Effects of Drought Stress on Yield and Some Physiological Characters of Three Spring Safflower (Carthamus tinctorius) Varieties

To do this study a factorial expriment based on a randomized compelet block design with three replications was carried out in research farm of Bahonar university, Kerman, in 2005. Drought stress was exerted by withholding water after stem extention stage (severe stress), after blossoming stage (moderat stress) and after flowering stage (mild stress). Irrigation in all growth stages was considered as control. The cultivars were Isfahan native, IL and LSP. Grain and biological yield, number of head per plant, oil percentage, specific leaf area and leaf relative water content were reduced significantly under drought stress. Leaf prolin concentration and grain protein percentage increased under stress condition. But drought stress did not significantly affect the number of grain per head, the 1000 grain weight and harvest index. Among the cultivars, the Isfahan native cultivar with the highest number of head per plant and number of grains per head, produced the highest yield. In all three cultivars, with increasing drought stress, the oil percentage decreased but leaf prolin concentration and grain protein percentage increased. The Isfahan native cultivar with the highest grain yield, oil percentage and grain protein percentage can be introduced as the best cultivar in this area. The leaf prolin concentration of this cultivar was higher than LSP while it had no significant difference with the IL cultivar. Therefore it is able to tackle with drought stress through osmotic adjustment and prolin accumulation. Totally, severe and medium stress had a significant negative effect on the measured characters. While in mild stress, no negative effect was observed. Thus, with a mild stress, it is possible to have the same yield and oil production as control and also a decline in production costs.