Growth, photosynthesis and production of safflower (Carthamus tinctorius L.) in response to different levels of salinity and drought

In order to investigate the effects of salinity and drought stress on the photosynthesis, growth and production responses of safflower, two experiments were performed in Isfahan, Iran using four different levels of saline water, four different levels of irrigation water, and their combinations which were applied at three different growth stages (stem elongation, heading, and flowering) in 2016 and 2017. A split-plot experiment based on complete block design was performed with three replicates. The plant height, leaf area index, relative water content, number of heads per plant, number of seeds per head, 1000-seeds weight, seed yield, oil content, net photosynthetic rate, stomatal conductance and transpiration rate decrease under salinity, drought, and simultaneous stresses. The reduction in seed yield caused by the 10 dS m-1 and 40% of irrigation treatment was higher at the heading stage (92.6%) when compared with the stem elongation (71.04%) and flowering (89.9%) stages. In general, the reduction in seed yield caused by salinity-drought stress was higher at the heading stage as compared with stem elongation and the flowering stages.