Soil cadmium (Cd) contamination threatens plant growth and agricultural productivity. Hibiscus syriacus L., valued for its ornamental, edible, and medicinal properties, is widely cultivated in Cd-contaminated areas of southern China.This study aimed to evaluate the effectiveness of nano-zinc oxide (nZnO) in alleviating Cd toxicity in H. syriacus, examining plant phenotypes, physiological and biochemical responses, root ultrastructure, and the accumulation and distribution of Cd and Zn within the soil-H. syriacus system. Pot experiments included Cd treatment (100 mg/kg) and combined soil or foliar applications of nZnO (50 and 100 mg/L), with plants harvested after 45 days. Compared to Cd treatment alone, the combined application of nZnO significantly increased biomass in roots, stems, and leaves, improved photosynthetic performance, osmotic regulation, and antioxidant levels, and mitigated root cell damage; Cd concentrated mainly in roots, and nZnO reduced root Cd levels by 0.24 %-9.06 %. SEM-EDS observations revealed that Cd predominantly accumulated in the root epidermis and cortex, with Cd stress leading to increased levels and localized aggregation of Cd in the xylem. By contrast, nZnO treatment alleviated this disruption. Leaf application of 50 mg/L nZnO showed the best results. These findings highlight nZnO as a promising nano fertilizer for alleviating Cd stress in plants.

Nickel (Ni) is a trace element that is toxic to plants and consequently results in toxicity symptoms and hazardous fitness problems in human beings through food chains. Nanoparticles (NPs) are being used in new ways to directly help plants handle Ni stress and act as nano-fertilizers. The purpose of the current study was to establish the use of biogenically produced zinc oxide nanoparticles (ZnONPs) to reduce Ni-induced toxic effect on the growth and development of watermelon (Citrullus lanatus). Watermelon seeds were sown in pot filled with five kg of soil and placed in a greenhouse. The watermelon plants were treated with Ni stress (70 mg/kg soil) at 20 DAS (days after sowing), and the treatment was applied directly into the soil. The supply of ZnONPs (100 mg/L) as foliar spray was given at 30 DAS and 38 DAS, and the sampling was performed at 55-60 DAS for biochemical and physiological analysis. The results showed that watermelon plants that were exposed to Ni had oxidative damage, which was shown by more electrolyte leakage, hydrogen peroxide, lipid peroxidation, pigment and osmolyte loss, and a loss of ultrastructural integrity in the chloroplasts. However, watermelon plants supplemented with ZnONPs under the Ni toxicity revealed significantly increased plant fresh weight (53.18%), plant dry weight (51.25%), and root length (32.14%). Moreover, the ZnONPs supplement has beneficial impacts on photosynthesis attributes, SPAD value (21.93%), and chloroplast structure observed by transmission electron microscopy (TEM) under Ni stress. Application of ZnONPs also substantially reduced the oxidative stress by lowering the levels of superoxide radical (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{O}}_{2}{-\cdot\:}$$\end{document}; 22.68%), hydrogen peroxide (H2O2; 21.18%), malondialdehyde (MDA; 21.34%), and electrolyte leakage (EL; 34.613%). The results showed that ZnONPs enhanced enzymatic activities of superoxide dismutase (SOD; 39.95%), peroxidase (POD; 19.95%), catalase (CAT; 32.85%), ascorbate peroxidase (APX; 25%) that metabolize reactive oxygen species (ROS); these increases correlated with the changes observed in the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{O}}_{2}{-\cdot\:}$$\end{document}, H2O2 and MDA after ZnONPs application. Application of ZnONPs increased the transcriptional levels of antioxidant defense genes as compared to the Ni plants alone. In conclusion, spraying ZnONPs on foliage has high effectiveness in increasing biomass, photosynthesis, protein and antioxidant enzymes, mineral nutrient concentrations, and lowering Ni concentrations in watermelon. The results indicate biogenically produced ZnONPs can be a promising technique for the remediation of Ni-contaminated soils.

The global wide threatening problem is the pollution, especially water and soil pollution are biggest threats to our people. The pollution not only damages the resources but also enters the ecosystem and impairs our health. The pollution disfigures the fertility of the soil and contaminates the groundwater table which is the most reliable source of all living organisms. Due to urbanization of people and scarcity of the water resources, the people rely on the groundwater for the domestic and drinking needs. Earlier researches include the bioremediation and physico-chemical mechanisms in removal of toxic/heavy metals from water but still faced several post-treatment issues. The advancement in science and technology paved a path as nanotechnology to overcome these problems. In this current investigation, the CuO nanoparticles (CuONPs) and ZnO nanoparticles (ZnONPs) were synthesized from endophytic fungal strain and characterized which were previously reported. The groundwater samples were collected near, in, and around of the garbage-dump site of Vellalore-Kurichi village, Coimbatore, Tamil Nadu, India; three areas were selected, and water samples were collected. The basic physico-chemical parameters such as BOD, COD, TDS, hardness, pH, chlorides, sulfates, nitrates, and heavy metal(s) of the collected samples were analyzed. The adsorption studies were initiated with three different concentrations of CuONPs and ZnONPs in 100 mL of polluted groundwater samples, and the kinetics was started with 0th min and extended till 180 min. The adsorption rate increased with the increase in time; the CuONPs and ZnONPs adsorbed the few pollutants that also included arsenic (V) effectively. The nanoremediated samples were further taken to determine the effectiveness in aiding the plant growth promotion, and this was executed in Trigonella sp. plants. The plants were grown well which was compared to the control plants, and the phytochemical assessment was carried out. The presence of phytochemicals of the plants grown in nanoremediated samples was similar to that of control plants. Further, the CuONPs and ZnONPs have the ability in remediating the pollutants/contaminants in the groundwater.

Zinc oxide nanoparticles (ZnO NPs) are inorganic compounds listed as generally recognized as safe (GRAS) materials and have been used in plant production as well as for plant disease control. This study investigated the antibacterial efficacy of ZnO NPs with various surface areas against Xanthomonas campestris pv. campestris, assessed the effectiveness of ZnO NPs in controlling black rot disease in Chinese kale, and examined the influence of ZnO NPs application on soil bacterial communities. The results showed that ZnO NPs with high surface area effectively inhibited X. campestris pv. campestris by restraining growth and causing cell damage. Seed treatment and foliar spray application of high surface area ZnO NPs at 250 mu g/mL significantly reduced the disease severity of black rot. Furthermore, in the greenhouse experiment, the soil bacterial communities in the treatment of plants applied with ZnO NPs did not differ from those in soil of nontreated plants. Therefore, ZnO NPs have the potential to serve as an alternative substance for plant disease management.