Histologie des méristèmes d'accroissement diamétral primaire et secondaire et de leurs dérivés chez le Cordyline indivisa (Agavacées)

Abstract

In Cordyline indivisa Kunth, the primary and secondary thickening meristems of 16- to 18-month-old specimens are continuous, but in cross sections, they show different histological features. Their respective provascular bundles differ in their appearance, the way they are produced, and the way they differentiate. A transition zone, which extends longitudinally for about 2 mm, is characterized by the simultaneous presence of the two meristems. In cross sections, the first periclinal divisions of the secondary meristem are seen (i) in the primary meristem, (ii) in the adjacent cortical parenchyma, and (iii) in regions where the meristematic ring is interrupted. Structural continuity between the two meristems is responsible for the presence of primary bundles which extend basipetally as secondary bundles.