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.