Synergistic Effects of Polyethylene Microplastics and PGPR Pseudomonas fluorescens on Biochemical and Physiological Responses in Potato (Solanum tuberosum)

Plastic pollution poses a significant threat to agricultural systems; however, its impacts on crop physiology and yield remain insufficiently understood. This study evaluated the effects of low-density polyethylene (LDPE) microplastics (0.1%, 0.5%, 1.5%, 3%, and 5% w/w) on the stress response, nutritional composition, growth, and yield of potato (Solanum tuberosum), and assessed the bioremediation potential of Pseudomonas fluorescens through a pot experiment. LDPE exposure induced pronounced oxidative stress in roots and tubers, as indicated by elevated MDA and H₂O₂ levels, alongside strong activation of antioxidant defences. Essential minerals (K, Na, Fe) decreased in roots by 44–50%, whilst tubers exhibited reductions in Ca (50%), carbohydrates (2.9%), and protein content (6.6%) at the highest LDPE level (5% w/w). These disruptions corresponded with significant declines in plant height, root length, and fresh biomass. Tuber yield decreased by 63% under 5% LDPE in the absence of bacterial treatment. In contrast, P. fluorescens application markedly mitigated stress, reducing MDA levels, enhancing mineral uptake, and improving tuber growth, carbohydrate deposition, and tissue integrity. Yield increased by 36.8% compared to LDPE-only treatments. Scanning electron microscopy revealed intact starch granules in tubers treated with 5% LDPE + P. fluorescens, whereas granules appeared structurally distorted under LDPE alone. Microplastic particles were also detected within tuber tissues, confirming MP accumulation. Although P. fluorescens improved crop health, the persistence of MP bioaccumulation underscores the need for additional remediation strategies, including microbial consortia and pre-cultivation bio-extraction approaches, to safeguard food quality and safety.