スギ成熟材部のフィブリル傾角の測定 : 剥離切片偏光顕微鏡法と圧締切片Ⅹ線回折法

Abstract

スギ成熟材部仮道管のフィブリル傾角を測定するため, 剥離切片を用いた偏光顕微鏡法と, 圧締切片を用いたX線回折法を検討した。剥離切片には多くの単一壁が認められ, 仮道管はS1層付近で剥離されることが多く, フィブリル傾角測定にはかなり有効であることがわかった。一方, 庄締した板目切片では仮道管が偏平になり, 放射壁のミクロフィブリルの影響が減少し, X線回折図では, セルロースIの (002) 面の回折スポットは分離される場合が多くなった。これによりフィブリル傾角の測定が容易に行えるようになった。この方法での測定値と偏光顕微鏡での測定値を比較してみると, 早材では近い値を得ることができた。しかし, 晩材では圧締後も偏平にならない放射壁が存在するために, 回折図での赤道付近の回折強度にはその影響があり, この方法での測定値は幾分小さな値を示した。

A polarizing microscopic method with splitted sections and on X-ray diffraction method with pressed sections were examined in order to measure fibril angles in mature wood of sugi (Cryptomeria japonica D.Don). The slides of splitted sections for polarizing microscopy were prepared from tangential and radial sections of 10 to 20 μm thick by FUJITA'S method. Many single walls were observed in splitted sections. Tracheid walls were splitted mostly in or near the S1-layers. It was confirmed that the splitted-section method was useful for the measurements of the small fibril angles in mature sugi wood. For measurements by the X-ray diffraction method thick tangential sections of about 1mm thick were immersed with water, pressed by the large paper clips and heated at 115℃ for 1 hour in an autoclave. They were then dried in an oven. X-ray diffraction diagrams (Laue method) were obtained, and brightness distribution curves of the 002 reflection were drawn by an image analizing system. Tracheids in pressed tangential sections were severely flattened. Diffraction from radial walls decreased in those pressed sections, and reflection spots of 002 plane of cellulose I frequently appeared as separate spots in brightness distribution curves of X-ray diffraction. The determination of the fibril angles from the curves can be, therefore, made readily, particularly in measurements on earlywood. An effect of pressing sections decreased for latewood tracheids because of their thick radial walls. A graphical method was used for separating the peaks when the double peaks were not separated clearly on the brightness curves. The fibril angles obtained by the X-ray method mentioned above were nearly corresponding with those obtained by the polarizing microscopic method with splitted sections in the measurements on earlywood. However the former revealed the smaller values than the latter in the measurements on latewood.