Effect of salicylic acid and selenium foliar application on physiological and agronomic characteristics of safflower (Carthamus tictorius L.) in drought stress conditions

In order to study the effect of salicylic acid and selenium foliar application on physiological characteristics, yield and yield components of safflower (Carthamus tictorius L.) under drought stress conditions, an experiment was conducted as split plot based on randomized complete block design with three replications. The main factor included irrigation in three levels, complete irrigation during growing season (Control), cutting irrigation at 50% flowering stage and cutting irrigation at 50% head forming stage. Sub factor was considered foliar application of safflower plants including non-spraying (Control), foliar application of salicylic acid, selenium and salicylic acid with selenium. Drought stress reduced biomass, yield and yield components, but it increased grain protein percentage, the superoxide dismutase activity and proline concentration. Also, the highest negative effect of drought stress observed in flowering stage, so that stress at flowering stage reduced 49% grain yield and 33% biomass of safflower. Foliar application improved yield, yield components and superoxide dismutase activity compared to non-spraying. However, between foliar application treatments was observed no significant difference in grain yield and superoxide dismutase activity, but foliar application of salicylic acid with 7198 kg ha-1 showed the highest biomass. The foliar application in stress and non-stress condition increased grain oil percentage, so that in complete irrigation and flowering stage stress were the highest grain oil concentration in treatments of salicylic acid foliar application and salicylic acid with selenium foliar application with 24% and 28%, respectively. The foliar application treatments increased proline concentration in stress condition compared to control and treatment of salicylic acid with selenium foliar application with 11 µM.g FW-1  showed the highest proline concentration in stress of flowering stage.  In general, foliar application of safflower with selenium, salicylic acid, or their simultaneous consumption can reduce the negative effect of drought stress in both stage.