| 1. |
- Milberg, Per, et al.
(författare)
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Do differences in plasticity during early growth lead to differing success in competition? A test using four co-occurring annual Papaver
- 2014
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Ingår i: Plant Species Biology. - : Wiley-Blackwell: No OnlineOpen. - 0913-557X .- 1442-1984. ; 29:1, s. 92-100
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Tidskriftsartikel (refereegranskat)abstract
- Plant species differ in their ability to transform available resources to biomass and to respond in a plastic way to environmental circumstances; we hypothesized that such differences among four weed taxa of Papaver would explain differences in their competitive response. We first compared two populations each of Papaver rhoeasL., P.dubiumL. ssp. dubium, P.dubiumL. ssp. lecoqii (Lamotte) Syme and P.argemoneL., grown in a greenhouse for 6 weeks in a nutrient gradient combined with two light treatments to elucidate possible differences in responses. As there were clear differences, a second experiment evaluated whether these differences also meant differences in competitive response, during early growth, when tested against two crops (wheat, rape). The assumption that competitive response was linked to the ability to transform nutrient and light to biomass was not supported: even though differences in extent of plasticity existed, the effect of competition was similar for the taxa. Thus, higher plasticity and ability to transform available recourses to biomass did not lead to stronger competitiveness for Papaver during early growth.
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| 4. |
- Bergstedt, Johan, et al.
(författare)
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Förändringar i Eklandskapet 1927 till 2013: i den första riksskogstaxeringens fotspår
- 2017
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Ingår i: Svensk Botanisk Tidskrift. - 0039-646X. ; 111:6, s. 331-343
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Tidskriftsartikel (refereegranskat)abstract
- Transects covering 90 km inan area south of Linköping in the province of Östergötland, SE Sweden, were relocated and reinventoried in 2013 using the same methodology as in the first national forest inventory of 1927. Data for land-use, forest type and species-specific tree sizes were obtained and compared with values from 1927. The results show that arable fields and pastures have decreased, while forests and areas covered by roads etc. have increased considerably. Picea abies has increased more than Pinus sylvestris. The reasons for the changes are discussed.
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| 5. |
- Karlsson, Laila, et al.
(författare)
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A Comparative Study of Germination Ecology of Four Papaver Taxa
- 2007
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Ingår i: Annals of Botany. - : Institutionen för fysik, kemi och biologi. - 0305-7364 .- 1095-8290. ; 99:5, s. 935-946
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims: Comparative studies of closely related taxa can increase understanding of adaptations and changes in seed dormancy and germination preferences in an evolutionary perspective. For such studies, a method to describe and compare the performance of taxa in a general way is needed. The germination ecology of four Papaver taxa was studied with the aim of describing and comparing their responses to different seasonal temperature regimes. Methods: Germination of Papaver argemone, P. rhoeas, P. dubium ssp. dubium and P. dubium ssp. lecoqii was investigated in three different artificial climates over 2.5 years. Seeds were collected in southern Sweden, and samples from different populations were used as replicates of taxa. Key Results: Despite substantial intra-taxa variation, there were clear taxon-specific responses. Most germination occurred in the warmest climate. In general, the warmer the climate the more germination occurred in autumn instead of spring. Papaver argemone, phylogenetically most distant from the others, was, in contrast to the other taxa, restricted to germinating only at lower temperatures. Conclusions: Seed dormancy and germination may be described by dormancy pattern, germination preferences and dormancy strength. The general dormancy pattern was a common feature for these taxa and therefore probably an evolutionary conservative character. Germination preferences varied between taxa, resulting in different temperature optima and intervals for germination, and dormancy strength was to some extent taxon-specific, but highly variable. The dormancy pattern explained how the taxa can perform as winter annuals in warmer climates, but mainly as summer annuals in colder climates. Hence, there is no need to interpret the within-taxon temporal differences in seedling emergence as local adaptations. In the field, an entire seed cohort will not germinate during a single season. Instead, emergence will be distributed over several seasons, regardless of local climate, weather and soil cultivation methods.
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| 6. |
- Karlsson, Laila, et al.
(författare)
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Comparing after-ripening response and germination requirements of Conyza canadensis and C. bonariensis (Asteraceae) through logistic functions
- 2007
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Ingår i: Weed research (Print). - : Blackwell. - 0043-1737 .- 1365-3180. ; 47:5, s. 433-441
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Tidskriftsartikel (refereegranskat)abstract
- Germination requirements and after-ripening effects during one year of dry storage at 15/5 and 25/15°C (day/night) were compared for Conyza bonariensis and C. canadensis (Asteraceae). A logistic function was fitted to the results from tests over time in various incubation conditions, using three populations of each species as replicates. Time required for response to dry storage was measured by using a new method; the third derivative of the logistic function. Therefore, a point when major germination was achieved could be detected, without having to rely on maximum germination (which is uncertain), individual data points or any subjectively chosen limit. Fresh seeds of both species were dependent on light for germination and after-ripening was mainly manifested by increasing germination in darkness. Low dormancy status and light requirement might indicate that soil cultivations should rapidly reduce the seed banks of these species, although fecundity and wind dispersal will affect population levels. The species differed in their germination response, with C. bonariensis germinating at lower temperatures than C. canadensis. This seemingly counter-intuitive result may explain the prevention of fatal germination of C. canadensis in cold conditions and its behaviour as a summer annual in northern climates, while C. bonariensis is restricted to warmer parts of the world.
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| 8. |
- Karlsson, Laila, et al.
(författare)
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Inter-species comparison of seed dormancy and germination of six annual Asteraceae weeds in an ecological context
- 2008
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Ingår i: Seed Science Research. - : Institutionen för fysik, kemi och biologi. - 0960-2585 .- 1475-2735. ; 18, s. 35-45
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Karlsson, Laila, 1965-
(författare)
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Seed dormancy and germination in an ecological context : comparative studies of annual weeds
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 10. |
- Karlsson, Laila, et al.
(författare)
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Seed dormancy and germination in the summer annual Galeopsis speciosa
- 2006
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Ingår i: Weed research (Print). - : Institutionen för fysik, kemi och biologi. - 0043-1737 .- 1365-3180. ; 46:5, s. 353-361
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Tidskriftsartikel (refereegranskat)abstract
- This study examined germination and dormancy in Galeopsis speciosa (Lamiaceae), a common summer annual weed in cold-temperate areas. Seeds collected in southern Sweden were subjected to several experiments. The seeds were dormant at maturity. Seeds sown outdoors after collection produced a small number of seedlings, that emerged early in the spring. After long cold stratification or stratification outdoors over two winters, the maximum germination was 40 to 50%; germination occurring over a wide range of temperatures. Warm stratification preceding cold stratification had no effect on germination, but repeated warm and cold periods seemed to promote germination. Gibberellic acid (GA) stimulated germination but full germination was only achieved after more than two months of incubation at the most suitable temperature regime tested. Excised embryos grew and developed into normal seedlings. With these results, the species does not fit into the currently used system for seed dormancy classifications. The response to GA and the growth of excised embryos indicate non-deep or intermediate physiological dormancy, but dormancy alleviation by stratification was not in line with the guiding principles for these classifications. Galeopsis speciosa has a strong dormancy that is sufficiently alleviated during the winter to allow germination of only part of a seed batch each year, hence a stepwise germination pattern occurs over a period of several years.
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