The velamen radicum is common among terrestrial monocotyledons. (7th September 2017)

• Record Type: Journal Article
• Authors: Zotz, Gerhard; Schickenberg, Nina; Albach, Dirk
• Is Part Of: Annals of botany. Volume 120:Number 5(2017)
• Page Start: 625
• Page End: 632
• Publication Date: 2017-09-07
• Subjects: Epidermis -- epiphytes -- life form -- orchids -- roots -- evolution -- velamen radicum; Botany -- Periodicals; 580
• DOI: 10.1093/aob/mcx097
• Languages: English
• ISSNs: 0305-7364

Abstract

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.