DEVELOPMENTAL ANATOMY OF DIRECT SHOOT ORGANOGENESIS IN LEAVES OF VITIS VINIFERA

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  • 1 Department of Viticulture and Enology, University of California, Davis, CA 95616

The developmental anatomy of direct shoot organogenesis from in vitro leaves of Vitis vinifera L. cv. French Colombard was studied by light microscopy. Regenerating petiole stubs of leaf explants were fixed at intervals and were sectioned longitudinally to determine the developmental sequence of direct shoot organogenesis. After 6 days, three distinct regions of meristematic activity were apparent within expanding petiole stub: the wound-response, organogenic, and vascularization regions. In the organogenic region, divisions of vacuolate outer cortical cells formed nodular bumps that sometimes became adventitious leaves. Promeristems, which had the potential to become adventitious shoot meristems, were also initiated asynchronously in the organogenic region. Promeristem initiation occurred by two or several synchronous cell divisions occurring in the epidermal and subepidermal cell layers. Adventitious shoots and leaves developed new vascular bundles that connected to the pre-existing vascular bundles of the explant.

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