Comparative toxicological effects of traditional and biodegradable microplastics on pepper (Capsicum annuum L.):...

Microplastics (MPs), as emerging environmental contaminants, increasingly threaten plant performance in agricultural ecosystems, yet the differential toxicity of traditional and biodegradable MPs remains unclear. Here, we conducted a 60-day soil culture experiment to evaluate the effects of six MPs, four traditional polymers and two biodegradable plastics, on pepper (Capsicum annuum L.) at 0.1 % and 0.5 % (w/w). Growth inhibition occurred in a type- and dose-dependent manner, with non-degradable PP-MPs and PS-MPs exerting stronger effects than biodegradable MPs. PBS-MPs caused the most severe oxidative stress, increasing H₂O₂ content by 205.4 %. Metabolomic analyses revealed metabolic reprogramming under MPs exposure, with flux shifting from photosynthetic carbon assimilation/glycolysis to the pentose phosphate pathway. Notably, PVC-MPs imposed stronger inhibition on carbon assimilation/glycolysis. Metabolomic analysis further revealed that oxidative stress was closely associated with metabolic reprogramming: biodegradable MPs (PLA, PBS) markedly disrupted aromatic amino acid biosynthesis (e.g., tyramine decreased by 73.8 %), thereby weakening the basis for antioxidant defense, whereas traditional PS-MPs specifically suppressed downstream phenylpropanoid metabolism (e.g., 4-hydroxycinnamic acid and sinapic acid decreased). Collectively, these findings demonstrate that biodegradable and traditional MPs induce phytotoxicity through distinct mechanisms: biodegradable MPs primarily trigger oxidative damage and perturb primary metabolism, whereas traditional MPs preferentially suppress energy metabolism and secondary defense pathways. This study provides mechanistic insights into MPs-induced stress responses in pepper and highlights potential risks of both traditional and biodegradable MPs to agroecosystem health.