Infodoc : Sciences, Techniques et Culture

Wood accounts for a major portion of land biomass and is an essential resource for man. The cells that make up wood are produced by the vascular cambium, a secondary meristem situated between the wood and bark. It is during the first fundamental process of xylogenesis — cell division — that the cambial cells produce what later become the xylem cells. They then got through a differentiation programme involving a succession of four phases before reaching their mature functional state: cell enlargement, secondary cell wall deposition, cell wall thickening and programmed cell death (apoptosis). These processes of xylogenesis determine the size and structure of the rings that are formed and hence the quantity and quality of the wood produced. At a time when efforts are being made to better[...]

Wood accounts for a major portion of land biomass and is an essential resource for man. The cells that make up wood are produced by the vascular cambium, a secondary meristem situated between the wood and bark. It is during the first fundamental process of xylogenesis — cell division — that the cambial cells produce what later become the xylem cells. They then got through a differentiation programme involving a succession of four phases before reaching their mature functional state: cell enlargement, secondary cell wall deposition, cell wall thickening and programmed cell death (apoptosis). These processes of xylogenesis determine the size and structure of the rings that are formed and hence the quantity and quality of the wood produced. At a time when efforts are being made to better understand the impact of climate change on wood formation and on optimising wood supply, thorough knowledge of the five cell processes involved in wood formation seems essential. This article offers an overview of this sequence.
Le bois représente une large partie de la biomasse terrestre et fournit une ressource essentielle à l’Homme. Les cellules constitutives du bois sont produites par le cambium vasculaire, un méristème secondaire situé entre le bois et l’écorce. C’est en suivant le premier processus fondamental de la xylogénèse, la division cellulaire, que les cellules du cambium engendrent les futures cellules du xylème. Ces dernières suivent ensuite un programme de différenciation comportant quatre processus successifs pour atteindre leur forme mature et fonctionnelle : l’élargissement cellulaire, le dépôt de la paroi secondaire, la lignification des parois cellulaires et enfin la mort cellulaire programmée (ou apoptose). Ces processus de la xylogénèse déterminent la taille et la structure du cerne formé et donc la quantité et la qualité du bois produit. À l’heure où l’on cherche à comprendre l’impact des changements climatiques sur la formation du bois et à optimiser son approvisionnement, une bonne connaissance des cinq processus cellulaires de la formation du bois semble essentielle. C’est pourquoi nous proposons d’en faire une brève synthèse dans cet article.