The influence of collecting date, temperature and moisture regimes on the germination of epiphytic bromeliads

The understanding that many aspects of the spatial and temporal patterns of epiphyte communities may be explained by the comportment of early life stages has given rise to a considerable number of germination studies in recent years. Unfortunately, protocols frequently use unproven assumptions and arbitrary experimental conditions. To make future studies as ecologically meaningful as possible we address a number of potential pitfalls with a series of experiments with seeds from a total of 16 species. We show that it is safe to collect capsules for experiments before natural dehiscence - there is afterripening even in the case of very early collections. The application of fluctuating temperatures is not imperative, because there is no consistent difference in the germination response under constant versus fluctuating temperatures. The effects of different osmotic potentials and intermittent drought of varying intensity on germination are qualitatively, but not quantitatively, comparable. Due to the greater ecological realism, we encourage the use of the latter. However, care must be taken to use realistic temperatures - the impact of intermittent drought on germination is modulated by temperature. This highlights the need for data on the in situ temperature regimes during germination as an important prerequisite towards more realistic experiments in the field of germination ecology of vascular epiphytes.