Germination behaviour of seeds of the New Zealand woody species Melicope simplex, Myoporum laetum, Myrsine divaricata, and Urtica ferox

Abstract

Germination rates, percentage germination success, and phenomena related to germination delay were determined for seeds from freshly collected fruit of Melicope simplex, Myoporum laetum, Myrsine divaricata, and Urtica ferox. The disseminule of Myoporum is unusual in having up to four seeds enclosed in fused endocarp tissue. The tests were carried out in an unheated, partially shaded glasshouse in Christchurch, in a range of conditions similar to those that the seeds might experience after natural dispersal. In the standard treatment (cleaned, kept moist, well lit) subsets of seeds in a cohort germinated at intervals over three, four, or five years, according to species. It took about one month (Urtica), two months (Myrsine), five months (Myoporum), or seven months (Melicope) for the first seeds to germinate. Some seeds of each species germinated through the winter and/or spring in the first year. Otherwise, there were episodes of germination, with different proportionate numbers germinating for each species, in each successive year, mainly in spring. The seeds, thus, exhibit deep dormancy, established to differing degrees in subsets of seeds within a cohort. This enables them to germinate in the favourable spring period and to spread risk. Final germination percentages, respectively, for Melicope, Myoporum, Myrsine, and Urtica, were 77%, 90%, 92%, and 59%. No Melicope seeds germinated in the dark and soil treatments. Rapid germination occurred for Myrsine seeds in the dark and Myoporum seeds on soil. When the endocarp of Myoporum disseminules was cut to expose the seeds the germination rate was very similar to that in the standard treatment; no seeds of this species germinated when left in fruit. It is very likely that seeds of the four species, (especially Urtica and Melicope) could form relatively long-term seed banks. As plant species with deeply dormant seeds seem to be relatively scarce in New Zealand lowland forests, the existence of this phenomenon could relate to the earlier phylogeny of the taxa which possess it. Relatives of both Urtica (in Europe) and Myoporum (in Australia) have deeply dormant seeds. © 1996 Taylor & Francis Group, LLC.