Primary Vascular Patterns in the Vitaceae

Vitaceous shoots can be classified into five distinct architectural patterns based on a three‐node sequence of tendril and axillary bud presence. The relationship between two of the more commonly occurring patterns and their primary vasculature was examined.Cissus alatawas chosen to represent pattern 5 (distichous phyllotaxy and continuous leaf‐opposed tendril/inflorescences) andVitis ripariato represent pattern 4 (distichous phyllotaxy and a three‐node modular pattern of interrupted leaf‐opposed tendril/inflorescences). Both species show architectural dorsiventrality in that the prophyll of the first‐order axillary bud is ventral and vascular dorsiventrality in that all midvein leaf traces arise from ventral vascular sympodia. Both taxa have an even number of vascular sympodia, with four inC. alataand six inV. riparia. Leaf traces are multilacunar, with seven traces inC. alataand five inV. riparia. The leaf‐opposed tendril/inflorescences have the same vascular architecture as the axillary buds and are derived from the same vascular sympodia, although there is no evidence from this study that the tendrils represent a vertically displaced serial axillary bud. Vascular architecture reflects the underlying three‐node modularity of these shoot patterns in two ways: first, leaf traces in both species most commonly arise three nodes below their point of departure from the stem, and second, the number of internodes the axillary bud traces traverse is dependent on the position of the tendril within the shoot module inV. riparia(pattern 4). Vegetative characters such as shoot architecture and primary vascular pattern should prove useful in phylogenetic analyses of this architecturally unique family.