Format: ORAL

Marie PEIGNARD, Sbastien GALLET, Xavier DAUVERGNE

Laboratoire Géoarchitecture. Université de Bretagne Occidentale - Brest (France)

Invasive alien species (ISA) are a serious threat to biodiversity. For several decades a plant species has been invading French Brittany coastline: Baccharis halimifolia. It is presently classified by the European Commission as a Shrub, ISA of concern for the European Union. Native to North America where it grows on intertidal marshes, this species belongs to the Asteraceae family. Currently, this species has been introduced on 4 continents: Europe, Oceania, Australia and New Zealand, mainly for its ornamental value and its function as a windbreak and soil stabilizer. It is gradually invading the French coastline, where it is becoming established in a variety of coastal environments such as salt marsh, rushes, reedbeds, roadsides and wasteland. This plant is susceptible to generate ecological and landscape impacts. This species occurs preferentially in environments with low to moderate salinity. We are interested in ecophysiological responses of this species to salt stress. The ecological characteristics of several populations were studied. Plant communities were characterized and biological traits were measured for each population in order to fully describe them. The abiotic characteristics of the soil were also reported, such as salinity and water content. In addition Sodium and potassium leaf concentrations and osmorality were measured and the osmolytes (e.g. glycine betane and oses) were characterized by 1H NMR (Nuclear Magnetic Resonance) and quantified by UPLC (Ultra Performance Liquid Chromatography). Finally, the same ecophysiological parameters were studied on plants grown under controlled conditions with a salt stress gradient. In addition, seed germination ability was studied as against the gradient of salinity. This work has enabled us to understand the adaptation of Baccharis halimifolia to salt stress. A better understanding of these adaptive mechanisms will enable us to propose new control strategies against Baccharis halimifolia and anticipate its dynamic of invasion.