Effects of withholding irrigation and foliar application of Z and Mn on fatty acid composition and seed oil content in winter safflower

To evaluate the effects of foliar application of manganese and zinc on safflower under drought stress, experiments were conducted in 2001_2002 and 2002 _2003 crop years in a research field, 17 kilometers from west of Isfahan, Iran. The Experimental design was split factorial in randomized complete block with three replications. Four drought stress including, full irrigation, withholding irrigation at vegetative growth stage, withholding irrigation at flowering stage, and withholding irrigation at seed filling stage, were randomized to the main plot units and 12 treatments from combination levels of three cultivars including, Zarghan 279, Varamin 295 and LRV5151, and four foliar applications including, no foliar application, foliar application of water, foliar application of Zinc Sulfate (3000 ppm) and foliar application of manganese sulfate (3000 ppm) were randomized to the subplot units. After harvest, oil yield and percent of seed oil were measured and fatty acids composition of oil was determined by GC. Four species of fatty acids, stearic (2.0 %), palmitic (8.3 %), oleic (17.3 %) and linoleic (71.9 %), were consisted of about 99.5 % of total fatty acids of oil on the average and no linolenic acid was measured in treatments. Results indicated that oil percent and yield and percent of palmitic acid were affected by significant interaction of stress, cultivar and foliar application factors. Withholding irrigation at flowering stage and Zarghan 279 and LRV5151 cultivars caused to increase of oil percent when manganese used as foliar application. Withholding irrigation at seed filling stage increased oil percent and yield in Zarghan 279 and LRV5151 cultivars when zinc or manganese used as foliar application. In some interaction levels zinc and manganese foliar application significantly increased palmitic and oleic acids whereas these foliar applications decreased linoleic acid percent. As a whole, drought stress during flowering stage imposed the most damage to oil percent and yield and also decreased linoleic acid content and increased stearic and oleic acid content. So in case of oil percent and fatty acid composition in safflower, flowering stage is more sensitive to drought than vegetative or grain filling stages and foliar application of zinc and manganese can compensate the negative effects of drought on safflower plant.