NONOSMOTIC EFFECT OF POLYETHYLENE GLYCOL ON PERCENT SURVIVAL AND GROWTH OF RICE

Salinity is one of the major environmental factors limiting crop productivity. For this reason, two greenhouse experiments were conducted in Faculty of Agriculture, Cairo University, Egypt, during the year 2015 using two rice varieties to evaluate the effects of various levels of osmotic stress caused by polyethylene-glycol 6000 (PEG) and NaCl. Furthermore, it was tested whether the inhibitory effect of salinity on growth, sodium and chloride concentration by two different varieties was greater under NaCl or PEG treatment. The first experiment was undertaken to separate osmotic and ionic aspects of salinity damage to rice (Oryza sativa L.).Seedlings of IR28 (salt-sensitive) and Nona Bokra (salt-tolerant) rice varieties were transferred to salinized nutrient solution containing 85 mol m-3NaCl (-3.0 bars) with or without   PEG 6000 (-2.0 bars, 45 gL-1).  Plants were grown up to 30 days in the salinized solutions. The second experiment was designed to determine the effect of salinity (85 mol m-3NaCl) with or without PEG 6000 (-0.5 bar, 11 g L-1)on growth, uptake and transport of sodium and chloride in two rice varieties differing in salt tolerance.  The results indicated that survival of salt-tolerant variety (Nona Bokra) was increased significantly by adding PEG (-2.0 bars). The addition of PEG also reduced the rate of death of rice plants compared with NaCl alone. Also, data showed that PEG 6000 (0.5 bar, 11 gL-1) reduce sodium concentration in root of IR28 and   Nona Bokra but its effect upon sodium concentration in shoot of the two varieties was more pronounced than the reduction of Na+ concentration in root.  Highly significant differences were obtained between zero and 11 gL-1 PEG. The result of this study is strongly indicated that addition of PEG dramatically lessened the toxicity of NaCl to rice seedlings.