Evénements structuraux et métaboliques dans les entre-nœuds des bourgeons axillaires du pois, en réponse à la levée de dominance

Abstract

Events associated with the release from dominance are described for internodes 1 and 2 of the axillary buds of Pisum sativum. During the inhibited state, most of the nuclei are found in the G1 phase of a diploid cycle. At the release from dominance, some nuclei in the G2 phase during inhibition enter into mitosis and the nuclei in G1 enter into the DNA synthetic phase. Until the 3rd day, a homogeneous reaction is registered for the whole of the two first internodes. Three maxima of mitotic activity are detected in the epidermis, the cortex, and the procambium and only one in the pith. From the 3rd day, the mitoses are localized at the uppermost part of these internodes: meanwhile, elongation occurs in their basal portion. At this level, the nuclear volumes are maximal at the 6th day. After release from apical dominance, the increase in DNA content reflects the resumption of the mitotic cycle and, subsequently, the onset of differentiation, with 4C level nuclei in the cortex and 8C nuclei in the pith. The cell growth of the epidermis, the cortex, and the pith, either radial or tangential, precedes the elongation phase.