Effect of deficit irrigation and foliar application of polyamines on seed and oil yields, water use efficiency and fatty acids production in spring safflower seed oil (Carthamus tinctorius L.)

The aim of this study was to investigate the effect of foliar application of polyamine compounds on seed and oil yields and fatty acids production in safflower under deficit irrigation stress. A split plot experiment based on randomized complete block design with four replications was conducted in the research farm of College of Agriculture, Shahed University in 2016-2017. Treatments were irrigation at two levels (normal irrigation and deficit irrigation (irrigation after 50 and 75% depletion of field capacity, respectively) as the main factor and foliar application of polyamine compounds at 10 levels (foliar application with water as control and foliar application with putrescine, spermidin and spermin at 0.05, 0.1 and 0.2 mM concentrations) as secondary factor. At each irrigation level, the putrescine foliar application significantly increased seed and oil yields, harvest index, water use efficiency and oleic acid. Increased levels of putrescine and spermin foliar application ranged from 0.05 to 0.2 mM under deficit irrigation stress conditions resulted in 40.4% and 38.3%, increase in the biological yield respectively, compared to control. Also, foliar application of the highest concentration of spermin (i.e. 0.2 mM) under water deficit stress significantly increased total yield of unsaturated fatty acids and reduced the percentage of palmitic acid. Spermidine foliar application significantly increased linoleic acid yield in safflower oil under water deficit conditions. It can be concluded that foliar application of polyamine compounds can increase seed and oil yields and water use efficiency and improve the quality of safflower oil in deficit irrigation conditions.