Journal Article

Lignification in poplar tension wood lignified cell wall layers

Arata Yoshinaga, Hiroshi Kusumoto, Françoise Laurans, Gilles Pilate and Keiji Takabe

Edited by Ron Sederoff

in Tree Physiology

Volume 32, issue 9, pages 1129-1136
Published in print September 2012 | ISSN: 0829-318X
Published online August 2012 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tps075
Lignification in poplar tension wood lignified cell wall layers

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The lignification process in poplar tension wood lignified cell wall layers, specifically the S1 and S2 layers and the compound middle lamella (CML), was analysed using ultraviolet (UV) and transmission electron microscopy (TEM). Variations in the thickness of the gelatinous layer (G-layer) were also measured to clarify whether the lignified cell wall layers had completed their lignification before the deposition of G-layers, or, on the contrary, if lignification of these layers was still active during G-layer formation. Observations using UV microscopy and TEM indicated that both UV absorbance and the degree of potassium permanganate staining increased in the CML and S1 and S2 layers during G-layer formation, suggesting that the lignification of these lignified layers is still in progress during G-layer formation. In the context of the cell-autonomous monolignol synthesis hypothesis, our observations suggest that monolignols must go through the developing G-layer during the lignification of CML and the S1 and S2 layers. The alternative hypothesis of external synthesis (in the rays) does not require that monolignols go through the G-layer before being deposited in the CML, or the S1 and S2 layers. Interestingly, the previous observation of lignin in the poplar G-layer was not confirmed with the microscopy techniques used in the present study.

Keywords: gelatinous layer; lignification; Populus deltoides × P. nigra; tension wood; transmission electron microscopy; ultraviolet microscopy

Journal Article.  4073 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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