Primary vascular patterns in the Vitaceae

Vitaceous shoots can be classified into five distinct architectural pattern s 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 alata was chosen to represent patt ern 5 (distichous phyllotaxy and continuous leaf-opposed tendril/infloresce nces) and Vitis riparia to represent pattern 4 (distichous phyllotaxy and a three-node modular pattern of interrupted leaf-opposed tendril/inflorescen ces). 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 tax a have an even number of vascular sympodia, with four in C. alata and six i n V. riparia. Leaf traces are multilacunar, with seven traces in C. alata a nd five in V. riparia. The leaf-opposed tendril/inflorescences have the sam e vascular architecture as the axillary buds and are derived from the same vascular sympodia, although there is no evidence from this study that the t endrils represent a vertically displaced serial axillary bud. Vascular arch itecture reflects the underlying three-node modularity of these shoot patte rns in two ways: first, leaf traces in both species most commonly arise thr ee nodes below their point of departure from the stem, and second, the numb er of internodes the axillary bud traces traverse is dependent on the posit ion of the tendril within the shoot module in V. riparia (pattern 4). Veget ative characters such as shoot architecture and primary vascular pattern sh ould prove useful in phylogenetic analyses of this architecturally unique f amily.