Phenotypic differences in response to submergence in rainfed lowland rice

Phenotypic differences in response to snbmergence was studied in tolerant and intolerant rainfed lowland rice varieties. Increase in submergence duration, in general, induced shoot elongation, root porosity and decreased the plant survival, tiller number per plant and root and shoot dry weight. The survival was higher in tolerant varieties FR 13A (87%) and Vaidehi (80%) than in intolerant varieties Mahsuri (27%) and IR 42 (13%). Tolerant varieties invariably had higher vigor (plant height and dry matter) before submergence though underwater shoot elongation was more in intolerant varieties. A correlation study between change in root porosity and plant survival showed a positive linear relationship with R² value of 0.57 and 0.88 for 5d and 10d submergence respectively. It is evident that root porosity has a significant impact on the survival behaviour of rice plants after submergence.