Seed dormancy of 80 tropical montane forest species in Sri Lanka, the first dormancy profile for a tropical montane forest community

Community-level seed dormancy studies are important in understanding the dynamics of plant communities and adaptations of species to their habitat. Our aim was to develop a seed dormancy profile for tropical montane forests of Sri Lanka, which are a global biodiversity hotspot, and compare it to the profile made using a world database for this vegetation type. Germination, imbibition and embryo length : seed length ratio of seeds were determined for 80 Sri Lankan montane forest species. Seeds of 31 species were fast-germinating with a median length of germination (MLG) <30 days and the remaining 49 were slow-germinating with MLG >30 days. Embryos of six fast-germinating species grew prior to radicle emergence, indicating morphological dormancy (MD). The other 25 fast-germinating species had non-dormant (ND) seeds. Manually scarified seeds of two species imbibed significantly more water than non-scarified seeds, revealing physical dormancy (PY). Embryos of 20 slow-germinating species grew prior to radicle emergence, confirming morpho-physiological dormancy (MPD). The remaining slow-germinating species had a fully developed embryo and thus physiological dormancy (PD). The percentage of species with ND seeds and with MD, MDP, PD and PY was 31, 7.5, 25, 34 and 2.5, respectively. Species with dormant seeds (70%) dominate the Sri Lankan montane forest community similar to the world database, with 85% dormant seeds. Seed dormancy may be an adaptation that prevents seeds from germinating during the Sri Lankan dry season from December to March when conditions are unfavourable for seedling growth due to low water availability.