Masato Yoshida, Yoshihiro Hosoo, Takashi Okuyama
Periodicity as a Factor in the Generation of Isotropic Compressive Growth Stress Between Microfibrils in Cell Wall Formation during a Twenty-Four Hour Period
Summary
Field emission scanning electron microscopy and energy-dispersive X-ray microanalysis were used to
investigate the generation of growth stress in connection with the deposition of cell wall materials along
the innermost surface of radial walls during secondary wall formation of differentiating tracheids of
Cryptomeria japonica. Samples were collected when the turgor pressure of the tree was low (16:00 h),
and when the pressure was high (6:00 h). In samples collected at 16:00 h, cellulose microfibrils deposited
on the innermost surface of radial walls were clearly evident and amorphous material was rarely
found. Conversely, in samples collected at 6:00 h, cellulose microfibrils were rarely observed and the
amorphous material was prevalent. Cellulose microfibrils were evident, however, after removing the
amorphous material with chlorite. The concentration of potassium on the inner surface of radial walls
was greater at 6:00 h than at 16:00 h. After chlorite treatment, the concentration of potassium measured
in the samples collected at 6:00 h decreased to a level equivalent to that in samples collected at 16:00 h
and thus potassium was found to be associated with the amorphous material on the cellulose microfibrils.
The amorphous material is probably a matrix of hemicellulose and monolignol, material that is
abundant on the inner surface of developing cell walls, especially during expansion (as a result of high
turgor pressure) of differentiating tracheids. A matrix of hemicellulose and lignin deposited in the
expanded gaps between cellulose microfibrils and daily expansion of the gaps probably produces an
isotropic compressive stress (growth stress). This paper demonstrates periodicity in cell wall formation
as a result of the cycles of compressive growth in the differentiating cell wall.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 09/2000
Pages: 469 - 473
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