Scientia Horticulturae 217 (2017) 164–172 Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti The physiological responses of various pomegranate cultivars to drought stress and recovery in order to screen for drought tolerance Mohammadreza Pourghayoumi a , Davood Bakhshi a,∗ , Majid Rahemi b , Ali Akbar Kamgar-Haghighi c , Ali Aalami d a Department of Horticultural Sciences, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran b Department of Horticultural Sciences, Faculty of Agricultural Sciences, Shiraz University, Shiraz, Iran c Department of Irrigation, Faculty of Agricultural Sciences, Shiraz University, Shiraz, Iran d Department of Plant Biotechnology, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran a r t i c l e i n f o Article history: Received 17 August 2016 Received in revised form 24 January 2017 Accepted 26 January 2017 Keywords: Punica granatum Water stress Photosynthesis Recovery Tolerant a b s t r a c t In order to screen pomegranate cultivars for drought tolerance, few rapid, less expensive and reliable methods were used. Two-year-old pomegranate (Punica granatum L.) plants of various commercial culti- vars namely Rabab-e-Neyriz’ (‘Rabab’), ‘Shishe-cap-e-Ferdows’ (‘Shishecap’), ‘Malas-e-Saveh’ (M-Saveh), ‘Malas-e-Yazdi’ (‘M-Yazdi’), and ‘Ghojagh-e-Qom’ (‘Ghojagh’) were grown in large containers filled with a mixture of leaf mould, sand, and soil (1:1:1, by volume) in greenhouse. The plants were subjected to 14-day drought stress by withholding irrigation, followed by re-watering for 7 days. Midday stem water potential ( stem ), leaf relative water content (RWC), membrane stability index (MSI), leaf dry mass per area (LMA), rapid test for drought tolerance (DTI), gas exchange parameters including net photosynthe- sis (A n ), leaf scale transpiration (T r ), and stomatal conductance (g s ), and intrinsic water use efficiency (IWUE) were determined in well-watered and drought-stressed plants. All cultivars showed an ability to tolerate drought stress, but ‘Ghojagh’ exhibited more tolerance, with a higher RWC and  stem and a greater osmotic adjustment. ‘Ghojagh’ also revealed higher cell membrane stability and IWUE and a lower reduction in net CO 2 assimilation rate. This study found that ‘M-Yazdi’ was more vulnerable to severe water stress, and displayed the lowest degree of cell membrane stability as compared to the other examined cultivars and showed no recovery for RWC at the end of recovery period. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Pomegranate (Punica granatum L.), from the family Punicaceae, is a popular fruit of tropical and subtropical regions that is native to the area stretching from Iran to the Himalayas in northern India (Fawole and Opara, 2013; Parvizi et al., 2016). It has been cultivated since ancient times and is mentioned in the Christian bibles and holy Quran (Rahimi et al., 2012). Drought is the most abiotic stress factor limiting plant growth and crop production in the world. Increase in fruit splitting or cracking and decrease in vegetative growth and yield is economically important losses in pomegranate orchards resulting from water stress. Drought tolerance is observed in almost all plant species, but its extent varies from species to species and even in cultivars of the same species (Jain et al., 2011). ∗ Corresponding author. E-mail addresses: bakhshi-d@guilan.ac.ir, bakhshidavood@hotmail.com (D. Bakhshi). Breeders look for new sources of variations when attempting to find drought tolerant plants with optimal characteristics for high rates of photosynthesis and productivity, but tolerance to water stress is very complex, due to the intricate of the interactions between stress factors and various physiological, biochemical, and molec- ular response affecting plant growth (Jaleel et al., 2009; Giancarla et al., 2012). A better understanding of how drought stress affects the physiology of the plant helps in the creation and selection of new drought tolerant cultivars. Plants experience drought stress, either when the water supply to roots becomes difficult or when the transpiration rate becomes higher than the rate of water uptake. These two conditions often occur under arid and semi-arid areas (Gholami et al., 2012). Different levels of drought stress could be observed in a plant. A moderate loss of water often leads to stoma- tal reactions, limiting CO 2 assimilation, stomatal conductance, and transpiration. Severe water stress, on the other hand, occurs when most of the protoplasmic water is lost and often leads to a major disruption of the metabolism, enzymatic antioxidant activities and http://dx.doi.org/10.1016/j.scienta.2017.01.044 0304-4238/© 2017 Elsevier B.V. All rights reserved.