Table_1_ZnO nanoparticles efficiently enhance drought tolerance in Dracocephalum kotschyi through altering physiological, biochemical and elemental contents.docx

Using nanofertilizers in certain concentrations can be a novel method to alleviate drought stress effects in plants as a global climate problem. We aimed to determine the impacts of zinc nanoparticles (ZnO-N) and zinc sulfate (ZnSO4) fertilizers on the improvement of drought tolerance in Dracocephalum kotschyi as a medicinal-ornamental plant. Plants were treated with three doses of ZnO-N and ZnSO4 (0, 10, and 20 mg/l) under two levels of drought stress [50% and 100% field capacity (FC)]. Relative water content (RWC), electrolyte conductivity (EC), chlorophyll, sugar, proline, protein, superoxide dismutase (SOD), polyphenol oxidase (PPO) and, guaiacol peroxidase (GPO) were measured. Moreover, the concentration of some elements interacting with Zn was reported using the SEM-EDX method. Results indicated that foliar fertilization of D. kotschyi under drought stress with ZnO-N decreased EC, while ZnSO4 application was less effective. Moreover, sugar and proline content as well as activity of SOD and GPO (and to some extent PPO) in treated plants by 50% FC, increased under the influence of ZnO-N. ZnSO4 application could increase chlorophyll and protein content and PPO activity in this plant under drought stress. Based on the results, ZnO-N and then ZnSO4 improved the drought tolerance of D. kotschyi through their positive effects on physiological and biochemical attributes changing the concentration of Zn, P, Cu, and Fe. Accordingly, due to the increased sugar and proline content and also antioxidant enzyme activity (SOD, GPO, and to some extent PPO) on enhancing drought tolerance in this plant, ZnO-N fertilization is advisable.

在特定浓度下使用纳米肥料，可作为一种新颖的方法来缓解植物在应对全球气候问题所面临的干旱胁迫。本研究旨在探究锌纳米颗粒（ZnO-N）和硫酸锌（ZnSO4）肥料对药用观赏植物 Dracocephalum kotschyi 干旱耐受性提升的影响。将植物分别施加三种剂量的 ZnO-N 和 ZnSO4（0、10 和 20 mg/L），在两种干旱胁迫水平下进行试验[50% 和 100% 的田间持水量（FC）]。测量了相对含水量（RWC）、电导率（EC）、叶绿素、糖、脯氨酸、蛋白质、超氧化物歧化酶（SOD）、多酚氧化酶（PPO）和愈创木酚过氧化物酶（GPO）。此外，利用扫描电子显微镜-能量色散X射线光谱法（SEM-EDX）报告了与锌相互作用的某些元素浓度。结果显示，在干旱胁迫下对 D. kotschyi 进行叶面施肥的 ZnO-N 能够降低电导率，而 ZnSO4 的应用效果较差。此外，在 50% FC 下，经 ZnO-N 处理的植物中糖和脯氨酸含量以及 SOD 和 GPO（在一定程度上 PPO）的活性均有所提高。在干旱胁迫条件下，ZnSO4 的应用能够增加该植物的叶绿素和蛋白质含量以及 PPO 的活性。基于研究结果，ZnO-N 和 ZnSO4 通过其对人体生理和生化特性的积极影响，改变锌、磷、铜和铁的浓度，从而提高了 D. kotschyi 的干旱耐受性。因此，鉴于 ZnO-N 施肥能够增加植物中的糖和脯氨酸含量，以及抗氧化酶活性（SOD、GPO 和在一定程度上 PPO）以增强该植物的干旱耐受性，因此推荐进行 ZnO-N 施肥。