Complex tendril branching in two species ofParthenocissus: implications for the vitaceous shoot architecture

Abstract

This study compares the developmental morphology of Parthenocissus quinquefolia Planch. (L.) (Virginia creeper) with that of Parthenocissus tricuspidata (Sieb. & Zucc.) Planch. (Boston ivy) to better understand how the tendril is related to the main shoot architecture of the Vitaceae. Tendril development is looked at from inception to maturity using scanning electron microscopy and epi-illumination microscopy. A tendril primordium is initiated low on the periphery of a shoot apical meristem; this pattern of development is reminiscent of typical monopodial shoot development. A tendril "shoot" in turn produces several bract-opposed branches and resembles the main shoot in its early development. However, a tendril develops through lateral growth, and because it lacks lateral buds, its architecture appears more sympodial than the main shoot. As more tendril branches are produced, the tendril "shoot" pattern of development gradually changes to a pattern of development reported in other vitaceous tendrils. This shift in development suggests how other vitaceous tendrils may be related to the shoot. Because tendril development in Parthenocissus can be demonstrated to be sympodial, it lends evidence to the idea that the unique monopodial-like system in members of the Vitaceae may be derived. The main shoot and tendril development are more similar than has previously been shown.Key words: Vitaceae, Parthenocissus, monopodial, sympodial, tendril, development.