Le méristème caulinaire des Angiospermes: nouveaux outils, nouvelles interprétations

Abstract

Resume.-Au cours de cette demiere decennia, des progres remarquables ant ete realises sur Ia morphogenese apicale. Des mutants, doni les deficiences revelent les anomalies de leur developpement, ant ete caracterises, specialement chez Arabidopsis thaliana, Antirrhinum majus et Zea mays. Plusieurs genes ant ete isoles, clones et leurs produits (mANA, proteine) ant ete localises au niveau du meristeme caulinaire. L'expression transgenique de genes "repor- Mots-c/es : developpement -genes -meristeme caulinaire -modele -morphogenese.Abstract.-During the last decade progress has been made on the shoot apex morphogenesis. Mutants, whose deficiencies reveal developmental anomalies, were characterised specially on Arabidopsis tha/iana, Antirrhinum majus et Zea mays. Several genes were isolated, cloned and their products (mANA, protein) localised at the level of the shoot apical meristem (SAM). Transgenic expression of reporter genes was also used. These researches allow one to present very new hypotheses and a new insight on the control of apical morphogenesis. Essential results concerning the vegetative shoot apex structure and functioning are presented. However the various types of genes, whose expression has been localised in the SAM, are emphasised. It is now possible to understand how the identity and the fate of cells are acquired to ensure the SAM construction during the embryonic phase, its maintenance during the vegetative phase and its gradual change during the inflorescence development. Early genic events correlated with the preparation to foliar initiation are set out as well as the most recent scenario on the intervention of several types of genes during the vegetative functioning of the SAM.

Plant Architecture: A Dynamic, Multilevel and Comprehensive Approach to Plant Form, Structure and Ontogeny

“…different potentialities (Lyndon, 1988;Nougarède, 2001); these masses develop into embryonic leaves, then leaves on elongated stems. The insertion zone of a leaf on the stem is referred to as a node and the stem portion which separates two successive nodes is called the internode.…”

Phase change-related variations of dome shape in Eucalyptus urophylla × Eucalyptus grandis shoot apical meristems

“…For instance, during the resting period, SAM are usually sharper than during budbreak (Owston 1969;Owston and Molder 1973). However, and apart from the transition between the vegetative and the reproductive state (Nougarède 2001;Sharma and Fletcher 2002), phase change-related modifications of SAM morphological characteristics have been so far only little investigated in arborescent species.…”