
32Le phenomene d'heteroblastie chez Les vegetaux: Comment l'expliquer?Acta Biotheoretica 43 (12): 6780. 1995.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 o…Read more

39Caracterisation de la structure d'un processus de croissanceCharacterization of the structure of a growth processActa Biotheoretica 44 (3): 359375. 1996.L'analyse d'une cinétique de croissance y est conduite à partir du modèle logistique généralisé de RichardsNelder. On distingue 2 types de processus dits mono et multilogistique. Dans le cas monologistique, le phénomène est correctement décrit par une seule fonction logistique. La cinétique de croissance est alors caractérisée par lea propriétés de chacune des phases G 1 à G 4, délimitées par les points singuliers Γmax, V max et Γmin. On appelle structure de croissance la contribution relati…Read more

71On the generalization of the logistic law of growthActa Biotheoretica 39 (34): 185195. 1991.This communication presents a discussion of some extensions of the formalism of Verhulst's simple logistics, which may constitute an autonomous growth model of a more general scope.For that purpose, the basis concept of growth diagram or trajectory is called upon, as it affords the graphic representation of the change in the growth variable y, using two relevant kinetic parameters: the instantaneous rate and the instantaneous acceleration. The two possible kinds of trajectories are in relation t…Read more

30ForewordActa Biotheoretica 43 (12): 11. 1995.The growth of the vein system of the leaf ofTropaeolum peltophorum was studied at the vein level and at the limb level.The vein growth kinetics depend on the position of the vein on the leaf: there is a proximal/distal gradient and a bilateral gradient of the growth parameters. The growth field of the veins is also dependent on time and on vein position.Specific correspondences exist between singular points of the global growth curves, the variations of the growth field and the vein position. Th…Read more

21The logistic function now constitutes the most widely used model for there presentation of growth kinetics of the continuous monotonous type in biological systems (populations, organisms, organs, ...). This ubiquity led to consider logistics from a phenomenological rather than mechanistic viewpoint. Whence the question : can logistics be given an interpretation, a signification which confers the rank of an "explicative" model to it? This Note presents some critical comments on the relationships …Read more

35Growth activity and structure at various organization levels in plantsActa Biotheoretica 41 (3): 231247. 1993.The growth activity of an organ (variable y) is defined simultaneously by the instantaneous absolute ratedy/dt and its variationd 2y/dt2. The use of these two descriptors allows a sigmoidal (i.e. continuous and non periodical, as observed for the logistic function) growth curve to be discretized into a series of 5 growth states or phases which are delimited by the following singular values: max, Vmax (=0), max, adult stage. The (V, ) plot, termedgrowth trajectory, visualizes, e.g. in the case of…Read more

33Kinetics of pleuridial growth in antithamnion plumula (rhodophyceae)Acta Biotheoretica 40 (23): 169175. 1992.The filamentous and branched thallus of Antithamnion plumula is constitued of two different kinds of branches with apical growth: the cladomial axes with a continuous or indefinite growth, and the pleuridia with a limited growth. The size of the pleuridia depends on their position with respect to the lateral cladomial axes.The growth kinetics of 35 pleuridia were analysed using Nelder's generalized logistics. Each sigmoidal curve, which was divided into four growth stages from the instantaneous …Read more

39Leaf dissymmetry and vein growth fieldActa Biotheoretica 43 (12): 8194. 1995.The growth of the vein system of the leaf ofTropaeolum peltophorum was studied (i) at the vein level (analysis of the growth kinetics and of the growth field of the 7 primary veins) and (ii) at the limb level (comparison of the growth of the veins).The vein growth kinetics depend on the position of the vein on the leaf: there is a proximal/distal gradient and a bilateral gradient of the growth parameters (=variation of the temporal organization of the kinetics). The growth field of the veins (=l…Read more