Author:
Dunbabin Matthew T.,Cocks P. S.
Abstract
The seed dormancy characteristics of 2 capeweed
[Arctotheca calendula (L.) Levyns] ecotypes
from Western Australia were studied to determine aspects of seed dormancy that
contribute to the success of this species in southern Australia. Short- and
long-term dormancy pattern of buried and soil surface seed, effect of summer
temperatures on afterripening, and effect of temperature on seed germination
were investigated using seed produced in a common environment.
There were large differences in the seed dormancy pattern of the 2 ecotypes
studied. On the soil surface, >95% of seed of the Mt Barker ecotype
became non-dormant and germinated in the first year, the remainder germinating
the following season. In contrast, only 5% of Mullewa seed germinated
in the first year, with 75% germinating in the second year and
20% of seed remaining dormant after 2 years. Cycling of dormancy was
observed for buried seed of both ecotypes, with periods of non-dormancy
corresponding with the likely timing of the break of the season. Dormancy
cycling was also apparent in seed stored under constant conditions in the
laboratory. Burial prevented germination of both ecotypes; however, the
ability to resist germination while buried was lost in 30% of the Mt
Barker seed in the second season. Differences in the duration of dormancy of
soil surface and buried capeweed seed have evolved as an adaptation to the
different environments likely to be experienced by plants at their site of
collection.
All seeds possessed primary dormancy at maturity, with any afterripening
during the first year occurring by the end of summer. Afterripening was
enhanced by exposure to typical soil surface temperatures, providing some
protection against germination during early summer rainfall. Protection from
late summer rains is insured by the inability of seed to germinate at
temperatures >30°C and a relatively slow rate of germination. These
features of capeweed seed dormancy, combined with the ability to evolve
genetically distinct populations suited to particular environments, help
explain why capeweed is so widespread and abundant across southern Australia.
Subject
General Agricultural and Biological Sciences
Cited by
20 articles.
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