Due to many uses of zinc oxide nanoparticles (ZnO NPs) in various industries, the release of these particles in the environment and their effects on living organisms is inevitable. In this study, the role of salicylic acid (SA) pretreatments in modulating the toxicity of ZnO NPs was investigated using a hydroponic system. After pretreatment with different concentrations of SA (0, 25, 75, and 150 μM), Chenopodium murale plants were exposed to ZnO NPs (50 mg L⁻¹). The results showed that exogenous SA increased the length, weight, chlorophyll, proline, starch, and soluble sugars in the plants. Besides, SA pretreatments improved water status in the plants treated with ZnO NPs. In SA-pretreated plants, increased activity of catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD) was associated with a decline in electrolyte leakage (EL %) and membrane peroxidation. Under NPs stress, SA pretreatments increased the content of phenolic compounds by increasing the activity of phenylalanine ammonia-lyase (PAL). Exogenous SA reduced the translocation of larger amounts of Zn to the shoots, with more accumulation in the roots. This result can be used to produce healthy food from plants grown in environments contaminated with nanoparticles. It seems that all concentrations of SA reduced the symptoms of ZnO NPs toxicity in the plant by strengthening the function of the antioxidant system and increasing the content of some metabolites. Findings also suggest that SA pretreatment can compensate for the growth reduction caused by ZnO NPs.

INTRODUCTION: The effect of the glass industry on urban soil metal characterization was assessed in the area of Firozabad, India. A comprehensive profile of metal contamination was obtained in five zones each containing five specific sites. FINDINGS: Zn, Cd, and As showed a greater accumulation, whereas accumulation of Ni and Cu was high in limited samples. Positive correlation was found for the metal pairs Cu-Zn, Cu-Co, and Cu-Cr at P < 0.01. Moderate positive correlation was also observed between Zn-Co, Mn-Cd, Mn-As, Pb-As, and Ni-Cu at P < 0.05. Integrated contamination indices indicate that 60% of the sites were heavily contaminated while 28% were moderately contaminated. Phytoremedial potential of native flora (twenty herbs, three shrubs, and two grasses) was also assessed by analyzing their metal uptake. Individual elements displayed remarkably different patterns of accumulation in soils as well as in plants. Mn, Zn, Cu, and As were predominantly partitioned in shoots, Co and Cd in roots while Pb, Cr, and Ni almost equally between shoots and roots. Most plants exhibited capabilities in mobilizing Co, Pb, Cr, and Ni in the root zone. CONCLUSION: Potential phytoextractors include Datura stramonium and Chenopodium murale while phytostabilizers include Calotropis procera and Gnaphalium luteo-album. Poa annua showed potential in both categories. None of the species showed phytoremedial potential for Co and Ni.

To understand toxic effect of Zn oxide nanoparticles (ZnO NPs) on Chenopodium murale, 40-day-old plants were exposed to 10, 50, and 250 mg L⁻¹ of NPs using hydroponic system under controlled light and temperature conditions. Aboveground parts and roots were harvested 3 and 6 days after treatments and evaluated for some growth and biochemical indices. By increasing the concentration of ZnO NPs, the content of Zn increased in the roots more than the shoots. Our findings showed that all ZnO NPs treatments resulted in a decrease in growth, total chlorophyll content and soluble proteins, while the content of carotenoids, lipid peroxidation, leaf hydrogen peroxide (H₂O₂), and leaf electrolyte leakage increased significantly compared with the control. These changes, along with increased proline content and catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD) activities in the treated plants, suggest that all concentrations of ZnO NPs used in this study strongly induced oxidative stress. A decline in growth-related indicators can be considered as an indicator of ZnO NPs phytoxicity in C. murale. Based on the concentration of Zn dissolved in the solution, the effects of Zn released into the nutrient solution may be greatly involved in induction of toxicity and retardation of growth at least under our experimental conditions. The results of this study suggest that an important mechanism of ZnO NPs phytotoxicity may be the exacerbation of oxidative stress and damage to biomembranes.

Chenopodium album and C. murale are cosmopolitan, annual weed species of notable economic importance. Their unique biological features, including high reproductive capacity, seed dormancy, high persistence in the soil seed bank, the ability to germinate and grow under a wide range of environmental conditions and abiotic stress tolerance, help these species to infest diverse cropping systems. C. album and C. murale grow tall and absorb nutrients very efficiently. Both these species are allelopathic in nature and, thus, suppress the germination and growth of native vegetation and/or crop plants. These weed species infest many agronomic and horticultural crops and may cause > 90% loss in crop yields. C. album is more problematic than C. murale as the former is more widespread and infests more number of crops, and it also acts as an alternate host of several crop pests. Different cultural and mechanical methods have been used to control these weed species with varying degrees of success depending upon the cropping systems and weed infestation levels. Similarly, allelopathy and biological control have also shown some potential, especially in controlling C. album. Several herbicides have been successfully used to control these species, but the evolution of wide-scale herbicide resistance in C. album has limited the efficacy of chemical control. However, the use of alternative herbicides in rotation and the integration of chemicals and biologically based control methods may provide a sustainable control of C. album and C. murale.