Mitigating the effects of PVC microplastics and mercury stress on rye (Secale cereale L.) plants using zinc oxide−nanoparticles

Abstract

AbstractIn present years, the use of zinc oxide nanoparticles (ZnO‐NPs) has received great attention due to increase in the nutrient accumulation by plants for improving the capability of agronomic Zn biofortification. Although, the emergence of polyvinyl chloride (PVC) microplastics (MPs) as pollutants in agricultural soils is increasingly alarming, presenting significant toxic threats to soil ecosystems. The present work studied the impact of different levels of PVC‐MPs, namely 0 (no PVC‐MPs), 2, and 4 mg L−1, along with mercury (Hg) levels of 0 (no Hg), 10, and 25 mg kg−1 in the soil, while concurrently applying with ZnO‐NPs at 0 (no ZnO‐NPs), 50, and 100 μg mL−1 to rye (Secale cereale L.) plants. This study aimed to examine plant growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress indicators, and the response of various antioxidants (enzymatic and non‐enzymatic) and their specific gene expression, proline metabolism, the ascorbic acid–dehydroascorbic acid (AsA–GSH) cycle, and cellular fractionation in the plants. The research outcomes indicated that elevated levels of PVC‐MPs and Hg stress in the soil notably reduced plant growth and biomass, photosynthetic pigments, and gas exchange attributes. However, PVC‐MPs and Hg stress also induced oxidative stress in the roots and shoots of the plants by increasing malondialdehyde (MDA), hydrogen peroxide (H2O2), and electrolyte leakage (EL) which also induced increased compounds of various enzymatic and non‐enzymatic antioxidants, and also the gene expression and sugar content. Furthermore, a significant increase in proline metabolism, the AsA–GSH cycle, and the pigmentation of cellular components was observed. Although, the application of ZnO‐NPs showed a significant increase in plant growth and biomass, gas exchange characteristics, enzymatic and non‐enzymatic compounds, and their gene expression and also decreased oxidative stress. In addition, the application of ZnO‐NPs enhanced cellular fractionation and decreased the proline metabolism and AsA–GSH cycle in S. cereale plants. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.