Trade-offs among functional traits reveal the strategies for plants to acquire and conserve resources. These functional traits have been described as the ‘spectra’ to separate species with different adaptation strategies and provide insights into species distribution and ecosystem processes. 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 most plant species because their leaves and roots are exposed to different environmental conditions, above- and below-ground.
In their new study published in AoBP, Qi et al. propose a model of interaction between leaf and root traits of Dendrobium, an important epiphytic taxon in the 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. These findings confirm the hypothesis that leaf and root traits have evolved in coordination for epiphytic orchids, and also provide insights into trait evolution and ecological adaptation.