Salinity Induced Accumulation of Free Amino Acids in Germinating Rice Seeds Differing in Salt Tolerance

Metabolic status of total and individual free amino acids were studied in endosperms and embryoaxes of four rice cultivars differing in salt tolerance, growing under increasing levels of saline stress. At all saline treatment levels and in controls salt tolerant cultivars had higher levels of total free amino acids in germinating seed parts than sensitives. Individual free amino acids which always maintained higher levels in germinating tolerant seeds over sensitives were aspartic acid, arginine, glycine and leucine. Salinity caused accumulation of free amino acids in germinating seed parts in all cultivars. Maximum accumulation was of arginine followed by leucine, alanine, valine, glutamine and proline. Individual amino acids accumulated greatly in tolerant cultivars than sensitives. Increased salinity caused decrease in the levels of aspartic acid, serine, glutamic acid, glycine, lysine and histidine in growing embryoaxes. Results suggest possible relationship between levels of free amino acids arginine, leucine, alanine, valine, glutamine and proline and degree of salt tolerance in rice. These all amino acids should be considered in combination as indices for salt tolerance in rice.