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Differential physiological and biochemical responses of lettuce cultivars to polyethylene microplastic stress
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Scientists exposed two types of lettuce to microplastic-contaminated soil and found that different lettuce varieties react differently, activating their own internal antioxidant defenses to cope with the stress. This matters because microplastics are already widespread in farm soils, and understanding how crops respond could help researchers breed more resilient produce, though this study looked at plant stress responses, not yet whether eating the lettuce itself poses risks to people.
Polyethylene microplastics are widespread soil contaminants that may threaten agroecosystem stability and crop quality. However, plant physiological and biochemical responses to microplastic exposure, particularly cultivar-specific responses, remain insufficiently understood. This study evaluated the ecotoxicological effects of polyethylene microplastics on two lettuce (Lactuca sativa L.) cultivars, ‘Little Gem Red’ (LGR) and ‘Little Gem Green’ (LGG), and examined their biochemical defense responses under stress conditions. A 35-day pot experiment was conducted using microplastic concentrations of 0, 50, 250, and 1000 µg/mL. Growth parameters, photosynthetic pigments, oxidative stress markers, antioxidant enzyme activities, total antioxidant capacity, and key phytochemicals were analyzed. Microplastic exposure induced non-linear and cultivar-dependent responses. In LGR, antioxidant enzyme activity increased rapidly under low microplastic exposure, with superoxide dismutase and ascorbate peroxidase reaching peak values of 17.03 ± 0.11 and 2.28 ± 0.039 U/mg protein, respectively, at 50 µg/mL. In LGG, maximum enzyme activities occurred at 250 µg/mL, with superoxide dismutase and ascorbate peroxidase reaching 21.76 ± 0.33 and 0.67 ± 0.003 U/mg protein, respectively. LGG also showed sustained increases in phenolics and flavonoids under higher microplastic exposure, indicating greater involvement of non-enzymatic antioxidant pathways. These findings demonstrate that lettuce cultivars employ distinct biochemical adjustment strategies in response to polyethylene microplastics and highlight the importance of considering intraspecific variation when assessing crop responses to microplastic-contaminated soils.
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Researchers tested how three common types of microplastics (polystyrene, polyethylene, and polypropylene) affect lettuce growth and soil health. All three types inhibited plant growth, disrupted antioxidant systems in the leaves, and altered the microbial communities in the soil around roots, with polystyrene and polypropylene causing the most disturbance.
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Researchers grew lettuce in water containing polyethylene microplastics for 28 days and found that the plastics changed the chemical signals the roots released and caused oxidative damage in the leaves. While the plants looked mostly normal on the outside, the microplastics altered the root chemistry in ways that could affect nutrient uptake and plant defense. This is relevant to human health because lettuce is widely consumed and may be grown in microplastic-contaminated water or soil.
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Researchers grew lettuce in contaminated soil mixed with different types of microplastics, including fibers, glitter, and fragments from bags and bottles. They found that microplastics altered how heavy metals like lead, cadmium, and copper moved through the soil and into the plants, sometimes increasing uptake of toxic metals in roots while decreasing others in leaves. The results raise concerns about food safety in agricultural areas where both microplastic and heavy metal contamination overlap.
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