Salinity Results in Polyamine Accumulation in Early Rice (Oryza sativa L.). Seedlings

Saline (NaCl) stress in germinated seedlings of rice cv. Rupsail causes an increase in polyamine content and concomitantly an enhancement of arginine decarboxylase (ADC) activity; in the case of putrescine, the increase is 100%. The responsiveness of coleoptiles and roots is different; ADC activity is maximum in roots and coleoptiles at 50 mM and 100 mM respectively. Difluoromethyl arginine, a potent inhibitor of ADC, reduces both polyamine accumulation and ADC activity. NaCl can enhance the activity of ADC by 1.6-fold in vitro. [14C]leucine incorporation into protein at 400 mM NaCl is decreased 4- and 10-fold in coleoptiles and roots, respectively. Efflux of sugar, amino acid, polyamines and total electrolytes increased gradually with the increase in concentration of salt. Influx of Na+ and Cl- and efflux of K+ in coleoptiles and roots are directly proportional to the concentration of NaCl applied.