PJB-2023-339
EFFECT OF ZINC OXIDE NANOPARTICLES IN STRESS ALLEVIATION FOR RICE PLANTS GROWN IN LEAD CONTAMINATED WATER
Irum Hassan
Abstract
Lead toxicity is harmful to plants, animals, and humans, as photosynthesis is inhibited, mineral nutrition and water balance are upset, growth is stunted, causes root chlorosis and blackening, affects hormonal status, and alters membrane structure and permeability. ZnO (zinc oxide) nanoparticles were proposed as a potential solution towards alleviating lead stress in plants due to zinc's role as a cofactor for various plant enzymes, chlorophyll formation, starch-to-sugar conversion, and auxin production. To determine the effects of ZnO nanoparticles on rice growth under lead stress (500 ppm and 1000 ppm), we experimented with an investigation into the physiological, biochemical, and antioxidant responses of ZnO-treated and non-treated rice variety Dir-97 in hydroponic culture. For treatment seeds were primed in a 5 ppm ZnO nanoparticle solution for 24 hours in the dark. When the lead concentration was raised, a pronounced drop in biomass was seen. Further, with increasing lead stress, we observed a stress response in the form of an increase in metabolic products, including total soluble sugars, total soluble proteins, and glycine betaine, along with antioxidants like catalase, ascorbate peroxidase, peroxidase, superoxide dismutase, and malonyl dialdehyde content in rice. In comparison, plants treated with nanoparticle solution showed a decrease in these contents. Our results indicate that the nanoparticle solution alleviated lead stress and positively affected plant development and growth by inducing physiological and morphological changes. However, high concentrations of zinc can increase membrane leakiness, and disturb the detoxification of reactive oxygen species, gene expression, and normal enzymatic activity. Therefore, we recommend using a low ppm nanoparticle solution for optimal benefits, while high ppm solutions should be avoided due to their negative role.
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