The effect of submergence on seed germination in trees from Amazonian floodplains

Rapid and exactly timed seed germination is essential for the establishment and survival of seedlings in Central Amazonian floodplains, where the non-flooded period is short. The peak of fruiting occurs at high water, and the seeds must tolerate extended periods of flooding and often submergence. Germination starts immediately after the retreat of the flood, but it is not clear if submergence is directly responsible for the inhibition of seed germination. In the present paper, an experiment was performed with twelve tree species from Amazonian floodplains to test whether seed germination occurs only in non-flooded seeds. Ten pairs of each species consisting of 1 plastic cup + seed + soil, and 1 cup + seed + soil + water (5 cm) were tested for germination. Thirty to 100 % of the non-submerged seeds germinated after seven weeks, compared to 0 % of the submerged seeds. Four species showed radicle growth, but no species produced a shoot as long as it was submerged. Independent from phylogenetic constraints and from growth strategies among the twelve chosen species, the timing of germination is closely linked to retreating flood water, guaranteeing efficient seedling establishment in the floodplains prior to re-submergence