Title: Seed persistence of the invasive aquatic plant, Gymnocoronis spilanthoides (Asteraceae)
Abstract: Seed persistence of Gymnocoronis
spilanthoides (D.Don) DC.; Asteraceae (Senegal tea), a serious weed of
freshwater habitats, was examined in relation to burial status and different
soil moisture regimes over a 3-year period. Seeds were found to be highly
persistent, especially when buried. At the end of the experiment, 42.0%, 27.3%
and 61.4% of buried seeds were viable following maintenance at field capacity,
water logged and fluctuating (cycles of 1 week at field capacity followed by 3
weeks' drying down) soil moisture conditions, respectively. Comparable viability
values for surface-situated seeds were ~3% over all soil moisture regimes.
Predicted times to 1% viability are 16.2 years for buried seed and 3.8 years for
surface-situated seed. Persistence was attributed primarily to the absence of
light, a near-obligate requirement for germination in this species, although
secondary dormancy was induced in some seeds. Previous work has demonstrated low
fecundity in field populations of G. spilanthoides, which suggests that
soil seed banks may not be particularly large. However, high levels of seed
persistence, combined with ostensibly effective dispersal mechanisms, indicate
that this weed may prove a difficult target for regional or state-wide
eradication. [Panetta, F.D. (2010) Seed persistence of the invasive aquatic
plant, Gymnocoronis spilanthoides (Asteraceae). Australian Journal of
Botany, 57 (8), pp. 670-674.]