Germination characteristics ofDiamorpha cymosa seeds and an ecological interpretation
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Laboratory-stored seeds ofDiamorpha cymosa (Nutt.) Britton (Crassulaceae) were germinated at monthly intervals starting shortly after maturity in late May and ending at approximately the time germination is completed in the field (November). Seeds were placed at 5, 10, 15, 20, 25, 30, 15/6, 20/10, 30/15 and 35/20°C at a 14-hr photoperiod (12/12 hr thermoperiods at the alternating temperature regimes) and in constant darkness. In June, seeds were almost completely dormant and thus germinated poorly or not at all under all conditions. As seeds aged from late May to November 1. germination at the 14-hr photoperiod increased in rate and total percentage, 2. the maximum germination temperature increased from 15 to 25°C at constant temperatures and from 20/10 to 30/15°C at the alternating temperature regimes and 3. the optimum temperature for germination increased from 15 to 15–20°C at constant temperatures but remained at20/10°C at alternating temperature regimes throughout the study. During the same period germination in constant darkness was negligible at constant and alternating temperature regimes. This pattern of physiological after-ripening apparently is an adaptation to summer-dry,winter-wet habitats such as rock outcrops of southeastern United States.
A short period of illumination with white light given after a 12-hr imbibition period in darkness promoted germination in the dark at 25/10°C but not at 15 or 25°C. A short period of illumination given during the imbibition period was much less effective in promoting germination in the dark. Drying up to 7 days did not cause light-stimulated seeds to lose their ability to germinate in darkness. The light requirement for seed germination probably does not play a role in restrictingD. cymosa to its well-lighted habitats on granite and sandstone outcrops.
KeywordsSandstone Germinate Constant Temperature Seed Germination White Light
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- Baskin, J. M., Baskin, C. C.: Germination eco-physiology ofDraba verna. Bull. Torrey Bot. Club97, 209–216 (1970).Google Scholar
- Baskin, J. M., Baskin, C. C.: Germination ecology and adaptation to habitat inLeavenworthia spp. Amer. Midl. Natur.85, 22–35 (1971a).Google Scholar
- Baskin, J. M., Baskin, C. C.: Germination ecology ofPhacelia dubia var.dubia in Tennessee glades. Amer. J. Bot.58, 98–104 (1971b).Google Scholar
- Baskin, J. M., Baskin, C. C.: Germination of winter annuals in July and survival of the seedlings. Bull. Torrey Bot. Club98, 272–276 (1971c).Google Scholar
- Baskin, J. M., Baskin, C. C.: Ecological life cycle and physiological ecology of seed germination ofArabidopsis thaliana. Canad. J. Bot.50, 353–360 (1972).Google Scholar
- Baskin, J. M., Baskin, C. C.:Gutierrezia dracunculoides new to Kentucky. Castanea (in press).Google Scholar
- Caudle, C., Baskin, J. M.: The germination pattern of three winter annuals. Bull. Torrey Bot. Club95, 331–335 (1968).Google Scholar
- McCormick, J. F., Platt, R. B.: Ecotypic differentiation inDiamorpha cymosa. Bot. Gaz.125, 271–279 (1964).Google Scholar
- McVaugh, R.: The vegetation of the granite flatrocks of the southeastern United States. Ecol. Monogr.13, 119–166 (1943).Google Scholar
- Newman, E. I.: Factors controlling the germination date of winter annuals. J. Ecol.51, 625–638 (1963).Google Scholar
- Oosting, H. J., Anderson, L. E.: Plant succession on granite rock in eastern North Carolina. Bot. Gaz.100, 750–768 (1939).Google Scholar
- Rollins, R. C.: The evolution and systematics ofLeavenworthia (Cruciferae). Contrib. Gray Herbarium Harvard Univ. No192, 3–98 (1963).Google Scholar
- Thompson, P. A.: Changes in germination responses ofSilene secundiflora in relation to the climate of its habitat. Physiol. Plant.23, 739–746 (1970).Google Scholar
- Vegis, A.: Dormancy in higher plants. Ann. Rev. Plant Physiol.15, 185–215 (1964).Google Scholar
- Wiggs, D. N., Platt, R. B.: Ecology ofDiamorpha cymosa. Ecology43, 654–670 (1962).Google Scholar