利用不同的顯微鏡技術研究翅柄鳳尾蕨（Pteris grevilleana Wall.）的脈狀異形細胞

Various Microscopic Methods for Investigating the Venuloid Idioblasts of Pteris grevilleana Wall

脈狀異形細胞（venuloid idioblast）（亦稱為假脈）泛指外觀像是葉脈的構造。在鳳尾蕨屬（Pteris）中的脈狀異形細胞，是一種細胞壁特別厚的長形表皮細胞。在本研究中，我們利用各種光學顯微鏡及掃描式電子顯微鏡技術研究翅柄鳳尾蕨的脈狀異形細胞。利用半偏光的光學顯微鏡技巧以及冷凍式桌上型掃描式電子顯微鏡技術，可以有效的觀察該異形細胞的形態並且偵測其分布。該異形細胞的邊緣為波浪狀，兩端尖或圓，分布在營養葉及孢子葉的上下表皮，其可在脈上、脈間或葉緣被找到，但不會出現在羽軸、小羽軸或者假孢膜上。就能量分散X射線光譜儀及組織化學染色的結果，顯示該異形細胞具有二氧化矽，而運用濕式灰化法（wet oxidation）得知其形態即類似於該異形細胞的矽酸體（silica body）。因此，翅柄鳳尾蕨的脈狀異形細胞可歸類為一種過去在鐵線蕨及書帶蕨類群中所被發現的矽異形細胞（spicular cells）。

Venuloid idioblasts are vein-like structures. In Pteris, they are long epidermal cells with very thick cell walls. In this study, venuloid idioblasts of Pteris grevilleana were investigated with various light microscopic (LM) and scanning electron microscopic (SEM) techniques and the main purposes of these microscopic techniques are summarized and discussed. To investigate the morphology and distribution of venuloid idioblasts, partial polarization LM technique and cryo-tabletop-SEM technique were used. The idioblasts had lobed margins, acute or round ends, and could be found on both upper and lower epidermis of fertile fronds and sterile fronds. They are distributed on veins, interveinal regions, and leaf margins, but not on costules, costae, and false indusia. By using histochemical staining and SEM with energy dispersive X-ray spectrometer (EDS), it was confirmed that the idioblasts contained silicon. In addition, the venuloid-idioblast-like silica bodies were extracted by wet oxidation method. These indicate that the venuloid indioblast in P. grevilleana is a kind of spicular cell (long epidermal cells containing silica bodies, which are found in Adiantoids and Vittarioids).