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The hormetic dose-risks of polymethyl methacrylate nanoplastics on chlorophyll a fluorescence transient, lipid composition and antioxidant system in Lactuca sativa
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Researchers found that polymethyl methacrylate nanoplastics caused hormetic dose-dependent effects in lettuce, reducing growth and water content while disrupting photosynthetic performance, lipid composition, and antioxidant systems at varying concentrations.
Nanoplastic pollution has become an increasing problem due to over-consumption and degradation in ecosystems. A little is known about ecological toxicity and the potential risks of nanoplastics on plants. To better comprehend the hormetic effects of nanoplastics, the experimental design was conducted on the impacts of polymethyl methacrylate (PMMA) on water status, growth, gas exchange, chlorophyll a fluorescence transient, reactive oxygen species (ROS) content (both content and fluorescence visualization), lipid peroxidation and antioxidant capacity (comparatively between leaves and roots). For this purpose, PMMA (10, 20, 50 and 100 mg L) was hydroponically applied to Lactuca sativa for 15 days(d). PMMA exposure resulted a decline in the growth, water content and osmotic potential. As based on assimilation rate (A), stomatal conductance (g), and intercellular CO concentrations (C), the decreased stomatal limitation (L) and, A/C and increased intrinsic mesophyll efficiency proved low carboxylation efficiency showing impaired photosynthesis as a non-stomatal limitation. PMMA toxicity increased the trapping fluxes and absorption with a decrease in electron transport fluxes caused the disruption in reaction centers of photosystems. The leaves and roots had a similar effect against PMMA toxicity, with increased superoxide dismutase (SOD) activity. Although, catalase (CAT) and peroxidase (POX) of leaves increased under 10 mg L PMMA, these defense activities failed to prevent radicals from attacking. Compared to the leaves, the lettuce roots showed an intriguing result for AsA-GSH cycle against PMMA exposure. In the roots, the lowest PMMA application provided the high ascorbate/dehydroascorbate (AsA/DHA), GSH/GSSG and the pool of AsA/glutathione (GSH) and non-suppressed GSH redox state. Also, 10 mg L PMMA helped remove high hydrogen peroxide (HO) by both glutathione peroxidase (GPX) and glutathione S-transferase (GST). Since this improvement in the antioxidant system could not be continued in roots after higher applications than 20 mg L PMMA, TBARS (Thiobarbituric acid-reactive substances), indicating the level of lipid peroxidation, and HO increased. Our findings obtained from PMMA-applied lettuce provide new information to advance the tolerance mechanism against nanoplastic pollution.
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Researchers compared the effects of engineered nanoparticles and polystyrene nanoplastics on lettuce and found that all types caused oxidative stress in roots at high concentrations. Each nanoparticle type triggered different defensive metabolic pathways in the plants, and nanoplastics specifically altered amino acid and vitamin metabolism. Since lettuce is widely consumed raw, these findings raise questions about how nanoplastic contamination in agricultural soil could affect the safety of leafy vegetables.
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Researchers studied the effects of polyethylene micro- and nanoplastics on lettuce plants, varying both particle size and concentration. They found that particle size played a pivotal role in influencing plant growth, photosynthetic activity, and metabolic processes, with nanoplastics generally causing more pronounced effects than larger microplastics. The study suggests that the smallest plastic particles pose the greatest risk to crop health by disrupting plant physiology at multiple levels.
Metabolic response of lettuce (Lactuca sativa L.) to polystyrene nanoplastics and microplastics after foliar exposure
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Researchers exposed lettuce plants to polystyrene nanoplastics and microplastics through their leaves and found that the particles altered the plant's metabolism differently depending on particle size. This foliar exposure pathway means that microplastics and nanoplastics settling on leafy vegetables from the air can change the plant's internal chemistry. Since lettuce is widely consumed raw, these metabolic changes raise questions about how microplastic-contaminated produce might affect nutritional quality and human health.
Foliar-applied polystyrene nanoplastics (PSNPs) reduce the growth and nutritional quality of lettuce (Lactuca sativa L.)
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When lettuce plants were exposed to polystyrene nanoplastics sprayed on their leaves, they grew significantly smaller and produced less nutritious food, with reduced essential amino acids and micronutrients. The nanoplastics were absorbed through leaf pores and could travel down to the roots, causing oxidative stress throughout the plant. This study warns that airborne nanoplastic pollution could reduce both the quantity and nutritional quality of food crops.
Nanoplastic Aggregation Driven by Environmental Components Reshapes Hormone Signaling and Energy Metabolism in Lactuca sativa
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Researchers found that environmentally driven aggregation of nanoplastics governs their toxicity to lettuce, with large aggregates causing up to 71% increases in oxidative stress markers and significant growth inhibition while small or dispersed aggregates produced only mild adaptive responses—showing that aggregate size, not just concentration, must be factored into ecological risk assessments.
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