211

2016

158–166

Scientia Horticulturae

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Pistachio (P. vera L., Anacardiaceae) is cultivated in regions where soil water deficits and salinity con-ditions are higher than usual. Despite adult pistachio trees having been documented as being droughttolerant; there is only a limited understanding of the physiological mechanisms pistachio cultivars useto survive drought. We therefore, carried out a greenhouse experiment to evaluate the effects of threeosmotic drought stress treatments including; control conditions (−0.1 MPa), moderate (−0.75 MPa) andsevere drought (−1.5 MPa) stress, using PEG 6000 for 14 days with a subsequent two weeks recoveryperiod. Carbohydrate contents, relative water content, water use efficiency, stomatal characteristics, andnitrogen 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 accu-mulation. Both drought stress treatments increased soluble carbohydrate and starch contents of theleaves. Relative water content was only affected by drought stress in Kaleghochi. Stomatal density andmorphology 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 instan-taneous WUE). There were no significant differences between the leaf carbon isotope compositions ofall pistachio cultivars under stress. This indicates that this relation may not be used to determine pista-chio cultivars with appropriate WUE via leaf carbon isotope composition within the time frame of theexperiment. Leaf nitrogen isotope composition decreased under drought stress regardless off the cultivar.

EA 33

1397/10/03

Dashagha

34