Correlated evolution of leaf and root anatomic traits in Dendrobium (Orchidaceae). Issue 4 (20th July 2020)

• Record Type: Journal Article
• Authors: Qi, Ying; Huang, Jia-Lin; Zhang, Shi-Bao
• Editors: Volder, Astrid
• Is Part Of: AoB plants. Volume 12:Issue 4(2020)
• Publication Date: 2020-07-20
• Subjects: Co-evolution -- elevation -- epiphyte -- water conservation -- water shortage; Plants -- Periodicals; Botany -- Periodicals; 580.5
• DOI: 10.1093/aobpla/plaa034
• Languages: English
• ISSNs: 2041-2851

Abstract

Abstract: The whole-plant economic spectrum concept predicts that leaf and root traits evolve in coordination to cope with environmental stresses. However, this hypothesis is difficult to test in many species because their leaves and roots are exposed to different environments, above- and below-ground. In epiphytes, both leaves and roots are exposed to the atmosphere. Thus, we suspect there are consistent water conservation strategies in leaf and root traits of epiphytes due to similar selection pressures. Here, we measured the functional traits of 21 species in the genus Dendrobium, which is one of the largest epiphytic taxa in the family Orchidaceae, and used phylogenetically independent contrasts to test the relationships among traits, and between traits and the environment. Our results demonstrate that species with a thicker velamen tended to have thicker roots, a thicker root cortex and vascular cylinder, and a larger number of vessels in the root. Correspondingly, these species also had higher leaf mass per area, and thicker leaf lower cuticles. Leaf and root traits associated with water conservation showed significantly positive relationships. The number of velamen layers, leaf density and the ratio of vascular cylinder radius to root radius were significantly affected by the species' differing environments. Thus, traits related to water conservation and transport may play an important role in helping Dendrobium cope with the cool and dry conditions found at high elevations. These findings confirmed the hypothesis that leaf and root traits have evolved in coordination, and also provide insights into trait evolution and ecological adaptation in epiphytic orchids. Abstract : Our study proposed a model of interaction between leaf and root traits of Dendrobium which is an important epiphytic taxon in Orchidaceae. Both leaves and roots of epiphytes are exposed to the atmosphere; thus, these two organs are under similar selective pressures. To cope with water stress in epiphytic habitats, leaf and root traits associated with water conservation show significantly positive relationships in Dendrobium species, and have evolved in coordination. Our findings provide insights into trait evolution and ecological adaptation in epiphytic orchids.