| چکیده انگلیسی مقاله |
In order to study the physiological responses of castor to foliar application of zinc nano-chelate and humic acid under limited irrigation, an experiment was conducted as split-factorial based on randomized complete block design with three replications in Damghan region during 2015-16 growing season. Irrigation as the main factor in three levels including normal irrigation (control), irrigation up to 75 BBCH (mild stress) and irrigation up to 65 BBCH (severe stress). Combination of spraying various concentrations of humic acid (non-application, application of recommended rate and two-fold recommended rate) and zinc nano-chelate (application and non-application) were as subplots of this experiment. The results showed that the effect of irrigation treatment, humic acid, and zinc nano-chelate were significant on the number of capsules, number of seeds, 100-seed weight, grain yield, oil percent, and chlorophyll content. Irrigation up to 65 BBCH resulted in a reduction of 11.9, 34.9, 24.2, 24.9, and 51.7 percent in 100-seed weight, grain yield, biological yield, percent and yield of oil compared to normal irrigation. With application of humic acid based on recommended amount obtained the highest grain yield (2098.8 kg.ha-1). Foliar application of zinc nano-chelate resulted in 14.4, 8.4 and 18.4 percent increase in the grain number, 100-seed weight, and grain yield. The highest oil content (45.4%) and oil yield (943.3 kg.ha-1) were obtained in the normal irrigation. The non-application of humic acid, as well as irrigation up to 65 BBCH, led to decrease in leaf chlorophyll content. The highest activity of superoxide dismutase enzyme was observed in non-application of zinc nano-chelate and two-fold consumption of humic acid under irrigation up to 65 BBCH conditions. The seed oil percent had a positive correlation with functional traits and total chlorophyll content and had a negative and significant correlation with antioxidant enzymes activity. Regression results showed that capsule number, 100-seed weight, grain yield, and oil yield were the main factors affecting seed oil percent. In general, the application of humic acid with recommended amounts and zinc nano-chelate led to improvement of growth and physiological traits and tolerance to limited irrigation in castor plant. |