Interactive effect of NaCl salinity and gibberellic acid on shoot growth, content of abscisic acid and gibberellin-like substances and yield of rice (Oryza sativa L. var GR-3)

Abstract

When rice (Oryza sativa L. var GR-3) plants were subjected to salt stress (12 dS/m) the extension growth and dry weight of the shoot system as well as the content of chlorophyll and gibberellin-like substances were found to be markedly reduced. Contrarily, the level of abscisic acid in the shoot system registered a rapid and massive increase in response to salinity. Compared to control, salt stressed plants showed higher concentration of Na+ and Cl− and lower concentration of K+ in the leaf tissue. Salinization also resulted in a considerable reduction in grain yield. Exogenous application of gibberellic acid (10 ppm) significantly increased the growth and yield of salt stressed plants. Gibberellic acid treatment reduced the net accumulation of Na+ and Cl− and maintained high level of K+ in the leaves of salinized plants. A significant fall in the content of abscisic acid and a marked increase in the amount of chlorophyll were also noticed in salinized plants in response to gibberellic acid administration. These results suggest that gibberellic acid improved the growth and yield of stressed rice plants presumably by hormonising the ionic status of the plants as well as by modulating the endogenous level of abscisic acid.