Laboratory of Plant Ecophysiology, Graduate School of Bioscience and Biotechnology, Fukui Prefectural University, Eiheiji, Fukui, Japan.
Plant Signal Behav. 2020;15(2):1719749. doi: 10.1080/15592324.2020.1719749. Epub 2020 Feb 3.
Passage cells are frequently found in the exodermis and the endodermis of the roots. Because passage cells lack an apoplastic diffusion barrier, they are thought to provide pathways for the transport of nutrients and the entrance of endomycorrhizal fungi. Exodermal passage cells possess Casparian strips but not suberin lamellae. So far, exodermal passage cells have not been associated with a particular internal structure. In some wetland plants, the outer part of the root (i.e., epidermis, exodermis, and sclerenchyma) of emerging lateral root primordia has an oxygen leaky zone called a window. The exodermis at the window site also lacks suberin lamellae, but it remains unclear whether the exodermis at the window site also lacks Casparian strips. Here, we report that several of the exodermal cells in the window of grown under aerated or deoxygenated stagnant agar nutrient solution also lack lignin, which is a major constituent of Casparian strips. The sclerenchyma cells that form part of the window also lacked lignin deposits. Sites at which lateral root primordia developed were highly permeable to an apoplastic tracer (periodic acid). These observations indicate that windows consist of a novel type of passage cell at the exodermis that lacks lignin as well as suberin lamellae.
通道细胞通常存在于根的外表皮和内皮层中。由于通道细胞缺乏质外体扩散屏障，它们被认为提供了养分运输和内生真菌进入的途径。外表皮通道细胞具有凯氏带，但没有栓质层。到目前为止，外表皮通道细胞还没有与特定的内部结构相关联。在一些湿地植物中，侧根原基的外部分（即表皮、外表皮和厚壁组织）有一个被称为窗口的氧气泄漏区。窗口处的外表皮也缺乏栓质层，但目前尚不清楚窗口处的外表皮是否也缺乏凯氏带。在这里，我们报告说，在充气或缺氧停滞琼脂营养溶液中生长的 的窗口中的几个外表皮细胞也缺乏木质素，木质素是凯氏带的主要成分。形成窗口一部分的厚壁组织细胞也缺乏木质素沉积物。侧根原基发育的部位对质外体示踪剂（过碘酸）具有高度通透性。这些观察结果表明，窗口由一种缺乏木质素和栓质层的新型通道细胞组成。
