Éléments du contrôle de la morphogenèse de la vigne in vitro: sympodisation

Abstract

In vitro growth of the grapevine, Vitis vinifera L., may result in the usurping development of the axillary buds at certain nodes and the sympodisation of the shoot. Many theories on the sympodial nature of the branches developped in situ have already been proposed. All these theories seem to be speculative. In this study, the usurpation is not hypothetical. All the morphological facts described here prove its reality. Sympodisation is closely related to tendril formation and occurs only if the young shoots grown in vitro bear tendrils. When present, usurpation is always observed in a node with tendril. Sympodisation is demonstrated by the observation of prefoliar characters and phyllotactic planes, which allow the order of the different planes to be determined. Based on these observations, we formulate a hypothesis to explain this phenomenon. The size of the apical meristem in in vitro conditions being much less than the normal size, a restricted area should remain after the simultaneous formation of a leaf and a tendril. However, if this meristematic residue remains relatively voluminous, the shoot apex may be regenerated. If not, the restoration can not take place and sympodisation will result.