G. Houle et al., The effect of salinity on different developmental stages of an endemic annual plant, Aster laurentianus (Asteraceae), AM J BOTANY, 88(1), 2001, pp. 62-67
Salinity reduces substrate water potential, thereby restricting water and n
utrient uptake by plants: salinity may also cause ionic imbalance and toxic
ity. Because substrate salinity fluctuates through the growing season, a pl
ant may be exposed to different salinity levels, at various stages of devel
opment, with potentially significant consequences on population dynamics. H
ere, we present the results of a study of the effect of substrate salinity
on seed germination, seedling emergence, and growth of Aster laurentianus,
an annual marsh plant, endemic to the Gulf of St. Lawrence and potentially
threatened. Seed germination was reduced in low salt concentration (10 g se
a salt/L) and completely inhibited by salinity levels greater than or equal
to 20 g sea salt/L. However, this inhibiting effect was reversible: seeds
from the salt treatments germinated readily after being washed in distilled
water. Though seedling emergence was diminished at low salinity levels, po
stemergence survival was little affected. Plant growth was reduced, but net
carbon assimilation rate was not affected by high salinity levels. Increas
ed root respiration and respiratory costs associated with salt tolerance mi
ght have contributed to lower C accumulation at higher salinity levels. All
developmental processes considered are thus negatively affected by substra
te salinity, with potentially significant consequences on population abunda
nce and distribution in salt marshes. Yet, the tolerance of this species to
high salinity levels after seedling emergence is remarkable. Seed germinat
ion represents a major bottleneck in the species life cycle, potentially co
ntrolling local distribution and abundance in the natural habitat.