La morphogenèse florale chez le pétunia. II. La fleur normale

Abstract

The scheme of floral morphogenesis is based on a histocytological analysis of organogenesis. Several points are emphasized: (i) the activity of the meristem during the development of inflorescence, the receptacle, and the placenta is always brought about by the iterative activity of the corpus initials, generating six superposed levels, each of them producing a type of lateral appendage: bract, calyx, corolla, stamens, carpels, and ovarian partitions; (ii) the evolution of cauline components is described: the corpus is responsible for the organogenesis of part of the corolla, the stamens, and the placenta; the second tunica layer is responsible for the calyx, the other part of the corolla, the carpels and reproductive cells, the protoderm of transmitting tissue, and the stigma; (iii) the calyx, corolla, and gynoecium are trifacial, while the stamens are pentafacial and the placenta is axial; (iv) there is no fusion: the calyx, corolla, and gynoecial tubes arise as an extension of the initiation started on separate sites; the corollo-staminal tube results from the elongation of the lower part of the corolla and of the base of the stamen filaments under the zone of interpetalous-corolla initiation; an anticlinal growth, joining face to face, produces the filling of the style. Thus, during flower morphogenesis, organogenous, histogenous, and differentiation patterns begin in well defined places, at given times.