Nanotechnology now plays a revolutionary role in many applications; nanomaterials have experienced significant importance in both basic and applied sciences as well as in bio-nanotechnology. Zinc oxide nanoparticles (ZnO-NPs) have become one of the most important metal oxide NPs in biological applications due to their beneficial impacts. The purpose of this study was to explore the effects of ZnO-NPs in reducing Cd toxicity by studying the growth, photosynthesis reactions, antioxidant system, oxidative stress, and protein content in Lycopersicon esculentum (tomato). ZnO-NPs induced an upregulation of antioxidative enzymes which protect the photosynthetic apparatus in plants. Seeds of tomato were sown to create nursery. At 20 days after sowing (DAS), seedlings were transferred to soil pots. Varied concentrations (0.4, 0.6 or 0.8 mM) of Cd were applied to the soil after 24 and 25 DAS. Zinc (Zn; 50 mg/L) and ZnO-NPs (50 mg/L) treatments were given continuously for 5 days from 31 to 35 DAS and sampling took place at 45 DAS. The results indicate that a Cd-generated oxidative burst in the form of elevated hydrogen peroxide (H2O2) levels resulted in a decline in cell viability through enhanced activity of the antioxidant system and proline content; the data increased on follow-up treatment with ZnO-NPs. Foliar application of ZnO-NPs significantly enhanced plant height, fresh, and dry weight of plant, leaf area, SPAD chlorophyll, photosynthetic attributes, i.e., net photosynthetic rate (PN), transpiration rate (E), internal CO2 concentration (Ci), and stomatal conductance (gs). Application of ZnO-NPs reduced the adverse effects generated by Cd and increased protein content, activities of nitrate reductase and carbonic anhydrase over the control in both stressed and non-stressed plants. Additionally, microscopic studies showed a marked increase in stomatal aperture after ZnO-NPs treatment in the presence or absence of Cd. This was associated with decrease in malondialdehyde and superoxide radical (O2−) levels. The present study suggests that ZnO-NPs can be effectively used to reduce the toxicity of Cd in tomato plants and may also be suitable for testing on other crop species.

中文翻译：

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氧化锌纳米粒子在对抗番茄中镉产生的负面影响中的作用

纳米技术现在在许多应用中发挥着革命性的作用；纳米材料在基础科学和应用科学以及生物纳米技术中都具有重要意义。氧化锌纳米颗粒（ZnO-NPs）由于其有益的影响已成为生物应用中最重要的金属氧化物纳米颗粒之一。本研究的目的是通过研究番茄（番茄）的生长、光合作用反应、抗氧化系统、氧化应激和蛋白质含量，探讨 ZnO-NPs 在降低 Cd 毒性方面的作用。ZnO-NPs 诱导抗氧化酶的上调，从而保护植物的光合器官。播种番茄种子以创建苗圃。在播种后 20 天 (DAS)，将幼苗转移到土盆中。不同的浓度（0.4、0.6 或 0. 在 24 和 25 DAS 后将 8 mM Cd 施用于土壤。锌 (Zn; 50 mg/L) 和 ZnO-NPs (50 mg/L) 从 31 到 35 DAS 连续给药 5 天，采样在 45 DAS 进行。结果表明，以升高的过氧化氢 (H2O2) 水平形式产生的 Cd 氧化爆发通过增强抗氧化系统的活性和脯氨酸含量导致细胞活力下降；使用 ZnO-NPs 进行后续治疗时数据增加。叶面喷施 ZnO-NPs 显着提高植物的株高、鲜重和干重、叶面积、SPAD 叶绿素、光合属性，即净光合速率 (PN)、蒸腾速率 (E)、内部 CO2 浓度 (Ci)、和气孔导度 (gs)。ZnO-NPs的应用减少了Cd产生的不利影响并增加了蛋白质含量，硝酸还原酶和碳酸酐酶的活性在胁迫和非胁迫植物中均高于对照。此外，显微镜研究表明，在存在或不存在 Cd 的情况下，ZnO-NPs 处理后气孔孔径显着增加。这与丙二醛和超氧自由基 (O2−) 水平的降低有关。目前的研究表明，ZnO-NPs 可以有效地用于降低番茄植物中 Cd 的毒性，也可能适用于其他作物物种的测试。