Study of some Physiological Characteristics in  Sahani',  Bidane-sefid and ‎ Farkhii Grapes During Drought Stress and their Subsequent Recovery

In order to evaluate the effect of different levels of drought stress on some physiological parameters in grapevine, a potted experiment with Iranian grapevine cultivars ‘Sahani’, ‘Bidane-sefid’ and ‘Farkhii’ was conducted in summer of 2008. The experiment was performed while employing four drought stress (water potential of soil,? s= -0.2, -0.6, -1, -1.5 MPa) treatments each in three replications. The experimental design was a factorial one on the basis of a randomized complete block design. Such physiological parameters as: leaf Relative Water Content (RWC), Membrane Stability Index (MSI), net photosynthesis (A), stomatal conductance (gs), transpiration (E), sub stomatal CO2 concentration (Ci) and water use efficiency (A/gs), were assessed in grape leaves subjected to different drought stress conditions and recovery of these parameters following rewatering. The study shows that RWC, MSI, A, gs, E, were decreased as soil water content was reduced. A/gs was maximum in all cultivars under -1 MPa. ‘Sahani’ benefitted from a higher photosynthesis, than ‘Bidane-sefid’ and ‘Farkhii’ under control as well as under -1 MPa treatments. ‘Sahani’ had a higher stability in gas exchange as compared with other cultivars. Ci value was first reduced and then increased in the three cultivars. Water use efficiency (A/gs) increased with increase in drought stress severity until -1 MPa. There was a close relationship observed between A and gs in all the cultivars. Results of the present experiment showed that gas exchange recovery (following rewatering) was fast under mild and moderate drought stress conditions, while under severe drought stress conditions, gas exchange recovery needed at least four days.