Effects of zinc oxide nanoparticles on enzymatic and nonenzymatic antioxidant content, germination, and biochemical and ultrastructural cell characteristics of Portulaca oleracea L.

Abstract

This report focuses on the application of zinc oxide nanoparticles (ZnO NPs) carrying phycomolecule ligands as a novel plant growth promoter aimed at increasing the crop productivity of purslane (<em>Portulaca oleracea</em> L.). Experiments were performed under controlled greenhouse conditions using a completely randomized design with nine replications. Purslane seeds were treated with four concentrations of ZnO NPs (0, 10, 100, and 500 mg L<sup>−1</sup>) and four concentrations of bulk ZnO (0, 10, 100, and 500 mg L<sup>−1</sup>). The ultrastructural characteristics of the leaves of the plants treated with of 500 mg L<sup>−1</sup> ZnO NPs were determined using transmission electron microscopy (TEM). The results indicated that the treatment with ZnO NPs increased the content of chlorophyll <em>a</em> and chlorophyll <em>b</em>, carotenoids, and total phenolic and flavonoid compounds significantly more than the treatment with bulk ZnO. Our findings also showed that the application of high concentrations of ZnO NPs is the most effective strategy to considerably induce the antioxidant capacity and enzymes of purslane plants. Furthermore, the seed germination percentage and sprout growth rates were significantly higher in the plants treated with 500 mg L<sup>−1</sup> of ZnO NPs (100% ±0.00), compared to the control plants (93.33% ±1.66). The TEM images revealed the concentration of ZnO NPs and cell membrane rupture, as well as a deformation in the shape of chloroplasts and a decrease in their number in the plants treated with 500 mg L<sup>−1</sup> ZnO NPs, compared to the control plants. Owing to their toxicity, high concentrations of ZnO NPs lead to oxidative stress in plants. Thus, our findings provide a new alternative strategy for increasing crop productivity, i.e., the application of ZnO NPs as a novel plant growth booster, in comparison with the bulk ZnO treatment.

Foliar Sprayed Green Zinc Oxide Nanoparticles Mitigate Drought-Induced Oxidative Stress in Tomato

“…Increased concentrations of AsA and phenolic compounds in tomato leaves have been reported in the present study when 25 and 50 mg/L ZnO-NPs were applied under all drought levels. These findings are consistent with those previously reported by Iziy et al [45], in which exogenous application of ZnO-NPs improved the phenolic content in Portulaca oleracea L. The significant reduction in AsA and phenols concentration and induction of MDA and H 2 O 2 in response to foliar application of 100 mg/L ZnO-NPs indicates decreases in antioxidant potential which could be due to Zn toxicity, since Zn, as a heavy metal, at this concentration, could be too high for tomato plants. Javed et al [46] studied the effect of ZnO-NPs on the phenolic content of Stevia rebaudiana and showed a marked decrease in phenols content due to treatment with 100 and 1000 mg/L NPs which results in a decrease in antioxidant activity.…”

Impacts of zinc oxide nano and bulk particles on redox-enzymes of the Punica granatum callus

“…Current data showed that with increased levels of NPs or BPs in the nutrient medium, POD activity decreased in pomegranate callus tissues, and these findings are consistent with earlier work that found adverse impacts of ZnONPs treatments on POD activity in purslane roots 55 . Unlike CAT activity, POD activity considerably decreased in NPs or BPs treated calli.…”

The antifungal effect of MgO and ZnO nanoparticles against powdery mildew disease of pepper (Capsicum annuum L.) under greenhouse conditions

“…However, a concentration of 20 mg L −1 caused a decline in peroxidase activity. These results were similar with previous research that discovered negative effects of ZnONPs treatments on peroxidase activity in purslane roots (Iziy et al, 2019). Low activities in antioxidant enzymes at the highest ZnONPs concentration could be attributed to the accumulation of free radicals in stressed plant tissues (Malar et al, 2016).…”