Effect of winter spray of volck oil on photosynthesis, gas exchange and physiological traits of two olive cultivars

This study was conducted to investigate the effect of foliar application of volck mineral oil (0, 1, 3 and 5%) on photosynthesis, gas exchanges and physiological traits of two olive cultivars (Manzanilla and Khediri) as split plot based on randomized complete block design with four replications during 2019-2020 in Ahvaz climatic conditions. The results showed that the application of 5% volck oil reduced photosynthesis in Khediri and Manzanilla cultivars by 40 and 52.4% compared to the control treatment in the second week after foliar application and then the photosynthesis rate increased again. In Khediri and Manzanilla cultivars, transpiration rate increased with the use of volck oil in all three concentrations compared to the control, but there was no definite trend. Stomatal conductance was higher in Khediri cultivar than Manzanilla cultivar and the highest stomatal conductance occurred 45 days after treatment. The lowest and highest leaf temperatures were recorded in control and 3% of volck oil treatment with mean temperatures of 29.34 and 32.17 ° C, respectively. In both cultivars, a decrease in radiation use efficiency was recorded in response to volck oil and high percentage of leaf drop (59.05%) was observed in Manzanilla. Therefore, in order to use high doses of volck mineral oil for olive trees, it should be done more cautiously due to the reduction of photosynthesis and increase in leaf temperature in both cultivars and the high rate of leaf drop in Manzanilla cultivar.