Salinity–sodicity induced changes in reproductive physiology of rice ( Oryza sativa) under dense soil conditions

Abstract

Seed set in rice under salinity stress is a major problem caused by a number of factors. The most important factor which is not explored yet in rice under field conditions is stigma receptivity and grain filling against salinity–sodicity stress. We conducted experiments to study the effect of salinity–sodicity on stigma receptivity and grain filling of rice (of different tolerance limits against salinity alone) under field conditions along with other parameters at reproductive phase. Our results showed that viability of pollens was reduced in all the cultivars under salinity–sodicity stress showing significant effect in the salt sensitive Basmati cultivars. The starch synthase activity (∝1-4 glucan-glucosyle transferases, EC 2.4.1.21) was inhibited more significantly in sensitive than in tolerant cultivars. In tolerant rice cultivars the degree of inhibition on all the parameters studied was less, thus showing better grain yield compared to sensitive cultivars. Results regarding stigma receptivity revealed that salinity–sodicity reduced F1 seed set when pollinator plants were grown under dense saline-sodic soil and pistillate plants under control soil. More deleterious effects were observed when both the pollinator and pistillate plants were grown under dense saline-sodic soil conditions. This reduction was highly significant in fine Basmati cultivars due to significant effect on stigma receptivity and starch synthase activity. The data suggest that stigma receptivity is more detrimental for seed set compared to pollen viability and other physiological parameters under dense saline-sodic conditions. In this study KS-282 proved to be the best cultivar for dense saline-sodic soil showing non-significant effect of salinity–sodicity induced changes in all physiological and biochemical functions, pollen viability, stigma receptivity coupled with higher activity of starch synthase towards grain filling and seed set, resulting in higher grain yield compared to all the test cultivars.