mM) and jasmonic acid (JA) (0.5 mM) on protein accumulation and amino acid composition of soybean seeds under different levels of salinity (0, 4, 7, and 10 dS/m NaCl, respectively). Treatment of SA improved protein percentage and per seed at different stages of seed development under all salinity levels. The highest protein yield was also recorded for SA treated plants, due to higher seed yield and protein content. In contrast, treatment with JA reduced seed protein content and yield as a result of reduction in seed yield. Lysine, methionine, phenylalanine, threonine, aspartic acid, glutamic acid, proline and tyrosine contents increased, but leucine and valine contents decreased with enhancing salinity. Foliar spray of SA improved isoleucine, leucine, lysine, methionine, valine, alanine, aspartic acid, glutamic acid, glycine and serine contents, but application of JA increased sulfur containing amino acids such as methionine and aromatic amino acids such as phenylalanine and tyrosine in soybean seeds. Treatment with SA had the greatest effect on enhancing protein quantity and quality under different levels of salinity.