Wierzbicka M
Laboratory of Electron Microscopy, Institute of Botany, University of Warsaw, Warsaw, Poland.
Plant Cell Environ. 1987 Jan;10(1):17-26. doi: 10.1111/j.1365-3040.1987.tb02075.x.
Lead migrating through the tissues of Allium cepa L. was found, by electron microscopy, autoradiography and other methods, to encounter at least three barriers to penetration. The layers of protoderm and hypodermic meristematic cells in the root meristematic zone and the layer of endodermis in the mature root zone were barriers to apoplastic transport. The central zone was a barrier to apoplastic and symplastic transport. It comprises the quiescent centre in the root meristem and the central part of the root cap. The cells of the deepest ground meristematic tissue layers seemed to act as a barrier, which keeps lead away from the procambium. Lead accumulated in roots but it was not uniformly distributed between their various tissues. The largest amount of lead accumulated both in ground meristematic and cortex tissues.
通过电子显微镜、放射自显影术和其他方法发现，铅在洋葱组织中迁移时至少会遇到三个渗透障碍。根分生组织区的原表皮层和皮下分生细胞层以及成熟根区的内皮层是质外体运输的障碍。中心区是质外体和共质体运输的障碍。它包括根分生组织中的静止中心和根冠的中心部分。最深层基本分生组织层的细胞似乎起到了屏障作用，使铅远离原形成层。铅在根中积累，但在根的不同组织中分布并不均匀。基本分生组织和皮层组织中积累的铅量最大。
