effect of salinity on growth, chlorophyll content and ions uptake of rice cultivars (oryza sativa) cultivars

rice (oryza sativa), a salt-sensitive species, has considerable genetic variation for salt tolerance within cultivars. to evaluate salinity effects on growth, chlorophyll content and ion uptake of two rice genotypes (ir29 and ir651, sensitive and tolerant respectively) accompany with two semi-tolerant iranian rice cultivars in a green house experiment were grown in normal condition till 6th leaf was fully expanded. seedlings were exposed to salinity, ec12 dsm-1 and normal conditions (ec=1.65 dsm-1, ushida solution base ec) for one week. samples were taken 0, 4, 12, 24, 48, 96, 168 h after imposing the treatments. after imposing the treatment, we used the youngest & oldest leaves for measuring na and k concentration and the youngest for chlorophyll. the scoring of leaves was from top to down (one for the young and four for old). stomatal conductivity also measured on the youngest leaf in time interval as follow: 12, 24, 48, 72, 96 and 120 hours after stress treatment. in this experiment root and shoot dry matter reduced significantly under stress in all cultivars but this reduction was less in tolerant genotype (ir651) compare to others. there were no differences in k concentration in the young leaves between cultivars but there was more accumulation of k in old leaf of ir651 under salt stress. nacl treatment caused to increasing significantly na in the young and old leaves of all cultivars except the young leaf of tolerant cultivar. chlorophyll concentration increased after 24 hrs of treatment but with long- time exposure a significant decline occurred in all cultivars.