The effect of salt stress (NaCl) on physiological and antioxidant activities in salt susceptible and resistant lines of oily sunflower (Helianthus annuus L.) at seedling stage

Salinity stress is one of the most important abiotic stresses that restrict growth and productivity of crop plants worldwide. In the present study, the effects of salinity stress on physiological activities of two sunflower genotypes were investigated at seedling stage. The experiment was conducted as factorial (first factor, genotype at two levels: C64 and C68 and the second factor, salinity at 5 levels: 0, 2, 4, 6, and 8 dS/m) based on completely randomized design with three replications. Analysis of variance showed that genotype × salt interaction was significant on proline, total chlorophyll and guaiacol peroxidase activity. With increasing salinity level, the content of proline and malondialdehyde increased. On the other hand, net photosynthesis rate and total chlorophyll content decreased. In this study, by applying salt stress, the total chlorophyll content decreased in both genotypes, but the reduction was higher in susceptible genotype (C64) than tolerant (C86) one. Also, with increasing salinity level, the amount of guaiacol peroxidase increased in tolerant genotype (C86) compared to susceptible (C64) one. According to the results of this experiment, different responses of C64 and C68 genotypes under salt stress are confirmed at the molecular level. Therefore, the above mentioned genotypes can be used in developing tolerant hybrid cultivars.