The secondary wall formation of compression wood tracheid. IV : Cell wall structure of transitional tracheids between normal wood and compression wood

Abstract

アカマツとスギの正常材からあて材, あて材から正常材へのそれぞれの移行域にある仮道管の壁構造を調べた。樹幹を傾斜させて得た正常材からあて材への移行域では, (1) S_3の欠落, (2) 二次壁の木化度および壁厚さの増大, (3) らせん状のうねと裂目の発達, および仮道管断面の円形化, (4) 細胞間隙の出現, の順にあて材仮道管の特徴が現われた。一方, 傾斜した樹幹を直立させて得たあて材から正常材の移行域では, (1) らせん状のうねと裂目の衰退, (2) 壁厚さの減少とS_3の復活, (3) 二次壁木化度の低下, (4) 細胞間隙の消失, の順に正常材仮道管に復活した。これらの一連の変化を正常材とあて材仮道管の分化過程と関連づけて考察した。

The cell wall structure of transitional tracheids between normal and compression wood tracheids in Pinus densiflora and Cryptomeria japonica were examined, being related to the differentiation. The transition from normal wood to compression wood proceeds as follows. (I) Lack of S3 and passing decrease of cell wall thickness were detected first of all. (II) Dense lignification of secondary wall and rapid thickening of S2 proceeded in parallel. (III) Helical ridges and cavities developed. Cross shape of tracheids became round. (IV) Intercellular spaces occurred. On the other hand, changes from compression wood to normal wood are as follows. (I) Degeneration of helical fidges and cavities led the changes. (II) Comeback of S3 and decrease of S2 thickness were followed. (III) Dense lignification of secondary wall dissolved. (IV) Intercellular spaces disappeared. Being lignification behavior as an exception, the sequences in the both cases are good consistent with the differentiation of normal or compression wood tracheids. Therefore the peculiarity of lignification was discussed.