Baskin Jerry M, Baskin Carol C
Department of Botany, University of Kentucky, 40506, Lexington, Kentucky, USA.
Oecologia. 1972 Mar;10(1):17-28. doi: 10.1007/BF00822759.
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.
对毛景天（Diamorpha cymosa (Nutt.) Britton，景天科）实验室保存的种子，从5月下旬成熟后不久开始，每月进行一次萌发试验，一直持续到田间萌发基本结束时（11月）。将种子置于5、10、15、20、25、30、15/6、20/10、30/15和35/20°C下，光周期为14小时（在变温条件下热周期为12/12小时），同时设置全黑暗条件。6月时，种子几乎完全休眠，因此在所有条件下萌发率都很低或根本不萌发。从5月下旬到11月种子老化过程中，1. 在14小时光周期下萌发速率和总萌发率增加；2. 恒温条件下最大萌发温度从15°C升至25°C，变温条件下从20/10°C升至30/15°C；3. 恒温条件下萌发最适温度从15°C升至15 - 20°C，而在整个研究过程中变温条件下一直保持在20/10°C。同一时期，在恒温及变温条件下全黑暗中的萌发率可忽略不计。这种生理后熟模式显然是对美国东南部岩石露头处夏季干燥、冬季湿润生境的一种适应。在黑暗中吸胀12小时后给予短时间白光照射，可促进种子在25/10°C黑暗条件下萌发，但在15°C或25°C时无效。吸胀期间给予短时间光照对促进黑暗中萌发的效果要差得多。干燥长达7天不会使经光刺激的种子丧失在黑暗中萌发的能力。种子萌发对光的需求可能并非将毛景天限制在花岗岩和砂岩露头光照良好生境的原因。
