Comparison of some biochemical substances in two indica rice varieties in response to salt stress at seedling stage

Rice (Oryza saliva) is particularly sensitive to salt stress during the seedling stage, with consequent poor crop establishment. Physiological responses to salinity were evaluated for contrasting genotypes, during the seedling stage. Two rice genotypes differing in their tolerance of salinity were evaluated in a set of greenhouse experiments under 0 and 12 dS/m of salinity during seedling stage. Photosynthetic CO2 fixation, stomatal conductance (gs) and transpiration decreased substantially because of salt stress, but with greater reduction in the sensitive cultivar IR 29. The tolerant line IR 651 had more responsive stomata that tended to close faster during the first few hours of stress, followed by partial recovery after a brief period of acclimation. However, in the sensitive line, gs continued to decrease for longer duration and with no recovery afterward. Soluble sugars and proteins concentration increased in leaves of IR 651only when subjected to salt stress. This suggests that sugars play an important role in osmotic adjustment (OA) in rice. Not significant differences were found in free proline levels at salinity stress in both the cultivars. It seems proline may not play a role in minimizing the damage caused by dehydration result of salinity.