An experiment was conducted to evaluate the effects of salt stress on safflower genotypes under greenhouse condition using hydroponics nutrient solutions. The experiment was arranged as factorial based on a completely randomized design with three replications. Five safflower genotypes of Arak2811, Nebraska10, SOD25, CA116, and CA128 and four salinity treatments of 0(S0), 0.3(S1), 0.5(S2), and 0.7(S3) percent of NaCl were used as experimental factors. The effects of salinity were studied at germination stage in laboratory and also at one and two months after imposing plants to salinity in greenhouse. The germination rate, germination percentage and the shoot and root length of germinated seeds were significantly reduced under salinity treatments. There were no interactions between the levels of salinity and genotypes for the rate and percentage of germination. However, the percentage of decrease in the growth of the shoot and root of germinated seeds was highest for Arak2811 compared to the other tested genotypes. Salinity had considerable effects on the growth parameters. Plant height, number of leaves per plant, shoot and root dry matter, and also the concentration of K, Ca, and Mg in plant tissues were decreased as the level of salt was increased in the solution. The concentration of Na and the ratio of a/ K in the leaves, stems and roots were higher in the plants affected by salt stress. Among tested genotypes CA128 showed to be more salt tolerance in terms of dry matter accumulation. There were significant correlations between the concentration of K, Ca, and Mg in plant tissues with plant growth parameters. The results of this experiment showed that salinity may have significant effects on the growth of safflower plants and the responses of safflower genotypes to salinity can be different.
