Climate-resilient tomato production: potassium nanoparticles regulate carbohydrate metabolism and oxidative defense under nanoplastic stress

Nanoplastics are emerging environmental contaminants that threaten sustainable crop production and food safety by disrupting mineral nutrient homeostasis, impairing physiological processes, and inducing reactive oxygen species (ROS)-mediated oxidative stress. Nanoparticle-based interventions have emerged as a promising strategy for mitigating nanoplastic-induced phytotoxicity and enhancing plant stress resilience. In the present study, the protective effects of potassium nanoparticles (K-NPs; 10 mmol L⁻ 1 ) against nanoplastic-induced stress (4 mg kg⁻ 1 soil) were investigated in Solanum lycopersicum using a randomized complete block design with five biological replicates per treatment. Nanoplastics were applied to the soil, whereas K-NPs were administered as a foliar spray at 30 days after sowing (DAS). Nanoplastic exposure markedly inhibited plant growth and physiological performance, significantly reducing root length (68.81%), shoot dry weight (20.53%), SPAD chlorophyll value (70.85%), net photosynthetic rate (46.67%), protein content (13.82%), and Ca 2 ⁺ content (41.01%) relative to the control. In contrast, foliar application of K-NPs effectively alleviated these adverse effects, significantly enhancing shoot length (17.25%), leaf area (10.89%), and glucose content (18.62%) under nanoplastic stress. Furthermore, nanoplastic exposure markedly increased oxidative damage, as evidenced by elevated malondialdehyde (40.47%), hydrogen peroxide (26.87%), and superoxide anion (42.35%) levels, indicating severe membrane lipid peroxidation and excessive ROS accumulation. K-NP treatment substantially suppressed the accumulation of these oxidative stress markers while enhancing the activities of key antioxidant enzymes, including superoxide dismutase, catalase, and peroxidase, thereby strengthening the cellular antioxidant defense system. In addition, K-NPs restored mineral nutrient homeostasis and improved physiological and biochemical performance under nanoplastic stress. Collectively, these findings demonstrate that foliar application of K-NPs effectively mitigates nanoplastic-induced phytotoxicity by enhancing antioxidant capacity, maintaining nutrient homeostasis, and preserving physiological functions, highlighting their potential as a sustainable nanotechnology-based strategy for improving crop resilience under emerging nanoplastic pollution.