In order to study the effect of alkaline stress on seed germination and seedling biochemical characteristics of two safflower cultivars, a laboratory experiment was conducted based on a completely randomized design with three replications in the Vali-e-Asr University of Rafsanjan. Experimental factors included the levels of alkaline with sodium bicarbonate (0, 10, 20, 30, 40, 50 and 60 mM) and two cultivars of safflower (Soffeh and 411). The result showed that alkaline stress had significant effects on seed germination characteristics. Increasing alkaline stress reduced percentage and rate of germination, length and dry weights of shoots and roots, K+ concentration and K+/Na+. However, alkaline increased malondialdehyde content, proline, total carbohydrate and Na+ concentration. In alkaline stress condition, there was a significant difference between cultivars in length of shoots and roots, proline content and K+ concentration. 411 cultivar showed notable superiority compared to Soffeh cultivar. Both cultivars had the highest malondialdehyde at 60 mM alkalinity and the lowest malondialdehyde obtained in Soffeh cultivar and control. The result of this research showed that 411 cultivar was better than Soffeh cultivar in proline and soluble sugar content, but these two cultivars had no significant differences in other traits.
