Flooding tolerance of forage legumes

STRIKER GG; COLMER TD

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2017 vol. 68 p. 1851 - 1872

0022-0957

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 with root porosity across eight species. Metabolism in hypoxic roots was influenced by internal aeration. Sugars accumulate in Medicago sativa due to growth inhibition from limited respiration and low energy in roots of low porosity (viz. 4.5%). By contrast, L. corniculatus with higher root porosity (viz. 17.2%) and O2 supply allowing respiration, better maintained growth 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 Medicago sativa, photosynthesis soon declines and in the longer-term (>10 days) 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 differ also 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 ability to recover after water subsides.