Laboratory of Wood Biology, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589 Japan.
Am J Bot. 2005 Jul;92(7):1077-84. doi: 10.3732/ajb.92.7.1077.
The structure of the intervascular pit membranes of four dicotyledonous species (Salix sachalinensis, Betula platyphylla var. japonica, Acer mono, and Fraxinus mandshurica var. japonica) was examined by field-emission scanning electron microscopy. The intervascular pit membranes of F. mandshurica var. japonica had thin surface layers and a dense middle layer, while no similar middle layer was detectable in the other three species. In F. mandshurica var. japonica, the entire area of each pit membrane was densely covered with microfibrils. In the other three species, by contrast, openings were found in the pit membranes. In some of the intervascular pit membranes of S. sachalinensis, B. platyphylla var. japonica, and A. mono, microfibrils were sparsely interwoven in small areas of the pit membranes and openings of up to several hundred nanometers in diameter were present in such regions. These porous regions tended to be located in peripheral areas of pit membranes. In S. sachalinensis and B. platyphylla var. japonica, ethanol-soluble extracts, whose chemical nature and function remain unknown, were heavily distributed over the intervascular pit membranes. Our observations suggest that the structure of intervascular pit membranes is more complicated than has previously been acknowledged.
通过场发射扫描电子显微镜观察了四种双子叶植物（柳属、日本白桦、日本槭和白蜡属）的血管间纹孔膜的结构。日本白蜡属的血管间纹孔膜具有薄的表面层和密集的中间层，而其他三种植物则没有类似的中间层。在日本白蜡属中，每个纹孔膜的整个区域都被微纤维密集覆盖。相比之下，在其他三种植物中，纹孔膜上存在开口。在柳属、日本白桦和日本槭的一些血管间纹孔膜中，微纤维在纹孔膜的小区域中稀疏交织，并且在这些区域中存在直径达数百纳米的开口。这些多孔区域倾向于位于纹孔膜的周边区域。在柳属和日本白桦中，大量分布着化学性质和功能未知的乙醇可溶性提取物。我们的观察结果表明，血管间纹孔膜的结构比以前认为的更为复杂。
