ネムノキとヤマザクラの道管のゴム状物質による閉そく

Abstract

柔細胞から道管内腔に分泌され, ついには道管を閉そくするゴム状物質の発生と形状をネムノキとヤマザクラでおもにSEMにより観察した。またチロース研究に用いた培養法により人為的にゴム状物質を発生させた。さらにネムノキの培養ゴム状物質を化学分析してその成分を調べた。ネムノキでは, 分泌は辺材の最内年輪で始まり, そこでは道管内壁をおおう薄い皮膜が観察され, 心材への移行部年輪ではさらに道管を水平に仕切る薄い隔膜が形成された (Fig. 1, 2)。また, 20℃と30℃の培養によって辺材部にも人為的にゴム状物質を分泌させることができた (Fig. 3, 4)。そしてこの発生の過程は辺材から心材にいたる自然の変化と良く似ていた。培養ゴム状物質を取り出して赤外分光分析とガスクロマトグラフィーで調べるとこれはD-mannose, D-galactose等を主成分とする多糖質であった (Fig. 8, 9)。ヤマザクラ着色心材部では多量のゴム状物質が種々の形状で道管内に分布していたが (Fig. 5), 20℃で培養したとき辺材部に発生したゴム状物質の形状もこれに類似していた (Fig. 6)。

Occurrences and shapes of gum secreted into vessel lumina from parenchyma cells were examined with SEM in NEMUNOKI (Albizia julibrissin) and YAMAZAKURA (Prunus jamasakura). In NEMUNOKI the gum begins to be secreted into vessel at the innermost annual ring of the sapwood and covers the vessel wall sculptures (Figs. 1 and 2b). At the light-colored intermediate wood and the dark-colored heartwood, thin plates of the gum holizontally partitioned off the vessel lumen (Figs. 1 and 2c). The gum was also secreted by the incubations at 20℃ and 30℃, and the occurrences were similar to the above described natural secretions. That is, it forms thin layer masking vessel walls at the early stage of incubations (Fig. 3b) and after all constructs the thin partitions at the later stage (Fig. 4b). This artificial gum was squeezed out (Fig. 7) and then analized by IR spectroscopy (Fig. 8) and gas chromatography (Fig. 9). It was polysaccharides composed of mannose, galactose and so on. In the colored heartwood of YAMAZAKURA, much gum was distributed at the vessel lumina (Fig. 5). But it shows no regular feature, differently from that of NEMUNOKI. The incubated gum at 20℃ is also adhered to the vessel walls in the curious manners (Fig. 6).