The effect of zinc oxide nano particles on growth, morphological and physiological characteristics of Persian oak (Quercus brantii Lindl.) seedlings under drought stress

In this study, the effect of zinc oxide nano particle (ZnO) on 18 different growth, morphological and physiological characteristics of Persian oak (Quercus brantii L.) seedlings was investigated under drought stress. Before doing the experiment, initial characteristics of the two-year-old seedlings were measured after transferring them to Semnan and passing two months for stabilization in the greenhouse condition. Statistical analysis were performed with a completely randomized design under a factorial experiment using two factors of drought stress (field capacity 80%, 60%, 40% and 20%) and zinc nano oxide (concentrations 0, 30, 100, 300 and 1000 mg/l) with four replications. After twice spraying with zinc nano oxide with one-month interval and growing in greenhouse conditions for 6 months, all seedlings were measured and reassessed. The results showed that with increasing drought stress and nano oxide concentration, the number and longitudinal growth of leaves, height and diameter growth of seedlings and the number of seedling branches decreased, while the number of leaves and percentage of nano blight and the number of dried leaves increased. The best treatment in terms of growth and qualitative traits was related to the combination of irrigation with 40% of field capacity along with a concentration of 30 mg/l zinc nano oxide. The results also showed that only superoxide dismutase enzyme had a significant difference compared to the control with increasing drought stress at different concentrations of zinc nano oxide; however no significant difference was observed throughout other tested enzymes (catalase, ascorbate peroxidase and guaiacol peroxidase). Overall, due to the lack of prominent effect on seedling characteristics and creating the scorching spots on the leaf surface in some treatments, the use of zinc nano oxide is not recommended to improve the drought resistance, establishment and growth of oak seedlings.