Le phenomene d'heteroblastie chez les vegetaux: Comment l'expliquer?

Heteroblastic development is often observed in Cormophytae, but it can also be characterized in Thallophytae as shown by the detailed investigation of the development of the algaAntithamnion plumula (Ceramiaceae, Rhodophyta). In this species, heteroblasty concerns (i) dimensional variables (such as pleuridia length and lateral cladome first tagma length) and (ii) variables that characterize the cell growth kinetics (main axis cells). Apex curvature also varies during ontogenesis.The generality of the property in plants led to search for its origin: apical meristem own dynamics, ontogenetic evolution of internal relationships, dialectical relationships between the plant and its environment.Some models were put forward to accout for the development ofAntithamnion but did not take into account the heteroblasty phenomenon. The investigations presented here are a first attempt at representation through formal grammar, based on double wall map systems. The model leads to the assumption of the occurrence of an oscillatory mechanism associated with a threshold that determines both qualitatively (axial cell of the cladomophoric or pleuridiophic type) and quantitatively the development of the whorls.