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 (5/15C, 5/25C, 15/25C, and 20/35C) with a 12-h dark/12-h light photoperiod (20 Ámol 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 5/15C temperature regime demonstrating the greatest and those at 20/35C 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 20/35C, 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 35C.

Key words: caryophyllaceae, dormancy, germination, light, Spergularia marina, temperature