Flooding induces a suite of adaptive plastic responses in the grass Paspalum dilatatum

. We studied individual responses to flooding in the perennial grass Paspalum dilatatum, a widespread species in the Flooding Pampa of Argentina, using plants established in species-diverse grassland microcosms. . . Flooding effects were evaluated on root and leaf sheath anatomy and shoot morphological traits. Leaf water status and CO2 exchange rates were monitored in flooded and unflooded plants under changing, natural and controlled atmospheric conditions. . Root porosity and leaf sheath aerenchyma increased with flooding. Leaf extension rates and tiller height were also higher in flooded plants, which resulted in a large fraction of the shoot architecture emerging above the water surface. Flooding enhanced stomatal conductance, leaf water potential and net photosynthesis, especially under conditions leading to high air-vapour pressure deficits. Therefore, flooded plants experienced fewer water deficits during periods of high atmospheric evaporative demand. . P. dilatatum showed tight regulation of water and carbon relations under severe soil-oxygen deficiency, even in the presence of natural competitors. The suite of adaptive responses documented here might help to explain the observed increase in abundance of this species during extensive floods.