Effect of heat on seed germination and viability in species of Cistaceae

Abstract

ABSTRACTBackground: Species of the Cistaceae family have hard-coated seeds and consequently require scarification for germination. It is widely assumed that the high temperature caused by fire is a scarifying agent that triggers seed germination in the Cistaceae. However, to date there is insufficient knowledge regarding species, populations and diverse variables associated with germination to consider such a fire trigger generally applicable.Aims: To test the relationship between exposure to fire and germination in 10 species of the Cistaceae family.Methods: We quantified after different heat treatments the germination and seed viability in 10 species of Cistus, Fumana, Halimium, Helianthemum and Tuberaria Final germination percentage, t50 and seed viability were determined.Results: Heat treatment increased germination in all except the species of Helianthemum; however, the rate of increase was dependent on species. Germination speed (t50) was less affected by heat than final germination, and seed viability did not decrease except for H. hirtum.Conclusions: Most of the species showed high tolerance and a positive response to heat although germination patterns were idiosyncratic of each species. This work evidences the wide range of germination responses to heat within Cistaceae, and consequently the differential role of fire within this plant family.