数種の広葉樹材繊維の横断面寸法の年輪内変動

Abstract

環孔材4種, 散孔材4種の横断面切片で, 画像解析装置を用いて繊維横断面の内こう寸法, 壁厚, 細胞壁率の年輪内変動および内こうフェレ径の頻度分布を検討した。内こうフェレ径では, 環孔材で孔圏から孔圏外への滅少が見られたが, 散孔材では年輪ターミナルに向かつての顕著な変化は見られなかった。内こう面積の変動には環孔材, 散孔材ともにフェレ径の変動と同様の傾向が見られたが, その変動の程度はフェレ径に比べて小さかった。年輪内における壁厚の変動は環孔材と散孔材の間で特徴的な違いを示さず, ターミナルに向かいわずかに増加する例も見られたが, 多くは少し変動する程度であった。細胞壁率は, 環孔材でイニシアルからターミナルへ増加する傾向が見られた。散孔材では多少の増減を示すものがあるものの, 変化が少なくほぼ一様であった。

Hardwood fibres have great variability in their shapes, dimensions and arrangement on the transverse section of wood, because of their elongation growth and adjustment to enlarging vessels during their differentiation. Application of an image analyzing system makes possible rapid measurements on such diversified fibre dimensions. This paper describes examples of the measurement on the cross-sectional dimensions of fibres and variation of these dimensions within the annual rings in several hardwood species by means of a simple image analyzing system (PIAS-II). Microscopic images were input to the system through a CCD-video camera attached to an ordinary microscope for biological use. In ring-porous wood, the radial and the tangential Feret's diameters of the fibre lumen decreased from the initial toward the terminal within an annual ring. In diffuseporous wood, Feret's diameters remained almost constant or fluctuated slightly toward the terminal without any remarkable decrease. The variation of lumen area within an annual ring showed similar behavior to that of Feret's diameter, but the former was much smaller than the latter. Fibre wall thickness was estimated from fractional lumen area and average lumen area of fibres. In some samples fibre wall thickness increased slightly toward the terminal within an annual ring, but in others both ring-porous wood and diffuse-porous wood it showed slight fluctuations through the annual ring. The fractional wall area of the fibres increased gradually toward the terminal in ringporous wood. This area was almost constant through the annual ring in diffuse-porous wood, though it showed a slight increase toward the terminal or a slight decrease around the center of the annual ring.