La pousse courte, un indicateur du degré de maturation chez le hêtre (Fagus sylvatica L.)

Abstract

In beech, no external morphological characters that allow an understanding of how an individual stem gradually and continuously evolves from a juvenile vegetative stage toward a mature flowering stage, has ever been demonstrated. The only known traits are marcescence, indicating a juvenile stage, and flowering, indicating passage to adult stage. However, in young trees growing under a forest shadow, these markers are not visible since marcescence is not expressed and the trees are too young to flower. This study was conducted to find one or more external morphological characters that indicate the state of differentiation in beech. For that purpose, a simultaneous description of tree architecture and the short, 1-year-old, foliated growth units (u.c.) of the trees was completed. Analysis showed that the morphology of short u.c.'s evolved according to their localization in the plant, the age of the plant, and the environment where in which it is developping. Analysis also revealed that this evolution was directly related to growth in height of trees, but also and above all, to the degree of complexity reached during the trees' development. Thus, evolution of short u.c.'s is a scale on which some traits expressing internal plant potentialities (marcescence, flowering) can be localized.