Shoot architecture in the Vitaceae

This paper examines the question of how the unique shoot architectural pattern of the Vitaceae, typically with leaf-opposed tendrils or inflorescences in a three-node modular repetitive pattern, can be related to the traditional concepts of monopodial and sympodial shoot development. Based on complete comparative morphological developmental studies of 13 species in six genera, supplemented with observations of 21 other taxa, we have found five shoot architectural patterns in the family. The pattern of shoot architecture is consistent within a species, but there may be more than one pattern present within a genus. Species that lack tendrils, thus exhibiting pattern 1, show sympodial growth. Taxa exhibiting patterns 2, 3, and 4, with tendrils at two of three nodes and with progressively one, two, or three axillary buds within the three-node cycle, grow monopodially, and taxa that exhibit pattern 5, with both tendrils and axillary buds at every node, achieve the pattern via either monopodial or sympodial growth, depending on the species. Although rare in the Vitaceae, pattern I is the only one shared with the sister family Leeaceae. We conclude that this was the original shoot architectural pattern, and that the monopodial pattern present in most species today is derived, and unique to the Vitaceae.