Populus euramericana の引張あて材のゼラチン層の構造

Abstract

木材の細胞膜構造についてより深い知見を得るための一つの課題として, Populus euramericanaの引張あて材のゼラチン層 (以下Gと略記) の微細構造を電子顕微鏡, X線回折法および赤外分光分析法を用いて研究した。試料のゼラチン層は, NorbergとMeierの方法を用いて引張あて材から分離して得た。引張あて材のゼラチン繊維の膜層構成はP+S_1+S_2+Gである。Gの解体試料を負染色して電子顕微鏡で観察した結果, Gのミクロフィブリルは長さの方向に非晶あるいは準結晶領域の存在を推定させるような周期構造は認められない。ミクロフィブリルの幅は50 - 70Åである。反射法によるGのX線回折強度曲線から, Gの結晶幅は37Å, 結晶化度は60％の値が測定された。またGの赤外分光分析の結果, Gにはリグニンがほとんど存在しないこと, また結晶性の高いセルロースからなることがわかる。

Ultrastructure of the gelatinous layer of tension wood fibers in Populus euramericana has been investigated using the techniques of electron microscopy, X-ray diffraction and infrared spectroscopy. The experimental specimens of gelatinous layers have been isolated from fibers using the methods reported by Norberg and Meier3). In the tension wood fibers examined, the inner thick "gelatinous" layer exists instead of the inner layer (S3) of the normal three-layered structure of the secondary wall (Figs. 1 ~ 4). It has been shown from electron microscopic observation of cellulose microfibrils of the gelatinous layer which were negatively stained that no paracrystalline regions are present in the longitudinal direction of the microfibrils and that the width of microfibrils is measured to be ca. 50 ~ 70Å (Fig. 5). It has been also estimated from the line broadening of X-ray diffraction that the breadth of the crystalline regions (micelles) is 37Å and that the degree of crystallinity of cellulose is 60% (Fig. 6 and Table). Evidence that the gelatinous layer has little lignin and is composed of cellulose of high degree of crystallinity, has been obtained by means of infrared spectroscopic studies (Fig. 7).