| 1. |
- Alatalo, Juha, 1966-, et al.
(författare)
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Pollen viability and limitation of seed production in a population of the circumpolar cushion plant, Silene acaulis (Caryophyllaceae)
- 2001
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 21:4, s. 365-372
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Tidskriftsartikel (refereegranskat)abstract
- Pollen viability among genders and limitation of female seed production in a natural trioecious population of the circumpolar cushion plant Silene acaulis was examined. Pollen viability was estimated by an in vitro pollen germination experiment. Both male and hermaphrodite flowers displayed large variation in pollen viability (0-53% in hermaphrodite and 0-54% in male flowers). There was a significant difference between genders in pollen viability: male plants had on average higher pollen viability than hermaphrodite plants. Resource and pollen limitation of seed production was studied by an experiment consisting of three treatments; (I) hand-pollination and removal of all other flowers on the cushion, (II) harid-pollination without removal of other flowers, and (III) open pollination without removal of flowers, Hand-pollination increased seed production, whereas removal of flowers had no effect on seed production. Abortion of pollinated ovules during seed development and seed mass did not differ among treatments. To control for effect of fruit number on seed production, data from naturally pollinated individuals was used. There was a positive correlation between both total number of seeds and fruit number, mean seed number per fruit and fruit number, respectively. These results indicate that seed production of S. acaulis is mainly limited by pollen availability whereas resource competition between fruits is not important as a limiting factor. The possible role of male quality differences between genders and pollen limitation of seed production for maintenance of trioecious reproductive systems is discussed.
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| 2. |
- Danilov, Roman, et al.
(författare)
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Autumn phytoplankton assemblages in temperate lakes of different eutrophication level in the middle part of Sweden
- 2000
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 20:2, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton assemblages were studied during autumn 1998 in oligo-, meso- and eutrophic lakes in central Sweden (62°54'N). Differences in phytoplankton assemblages have been detected both in space and time. In eutrophic lakes coccoid Chlorophyceae dominated quantitatively during September and October. Diatoms were the most diverse group in all types of lakes in September and in meso- and oligotrophic lakes in October. In November Cryptophyceae became the most abundant group in all lakes. The total richness of species decreased in the meso- and oligotrophic environments in November compared to September and October, whilst in the eutrophic environment it remained almost unchanged. Cluster analyses, using both presence-absence and presence-absence in combination with abundance matrices, showed similar results and a good resolution between the lakes of different eutrophication conditions. We conclude that the phytoplankton assemblages of the lakes studied depended on the trophic conditions and thus they can be used for resolution between different eutrophication levels.
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| 3. |
- Grandin, Ulf, et al.
(författare)
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Allozyme variation at a PGI locus in differently aged populations of Moehringia trinervia (Caryophyllaceae) in a successional area
- 2002
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 22:3, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- We studied genetic effects of the colonisation process during primary succession by analysing allozyme variation at a PGI locus in differently aged populations of Moehringia trinervia, which is a selfing annual with low dispersal ability. The populations studied come from islands and shores created in the 1880s by a drop in the water table of a Swedish lake and from old parts of a large island and of the mainland. The population age is known from five vegetation analyses over a century. We have also analysed the genetic composition of M. trinervia derived from seeds in the soil. Mainland populations had a higher genetic diversity than island populations that were little differentiated and differed genetically from the mainland populations. There was no temporal trend in the distribution of genetic variation on the new islands. The presence of alleles in the extant populations was associated with the proportion of that allele in the seed bank, indicating a main recruitment from the seed bank and not by repeated immigrations. We suggest that some of the new islands were colonised by a few early founders from the mainland. Later colonisation has occurred between adjacent islands, which preserves the founder effect and could explain the uniform, low genetic variation in the island populations
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| 4. |
- Gustafsson, Susanne
(författare)
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Flowering frequency in a small population of Gymnadenia conopsea : a five year study
- 2004
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 24:5, s. 599-605
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Tidskriftsartikel (refereegranskat)abstract
- This investigation evaluates the usage of genetic markers, microsatellites, to distinguish and re-identify individual plants in a population of the orchid Gymnadenia conopsea. The study also illustrates the problem in estimating the size of a population from single year sampling as individuals can rest underground or occur in vegetative states; information extremely important for the understanding of population dynamics as well as providing information for conservation management. The total population size was, based on information from microsatellite loci, estimated to 84 individuals and vastly larger than the annual number of flowering plants (mean 31.4 individual s/year). Flowering frequency varied from 24-49%, 53 individuals flowered once, five individuals were flowering four years and a single individual was flowering five years. A common pattern was one or two flowering periods followed by a non-flowering period. The observed number of alleles and the observed and expected heterozygosity varied among loci, although allele frequencies and genotype frequencies did not vary significantly among years.
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| 5. |
- Thulin, Mats
(författare)
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A new genus of Sapindaceae from Somalia
- 2004
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 24:5, s. 509-511
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Tidskriftsartikel (refereegranskat)abstract
- The new genus Hirania (Sapindaceae), with the single species H. rosea from south-central Somalia, is decribed and illustrated. It is a shrub with simple, entire leaves, alternate or crowded on short-shoots, and without stipules. The inflorescences are branched with monochasially arranged, unisexual flowers. The flowers (only male ones known) are zygomorphic with five sepals with gland-tipped hairs along margins, four pink, subequal, clawed petals without appendages, and eight, glabrous stamens. The dark purple disk is narrow and tubular and consists of an upper broader segment partly enclosing a lower narrower segment. The closest relative is believed to be the Australian genus Diplopeltis.
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| 6. |
- Thulin, Mats
(författare)
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A new species of Atriplex (Chenopodiaceae) from Somalia
- 2004
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 24:5, s. 507-508
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Tidskriftsartikel (refereegranskat)abstract
- Atriplex erigavoensis, a new species from gypsum silt in northern Somalia, is described and illustrated. It is distinctive particularly by the dorsal appendages of the female bracteoles that look like an extra pair of small bracteoles.
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| 7. |
- Thulin, Mats
(författare)
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Expansion of Crabbea (Acanthaceae) and the description of two new species from Somalia
- 2004
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 24:5, s. 501-506
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Tidskriftsartikel (refereegranskat)abstract
- Crabbea is expanded to include the monotypic Golaea and Acanthostelma, both endemic in northern Somalia. The new combinations C. migiurtina (=Golaea migiurtina) and C. thymifolia (=Acanthostelma thymifolium) are made and the names are lectotypified. The new species C. pinnatifida and C. albolutea, both endemic in Somalia, are described and illustrated.
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| 8. |
- Thulin, Mats
(författare)
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New species of Tephrosia (Fabaceae) from Somalia and Yemen
- 2004
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 24:5, s. 513-517
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Tidskriftsartikel (refereegranskat)abstract
- The new species Tephrosia flava, from limestone areas in north-eastern Somalia, and T mahrana, from wadis in the deserts of south-eastern Yemen, are described and illustrated.
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| 9. |
- Tolvanen, A, et al.
(författare)
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Resource allocation patterns in a forb and a sedge in two arctic environments - short-term response to herbivory
- 2004
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 22:6, s. 741-747
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Tidskriftsartikel (refereegranskat)abstract
- The present work investigates C and N allocation patterns in two forage plants: a forb, Oxyria digyna, and a sedge, Eriophorum angustifolium, in subarctic Sweden and high arctic Canada. Short-term changes in concentrations after simulated or natural herbivory (caused by Gynaephora groenlandica on Oxyria in the high arctic habitat) were also investigated. There were no clear differences in concentrations of C and N between the high arctic and subarctic sites in either species. In Oxyria of the subarctic habitat, the minimum N concentrations occurred at earlier phenological stages compared with plants in the high arctic habitat. Simulated herbivory increased the concentration of C in belowground tissues relative to those in control plants in Oxyria at the subarctic site, which may indicate increased allocation of non-C compounds to the growing shoots or daughter ramets. Herbivory by Gynaephora groenlandica caterpillars increased the N concentrations of Oxyria both in aboveground and belowground tissues, possible indicating increased uptake of N in the high arctic habitat. Eriophorum did not show clear trends in concentrations relating to habitat, phenology or simulated herbivory. The difference between Oxyria and Eriophorum in their response to herbivory apparently resulted from contrasting growth habits between the species. Tiller death after reproduction and long leaf life span may be the main reasons for the lack of clear patterns in concentrations in Eriophorum. Compensation after herbivory may be attained by the early production of daughter tillers in Eriophorum instead of the regrowth of the damaged ramets, as in Oxyria. Monitoring the responses for only one season is apparently a too short time period in these long-lived plants.
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| 10. |
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