Investigation of the Effects of Some Environmental Factors on Seed Germination and Early Seedling Stage Salt Tolerance of Extreme Halophyte Salsola crassa

Germination of halophyte plant species is controlled by several environmental factors, in particular light, temperature and salinity. Salsola crassa is an annual halophytic species adapted to highly saline soils. Although salinity tolerance level of this species was evaluated at seedling stage, there is no literature on salinity tolerance at germination stage. In this study, therefore, effects of 9 salt concentrations (0, 100, 200, 300, 400, 500, 600, 700 and 800 mM NaCl), 6 temperature treatments (10, 15, 20, 25, 30 and 35C) and photoperiod (12 h photoperiod and continuous darkness) on seed germination of S. crassa were investigated. The highest germination percentages (98-99%) were obtained in distilled water, at 20 and 25C temperature applications and 12 h photoperiod. An increase in salt concentration caused marked decrease in seed germination especially at low and high temperature treatments. Lower (10 and 15C) and higher (35C) temperature treatments caused marked inhibition in seed germination at both control and salt treatments. There were significant differences between the light and dark treatments in all temperature and salt treatments (P < 0.05). These results show that the stress tolerance of S. crassa at germination stage is affected by the interaction of light, temperature and salinity. In the second stage of this study, the effects of different NaCl concentrations (0, 100 and 300 mM) on some growth parameters (fresh and dry weights), Na+-K+ content, and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the hydropoically grown S. crassa were investigated. As compared to control, 100 and 300 mM NaCl concentrations increased growth parameters of shoot tissue, while only 100 mM NaCl application caused an increase in root tissue. Na+ accumulation increased with increasing salinity concentration, while K+ accumulation decreased. Moreover, more Na+ accumulation was detected in the aerial parts. Salt stress caused an increase in POD and CAT activity of root tissue, while it led to inhibition in leaf tissue. These results suggest that S. crassa is highly tolerant to salt stress.