Polyamines in various rice (Oryza sativa) genotypes with respect to sodium chloride salinity

Physiological responses of various rice genotypes were studied in relation to salt (NaCl) stress. Cultivars CSR‐1 and Dular germinated well in different NaCl regimes compared to cvs Rupsail, Assam Getu and M‐1–48. At 100 mM NaCl, the lowest germination was observed in cv. M‐1–48. Cvs CSR‐1 and Dular were relatively effective in maintaining high concentrations of polyamines as well as arginine decarboxylase (EC 4.1.1.19) activity in coleoptiles and roots in a non‐stressed condition. The activities of two biodegradative enzymes, diamine oxidase (EC 1.4.3.6) and polyamine oxidase (EC 1.4.3.4), were lowest in cv. CSR‐1. The polyamine content was not significantly altered when seedlings of cv. CSR‐1 were exposed to 100 mM NaCl. However, in cv. M‐1–48 enhancement of arginine decarboxylase activity with concomitant accumulation of polyamines was observed. Leakage of metabolites and changes in the levels of Na+ and Cl− were prominent in cv. M‐1–48 under saline conditions. The results suggest a correlation between polyamine and salt stress‐induced responses in rice genotypes.