Diversity of Shoot Organization in the Araceae

Abstract

Morphological units in the Araceae are discussed and defined. The fundamental unit is the segment (an internode and its leaf or leaves), of which there are two basic types, the monopodial segment and the branching segment. Segments are assembled into chains to form articles (also called axes), which terminate in inflorescences, and are the product of the activity of a single apical meristem. Successive articles are assembled into chains which are physiognomically unbranched shoots. Shoot organization in the Araceae is discriminated into types on the basis of five characteristics: whether the shoot is renewed after flowering, whether renewal axes are proleptic or sylleptic, whether renewal axes develop from an axillary position, whether renewal axes have a variable or a constant number of leaves, and the number of leaves on renewal axes with a constant leaf number. The types of growth are described, illustrated, and organized into a hierarchical scheme, and a terminology is provided. A list of species representing each of the types is given.