Plastic particles deposited from the atmosphere can be absorbed by crops and have significant effects on crops. However, current knowledge regarding the particle size effects on the phytotoxicity of airborne plastic particles to leafy vegetables is limited. Therefore, in the present study, we examined the effects of foliar exposure to polystyrene nanoplastics (PS NPs, 100 nm) and polystyrene microplastics (PS MPs, 1 μm) of different concentrations on the biomass, physiological and biochemical indexes (i.e., chlorophyll, antioxidant enzyme and malonaldehyde (MDA), nutritional quality), and the metabolism of lettuce (Lactuca sativa L.). PS concentration, rather than particle size, exerted significant effects on these physiological and biochemical indexes. Both PS NPs and PS MPs at the high concentration of 35.0 mg L⁻¹ decreased the contents of chlorophyll a, chlorophyll b, and total chlorophyll in lettuce leaves. Further, the nutritional quality of lettuce leaves was generally improved as evidenced by the increased soluble protein and soluble sugar as well as the decreased nitrate. The decrease of superoxide dismutase activity and accumulation of MDA suggested oxidative stress induced by PS NPs and PS MPs. Metabolomics analysis showed that foliar exposure to PS NPs disturbed the energy metabolism, glutathione metabolism, and ABC transporter, whereas PS MPs perturbed the lipid metabolism and cutin, suberin and wax biosynthesis in lettuce leaves. The different metabolic responses between PS NP and PS MP treatments highlighted the importance of particle size in investigating the phytotoxicity of airborne plastic particles. These results provided effective information for the risk assessment of airborne plastic particles.

中文翻译：

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生菜 （Lactuca sativa L.） 叶面暴露后对聚苯乙烯纳米塑料和微塑料的代谢反应


从大气中沉积的塑料颗粒可以被农作物吸收，并对农作物产生重大影响。然而，目前关于颗粒粒度对空气中塑料颗粒对叶菜植物毒性的影响的知识是有限的。因此，在本研究中，我们研究了叶面暴露于不同浓度的聚苯乙烯纳米塑料 （PS NPs， 100 nm） 和聚苯乙烯微塑料 （PS MPs， 1 μm） 对生菜生物量、生理生化指标（即叶绿素、抗氧化酶和丙二醛 （MDA）、营养品质）和代谢的影响L.).PS 浓度而不是粒径对这些生理生化指标有显著影响。高浓度 35.0 mg L⁻¹ 的 PS NPs 和 PS MPs 均降低了生菜叶片中叶绿素 a 、叶绿素 b 和总叶绿素的含量。此外，生菜叶的营养品质普遍得到改善，可溶性蛋白和可溶性糖的增加以及硝酸盐的减少证明了这一点。代谢组学分析表明，叶面暴露于 PS NPs 会干扰莴苣叶片的能量代谢、谷胱甘肽代谢和 ABC 转运蛋白，而 PS MPs 会扰乱莴苣叶片的脂质代谢和角质、软木素和蜡质的生物合成。PS NP 和 PS MP 处理之间的不同代谢反应突出了粒径在研究空气中塑料颗粒的植物毒性中的重要性。 这些结果为空气中塑料颗粒的风险评估提供了有效的信息。