Effect of potassium silicate on water use efficiency, quantitative traits and essential ‎oil yield of damask rose (Rosa damascena Miller) under water deficit stress ‎

Damask rose is a perennial and drought- resistant plant. In order to envestigate effect of potassium silicate on quantitative traits and essential oil of damask rose (Rosa damascena Miller) under water- deficit stress, an experiment was carried out as a split-plot based on a randomized complete block design with three replications at the Karimeh Zaer Farm, Qom province, Iran, in 2018. The main plot was water deficit stress at four levels (100 (without stress), 75, 50 and 25% of the plant water requirement) and the sub plot was spraying with potassium silicate at seven levels (without spraying, spraying with a concentration of 0.2 and 0.4% in the spring or summer alone or combination). The results showed that water deficit stress increased the essential oil percentage. Irrigation equivalent to 25, 50 and 75% the plant water requirement increased water use efficiency by 1.3, 1.9 and 3.3 times in comparison with the control, respectively. Foliar application with different rates of potassium silicate increased leaf silica rate under optimum and water deficit stress. The maximum of essential oil yield was recorded from foliar application of 0.2% of potassium silicate in the spraying along with summer under 25% f the plant water requirement and treatment of the foliar application of 0.4% of potassium silicate in the spraying along with summer under 50% the plant water requirement, respectively. Results showed that with foliar application of potassium silicate under water deficit stress equal to 50 and 25% the plant water requirement could increase quality and quantity damask rose.