New Zealand Journal of Botany abstract
Germination behaviour of seeds of the New Zealand woody species Melicope
simplex, Myoporum laetum, Myrsine divaricata, and Urtica
ferox
C. J. BURROWS
Department of Plant and Microbial Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
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.
Keywords seeds; germination; simulating nature; deep
dormancy; long-term seed banks; phylogenetic influences
B95043
Received 6 October 1995; accepted 20 December 1995
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