Germination Responses to Light and Alternating Temperatures in European Populations of Dactylis Glomerata L.

Summary Germination responses to light and alternating temperatures were investigated in a range of populations of Dactylis glomerata L. of contrasting origin. Despite quantitative variation, similar responses to both factors were recorded in 12 British populations. In 11 European populations, levels of response were dependant on original dormancy status and apparently related to climatic origin. Whereas northern European populations required both light and alternating temperatures for maximum germination, Mediterranean populations germinated to high levels in complete darkness at a constant temperature. In Mediterranean populations, germination capacity declined sharply with increasing daily photoperiod in light from warm white fluorescent tubes. It is postulated that different patterns of response in European populations were related to differences in a basic mechanism of germination control involving phytochrome.