Combined exposure of PVC-microplastic and mercury chloride (HgCl 2 ) in sorghum ( Pennisetum glaucum L.) when its seeds are primed titanium dioxide nanoparticles (TiO 2 –NPs)

The present work studied the impact of different levels of PVC–microplastics (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 titanium dioxide–nanoparticles (TiO 2 –NPs) at 0 (no TiO 2 –NPs), 50, and 100 µg mL −1 to sorghum ( Pennisetum glaucum 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 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 (H 2 O 2 ), 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 TiO 2 –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 TiO 2 –NPs enhanced cellular fractionation and decreased the proline metabolism and AsA-GSH cycle in P . glaucum 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.