Analyse de la croissance primaire de rameaux de pommier (Malus ×domestica Borkh.) au cours d'une saison de végétation

Abstract

Primary growth resulting from the activity of the apical meristem of apple branches (Malus ×domestica Borkh., cv. Braeburn) was followed over one period of vegetation. For each metamere successively developed, foliar surface expansion as well as growth in length and in diameter of the lower internode were measured at regular intervals. These elementary parameters are resumed using two synthetic variables expressing for each metamere its overall dimension (T) and the relative significances of the foliar component (foliarization) or the axial component (axialization) (D). It appears that the evolution of the last two parameters are morphometric markers for the different ontogenetic phases covered by the branch over 1 year of growth. Two phases were especially studied: the transition preformation–neoformation (corresponding to the setting up of the first 9–11 metameres), characterized by strong axialization dynamics, and the intra-annual end of growth, preceded by an important foliarization of the underlying metameres. This analysis of primary growth using the metamere dimension and foliarization or axialization concepts is discussed on the basis of recent hypotheses related to the evolution of the physiologic function of branches during their setting in place. Key words: primary growth, preformation, neoformation, rhythmic growth, Malus ×domestica.