Biology Reference
In-Depth Information
species were germinated in a petri-dish in a growth chamber (23°C, 12 hour cycles
of light and dark), after which they were transplanted into pots and placed in the
greenhouse. Each species was replicated five times, with one plant per pot. Pots
were arranged randomly on benches at a density of 1 pot per 0.093 m2.
The plants were exposed to 16 hours of daylight each day, with maximal nat-
ural light levels at ca 1200 µE. Before sunrise and after sunset, artificial lights
(250-300 µE) were used to supplement the light exposure to 16 hours of light per
day. The greenhouse was kept at an average temperature of 23.1°C during the day
and dropped to 20.0°C at night. The plants were fertilized every 2 weeks with 200
ml per pot of a 2g/L concentration of 20-20-20 N-P-K fertilizer.
For each plant, age at first flower, bud development time, and flower longevity
were measured. Emergence of the first pair of true leaves, after the cotyledons, was
considered day 1 of the plant's life. Age at first flower was measured in days from
day 1 to when the first flower opened on each plant. Bud development time (n =
3 buds per plant) was calculated as the number of days from the first appearance
of a new bud until the flower opened. The same three buds on each plant were
then monitored every day after opening, and the number of days until the flower
senesced flower longevity) was recorded for each. A flower was considered to be
senesced when the corolla wilted, fell apart, or became discolored, as designated
by Primack [17]. Any flower that was open for only one day was considered a
one-day flower, regardless of whether it was open for the whole day or only part.
Flowers in the Asteraceae were considered withered when the whole inflorescence
had senesced, rather than the individual florets [17].
For bud development time and flower longevity, the three replicate measure-
ments for each plant were averaged, and then these values for the five replicate
plants were averaged to obtain a mean value for the species. The data were ana-
lyzed with a standard least squares one-way analysis of variance (ANOVA) model,
with a post-hoc contrast between selfers and outcrossers. These analyses were done
for each family and genus separately in order to control for phylogeny at these
levels. In cases where the data were non-normal, a log-transformation was applied
which corrected the distribution.
Authors' Contributions
RS collected the data, performed most of the analyses, participated in the design
of the study, and wrote the first draft as a B.Sc.(Hons) thesis. LWA conceived of
the study, participated in its design and coordination, and wrote the final draft for
submission to BMC. Both authors read and approved the final manuscript.
