College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, PR China.
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, PR China.
Environ Pollut. 2020 May;260:114055. doi: 10.1016/j.envpol.2020.114055. Epub 2020 Jan 23.
Due to the potential toxicity of polycyclic aromatic hydrocarbons (PAHs) to humans, the uptake and translocation of PAHs in food crops have gained much attention. However, it is still unclear whether phloem participates in the acropetal translocation of PAHs in plants. Herein, the evidence for acropetal translocation of phenanthrene (a model PAH) via phloem is firstly tested. Wheat (Triticum aestivum L.) new leaves contain significantly higher phenanthrene concentration than old leaves (P < 0.05), and the inhibitory effect on phenanthrene translocation is stronger in old leaves after abscisic acid and polyvinyl alcohol (two common transpiration inhibitors) application. Phenanthrene concentration in xylem sap is slightly higher than in phloem sap. Ring-girdling treatment can significantly reduce phenanthrene concentration in castor bean (Ricinus communis L.) leaves. Two-photon fluorescence microscope images indicate a xylem-to-phloem and acropetal phloem translocation of phenanthrene in castor bean stem. Therefore, phloem is involved in the acropetal translocation of phenanthrene in wheat seedlings, especially when the xylem is not mature enough in scattered vascular bundle plants. Our results provide a deeper understanding of PAH translocation in plants, which have significant implications for food safety and phytoremediation enhancement of PAH-contaminated soil and water.
由于多环芳烃 (PAHs) 对人类具有潜在毒性，因此食物作物中 PAHs 的吸收和迁移引起了广泛关注。然而，PAHs 是否通过韧皮部在植物中进行向顶转移仍不清楚。本文首次验证了菲（一种模型 PAH）通过韧皮部进行向顶转移的证据。小麦（Triticum aestivum L.）新叶中的菲浓度明显高于老叶（P<0.05），并且在脱落酸和聚乙烯醇（两种常见的蒸腾抑制剂）处理后，老叶对菲迁移的抑制作用更强。木质部汁液中的菲浓度略高于韧皮部汁液。环割处理可显著降低蓖麻（Ricinus communis L.）叶片中的菲浓度。双光子荧光显微镜图像表明，在蓖麻茎中存在菲从木质部到韧皮部和向顶韧皮部的转移。因此，在分散维管束植物中，当木质部不够成熟时，韧皮部参与了小麦幼苗中菲的向顶转移。我们的研究结果为 PAH 在植物中的迁移提供了更深入的了解，这对于食品安全以及受 PAH 污染的土壤和水的植物修复增强具有重要意义。
