Jonas Hafrén, Takeshi Fujino, Takao Itoh, Ulla Westermark, Noritsugu Terashima
Ultrastructural Changes in the Compound Middle Lamella of Pinus thunbergii During Lignification and Lignin Removal
Summary
The structure of the middle lamella in Pinus thunbergii has been studied by the rapid-freeze deep-etching
(RFDE) technique in combination with transmission electron microscopy (TEM). The ultrastructure
of the compound middle lamella was studied in the early phases of the development of woody tissue in
the cambial and differentiating xylem, before the heavy incrustation with lignin had occurred. Lignified
middle lamella in the xylem was studied both directly and after delignification. It was found that the
structure of the unlignified middle lamella in the cambium/developing xylem consists of a fine irregular
network probably containing pectin and hemicellulose. As a result of lignin incrustation, the middle
lamella becomes increasingly dense and the surface structure of the fully lignified middle lamella
appeared to be compact and partly covered with globular structures. After delignification of the lignified
middle lamella a thin network with a different structure was revealed. This network probably mainly consists
of hemicellulose. No microfibrils of the type that occurs in the primary and secondary walls were
found in the middle lamella.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 04/2000
Pages: 234 - 240
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