アカマツ仮道管一次壁におけるセルロースミクロフィブリル構造の電顕観察

Abstract

一次壁形成中の新生木部細胞を用いて, 一次壁のセルロースミクロフィブリルの構造をシャドウイング法, 負染色法, 回折コントラスト法ならびに電子線回折法によりTEM観察した。形成段階にある一次壁は, アモルファス状の非セルロース性物質を多く含んでいた。この物質を除去するため2 - 3の化学処理を試みたところ, 3％HCl (80℃, 1h) 処理により最も効果的にセルロースミクロフィブリルを露出させることができた。観察されたミクロフィブリルはかなり通直で, その幅は4 - 5nmであった。また一次壁の電子線回折像は, 二次壁で得られるような典型的なセルロース I のパターンではなく, 非常に散漫な回折像であった。以上より, 一次壁のセルロースミクロフィブリルは二次壁のそれより幾分大きな4 - 5nmの幅をもつこと, さらに結晶性が悪いこと, が推定された。

The sturucture of cellulose microfibrils in the primary wall was investigated by using several electron microscopic methods, namely, shadowing, negative staining and diffraction contrast imaging in bright field mode together with electron diffraction. The differentiating xylem of Akamatsu wood just forming primary walls was selected as a sample. The primary wall during this stage contained unnegligible amount of non-cellulosic substances which are considered to be in amorphous state. Among several chemical treatments aiming to remove the substance, the highest efficiency in removal was achieved by 3% HC1 treatment (80℃, 1h) which resulted in isolation of individual cellulose microfibrils. The observed cellulose microfibrils were considerably rigid, having a dimension of 4-5nm in width. However, electron diffraction pattern obtained from the primary wall was not typical of cellulose I which one can take from secondary wall but a diffused halo-like pattern. These results indicate that the width of a cellulose microfibril in the primary wall (45mn) is slightly larger, and its crystallinity is lower in comparison with the cellulose microfibrils in the secondary wall.