It has been well documented that cortical microtubules are involved in determining the orientation of newly deposited cellulose microfibrils in the plant cell wall, because the parallelism between them has been frequently observed. However, some exceptions have also been described. Therefore, more detailed additional data are needed on the simultaneous progressive changes in the orientation of cortical microtubules and cellulose microfibrils during cell wall formation. The present study has been designed to observe the orientation of cortical microtubules and cellulose microfibrils in the developing tracheid and/or fiber wall to elucidate their correlation on woody plants. Confocal laser scanning microscopy and field emission scanning electron microscopy have been used for the investigation.
During the secondary wall formation of tracheids in Abies sachalinensis, cortical microtubules changed their orientation progressively from a flat helix to a steep helix and then changed from a steep helix to a flat helix. The orientation of newly deposited cellulose microfibrils on the inner surface of developing cell wall showed a similar rotative change to that of cortical microtubules. The evidence from the results suggests that the microtubular orientation is closely related to the ordered orientation and deposition of cellulose microfibrils in the secondary wall of tracheid.
Key words: cortical microtubules, cellulose microfibrils, tracheid, cell wall.
Correspondence: Ryo Funada, Department of Forest Science, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan
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