Evaluation of Yield, Yield Components and Photosynthesis of Safflower (Carthamus tinctorius L.) in Response to Combined Salinity and Drought Stresses at Vegetative Growth Stage

The research was carried out to evaluate the response of safflower (Carthamus tinctorius L.) to salinity, drought and combined salinity- drought stresses at its vegetative stage and share of their effects on reduction of yield, yield components and photosynthesis of plant. For this purpose, a split plot experiment based on randomized complete block design was carried out at Agricultural Education Center of Kabotarabad- Isfahan in 2016-2017. In this study, response of spring safflower (Sofeh variety) to four salinity stress levels (2.5, 5, 10 and 15 dS/m) and four drought stress levels (100%, 80%, 60% and 40% F.C.) at vegetative growth stage were evaluated. The results showed that mean values of most traits were significantly reduced with increasing salinity and drought stress levels, in such a way that severe drought (Irrigation based on 40% field capacity) and salinity (15 dS/m) treatments produced lowest values for all traits. Seed oil content decreased with increasing salinity but this decrease (7.4%) was significant only at highest salinity level (15 dS/m). The highest level of combined salinity-drought stress decreased seed yield (87.13% decrease) more than the highest level of each of drought (71.40% decrease) and salinity (55.56% decrease) stresses as compared to control treatment (without drought and salinity stress), and the share of drought stress in reduction of seed yield was higher than the salinity stress (71.40% and 55.56%, respectively). Thus, growing safflower with minimum loss of seed yield, by irrigation with 80% F.C. and water salinity with 5 dS/m at the vegetative growth stage is possible.