Radial distribution of heartwood phenols and the cytological changes of ray parenchyma cells associated with heartwood formation in Japanese red pine (Pinus densiflora Sieb. et Zucc.)

Abstract

アカマツ (Pinus densiflora) の心材形成の特徴について, 心材フェノール成分の放射方向における分布とエイジングに伴う細胞学的変化の観察から検討した。得られた結果は以下の通りである。(1) 供試材の辺・心材境界は明瞭であり, 移行材 (または白線帯) は含まれていなかった。(2) メタノール抽出物は辺材では少なく, 辺・心材境界で急激に増加した。(3) メタノール抽出物の薄層クロマトグラフィーによる分析から, ピノシルビン及びそのモノメチルエーテルが心材での主成分であることがわかった。また, これらは辺・心材境界で急激に形成された。(4) 放射柔細胞の生存率は辺材部を通して辺・心材境界までほぼ100%であった。辺・心材境界の狭い範囲 (1年以内) で, 0%に減少した。(5) 貯蔵物質は脂質が中心であった。これらは辺材部で中性脂質の性質を示したが, 辺・心材境界で急激に他の成分へと変化したと推定された。(6) 含水率は辺材部で高く, 心材部で減少した。また, 6月と10月を比較すると, 辺材内層部で含水率が6月に比べ10月に減少することが特徴的であった。以上の結果から, (7) アカマツの心材形成に関わる変化は, 辺・心材境界の非常に限られた領域で急激に起こっている事が判明した。しかし, 6月と10月の比較から夏以降に心材化が進むこと, また辺・心材境界で起こっている特徴は, スギ等における心材形成の特徴と類似していること, が推定された。

To clarify the characteristics of heartwood formation in Japanese red pine (Pinus densiflora) radial distribution of heartwood phenols and cytological structure were investigated. The results were : (1) The boundary between sapwood and heartwood was distinct although the intermediate wood (or white zone) was not recognized. (2) Methanol extractives were small amount in sapwood and increased in the transition zone from sapwood to heartwood. (3) From the analysis of methanol extractives by thin layer chromatography it was revealed that pinosylvin and its monomethyl ether were the two main heartwood phenols. In sapwood they were in trace amount but they increased abruptly in the transition zone. (4) The percentage of living ray parenchyma cells was almost 100% in the sapwood and in the transition zone from sapwood to heartwood (within one annual ring) it decreased to 0%. (5) Main reserve substance was lipids. In sapwood they showed neutral lipidic nature. In the transition zone they abruptly changed quantitatively and qualitatively. (6) Moisture content was high in sapwood and it decreased in heartwood. Comparing June and October it was a distinctive feature that higher moisture content in the inner sapwood in June decreased in October. (7) From the characteristics mentioned above it was revealed that all of the investigated features showed abrupt changes in the very narrow region between sapwood and heartwood. From the comparison of the characteristics between June and October it was considered that heartwood formation progressed after summer. From the comparison of the features of heartwood formation between Japanese red pine and Japanese cedar, moreover, it was concluded that the investigated characteristics of Japanese red pine basically resembled to those of Japanese cedar.