The action of temperature fluctuations on hard seeds of subterranean clover

Abstract

Burrs of three cultivars of subterranean clover (Trifolium subterraneum) were placed in soil in a cold frame at Canberra so that they were subjected to daily temperature fluctuations of the order of 20-54�C. After three months and eight months the proportion of permeable seeds was significantly increased. Such seeds were conductive to water at one specific region of the testa-the strophiole. In a further experiment, under laboratory conditions, hard seeds were subjected to temperature fluctuations of 23-60�C with cycle lengths varying from 15 minutes to 1 hour. There was no reduction in the percentage of hard seeds except in two trials when that portion of each cycle at 60�C was greater than 45 minutes.