The effect of zinc sulfate under boron toxicity conditions on some morphophysiological and biochemical properties of grapevine (Vitis vinifera L.)

Boron is an essential plant micronutrient that is involved in the cell wall and membrane structure and functioinig. Boron is often found in high concentrations in association with agriculture in arid  and semi-arid regions. In order to investigate the effect of zinc sulfate on some morphological, physiological and biochemical characteristics of two grapvine cultivars under toxicity of boron, a greenhouse experiment was conducted taking into account three factors of two grapevine cultivars (Ghezel Ozum and Hosseini), four levels of boric acid (nutrient solution including 0.25 (control)), 2.5, 5 and 10 mg l-1 and tree levels zinc sulfate (foliar spray), 0 (control), 3 and 6 g l-1 in a factorial based on randomized complete design of four replicate for the lasted six months. The results indicated that leaf fresh weight in treatments of 5 and 10 mg l-1 boron (without zinc sulfate) were 68.55 and 49%, respectively and leaf dry weight in treatments of 5 and 10 mg l-1 boron (without zinc sulfate) decreased by 65.44 and 86.9%, respectively, compared to the control. With the increas in boric acid levels, the contents activities of catalase enzymes, proline, soluble sugars, and total protein in plant tissues were increased. At a concentration of 6 g l-1 zinc sulfate and 10 mg l-1 boron, the amount of soluble sugar in Ghezel Ozum cultivar increased 6.35 times and in Hosseini cultivar increased 5.3 times compared to the control treatment. With the application of 6 g l-1 zinc sulfate, the amount of total protein at the level of 5 mg l-1 boron increased 1.53 times and at the level of 10 mgl-1 boron, the amount increased 1.77 times compared to the control. Boron toxicity also reduced the concentrations of No3-, Ca2+, Mg2+ and Fe2+ but increased boron levels in both cultivars. The lowest amount of iron was observed in both cultivars at 10 mg l-1 boron. The highest amount of leaf boron (200.51 mg kg-1 dry matter) was observed at a concentration of 10 mg l-1 boron. Under toxicity of boron, application of Zinc sulfate caused increase in growth efficiency, antioxidant enzymes activites and the amount of compatible osmolites but reduced accumulation of boron ions in two cultivars. In conclusion, Hosseini was more tolerant with respect to most characters as compared to Ghezel Ozum and the application of zinc sulfate ameliorated the adverse effects of boron toxicity, in both cultivars.