Gerhard Zotz1, Nina Schickenberg1, Dirk Albach2. 1. University of Oldenburg, Institute of Biology and Environmental Sciences, Functional Ecology Group, Box 2503, D-26111 Oldenburg, Germany. 2. University of Oldenburg, Institute of Biology and Environmental Sciences, Plant Biodiversity and Phylogeny, Box 2503, D-26111 Oldenburg, Germany.
Abstract
Background: The velamen radicum, a spongy and usually multiple-layered root epidermis composed of dead cells at maturity, is a textbook example of an adaptation that is typically associated with epiphytic orchids. Scope: Based on an extensive literature review, the occurrence of this structure was documented in approximately 240 genera of terrestrial monocotyledons (162 orchid and 74 non-orchid genera) and in one genus of dicotyledons. Mapping this character on a phylogenetic tree reveals that a velamen is found throughout the monocotyledons, ranging from members of early-branching Araceae to derived Cyperaceae. Conclusion: The current depiction of the velamen radicum in angiosperms and its almost exclusive association with the epiphytic lifestyle in orchids is misleading, which inevitably leads to a biased view of its evolution and function. The findings propose a re-evaluation of the occurrence, evolution and function of the velamen radicum in both terrestrial and epiphytic angiosperms.
Background: The velamen radicum, a spongy and usually multiple-layered root epidermis composed of dead cells at maturity, is a textbook example of an adaptation that is typically associated with epiphytic orchids. Scope: Based on an extensive literature review, the occurrence of this structure was documented in approximately 240 genera of terrestrial monocotyledons (162 orchid and 74 non-orchid genera) and in one genus of dicotyledons. Mapping this character on a phylogenetic tree reveals that a velamen is found throughout the monocotyledons, ranging from members of early-branching Araceae to derived Cyperaceae. Conclusion: The current depiction of the velamen radicum in angiosperms and its almost exclusive association with the epiphytic lifestyle in orchids is misleading, which inevitably leads to a biased view of its evolution and function. The findings propose a re-evaluation of the occurrence, evolution and function of the velamen radicum in both terrestrial and epiphytic angiosperms.
Authors: Guillaume Chomicki; Luc P R Bidel; Feng Ming; Mario Coiro; Xuan Zhang; Yaofeng Wang; Yves Baissac; Christian Jay-Allemand; Susanne S Renner Journal: New Phytol Date: 2014-10-23 Impact factor: 10.151