Evaluation of physiological and yield characteristics of safflower cultivars in response to salicylic acid foliar application and late- season heat stress

In order to investigate the simultaneous effects of natural high temperature stress and salicylic acid foliar application on photosynthetic capacity and yield of safflower, a field experiment was carried out as a split-factorial, at Shahid Chamran University of Ahvaz in 2017-18. Experimental factors included three temperature treatments (control, mild and severe temperature stresses) as the main plot, salicylic acid application at three levels (0, 200 and 400 ppm) and safflower cultivars as sub plots. Results showed that under control temperature and SA application, the important characteristics such as seed yield, photosynthesis and transpiration rates had significant superiority than similar treatments. At mild-temperature stress, spraying modulated negative effect of temperature on the important characters, and there was no significant difference between two concentrations of salicylic acid (200 and 400ppm). By the intensity of temperature stress, differences between safflower cultivars and the spraying concentrations were appeared; so that, under severe temperature stress, Goldasht and Faraman cultivars had more stability, photosynthesis sustainability and growth. In all cultivars, photosynthesis rate high positive correlation with yield. According to the physiological changes and safflower yield in response to intensify environmental temperature and semi-resistant severe-temperature stress, it seems that salicylic acid spraying was more effective on completing the growth stages and achiving the potential yield of Goldasht and Faraman cultivar at high-temperature stress.