The phase change phenomenon is classically defined as the successive different changes which occur in plants during the transition from the juvenile to the mature condition (ROHMEDER, 1957; ROBINSON and WAREING, 1969; HACKETT, 1983, 1985). It includes all the characteristics affected by the maturation process associated with ontogenetic development during time course, such as changes in morphology, in physiological condition, and other differences which could be subtler to discern. Although phase change concerns all vegetal organisms, the expression of the phenomenon appears most obviously in woody perennials plants and particularly in arborescent species (HACKETT, 1983).