超薄切片の脱成分処理によるベスチャーおよびいぼ状層の化学成分

Abstract

広葉樹の道管壁孔に見られるベスチャーと針葉樹仮道管に見られるいぼ状層について, 超薄切片上の脱成分処理法によってその化学成分を検討した。その結果, ベスチャーといぼ状層は脱リグニン (亜塩素酸ナトリウム), 脱ヘミセルロース (水酸化カリウム) の各単独処理ではかなり蝕刻されても消失することはなかったが, 両処理を組み合わせて行なうと完全に消失した。したがって, 両者の主成分はリグニンとヘミセルロースであると思われる。また, ベスチャーでは脱リグニン・脱ペクチン (シュウ酸アンモニウム) の組み合わせ処理で蝕刻の度合が進んだことから, ペクチンもいくらか含まれると思われる。いぼ状層においては脱ぺクチン・脱ヘミセルロースの組み合わせ処理によって, いぼ状層がS_3に接した一層とその上に載ったいぼ状突起部とに分かれて見えることがあった。

Chemical compositions of vestures and warts were examined by means of de-component treatments of the ultrathin sections. The current year wood blocks of Robinia pseudoacacia L., and Albizia julibrissin Durazz., which were offered for the examination of vestures, and Thuja orientalis L. for the warts were embedded in epoxy resin after the GA-OsO4 or GA-KMnO4 fixations. Transverse sections of ca. 100nm thick were sliced successively from the specimen block and the main part of them were washed with several reagents for removal of cell wall components after the de-embedding of epoxy resin1) (Table 1), and the rest was post-stained with lead citrate. The effects of these de-component treatments were examined under TEM, and summarized in Tables 2 and 3. (1) Both vestures and warts were etched moderately by the treatment of either NaC1O2 or KOH (Figs. 5, 6. 7, 8), whereas they were removed completely by the combinated treatment of them. Therefore, the main components of vestures and warts are thought to be lignin and hemicelluloses. (2) Since the vestures were removed moderately by the treatment of (NH4)2C2O4 after NaC1O2 (Fig. 9), a small amount of pectic substances are thought to be contained in vestures. On the contrary, such effects were not observed in warts. (3) After the treatments of (NH4)2C2O4-KOH, "warts" and "warty membrane" were discerned in the warty layer (Fig. 10). The warts were not covered with the membrane, but they simply adhered to it. (4) The density of the vestures and the warts was almost unchanged by the HF treatment, and porous structure observed in the secondary wall was not detected in the vestures (Figs. 11, 12). Based on the observations, it was concluded that the fibrillar cellulose does not exist in the vestures and the warts. (5) As to the vesture-like projections on the lumen surface in Albizia vessel, the same effect as the vestures were noticed. Judging from their morphological resembrance (Fig. 2) and the similarity in chemical components, the projection also can be called a "vesture".