Currently, microplastic pollution represents a major problem and the mechanisms of resistance to microplastic pollution in plants have not been investigated extensively. Therefore, in this study, cucumber plants were treated with polystyrene (PS) of two different particle sizes (5 and 0.1 µm) to explore the effect of PS on the phenylpropane metabolic pathway. The results indicated that the 5 µm PS treatment significantly promoted the increase in cucumber plant height, while 0.1 µm PS treatment significantly promoted the achievement of maximum root length. Both 5 and 0.1 µm PS treatments significantly promoted the increase in fresh and dry weight of the aboveground and underground parts of the cucumber plants. In addition, the metabolites of the phenylpropane metabolic pathway, including naringenin, pinobanksin, caffeoylquinic acid, and sinapyl alcohol, were significantly accumulated in cucumber leaves treated with PS (5 and 0.1 µm). This indicates that cucumber plants can resist the stress caused by microplastic pollution by increasing the accumulation of metabolites such as flavonoids and phenolic acids. Treatment with both particle sizes of PS also significantly downregulated the expression of phenylalanine ammonia-lyase, trans-cinnamate 4-monooxygenase, hydroxycinnamoyl transferase, cinnamoyl-CoA reductase, peroxidase, and other enzyme-related genes, indicating that PS treatment decreased the stability of the cell wall and membrane by decreasing the rate of lignin synthesis and significantly increasing the relative permeability of the plasma membrane. Changes in β-glucosidase activity and increase in levels of soluble protein and soluble sugar content represent strategies adopted by plants to maintain the structure of cell walls and cell membranes. The results of the present study provide new insights into the mechanisms underlying plant resistance to microplastic pollution.

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聚苯乙烯微塑料对黄瓜植株苯丙烷代谢途径的影响

目前，微塑料污染是一个主要问题，植物抵抗微塑料污染的机制尚未得到广泛研究。因此，在本研究中，用两种不同粒径（5μm和0.1μm）的聚苯乙烯（PS）处理黄瓜植物，以探讨PS对苯丙烷代谢途径的影响。结果表明，5μm PS处理显着促进黄瓜株高的增加，0.1μm PS处理显着促进最大根长的实现。 5和0.1 µm PS处理均显着促进了黄瓜植株地上和地下部分鲜重和干重的增加。此外，苯丙烷代谢途径的代谢物，包括柚皮素、Pinobanksin、咖啡酰奎尼酸和芥子醇，在经过 PS（5 和 0.1 µm）处理的黄瓜叶片中显着积累。这表明黄瓜植株可以通过增加黄酮类、酚酸等代谢物的积累来抵抗微塑料污染带来的胁迫。两种粒径的PS处理也显着下调苯丙氨酸解氨酶、反式肉桂酸4-单加氧酶、羟基肉桂酰转移酶、肉桂酰辅酶A还原酶、过氧化物酶和其他酶相关基因的表达，表明PS处理降低了PS的稳定性。通过降低木质素合成速率并显着增加质膜的相对渗透性来破坏细胞壁和细胞膜。 β-葡萄糖苷酶活性的变化以及可溶性蛋白质和可溶性糖含量水平的增加代表植物维持细胞壁和细胞膜结构所采取的策略。本研究的结果为植物抵抗微塑料污染的机制提供了新的见解。