Anti-Transpiration Effect of Kaolin on Some Physiological Traits of Four Olive Cultivars

To reduce transpiration and increase water use efficiency of olive trees in Ahvaz, the antitranspirant effects of of three levels of kaolin (0, 2.5% and 5%) on four varieties of olive (Mission, Conservolea, Keylet, Bledy) was carried out in a four-month period, with three replications. The results showed that Kaolin have a significant effect on plant water potential, leaf relative water content and stomatal resistance in the morning and midday. The highest and the lowest stomatal resistance of morning belonged to control treatment in Keylet and Bledy cultivars, respectively. Maximum and minimum stomatal resistances of midday were related to 5% kaolin in Conservolea and 2.5% kaolin in Bledy cultivars, respectively. Maximum and minimum plant water potential was observed in 2.5% kaolin and control treatments, respectively. The highest and the lowest leaf relative water content were observed in 2.5% kaolin in Keylet cultivar and control treatment in Mission cultivar, respectively. Kaolin did not have significant effect on leaf chlorophyll content, but reduced its proline content. This shows the positive role of kaolin on reduction of plant water stress by increasing the leaf relative water content and plant water use efficiency.