Combined Phytotoxicity of Microplastics andLead on the Growth and Physio-BiochemicalCharacteristics of Tobacco (<i>Nicotiana tabacum</i>)

Microplastic and heavy metal contaminants have attracted global concern due to their ubiquitous presence and long-lasting persistence, yet little is known about their interactions on plant growth performance.Here, different concentrations of polyethylene (PE)-microplastics (MPs) and lead (Pb) were applied to soils to investigate their impacts on tobacco plants.Our results showed that tobacco plants grown in PE-MP-and Pb-contaminated soils displayed a significant reduction in leaf pigment content, photosynthetic efficiency, and plant biomass, as well as a remarkable increase in the contents of hydrogen peroxide, superoxide ions, and malondialdehyde.The Pb contents in plant roots decreased from 886 mg kg -1 to 765 mg kg -1 with increasing concentrations of PE-MPs, while the leaf Pb concentrations remained unaffected.The impaired photosynthetic performance in tobacco leaves was attributed to Pb stress, causing stomatal closure and PE-MP-induced nonstomatal limitation.Moreover, the coexistence of PE-MPs and Pb damaged the PSII reaction center, disturbed the electron transport process, and reduced photosynthetic efficiency.To alleviate oxidative damage, the contents of proline and soluble sugar, along with the antioxidant enzyme activities, underwent a significant increase in tobacco plants.This work offers valuable insights for addressing the challenges posed by the emergence of contaminants in agricultural production.