Flooding tolerance of forage legumes.
We review waterlogging and submergence tolerances of forage (pasture) legumes. Growth reductions from waterlogging in perennial species ranged from >50% for Medicago sativa and Trifolium pratense to <25% for Lotus corniculatus, L. tenuis, and T. fragiferum. For annual species, waterlogging reduced Medicago truncatula by ~50%, whereas Melilotus siculus and T. michelianum 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 M. sativa due to growth inhibition from limited respiration and low energy in roots of low porosity (i.e. 4.5%). In contrast, L. corniculatus, 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 M. sativa, photosynthesis soon declines and in the longer term (>10 d) leaves suffer chlorophyll degradation, damage, and N, P, and K deficiencies. In tolerant L. corniculatus and L. tenuis, 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.
IFEVA, Universidad de Buenos Aires, CONICET, Facultad de Agronomía, Avenida San Martín 4453, CPA 1417, DSE Buenos Aires, Argentina.|School of Plant Biology, Faculty of Science, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Australia.
Gustavo G
GG
Striker
School of Plant Biology, Faculty of Science, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Australia.|The UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Australia.
Timothy D
TD
Colmer
D018556:Crops, Agricultural / Q000502:physiology; D007887:Fabaceae / Q000502:physiology*; D055868:Floods; D000070116:Lotus / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology*; D018520:Plant Shoots / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology*; D014867:Water / Q000502:physiology*
D014867:Water
Aerenchyma; N2 fixation under hypoxia; nitrogen deficiency; photosynthesis and stress; plant submergence stress; root hypoxia; root porosity; waterlogging tolerance.