Morphological and physiological responses of grafted Sultana grapevine on Iranian ‎and American rootstocks to drought stress

Drought stress has different effects on plant growth and metabolism and is one of the most important factors limiting the growth of grapes. In order to investigate the effect of drought stress on some morphological traits and gas exchanges, own-rooted Sultana cultivar and grafted on Rasheh grape and 1103-P rootstocks were selected. This research was conducted by factorial arrangement in completely randomized design with three levels of drought stress and four replications at 2015-2016. Drought stress was applied after plants growth. The time of plants arrival to medium and severe stress levels was determined by weighted-volumetric method. Membrane stability index (MSI), leaf relative water content (RWC), leaf area (LA), leaf mass area (LMA), specific leaf area (SLA), chlorophyll a, chlorophyll b, photosynthesis rate (A), stomatal conductance (gs) and transpiration rate (E) were measured. The results showed that drought stress significantly decreased MSI and RWC. LA and LMA showed a significant difference between two levels of stress treatments. Under stress conditions, the SLA values ​​of the non-grafted Sultana were significantly different. Chlorophyll a and chlorophyll, gs and E decreased significantly by increasing drought stress. The results of measured traits of this study indicated the positive effect of the rootstocks used on increasing the resistance of susceptible Sultana grapes to drought conditions compared to non-grafted ones. Based on the findings of this research, Iranian grape variety (Rasheh) as the rootstock, as well as the famous American rootstock (1103), showed good tolerance to drought stress.