Effect of high temperatures on seed germination of two woody Leguminosae

Cytisus scoparius and Genista florida regenerate after fire by stump-sprouting but also by seed. Seeds of these species were heated to a range of temperatures similar to those registered on the surface soil during natural fires (from 50 to 150 °C) and a range of exposure times (from 1 to 15 min). No germination was observed at high temperatures, ≥130 °C, when the exposure time was 5 min or more. However, moderate heat treatments (at 70 and 100 °C) significantly increased the rate of germination relative to controls. Cytisus scoparius is more favoured by fire action than Genista florida, with germination rates slightly greater following 100 °C for 5 min and 130 °C for 1 min than after mechanical scarification.