Heat Shock Germination Responses of Three Eastern North American Temperate Species

Abstract

The requirement for heat shock to break physical dormancy of hard seeds is a widely known strategy for recruitment in fire maintained ecosystems. Despite extensive work by fire ecologists in the southeastern United States, heat shock response has been demonstrated for only a few eastern North American temperate species. In this study germination responses to dry and wet heat were investigated for three species with physical dormancy: Galactia regularis (Fabaceae), Lupinus perennis (Fabaceae), and Rhus copallinum (Anacardiaceae). Control, wet heat (1 min boiling), and dry heat (10 min at 60, 70, 80, 90, 100, and 110°C) treatments were independently applied in the laboratory. Maximum germination occurred at 80°C for G. regularis and L. perennis and was significantly greater than both control and boiling treatments. For R. copallinum, maximum germination occurred at 90°C for all populations investigated and was significantly greater than the control group in three of four populations. Heat shock germination may play a larger role in post fire recruitment in the flora of the eastern United States than currently recognized.