Assessment of cell membrance leakage by electrolyte efflux at various temperatures in germinating rice seeds

The data on germination % upto 96 h show that there were significant differences among the varieties. About 77 to 100% of seeds were germinated. At the high temperature stress majority of the seeds geminated upto 40 degree C however, in response to further increase in temperature no germination was observed. The optimum temperature was 35 degree C. At this temperature all cultivars except Shadab performed better. However Cv. Shadab produced highest shoot length at 30 degree C. At 40 degree C lesser shoot length in all cultivars was recorded. There was no shoot growth at 24 h. The root length was faster after 48 h growth period. The fastest growth rate was observed between 48 to 72 h in all cultivars. The temperature range of 30-35 degree C was the most suitable in term of seedling growth in all cultivars. The ion efflux increased with the increase in the temperature in all the five cultivars studied. However, at 40 degree C maximum and at 30 degree C min ion efflux from the shoots was observed in all cultivars. The pattern of ion efflux in response to temperature was almost similar as compared to that of shoot i.e. as the temperature increases so the ion efflux increased. Similarly the lowest EC was recorded at lowest temperature i.e. 30 degree C. Further increase in temperature (40 degree C and above) resulted in highest ion efflux. At 50 degree C all the cultivars except Shua-92 effluxed 90% of their total electrolytes while, Cv Shua-92 appeared to be slightly heat tolerant and efuxed only 72.34% of its total electrolytes. The highest moisture content (M.C) was in the Cv. Shadab (13.65%) while lowest moisture content was in Cv. Shua-92 i.e. 11.6%. As regards the relative water contents (R.W.C) of seeds, Cv. IRRI-6 exhibited the highest R.W.C (43.15%), while it was lowest in Cv. Shua (34.01%). It was concluded that the temperature range between 30-35 degree C is found to be optimal for rice. The temperature above this range appears to be harmful in terms of germination of seeds and early growth of seedlings.