Seed germination ecology of common bladderwort (Utricularia vulgaris L.)

Abstract

Generative reproduction of the carnivorous aquatic plant Utricularia vulgaris (Lentibulariaceae) from seeds may be a critical process in the recovery of natural populations following temporary drying of habitat, and in the colonisation of new potential sites through dispersal of seeds by water birds. However, little is presently known about the seed ecology and germination biology of this species. We tested the germination response of seeds under various temperature and seed storage regimes, to examine the processes required for seed dormancy alleviation and the effects of different germination solution and temperature on germination probability. Seeds likely possess non-deep simple morphophysiological dormancy alleviated by warm stratification. Highest germination success was recorded for warm-stratified seeds and seeds exposed to ethylene. Seeds were photophilous, with germination more successful at 21 °C than at 25 °C and greatest in slightly alkaline (pH 8) germination solution containing KHCO3, CaCl2 and MgSO4 mimicking the mesotrophic humic waters in which the species naturally occurs. In the alkaline solution, 97 % of seeds rose to the surface prior to germination. In natural habitats, this effect may facilitate seedlings reaching the warmer and irradiated water surface. As seed germination success appears linked to light availability, water chemistry, and seed position in the water column, careful management and ecological restoration of remnant habitats harbouring this species may need to ensure positive conservation outcomes.