Beschreibung:
<p>We review waterlogging and submergence tolerances of forage (pasture) legumes. Growth reductions from waterlogging in perennial species ranged from >50% for <italic>Medicago sativa</italic> and <italic>Trifolium pratense</italic> to <25% for <italic>Lotus corniculatus, L. tenuis,</italic> and <italic>T. fragiferum</italic>. For annual species, waterlogging reduced <italic>Medicago truncatula</italic> by ~50%, whereas <italic>Melilotus siculus</italic> and <italic>T. michelianum</italic> were not reduced. Tolerant species have higher root porosity (gas-filled volume in tissues) owing to aerenchyma formation. Plant dry mass (waterlogged relative to control) had a positive (hyperbolic) relationship to root porosity across eight species. Metabolism in hypoxic roots was influenced by internal aeration. Sugars accumulate in <italic>M. sativa</italic> due to growth inhibition from limited respiration and low energy in roots of low porosity (i.e. 4.5%). In contrast, <italic>L. corniculatus</italic>, with higher root porosity (i.e. 17.2%) and O₂ supply allowing respiration, maintained growth better and sugars did not accumulate. Tolerant legumes form nodules, and internal O₂ diffusion along roots can sustain metabolism, including N₂ fixation, in submerged nodules. Shoot physiology depends on species tolerance. In <italic>M. sativa</italic>, photosynthesis soon declines and in the longer term (>10 d) leaves suffer chlorophyll degradation, damage, and N, P, and K deficiencies. In tolerant <italic>L. corniculatus</italic> and <italic>L. tenuis</italic>, photosynthesis is maintained longer, shoot N is less affected, and shoot P can even increase during waterlogging. Species also differ in tolerance of partial and complete shoot submergence. Gaps in knowledge include anoxia tolerance of roots, N₂ fixation during field waterlogging, and identification of traits conferring the ability to recover after water subsides.</p>