Format: ORAL

Florian DELERUE

Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, Pessac, France

Data base of plant traits are now available at the global scale, and functional axes of variation among plants are well defined. Here, we present the synthesis of two recent studies revealing the position of herbaceous metallophyte species along these functional axes, with a special focus on hyper-accumulators. These studies covered the major kinds of metalliferous ecosystems either spontaneous or anthropogenic and in diverse biogeographical regions: Cu-rich environments including the copper hills in central Africa; Zn-Pb-Cd rich calamine substrates and Ni-Co-Cr rich serpentinic substrates in Western Europe. Shoot and root functional traits have been characterized following standardized protocols for 348 species present in 30 metalliferous communities, as well as leaf metal concentration and soil biogeochemical properties. In all cases metallophyte species exhibited small size like many species growing on other harsh substrates, some being among the shortest plants worldwide. This confirm a constant impact of metal-stress on plant stature. Additionally, an important variability regarding the leaf resource economics axis related to soil resource acquisition was found. Metallophyte communities are composed by a mix of conservative species (slow resource acquisition, long-lasting leaves) together with acquisitive species (fast resource acquisition and growth, short-lasting leaves). Remarkably, hyper-accumulating species were found among the most acquisitive species in the metalliferous communities studied. These results offer new perspectives regarding the evolution of metal-accumulation in plants. Fast-growing species maintain high soil resource acquisition on harmful substrates, leading to an important inflow of metals into their leaves. This may represent a first step towards hyper-accumulation if specific physiological adaptations are selected afterwards. Future studies should test the genericity of these results, by focusing on woody species present in some serpentinic regions. Additionally, the importance of the collaboration with mutualistic fungi (another functional axis related to both soil resources acquisition and plant-metal relationships) for hyper-accumulating species should be specified.