クリの辺材内における培養チロースの発達の相違

Abstract

培養チロースの辺材部内における発達の違いを明らかにするために, クリを用いその孔圏道管について観察した。その結果, それぞれの供試木内では次のことが認められた。(1)当年輸における培養チロースの発達はほぼ一様である。(2)培養チロースの発達は辺材内部ほど遅くなる傾向がある。(3)天然チロースを形成する辺材―心材移行域において, 培養チロースの発達は最も遅い。(4)辺材内部では培養チロースの数が少なく, その発達は一斉でない。なお, 辺材内部ほど培養チロースの発達が遅くなる傾向は, 辺材幅を基準とした形成層から各年輪界までの相対距離に依存していた。一方, 各供試木間においては, 同一温度で培養した場合でも培養チロースの発達に若干の差が認められた。

The development of incubated tyloses in earlywood vessels were examined within all the sapwood of Castanea crenata SIEB. et ZUCC. Particularly, the elongating stages of incubated tyloses in every annual ring of the sample wood were compared with each other. Each sample tree was felled in various seasons, and the trunk was cut immediately into 3 cm-thick discs (Table 1, Fig. 1). Large discs were further cut into cubic blocks containing the bark, sapwood, and outer heartwood (Fig. 2 a). The incubation discs or blocks were placed in the growth chambers5) which were sealed up in polyethylene bags containing a small amount of water at the bottoms. The growth chambers were kept in the laboratory maintained at 20℃ or 26℃. The incubation discs or blocks themselves were also moistened at intervals of 2 or 3 days. After a certain incubation time (Tables 2 to 6), one disc or block was taken out from the growth chamber and cut to obtain the observation plane (Fig. 2a). The development of incubated tyloses in the area shown in Fig. 2 b was observed with a stereoscopic microscope. Incubated tyloses in sample trees A and B were also observed with SEM and TEM by the ordinary method. The following (1) to (4) were found in each sample tree (Tables 3 to 6). (1) Incubated tyloses developed similarly in the outermost annual ring. (2) Incubated tyloses within sapwood tended to develop more slowly in the inner part than in the outer part. (3) Incubated tyloses developed most slowly in the transition zone in which natural tyloses were developing6) (Figs. 3 and 4). (4) Incubated tyloses were fewer and did not develop simultaneously in the inner sapwood (Figs. 3 to 5). Judging from Tables 3 to 6 and (1) to (3) described above, the development of incubated tyloses appears to be dependent on neither the distance nor the number of annual ring from cambium, but significantly on the relative distance (value relative to the width of sapwood) (Figs. 6 and 7). The tendency to develop more slowly with the increase of relative distance is more remarkable in the outer sapwood. Comparing the development of incubated tyloses in sample trees A, B, D, and E incubated at 20℃, incubated tyloses in the outermost annual rings developed more slowly in dormant season (in sample trees A and E) as well as those in Quercus serrata THUNB5). The development of incubated tyloses in the inner sapwood seems to be less dependent on the seasons. The activity of ray parenchyma cell in the inner sapwood may be low and less variable in all the sample trees examined.