For vascular epiphytes, having the ability to capture both dry and wet atmospheric deposition and to permanently attach to their host plants are essential for establishment and survival in the canopy. Root systems must perform a dual function of nutrient acquisition and anchorage during their lifespan. Unlike mistletoe roots, the roots of vascular epiphytes do not penetrate the host tissues but instead achieve attachment by growing in close contact to the surface of the substrate. However, our understanding of the relative roles of roots in providing nutrition and anchorage is currently fragmented and not well understood. To date, research on attachment strategies in plants is almost entirely limited to climbers.
This context motivates the EPI-ROOTS project, in which we aim to explore the strategies employed by diverse epiphytic plants for rooting and absorbing water and nutrients. Specifically, this project will address two questions: (1) how diverse are the attachment mechanisms and nutritional functions of the adventitious root systems across various epiphytic species? and (2) how do root structure and functions (anchorage and nutrition) change with ontogeny?
We first propose to explore two root functions – anchorage and nutrition – by comparing species from Orchidaceae, Bromeliaceae, Araceae, and Polypodiaceae families, which together account for more than 80% of all epiphytic species in the Neotropics. Then, to properly explore the effect of ontogeny on anchorage and nutrient acquisition, we will compare the root systems of different ontogenetical stages on two species, one from the Araceae family and another from Bromeliaceae family. We will use an interdisciplinary approach to characterize various root functional traits related to anchorage and water and nutrient acquisition. Morpho-anatomical, histochemical, and biomechanical analyses will enable us to characterize the root architecture and attachment strategies. Anatomical studies, enzymatic activities, and the mycorrhizal status of the roots will provide us with information on nutritional strategies.
This exploratory project will yield a novel understanding of the diversity of attachment and nutritional functions of adventitious roots in various epiphytic species from representative families and according to ontogeny. Overall, the EPI-ROOTS project will provide insights into the persistence of epiphytic species that constitute a major plant component in many humid tropical forests.