Heat stimulated germination in relation to seed characteristics in fynbos legumes of the Western Cape Province, South Africa

Abstract

Seeds of 13 Aspalathus species and three other Fabaceae species from the fynbos vegetation of the Western Cape Province, South Africa were exposed to pre-germination treatments comprised of combinations of four different temperatures (60 °C, 80 °C, 100 °C, 120 °C) and three time durations (5, 15 or 30 minutes). The ‘heat-sum’ (product of temperature and time) most effective in stimulating germination in a particular species was shown to be negatively correlated with a specific seed characteristic, namely the proportion of whole seed to embryo plus cotyledon mass. It may thus be possible to predict the temperature-time combination most effective for stimulating germination in Aspalathus species and possibly other members of the Fabaceae by using this ratio. However, predicting the number of seeds likely to germinate in the field after fires of different intensity requires further information concerning the distribution of seeds in the soil which is currently unknown for fynbos legumes.