Zinc alleviates salt stress and increases antioxidant enzyme activity in the leaves of pistachio (Pistacia vera L. ‘Badami’) seedlings

The mechanism(s) by which Zn alleviates NaCl stress was investigated in Pistacia vera L. ‘Badami’. Pistachio seedlings were treated with 0, 800, 1600, 2400, and 3200 mg of NaCl kg^–1 of soil, along with Zn (0, 5, 10, and 20 mg kg^–1 of soil). NaCl stress induced high oxidative stress, increasing lipid peroxidation, electrolyte leakage, and lipoxygenase (LOX, E.C. 1.13.11.12) activity to high levels. Zn supplement efficiently reduced all these adverse effects of salt stress. However, there were no significant differences among the above parameters in plants treated with Zn only. NaCl stress significantly increased the activity of antioxidant enzymes. The activity of antioxidant enzymes (superoxide dismutase [SOD, E.C. 1.15.1.1], catalase [CAT, E.C. 1.11.1.6]. and ascorbate peroxidase [APX, E.C. 1.11.1.11]) increased significantly in NaCl + Zn-treated plants, as compared with those treated with either NaCl or Zn alone. These results support the positive effects of Zn on antioxidant enzyme activity scavenging the reactive oxygen species produced in response to salt stress. Zinc treatment caused a significant increase in the amount of phenolics and in ascorbic acid content, as compared with salt treatment alone. Zinc treatment alone did not result in very high antioxidant enzyme activity in non-stressed plants.