Changes in Morphological, Physiological Traits and Enzyme Activity of Grafted and Ungrafted Grapevine Rootstocks Under Drought Stress

American grapevine rootstocks are used as the most efficient control method for phylloxera disease. Vitis vinifera species are grown over these rootstocks. The rootstocks may have different drought tolerances. In present study, morphological and physiological responds and enzyme activities of grafted and ungrafted grapevines were investigated under drought stress. The rootstocks Rupestris du Lot, 420A, 5BB, SO4, 8B, 110R, 1103P, 140Ruggeri and Ramsey and KaEuro7 clone of Sultani Seedless grape cultivar were used as the plant material of this study. Drought stress was exerted as water deficits and stress treatments were terminated when the available moisture level dropped to 5%. Current findings revealed that grafted plants were less influenced morphologically from the droughts than the ungrafted ones. In control group, average leaf water potential was measured as -0.51 MPa for ungrafted plants and -0.46 MPa for grafted plants. In stress group, leaf water potential was measured as -2.03 MPa for ungrafted plants and as -1.69 MPa for grafted ones. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzyme activities of both grafted and ungrafted plants increased with drought stress. Considering the enzyme activities of ungrafted plants in control and stress groups, it was observed that SOD activity increased from 508 (unit/mg protein) to 852 (unit/mg protein); APX activity increased from 153 (micromole/mg protein/min) to 584 (micromole/mg protein/min). In grafted plants, SOD activity increased from 639 (unit/mg protein) to 796 (unit/mg protein); APX activity increased from 414 (micromole/mg protein/min) to 1002 (micromole/mg protein/min). The drought resistant rootstocks (like 140Ru, 110R) exhibited higher enzyme activity in both control and stress groups than drought sensitive rootstocks (like 5BB, SO4).