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Inter-species comparison of seed dormancy and germination of six annual Asteraceae weeds in an ecological context
Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.
Haramaya University.
Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.ORCID iD: 0000-0001-6128-1051
2008 (English)In: Seed Science Research, ISSN 0960-2585, Vol. 18, 35-45 p.Article in journal (Refereed) Published
Abstract [en]

To understand germination timing in an ecological context, the response to environmental events that affect seed dormancy is central, and has to be combined with knowledge of germination responses to different circumstances. In this study, seed dormancy, germination, and emergence phenology of six annual co-occurring weedy Asteraceae species were investigated. Three pre-treatments (warm and cold stratification, and dry storage) were tested as possible dormancy affecting environmental events. Seeds were also sown outdoors. Species-specific differences were revealed in analyses. To facilitate general descriptions of dormancy patterns and germination preferences separately, condensed responses to the different possible dormancy affecting treatments and relative germination in different environments were plotted, giving species-specific patterns. Most species exhibited decreased dormancy to two or three pre-treatments. Dormancy was most effectively reduced by cold stratification for three species (Guizotia scabra, Parthenium hysterophorus, Verbesina encelioides), by warm stratification for two (Bidens pilosa, Galinsoga parviflora) and by dry storage for one (Tagetes minuta). All species germinated more when provided with light than in continuous darkness. Temperature levels most suitable for germination varied from low (15/5-20/10°C) for Verbesina encelioides to high (25/15-30/20°C) for Bidens pilosa. It is concluded that, even though the species have different dormancy patterns and germination preferences that suggest different possible distribution ranges, the species achieve similar emergence timing in the field in environments with a pronounced dry period after dispersal and small annual temperature fluctuations.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi , 2008. Vol. 18, 35-45 p.
Keyword [en]
Bidens pilosa, Galinsoga parviflora, Guizotia scabra ssp. schimperi, Parthenium hysterophorus, Tagetes minuta, tropical weeds, Verbesina encelioides
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-11879DOI: 10.1017/S0960258508888496OAI: diva2:18281
Original publication: Laila M. Karlsson, T. Tamado and Per Milberg, Inter-species comparison of seed dormancy and germination of six annual Asteraceae weeds in an ecological context, 2008, Seed Science Research, (18), 35-45. Copyright: Cambridge University Press, from: 2008-05-22 Created: 2008-05-22 Last updated: 2014-10-08
In thesis
1. Seed dormancy and germination in an ecological context: comparative studies of annual weeds
Open this publication in new window or tab >>Seed dormancy and germination in an ecological context: comparative studies of annual weeds
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [da]

Germination ecology studies, i.e. studies of interactions between characteristics of the seeds and environmental circumstances, provide understanding of spatial and temporal patterns of emergence of wild species, as weeds in the field. A large number of species have seed dormancy, i.e. seeds respond to circumstances not directly evoking germination. Thus, germination may occur only if specific environmental events have occurred in the seeds' past life story, and/or if a suitable time period has passed since ripening on mother plants. In this thesis, three characteristics, i.e. dormancy pattern, germination preferences and dormancy strength, hypothesised as mutually independent seed characteristics, are used to describe dormancy and germination in an ecological context. This conceptual model may be used for descriptions of differences between species, to understand emergence patterns in the field from controlled germination tests, and probably for increasing the understanding of evolution of ecological important properties of seed dormancy and germination.

Fifteen annual weedy taxa were investigated: two groups of temperate climate weeds, Lamium and Papaver, and one group of tropical weeds, co-occurring Asteraceae species of different genera. Intra-species variations in germination occurred for all species, but species-specific germination responses within all groups were revealed in analyses. All species showed some kind of species-specific dormancy pattern that was expressed as increased germination in response to one or more environmental factor not required for the actual germination.

For Lamium and Papaver, the general dormancy pattern was genus-specific. Germination preferences varied slightly within genus. Dormancy strength was to some extent species-specific, but highly variable. The species belonging to Asteraceae showed differences in dormancy pattern. It is shown how such differences can be visualized and compared by plotting response time and achieved germination in two-dimensional graphs, giving species-specific pictures.

Dormancy pattern and germination preferences explained how Papaver can perform as winter annuals in warmer climates, but substantially as summer annuals in colder climates, without local adaptations. For Lamium, the results indicate a local adaptation of increasing dormancy strength: in relatively cold climate in Sweden, a strong dormancy restricted a part of each cohort from germinating during autumn, thus preventing from winter mortality. For the Asteraceae, five of six species clearly responded to cold pretreatment, which is noteworthy considering the small seasonal temperature differences in the study area and in the areas of origin for the species. The six Asteraceae achieved similar emergence timing in the field by responding to different environmental factors.

Together, the results from these fifteen species indicate that dormancy pattern is an evolutionary conservative characteristic, dormancy strength is relatively easily changed, and germination preference is intermediate.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2007. 56 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1088
Asteraceae, Bidens, Compositae, deadnettle, Galinsoga, germination timing, Guizotia, evolution, Labiatae, Lamiaceae, Lamium, morphophysiological dormancy, Papaveraceae, Papaver, Parthenium, physiological dormancy, poppy, summer annual, Tagetes, Verbesina, winter annual
National Category
Biological Sciences
urn:nbn:se:liu:diva-11444 (URN)978-91-85715-29-9 (ISBN)
Public defence
2007-04-17, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 09:30 (English)
Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2014-10-08

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