ANALYSIS OF THE PRIMARY GROWTH OF APPLE T REE BRANCHES (MALUS-X-DOMESTICA BORKH) DURING ONE VEGETATION SEASON

Primary growth resulting from the activity of the apical meristem of a pple branches (Malus xdomestica Borkh., cv. Braeburn) was followed ove r one period of vegetation. For each metamere successively developed, foliar surface expansion as well as growth in length and in diameter o f the lower internode were measured at regular intervals. These elemen tary parameters are resumed using two synthetic variables expressing f or each metamere its overall dimension (T) and the relative significan ces of the foliar component (foliarization) or the axial component (ax ialization) (D). It appears that the evolution of the last two paramet ers are morphometric markers for the different ontogenetic phases cove red by the branch over 1 year of growth. Two phases were especially st udied: the transition preformation-neoformation (corresponding to the setting up of the first 9-11 metameres), characterized by strong axial ization dynamics, and the intra-annual end of growth, preceded by an i mportant foliarization of the underlying metameres. This analysis of p rimary growth using the metamere dimension and foliarization or axiali zation concepts is discussed on the basis of recent hypotheses related to the evolution of the physiologic function of branches during their setting in place.