CARTER, CHRISTY TUCKER* AND IRWIN A. UNGAR. Department of Environmental and Plant Biology, Ohio University, Athens, Ohio, 45701 USA. - Germination response of Spergularia marina to seasonal changes in temperature and light.
Seeds of Spergularia marina were collected in October, 1998,
from an inland salt marsh in Rittman, Ohio, to test for seasonal
change in germination responses to different temperature regimes and
light vs dark treatments. To allow for exposure to natural
temperature and moisture conditions, seeds contained in polyester bags
were buried outdoors at the Ohio University greenhouse during
November, 1998. Fresh seeds and seeds harvested monthly were tested
for germinability. Four replicate petri dishes each containing 25
seeds were exposed to four alternating (12-h night/12-h day)
temperature regimes (5/15°C, 5/25°C,
15/25°C, and 20/35°C) with a 12-h dark/12-h
light photoperiod (20 µmol m-2s-1) for 20 days.
An identical set of replicates was exposed to the same temperature
regimes, but instead received 24-h dark for 20 days. Means ±SE were
calculated monthly for each temperature and a two-way ANOVA and
Bonferroni post-hoc test were performed on arcsin square root
transformed data. We found that no fresh seeds germinated in light or
dark treatments. For seeds exposed to 24-h dark, less than 4%
germinated at any temperature for any given month. From the two-way
ANOVA and Bonferroni tests, germination responses at all temperatures
were found to be significantly different (P<0.0001) with seeds in the
5/15°C temperature regime demonstrating the greatest and
those at 20/35°C the lowest germination. Length of burial
was also found to significantly (P<0.0001) influence germination and
there was a significant (P<0.0001) interaction between temperature and
length of burial. Except for 20/35°C, germination
increased in the remaining three temperature regimes over the 12 month
period. Spergularia marina seeds had both primary and
conditional dormancy, but did not demonstrate a secondary dormancy.
Seeds are probably inhibited from germinating in the field when they
are buried and during the summer when temperatures are high and often
exceed 35°C.
Key words: caryophyllaceae, dormancy, germination, light, Spergularia marina, temperature