Détermination de l'ébauche foliaire, du bourgeon axillaire et de l'entre-noeud chez le Manihot esculenta : étude microchirurgicale

Abstract

A microsurgical study on Manihot esculenta shows that foliar initiation occurs more than two plastochrons before bulging out. Initiation of the axillary bud of the leaf occurs at the beginning of bulging out. Injuries produced along the path of the future procambial bundle of the older foliar initial create a delay in the bulging out of this initial, which will occur only after the bulging out of the following initial. This delay generates a reversal of the final vertical stem spacing of the two leaves that emerge from those two initials. Therefore, with each leaf bulging out, a preinternode appears above the first primordium. The vertical spacing of leaves does not necessarily result from the vertical spacing of initials. Moreover, the position of the foliar initial is affected by information moving in the apex, especially from the bulging out of the first primordium. The nature of this information is discussed and the results obtained are analysed in the light of the literature on phyllotaxy. Key words: cassava, leaf, foliar initiation, apical meristem, phyllotaxy, internode.