La variation somatique et l'évolution chez les plantes supérieures

Abstract

Higher plants grow both by cell multiplication in apical vegetative meristems, becoming floral, without germinal lineage differentiating in the first stages of the life cycle. Moreover, the volume of cells grow at the same time as they differentiate and many cells can return to the meristematic status (totipotency). Then, somatic mutations, as well as somatic recombinations, amplifications and transpositions can have evolutionary consequences. It appeared that such an impact has not really been taken into account in the elaboration of the theory of biological evolution. The impact of somatic mutations at the time of gametogenesis is discussed as a function of i) the final morphology of the plant and ii) the duration of the life cycle. If one accept the hypothesis that the higher proportion of mutations, advantageous, neutral or adaptive, occur during somatic development, this leads to conclude that somatic development plays two roles, more or less shared according to the mutations: it acts as a filter or as an amplifier of the relative number of mutant gametes produced. If these developmental effects are associated with the modes of dispersal of pollen and seeds, they could well explain how Angiosperms have so rapidly radiated and evolved.