Different strategies of Lotus japonicus, L. corniculatus and L. tenuis to deal with complete submergence at seedling stage.

Two main strategies allow plants to deal with submergence: (i) escape from below water by means of shoot elongation, or (ii) remaining quiescent under the water until water subsides and then resume growth. We investigated these strategies in seedlings of Lotus japonicus, L. corniculatus and L. tenuis subjected to control and submergence for 12 days, with a subsequent 30-day recovery period. All three species survived submergence but used different strategies. Submerged seedlings of L. japonicus exhibited an escape strategy (emerging from water) as a result of preferential carbon allocation towards shoot mass and lengthening, in detriment to root growth. In contrast, seedlings of L. corniculatus and L. tenuis became quiescent, with no biomass accumulation, no new unfolding of leaves and no shoot elongation. Upon de-submergence, seedlings of L. japonicus had the lowest recovery growth (a biomass and shoot height 58% and 40% less than controls, respectively), L. corniculatus was intermediate and L. tenuis showed the greatest recovery growth. Previously submerged seedlings of L. tenuis did not differ from their controls, either in final shoot biomass or shoot height. Thus, for the studied species, quiescence appears to be an adequate strategy for tolerance of short-term (i.e., 12 days) complete submergence, being consistent with field observations of L. tenuis colonisation of flood-prone environments.