Variation of relative water content, water use efficiency and stomatal density during drought stress and subsequent recovery in pistachio cultivars (Pistacia veraL.)

Abstract

Pistachio species belong to the Anacardiaceae family. Pistacia vera L., cultivated pistachio, is the most important species in the genus. Pistachio is a major orchard crop in Iran, whereby 'Akbari', 'Kaleghochi' and 'Ohadi' are very common cultivars. Pistachio has a high resistance to soil drought conditions but differences exist between cultivars. This greenhouse study was conducted to evaluate the effects of an osmotic drought stress (Ψs=-0.75 and Ψs=-1.5 MPa) on relative water content (RWC), water use efficiency (WUE) and stomatal characteristics in the cultivars mentioned above. Results reveal that the different osmotic drought stress levels applied significantly lowered RWC compared to a well-watered control. At the same time, the treatments significantly increased WUE compared to the control. WUE varied in different cultivars but differences were not significant. There were no significant differences between the different drought stress levels as for their influence on stomatal length, width and numbers, but cultivars showed different stomatal characteristics between them: 'Ohadi' and 'Kaleghochi' had widest stomata, whereas 'Akbari' had most stomata. In conclusion, drought stress treatments lowered RWC and leaf water potential. Therefore, under osmotic stress conditions, pistachio cultivars showed drought tolerance mechanism to cope with water deficiency. Also the results of this study show that drought stress treatments increased WUE. However, further research in field condition and under more severe drought treatments is needed to confirm this survey's research.