Effect of Sodium Chloride Levels on Growth,Water Status,Uptake, Transport,and Accumulation Pattern of Sodium and Chloride Ions in Young Sunflower Plants

There is a paucity of information on the critical content, threshold levels, uptake, transport, and accumulation of sodium (Na⁺) and chloride (Cl^?) ions in young sunflower plants. Effect of salinity was analyzed in root, stem, leaves, and buds by raising plants in fine sand irrigated with Hoagland's solution and supplemented with 10–160 mM sodium chloride (NaCl) for 30 days. Maximum sensitivity index, reduction in growth, and water content were observed in buds. Maximum Na⁺ and Cl^? contents were obtained in old leaves and stems under low salinity but in roots at high salinity. Uptake, transport, and accumulation rate of Cl^? were more than those of Na⁺, and for both ions they increased with increasing NaCl concentration but decreased with increasing exposure time. Growth reduction at low salinity seems to be because of Cl^? toxicity, but Na⁺ toxicity and water deficiency could also be the causes at high salinity.