Phenotypic Trait Variation And Life Strategy In Ranunculus Reptans L. Facing Water Level Changes

In defence against environmental constraints, plants respond by changing their morphology and/or physiology and this reaction can be a manifestation of a life strategy. Amphibious plants are good models to test for life strategies because they display plastic responses to aquatic and terrestrial conditions. In our study we investigated the architecture and phenotypic responses of the boreal plant Ranunculus reptans L. to water level changes by observing spontaneous aquatic populations during their flowering period and by conducting experimental transplantation. We interpret these data (1) in terms of adaptation to aquatic versus terrestrial conditions, and (2) as a manifestation of the life strategy. We document a radical change in R. reptans architecture and reproduction. Reduction of plant size, elongation of leaves and stolons, vegetative reproduction are characteristic of aquatic plants. Terrestrial plants are bigger, with wider lanceolate leaves and shorter stolons leading to higher density; they reproduce vegetatively and generatively. R. reptans appeared to follow the avoidance life strategy: (1) small growth form in aquatic conditions minimises the frontal area and diminishes the risk of uprooting; (2) elongated submerged leaves decrease hydraulic resistance and mechanical damages; (3) formation of individuals with multiple axes reduce the risk of uprooting by waves; (4) capacity to quickly reconfigure the architectural traits of aquatic and terrestrial plants adjusts them to changes in environmental conditions. Our findings thus suggest that R. reptans is phenotypically plastic and adjusts vegetatively to water level, essentially reflecting an avoidance strategy, while using complementarily terrestrial and aquatic conditions in its reproduction.