マダケ, ハチクおよびモウソウチクの稈の細胞構造 (1)

Abstract

マダケ, ハチクおよびモウソウチクの3種の節間稈壁の細胞構造を調べ, その概要と3種間で認められた相違点について報告した。1) 表皮には主構成要素である厚壁長細胞の外に2種の薄壁短細胞があり, その一方がケイ酸細胞で, ケイ素化合物を含むことがEDXAにより確認された。2) 後生木部の道管は普通単せん孔であるが, 時に多孔せん孔が認められた。また, 一対の大径道管の間に小径道管が認められた。3) 稈壁の内側に髄腔に沿って髄冠細胞層が形成され, それらの細胞は接線方向に長く, 小径で, 成熟にともない壁が肥厚・木化する。壁肥厚と木化はモウソウチクで特に顕著に認められた。4) 横断面で計測された維管束, 維管束鞘, 道管ならびに基本組織柔細胞の径は, モウソウチクで最も大きく, マダケがそれに次ぎ, ハチクで最も小さい値を示した。5) マダケでは, 基本組織柔細胞は樽形を示し, 円筒形の柔細胞が軸方向に整然と並んでいるハチクと明瞭に区別された。モウソウチクでは, 基本組織柔細胞はやや樽形でマダケに似るが, 厚壁であった。また, マダケ, ハチクに比べ髄冠層が厚く, その細胞はやや小径であった。

The cellular structure of culm wall was investigated in the internodes of madake (Phyllostachys bambusoides Sieb. et Zucc.), hachiku (P. nigra Munro var. Henonis Stapf) and mosochiku (P. pubescens Mazel ex Houz. de Leh.). The sample culms were grown in the Kamikamo Experimental Station of the Kyoto University Forests, Kyoto City and were three or more years old. The internode at breast height, the longest inter-node in the culm and the upper internode having the same length as that of the breast height were collected from each sample culm (Table 1). 1) Major elements of the epidermis are thick-walled long cells and thin-walled short cells of two types. One of the latter is a silica cell which was confirmed by EDXA. 2) Vessels in metaxylem ordinarily have simple perforation plates but occasionally have multiple perforation plates. Small-diametral functional vessels are found between a pair of large-diametral vessels in metaxylem. Vessel wall pitting may have a diagnostic value to identify these species. 3) A cellular layer, a medullary sheath, is formed in the inner side of culm wall along the pith cavity, and the cells composing the layer are long in tangential direction, small-diametral in radial and longitudinal direction. The cell walls of them are thickened and lignified in maturation. Heavily thickened and lignified cells of medullary sheath are found in mosochiku culm walls. 4) Cross-sectional dimensions of the vascular bundles, metaxylem vessels and parenchyma cells in grand tissue are largest in mosochiku and smallest in hachiku. 5) The culm wall of madake is distinguished by barrel type parenchyma cells from that of hachiku, by inferior medullary sheath from that of mosochiku. 6) The culm wall of hachiku has smallest vascular bundles and is highest in the number of bundles per unit area. It is distinguished by cylindrical parenchyma cells from those of madake. 7) The culm wall of mosochiku is distinguishable by thick-walled, barrel type parenchyma cells, and by a wider medullary sheath composed of small-diametral, heavily thickened and lignified cells.