クスノキにおける交錯木理の形成とその意義(第1報) : 交錯木理の出現状況

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年輪界が明瞭なクスノキを用いて,交錯木理の出現状況を検討した.その結果を要約すると,次のとおりである.軸方向木部細胞は,髄付近では樹幹軸にほぼ平行に配向したが,髄から離れるにつれて樹幹軸に対して斜めに配向し始め,S旋回とZ旋回を交互に繰り返した.交錯木理形成の明確な開始時期や,S旋回とZ旋回のどちらから始まるかは,髄付近では交錯木理が存在していてもその程度が小さいためはっきりしないが, 髄から3～10年輪目あたりから明らかな交錯木理が認められた.また,S旋回ないしはZ旋回の繊維傾斜度は,数年輪ごとに年輪界付近でピークに達し,その後樹幹軸に平行な方向へ向かって減少し始めた.しかし,その周期性に髄からの距離ないしは年輪数の明らかな関与を見い出すことはできなかった. 師部から木部に向かって接線面における繊維傾斜度を連続的に測定した結果,師部0にも交錯木理様のものが形成されていた.また,形成層帯細胞の繊維傾斜度は供試木間で異なったが,いずれの供試木でも形成層帯細胞とそれに近接している師部細胞および木部細胞はほぼ同じ繊維傾斜度を示した.このことは,形成層帯細胞の配向方向と接線面分裂後の新生細胞の伸長方向が一致していることを示し,交錯木理が形成される理由は,形成層始原細胞が周期的にS旋回とZ旋回を繰り返して配向するためと推測された.Interlocked grain is mainly formed in tropical broadleaved trees and also formed in Lauraceae species in the temperate regions. In this study, variations of grain angle in the radial direction of Cinnmomum camphora stems showing clear annual ring boundary were investigated. The results obtained were summarized as follows: Axial elements arranged in approximately parallel to the stem axis in the region near the pith, but began to be sloped against the stem axis with increasing annual ring numbers from the pith, and then alternately repeated S-helix and Z-helix (Figs. 1 and 2) . As interlocked grain was not recognized or was shallow in the region near the pith, the annual ring and the slope direction in that formation of interlocked grain initiated were obscured . The annual ring having clear interlocked grain was over third to tenth ring from the pith. The slope of grain in the S-helix or Z-helix reached to the peak in the vicinity of annual ring boundary at intervals of several years, and began to turn to the opposite direcrion (Figs. 1 and 3) . There was no significant relation between intervals from the peak to the next peak of grain angle and the distance or the ring numbers. Variation patterns of grain angle from bark to wood near the cambial zone were obtained (Fig. 4). It was clarified that 1) interlocked grain-like-one formed in the bark, 2) the grain angle in the cambial zone was different among sample trees, and 3) it was almost the same value as in the phloem cells and xylem cells adjacent to the cambium. This means that the slope direction of cambial cells corresponds to the elongation direction of newly formed phloem and xylem cells. Therefore, the reason for the formation of interlocked grain was that the cambial cells periodically repeated S-helix and Z-helix.
九州大学の論文

クスノキにおける交錯木理の形成とその意義(第1報) : 交錯木理の出現状況

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