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| 概要 |
林木育種に当って晩材仮道管接線壁に存在する有縁壁孔の孔口角が材質指標になり得るか否かをスギを用いて検討した。まず,無欠点小試験体で曲げ試験を行い,孔口角と曲げヤング率および比曲げヤング率との関係を調べた。この結果,孔口角と曲げヤング率および比曲げヤング率との間には0.1%水準で有為な負の相関関係が存在し,孔口角は簡便なヤング率指標として利用できる可能性が確かめられた。次に,孔口角の樹幹放射方向の変...動を観察した。すべての供試木で孔口角は髄付近で大きく,年輪数の増加に伴って減少し,15年輪目付近からほぼ安定した。しかも,孔口角が髄付近で大きかったものは放射方向の全年輪をとおして孔口角が大きい値で推移し,小さかったものは小さい値で推移する傾向を示した。そこで,未成熟材の各年輪の孔口角と成熟材の孔口角との間の相関係数を算出すると,髄から3年輪目ですでに20年輪目の孔口角との間に0.1%水準で有為な相関関係が存在した。このことから,初期成長の段階の孔口角から成木に達したときの孔口角が予測できると推測された。
Small clear specimens for bending test were made from juvenile wood and mature wood of several sugi(Cryptomeria japonica) cultivars. After bending test in air-dry condition, pit aperture angles in the tengential walls of latewood tracheids were measured. As the result, there were significant correlations at 0.1% level between pit aperture angle and modulus of elasticity, and specific modulus of elasticity. Pit aperture angles of latewood tracheids were measured in each annual ring from the 3rd to the 20th ring from the pith at the breast height of twenty sugi trees. Variation pattern of pit aperture angles from juvenile wood to mature wood was almost the same in all trees, but the values of the angles were different among individual trees. There was a tendency that the trees having large angles near the pith showed relatively large angles in the mature wood, though the angles decreased outwards. The pit aperture angle at the 20th ring from the pith was regarded as the representative of angles in mature wood. The relation between the angle at a given ring in juvenile wood and at the 20th ring was investigated. The angles in juvenile wood were closely related to the angle at the 20th ring. This result suggested that the angles in mature wood could be estimated by using the angles at the rings near the pith.続きを見る
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