Variation in biochemical characteristics, water status, stomata features, leaf carbon isotope composition and its relationship to water use efficiency in pistachio (Pistacia vera L.) cultivars under drought stress condition

Abstract

Pistachio (P. vera L., Anacardiaceae) is cultivated in regions where soil water deficits and salinity conditions are higher than usual. Despite adult pistachio trees having been documented as being drought tolerant; there is only a limited understanding of the physiological mechanisms pistachio cultivars use to survive drought. We therefore, carried out a greenhouse experiment to evaluate the effects of three osmotic drought stress treatments including; control conditions (−0.1MPa), moderate (−0.75MPa) and severe drought (−1.5MPa) stress, using PEG 6000 for 14days with a subsequent two weeks recovery period. Carbohydrate contents, relative water content, water use efficiency, stomatal characteristics, and nitrogen and carbon isotope composition were evaluated in three Iranian pistachio cultivars, i.e. Akbari, Kaleghochi and Ohadi.Results revealed that the drought stress treatments induced osmotic adjustment by carbohydrate accumulation. Both drought stress treatments increased soluble carbohydrate and starch contents of the leaves. Relative water content was only affected by drought stress in Kaleghochi. Stomatal density and morphology varied with pistachio cultivars but was hardly affected by the stress treatments.Drought stress significantly increased the overall mean of water use efficiency (intrinsic and instantaneous WUE). There were no significant differences between the leaf carbon isotope compositions of all pistachio cultivars under stress. This indicates that this relation may not be used to determine pistachio cultivars with appropriate WUE via leaf carbon isotope composition within the time frame of the experiment. Leaf nitrogen isotope composition decreased under drought stress regardless off the cultivar.