Two Rumex Species from Contrasting Hydrological Niches Regulate Flooding Tolerance through

Global climate change has increased flooding events, which affect both natural vegetation dynamics and crop productivity. The flooded environment is lethal formost plant species because it restricts gas exchange and induces an energy and carbon crisis. Flooding survival strategies have been studied in Oryza sativa, a cultivated monocot. However, our understanding of plant adaptation to natural flood-prone environments remains scant, even though wild plants represent a valuable resource of tolerance mechanisms that could be used to generate stress-tolerant crops. Here we identify mechanisms that mediate the distinctflooding survival strategies of two relatedwild dicot species:Rumexpalustris andRumexacetosa.Whole transcriptome sequencing and metabolite profiling reveal flooding-induced metabolic reprogramming specific to R. acetosa. By contrast, R. palustris uses the early flooding signal ethylene to increase survival by regulating shade avoidance and photomorphogenesis genes to outgrow submergence andby priming submerged plants for future lowoxygen stress. These results providemolecular resolution of flooding survival strategies of two species occupying distinct hydrological niches. Learning how these contrastin