Original paper

Diversity behind uniformity inflorescence architecture and flowering sequence in Apiaceae-Apioideae

Reuther, Kerstin; Claßen-Bockhoff, Regine

Abstract

Plant architecture determines the degree to which a certain individual can respond to environmental factors. Inflorescences of the Apioideae are often regarded as being uniform, but species vary in spatial and temporal arrangement of their flowers and umbels expressed in different patterns of sex distribution, dichogamy and flowering sequence. We are interested in this subtle diversity, and we seek to elucidate how much apioid architecture influences sex expression and the mating system and varies within the given constraints. To show the static and dynamic characters shaping inflorescence architecture nine species are illustrated in detail: Anthriscus caucalis Bieb., Anthriscus sylvestris (L.) Hoffm., Daucus carota L., Echinophora spinosa L., Myrrhis odorata (L.) Scop., Oenanthe pimpinelloides L., Trinia glauca (L.) Dum., Xanthoselinum alsaticum L. (Schur), Zizia aurea (L.) W.D.J. Koch). They differ in their monopodial or sympodial architecture, racemose and cymose branching pattern, determinate and indeterminate organisation of their umbellets, protandry or protogyny and hermaphroditic, andromonoecious or dioecious sexual system. However, they correspond in their modular construction and strong tendency to avoid geitonogamy and to promote outcrossing predominantly by synchronous and sequential flowering rhythms. We conclude that diversity in the umbel's architecture is less relevant for the mating system than the overall modular construction of the plant and the regulation of the flowering sequence.

Keywords

apioideaedichogamyinflorescence architecturemodular constructionsex distribution