Evaluation of Physiological Characteristics, Yield, Yield Components, and Oil Yield of Dragon’s Head ‎under Deficit Irrigation Conditions in Response to Foliar Application of Brassinosteroid

The present study has been conducted to investigate the effect of Brassinosteroid on some physiological traits, yield components, seed yield, and oil of Dragon’s head under deficit irrigation conditions. The experiment has been conducted as split-plot based on a randomized complete block design with three replications during 2016-2017 and 2017-2018 in the research farm of Agricultural Research and Training Center and Natural Resources of Zanjan Province. Experimental treatments include deficit irrigation (normal or control irrigation, irrigation cut-off from the beginning of flowering to the end of maturity, irrigation cut-off from the beginning of branching (emergence of the sixth pair of main stem leaves to physiological maturity) in main and foliar spraying with Brassinosteroid with concentrations of 0.5, 1.5, 1.5 μM, and control, all applied in the sub plots. Results show that irrigation cut-off from the beginning of branching has decreased in total the chlorophyll content (42.8%), number of capsules per plant (62.7%), number of seed per plant (66.1%), 1000-seed weight (22.3%), biological and seed yield (62.1%), harvest index (30.8%), and oil yield (75.1%). Foliar application with Brassinosteroids has only significantly increased the leaf total chlorophyll concentration and seed oil percentage under different levels of irrigation cut-off stress. There is a statistically significant difference between foliar application levels with Brassinosteroids for leaf total chlorophyll concentration and seed oil percentage traits. There is a need for complementary researches to prove the effectiveness of foliar application with this growth regulator to improve growth and yield of Dragon’s head under deficit irrigation conditions.