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  • 1. Alexandre, Ana
    et al.
    Silva, Joao
    Buapet, Pimchanok
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Björk, Mats
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Santos, Rui
    Effects of CO2 enrichment on photosynthesis, growth, and nitrogen metabolism of the seagrass Zostera noltii2012Inngår i: Ecology and Evolution, ISSN 2045-7758, Vol. 2, nr 10, 2620-2630 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Seagrass ecosystems are expected to benefit from the global increase in CO2 in the ocean because the photosynthetic rate of these plants may be C-i-limited at the current CO2 level. As well, it is expected that lower external pH will facilitate the nitrate uptake of seagrasses if nitrate is cotransported with H+ across the membrane as in terrestrial plants. Here, we investigate the effects of CO2 enrichment on both carbon and nitrogen metabolism of the seagrass Zostera noltii in a mesocosm experiment where plants were exposed for 5 months to two experimental CO2 concentrations (360 and 700 ppm). Both the maximum photosynthetic rate (Pm) and photosynthetic efficiency (alpha) were higher (1.3- and 4.1-fold, respectively) in plants exposed to CO2-enriched conditions. On the other hand, no significant effects of CO2 enrichment on leaf growth rates were observed, probably due to nitrogen limitation as revealed by the low nitrogen content of leaves. The leaf ammonium uptake rate and glutamine synthetase activity were not significantly affected by increased CO2 concentrations. On the other hand, the leaf nitrate uptake rate of plants exposed to CO2-enriched conditions was fourfold lower than the uptake of plants exposed to current CO2 level, suggesting that in the seagrass Z. noltii nitrate is not cotransported with H+ as in terrestrial plants. In contrast, the activity of nitrate reductase was threefold higher in plant leaves grown at high-CO2 concentrations. Our results suggest that the global effects of CO2 on seagrass production may be spatially heterogeneous and depend on the specific nitrogen availability of each system. Under a CO2 increase scenario, the natural levels of nutrients will probably become limiting for Z. noltii. This potential limitation becomes more relevant because the expected positive effect of CO2 increase on nitrate uptake rate was not confirmed.

  • 2. Amer, Ranya
    et al.
    Diez, Beatriz
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    El-Shehawy, Rehab
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Diversity of hepatotoxic cyanobacteria in the Nile Delta, Egypt2009Inngår i: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 11, nr 1, 126-133 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optimized denaturing gradient gel electrophoresis (DGGE) fingerprinting and real-time PCR were performed to identify and quantify the potential hepatotoxic microcystin-and nodularin-producing cyanobacteria present in freshwater samples collected during different seasons at three different sites from the Nile River Delta. The combined use of molecular gene markers (targeting the aminotransferase domain of the hepatotoxin synthetase modules and the 16S rRNA gene) and light microscopy demonstrated the dominance of different freshwater Microcystis phylotypes, including the potential hepatotoxin producers M. wesenbergii and M. aeruginosa, several Synechococcus and Cyanobium phylotypes, as well as the presence of Nodularia spumigena and Cylindrospermopsis raciborskii in the samples ""collected during summer 2006 and winter 2007''. Certain seasonal changes (summer and winter) in Microcystis microdiversity were detected. Real-time PCR revealed no difference in the quantities of potential hepatotoxin-producing cyanobacterial communities between summer and winter, but did show differences between the three sampling sites investigated. The expression of the aminotransferase domain analyzed by DGGE fingerprinting demonstrated that all Microcystis phylotypes present in the samples might have been active at the time of the sampling. Statistical analysis showed a significant effect of TP, and not TN, on the relative abundance of the potentially hepatotoxic cyanobacterial community.

  • 3.
    Anderberg, Arne A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Eldenäs, Pia
    Laboratory for Molecular Systematics, Swedish Museum of Natural History.
    Bayer, Randall J.
    Australian National Herbarium, Centre for Plant Biodiversity Research.
    Englund, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Evolutionary relationships in the Asteraceae tribe Inuleae (incl. Plucheeae) evidenced by DNA sequences of ndhF; with notes on the systematic positions of some aberrant genera2005Inngår i: Organisms Diversity & Evolution, ISSN 1439-6092, E-ISSN 1618-1077, Vol. 5, nr 2, 135-146 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phylogenetic relationships between the tribes Inuleae sensu stricto and Plucheeae are investigated by analysis of sequence data from the cpDNA gene ndhF. The delimitation between the two tribes is elucidated, and the systematic positions of a number of genera associated with these groups, i.e. genera with either aberrant morphological characters or a debated systematic position, are clarified. Together, the Inuleae and Plucheeae form a monophyletic group in which the majority of genera of Inuleae s.str. form one clade, and all the taxa from the Plucheeae together with the genera Antiphiona, Calostephane, Geigeria, Ondetia, Pechuel-loeschea, Pegolettia, and Iphionopsis from Inuleae s.str. form another. Members of the Plucheeae are nested with genera of the Inuleae s.str., and support for the Plucheeae clade is weak. Consequently, the latter cannot be maintained and the two groups are treated as one tribe, Inuleae, with the two subtribes Inulinae and Plucheinae. The genera Asteriscus, Chrysophthalmum, Inula, Laggera, Pentanema, Pluchea, and Pulicaria are demonstrated to be non-monophyletic. Cratystylis and Iphionopsis are found to belong to the same clade as the taxa of the former Plucheeae. Caesulia is shown to be a close relative of Duhaldea and Blumea of the Inuleae-Inulinae. The genera Callilepis and Zoutpansbergia belong to the major clade of the family that includes the tribes Heliantheae sensu lato and Inuleae (incl. Plucheeae), but their exact position remains unresolved. The genus Gymnarrhena is not part of the Inuleae, but is either part of the unresolved basal complex of the paraphyletic Cichorioideae, or sister to the entire Asteroideae.

  • 4.
    Anderberg, Arne A.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Englund, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Beentje, Henk
    On the systematic position of Inula rungwensis2008Inngår i: Compositae Newsletter, ISSN 0284-8422, Vol. 46, 83-84 s.Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The systematic position of Inula rungwensis Beentje is discussed. It is concluded that it is conspecific with Gerbera piloselloides (L.) Cass. of the tribe Mutisieae.

  • 5.
    Anderberg, Arne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Manns, Ulrika
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Källersjö, Mari
    Phylogeny and floral evolution of the Lysimachieae (Ericales, Myrsinaceae): evidence from ndhF sequence data.2007Inngår i: Willdenowia, ISSN 0511-9618, E-ISSN 1868-6397, Vol. 37, 407-421 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Earlier hypotheses of floral evolution in Lysimachia and related genera were tested by phylogenetic analysis of DNA sequences from the plastid gene ndhF. It is concluded that taxa with flowers provided with oil-producing trichomes are not advanced and buzz-polinated species with anther cone are not ancestral as earlier proposed. Instead, species of Lysimachia with buzz-pollinated flowers belong to one derived clade, species with flowers provided with nectar producing trichomes belong to another, both groups have evolved from yellow flowered oil-producing ancestors. We also show that Lysimachia and most of its subgenera as well as the genera Anagallis, Pelletiera and Asterolinon are paraphyletic or polyphyletic as presently circumscribed, and that Trientalis and a few American species of Lysimachia are the closest relatives of the other species of Lysimachia + Anagallis, Asterolinon, Pelleriera and Glaux. The subgeneric classification and the biogeographical patterns are briefly discussed.

  • 6.
    Anderhag, Per
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Hepler, P. K.
    Lazzaro, M. D.
    Microtubules and microfilaments are both responsible for pollen tube elongation in the coniferPicea abies (Norway spruce)2000Inngår i: Protoplasma, ISSN 0033-183X, E-ISSN 1615-6102, Vol. 214, nr 3, 141-157 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    InPicea abies (Norway spruce), microtubules and actin microfllaments both form a dense matrix throughout the tube mainly parallel to the direction of elongation. In these conifer pollen tubes the organization of this matrix is different from that in angiosperms. This study tests our hypothesis that differences in cytoskeletal organization are responsible for differences in tube growth and physiology. Pollen grains were germinated in media containing cytoskeletal disrupters and analyzed for germination, tube length, tube branching, and tip swelling. Disruption of microtubules significantly inhibits tube elongation and induces tube branching and tip swelling. Tip swelling is probably caused by disruption of the microtubules in the tip that are perpendicular to the direction of elongation. Confocal microscopy indicates that colchicine and propyzamide cause fragmentation of microtubules throughout the tube. Oryzalin and amiprophosmethyl cause a complete loss of microtubules from the tip back toward the tube midpoint but leave microtubules intact from the midpoint back to the grain. Disruption of microfilaments by cytochalasins B and D and inhibition of myosin by N-ethylmaleimide or 2,3-butanedione monoxime stops tube growth and inhibits germination. Microfilament disruption induces short branches in tubes, probably originating from defective microfilament organization behind the tip. In addition, confocal microscopy coupled with microinjection of fluorescein-labeled phalloidin into actively growing pollen tubes indicates that microfllament bundles extend into the plastid-free zone at the tip but are specifically excluded from the growing tip. We conclude that microtubules and microfilaments coordinate to drive tip extension in conifer pollen tubes in a model that differs from angiosperms.

  • 7.
    Andersson, Petter
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Olfactory cues and insects - scaling relations and immigration rates2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For herbivorous insects, location of host plants and habitat patches strongly depend on the type of sensory cue that is used during the search process and the probability of detecting a patch depends on the relative attraction between patches of different size. The visual impression of a patch increases predictably with the patch diameter and consequently, immigration rates of visually searching insects are often predicted by the scaling to patch size of visual cues. However, for olfactory cues, the relative attraction between small and large patches is unknown, but has been suggested to increase faster with patch size than visual information. In this thesis, I explore the scaling relation between olfactory cues and patch size. I measured odor attraction of patches of different size and estimated scaling rules for olfactory information. The estimated scaling rules were tested with simulations and a field experiment, where immigration rates of olfactory searching insects were quantified. The estimated scaling rules for olfactory information suggested that the relative attraction did not deviate fundamentally from the scaling of visual cues to patch size. Both the simulations and the field immigration experiment supported this suggestion. Therefore, I conclude that visual and olfactory cues scale roughly to patch size in a similar way, i.e. to the patch diameter. This thesis demonstrates the importance of considering species traits for the understanding of insect responses to habitat heterogeneity.

  • 8.
    Andersson, Petter
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Quantitative aspects of plant-insect interactions in fragmented landscapes:  the role of insect search behavior2009Bok (Annet vitenskapelig)
    Abstract [en]

    Insects searching for host plants in the landscape are challenged by habitat fragmentation and heterogeneity. Host plants or habitat are usually distributed in scattered patches that may differ in size, shape and isolation. The ability of finding these patches strongly depends on the insect´s search behavior and the sensory cues used for detecting and locating patches. Here, I describe sensory systems of insects, such as vision, olfaction and taste, in relation to host plant search. I discuss quantitative patterns of insect distributions and density-area relations arising from search behavior. Migration pattern may be strongly affected by the cue used by the insect in the patch detection process. The relation between visual cues and patch size is well known, but we lack knowledge about how olfactory cues are connected to patch size. Since search behavior affects the spatial distribution of insects, I briefly describe consequences for host plants. Finally, I describe the main objectives of my PhD-project.

  • 9.
    Andersson, Petter
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    The importance of search behavior and movements for spatial distributions of herbivorous insects2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Insect populations commonly show large spatial variation in density, and much variation have been shown to be explained by the search behavior applied by the insect when locating habitat patches. This thesis explores the importance of odor-mediated attraction for immigration rates of herbivorous insects in relation to the size of the patches and the density of host plants within the patches. By using electroantennogram and measuring moth antennal responses to sex pheromones and thereby estimating the relative odor-mediated attraction from odor patches in field experiments (Paper I, III), I show that the length of the odor plumes emanating from the patches increase proportional with the square-root of the number of odor sources. In laboratory and field experiments (with the weevils Cionus scrophulariae and C. tuberculosus and the host plant figwort Scrophularia nodosa; Paper II) and meta-analyses on multiple insect herbivores (Paper III), I examined whether the relative increase in plume length could also predict the immigration rates of olfactory searching insects in relation to patches with increasing area and increasing density of host plants. The experiments (Paper II) and meta-analyses (Paper III) showed that the observed immigration rates of olfactory searching insects was well predicted by the relative increase in plume length, as estimated from the electroantennogram measurements (Paper I, III). The importance of immigration rates, relative to the effect of emigration and local growth was also investigated for the Cionus weevils in natural S. nodosa patches (Paper IV). This study showed that the density-patch size relationships of the weevils during early season were predicted by the net scaling of emigration and immigration rates, and differences in density-patch size relationships between the two species could be explained by inter-specific differences in their emigration rates from small patches. In conclusion, this thesis shows that search behavior can be used to predict immigration rates and spatial distributions of insects, with implications for pest control, conservation ecology and general ecological theory.

  • 10.
    Andersson, Petter
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Immigration of olfactory searching insects into host plant patches: testing scaling rules for olfactory information2011Inngår i: Arthropod-Plant Interactions, ISSN 1872-8855, E-ISSN 1872-8847, Vol. 5, 269-277 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herbivorous insects are commonly faced with host plants being distributed in scattered patches across a landscape. Immigration rates into habitat patches may strongly depend on the sensory cues used in the patch location process, and immigration rates of insects can be predicted based on the scaling of sensory cues. Here, we tested recent estimates of the scaling of olfactory information to patch size, which predicts a scaling coefficientf z = -0.5 (A^z, where A = patch size, z = scaling coefficient). We predicted that immigration rates of olfactory searching insects into patches of different sizes should scale according to the estimated slope. We investigated attraction of the weevils Cionus tuberculosus and Cionus scrophulariae to odors from figwort Scrophularia nodosa and quantified immigration rates of weevils into differently sized patches. We also investigated oviposition rates of the sawfly Tenthredo scrophulariae. The slope in the regression between density and patch size for herbivores was then compared with the predicted scaling coefficient. Using olfactometers, we found that weevils were attracted to figwort odors. Weevil densities were significantly affected by patch size, and the slope in the relationship between density and patch size was z = -0.53. The slope in the relationship between larval densities of sawflies and patch size was less negative with a slope of z = -0.15, indicating differences in search behavior compared with the weevils. The density–patch size relationship for the weevils closely matched the predicted slope and supported the previous estimations of the scaling of olfactory informationto patch size.

  • 11.
    Andersson, Petter
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    What shapes local density?: The importance of migration rates and local growth for density-patch size relationships in two Cionus weevils2012Inngår i: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 37, nr 1, 90-98 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. The relative effect of migration and local growth on the spatio-temporal density-distribution of two co-existing herbivorous weevils, Cionus scrophulariae L. and C. tuberculosus Scop., in 32 host plant Scrophularia nodosa L. patches of varying sizes was investigated. 2. Predictions of the temporal development of the slope in the density-patch size relationships were derived from a basic population model with scale-dependent migration rates. The model indicated that the slopes in the density-patch size relationships during the early season should be reflected by the net scaling of immigration and emigration rates, whereas the slopes during the later season should increase as a result of local growth. 3. Emigration rates of the weevils were estimated in a field experiment, were the weevils coexisted in space and time. These results were then combined with a previous estimate of immigration rates in order to determine the net scaling of migration rates. 4. The emigration rate differed between species, caused by different movement rates in small patches, which could explain differences in the general slope of the density-patch size relationships of the weevils in the natural figwort patches throughout the summer. The slopes in the relationships in the early season were largely predicted by the net scaling of migration rates. The slope also increased in the later season for C. tuberculosus, whereas the slope decreased for C. scrophulariae. 5. It was concluded that the understanding of both inter- and intra-specific variations in density-patch size relationships of insect herbivores can be improved using population models incorporating scale-dependent migration and local growth.

  • 12.
    Andersson, Petter
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Löfstedt, Christer
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Insect density-plant density relationships – a modified view of insect responses to resource concentrationsArtikkel i tidsskrift (Fagfellevurdert)
  • 13. Andreasen, Katarina
    et al.
    Manktelow, Mariette
    Razafimandimbison, Sylvain
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Stockholms universitet, Naturvetenskapliga fakulteten, Bergianska botaniska trädgården (tills m Kungl. Vetenskapsakademien).
    Successful DNA amplification of a more than 200-year-old herbarium specimen: recovering genetic material from the Linnaean era2009Inngår i: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 58, nr 3, 959-962 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The limit for successful DNA extraction was tested by amplification and sequencing of an over 200-year-old herbarium specimen collected by Adam Afzelius, a student of Carl Linnaeus. We amplified and sequenced a 800-bp region between 16S ribosomal DNA and the 3′ part of the trnI gene (16S-trnI) in the chloroplast genomeof Phaulopsis talbotii S. Moore (Acanthaceae). To test the replicability and to control for contamination the procedure was performed in sealed vials and with negative PCR controls. The procedure was also repeated in a separate laboratory. In addition, the chloroplast rpl16 intron was successfully amplified and sequenced and the rps16 intron amplified. Sequences of taxa closely related to Acanthaceae were found to be most similar to the produced sequences. The results suggest that molecular investigations of other 18th century botanical collections are feasible and that molecular methods could be employed for comparative studies to extant plant collections. An important application would be to identify descendants or clones of Linnaean lectotypes by comparing DNA from these with potentially remnant plants from Linnaeus’ cultivations.

  • 14. Andriamihajarivo, Tefy H.
    et al.
    Razafimandimbison, Sylvain G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Karehed, Jesper
    Phyllopentas flava (Rubiaceae), a New Morphologically Heterodistylous and Functionally Dioecious Species from Madagascar2011Inngår i: Systematic Botany, ISSN 0363-6445, E-ISSN 1548-2324, Vol. 36, nr 4, 1024-1027 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new species of the Afro-Malagasy genus Phyllopentas Karehed & B. Bremer, Phyllopentas flava Razafim., T. Andriam. et Karehed, is described and illustrated. This plant is restricted to the Itremo region in southeastern Madagascar and is distinct morphologically from the other species of the genus by its pubescent, narrowly ovate to narrowly elliptic leaves, grey-whitish and thickly hairy midribs and secondary veins on the lower surfaces of leaves, and functionally dioecious and heterodistylous flowers. Summaries of distribution, phenology, habitat, and ecology are given and a conservation assessment is also provided.

  • 15. Antonelli, A
    et al.
    Nylander, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Persson, C
    Sanmartín, I
    Tracing the impact of the Andean uplift on Neotropical plant evolution: evidence from the coffee family2009Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, nr 24, 9749-9754 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent phylogenetic studies have revealed the major role played by the uplift of the Andes in the extraordinary diversification of the Neotropical flora. These studies, however, have typically considered the Andean uplift as a single, time-limited event fostering the evolution of highland elements. This contrasts with geological reconstructions indicating that the uplift occurred in discrete periods from west to east and that it affected different regions at different times. We introduce an approach for integrating Andean tectonics with biogeographic reconstructions of Neotropical plants, using the coffee family (Rubiaceae) as a model group. The distribution of this family spans highland and montane habitats as well as tropical lowlands of Central and South America, thus offering a unique opportunity to study the influence of the Andean uplift on the entire Neotropical flora. Our results suggest that the Rubiaceae originated in the Paleotropics and used the boreotropical connection to reach South America. The biogeographic patterns found corroborate the existence of a long-lasting dispersal barrier between the Northern and Central Andes, the "Western Andean Portal.'' The uplift of the Eastern Cordillera ended this barrier, allowing dispersal of boreotropical lineages to the South, but gave rise to a huge wetland system ("Lake Pebas'') in western Amazonia that prevented in situ speciation and floristic dispersal between the Andes and Amazonia for at least 6 million years. Here, we provide evidence of these events in plants

  • 16. Appelhans, M. S.
    et al.
    Smets, E.
    Razafimandimbison, Sylvain G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Haevermans, T.
    van Marle, E. J.
    Couloux, A.
    Rabarison, H.
    Randrianarivelojosia, M.
    Kessler, P. J. A.
    Phylogeny, evolutionary trends and classification of the Spathelia-Ptaeroxylon clade: morphological and molecular insights2011Inngår i: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 107, nr 8, 1259-1277 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background and Aims The Spathelia-Ptaeroxylon clade is a group of morphologically diverse plants that have been classified together as a result of molecular phylogenetic studies. The clade is currently included in Rutaceae and recognized at a subfamilial level (Spathelioideae) despite the fact that most of its genera have traditionally been associated with other families and that there are no obvious morphological synapomorphies for the clade. The aim of the present study is to construct phylogenetic trees for the Spathelia-Ptaeroxylon clade and to investigate anatomical characters in order to decide whether it should be kept in Rutaceae or recognized at the familial level. Anatomical characters were plotted on a cladogram to help explain character evolution within the group. Moreover, phylogenetic relationships and generic limits within the clade are also addressed. Methods A species-level phylogenetic analysis of the Spathelia-Ptaeroxylon clade based on five plastid DNA regions (rbcL, atpB, trnL-trnF, rps16 and psbA-trnH) was conducted using Bayesian, maximum parsimony and maximum likelihood methods. Leaf and seed anatomical characters of all genera were (re) investigated by light and scanning electron microscopy. Key Results With the exception of Spathelia, all genera of the Spathelila-Ptaeroxylon clade are monophyletic. The typical leaf and seed anatomical characters of Rutaceae were found. Further, the presence of oil cells in the leaves provides a possible synapomorphy for the clade. Conclusions The Spathelia-Ptaeroxylon clade is well placed in Rutaceae and it is reasonable to unite the genera into one subfamily (Spathelioideae). We propose a new tribal classification of Spathelioideae. A narrow circumscription of Spathelia is established to make the genus monophyletic, and Sohnreyia is resurrected to accommodate the South American species of Spathelia. The most recent common ancestor of Spathelioideae probably had leaves with secretory cavities and oil cells, haplostemonous flowers with appendaged staminal filaments, and a tracheidal tegmen.

  • 17. Appelhans, Marc S.
    et al.
    Kessler, Paul J. A.
    Smets, Erik
    Razafimandimbison, Sylvain G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Janssens, Steven B.
    Age and historical biogeography of the pantropically distributed Spathelioideae (Rutaceae, Sapindales)2012Inngår i: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 39, nr 7, 1235-1250 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aim The family Rutaceae (rue family) is the largest within the eudicot order Sapindales and is distributed mainly in the tropical and subtropical regions of both the New World and the Old World, with a few genera in temperate zones. The main objective of this study is to present molecular dating and biogeographical analyses of the subfamily Spathelioideae, the earliest branching clade (which includes eight extant genera), to interpret the temporal and spatial origins of this group, ascertaining possible vicariant patterns and dispersal routes and inferring diversification rates through time. Location Pantropics. Methods A dataset comprising a complete taxon sampling at generic level (83.3% at species level) of Spathelioideae was used for a Bayesian molecular dating analysis (beast). Four fossil calibration points and an age constraint for Sapindales were applied. An ancestral area reconstruction analysis utilizing the dispersalextinctioncladogenesis model and diversification rate analyses was conducted. Results Dating analyses indicate that Rutaceae and Spathelioideae are probably of Late Cretaceous origin, after which Spathelioideae split into a Neotropical and a Palaeotropical lineage. The Palaeotropical taxa have their origin inferred in Africa, with postulated dispersal events to the Mediterranean, the Canary Islands, Madagascar and Southeast Asia. The lineages within Spathelioideae evolved at a relatively constant diversification rate. However, abrupt changes in diversification rates are inferred from the beginning of the Miocene and during the Pliocene/Pleistocene. Main conclusions The geographical origin of Spathelioideae probably lies in Africa. The existence of a Neotropical lineage may be the result of a dispersal event at a time in the Late Cretaceous when South America and Africa were still quite close to each other (assuming that our age estimates are close to the actual ages), or by Gondwanan vicariance (assuming that our age estimates provide minimal ages only). Separation of land masses caused by sea level changes during the Pliocene and Pleistocene may have been triggers for speciation in the Caribbean genus Spathelia.

  • 18.
    Arvanitis, Leena
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Plant polyploidy and interactions with insect herbivores2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Polyploidization has been suggested to be a common mechanism for plant speciation. Polyploidy is associated with changes in plant traits and altered habitat preference. Antagonistic and mutualistic animals are known to discriminate between plants based on variation in such plant traits, suggesting that interactions may have an important role in divergence of plant polyploids after the polyploidization. In this thesis, I investigated the effect of insect herbivores on divergence of plant polyploids in a system consisting of the predispersal seed predator butterfly Anthocharis cardamines, the bud gall forming midge Dasineura cardaminis, and tetraploids and octoploids of the herb Cardamine pratensis. Octoploid populations occurred more often in shaded and nongrazed habitats than tetraploids. Octoploid plants were larger and had fewer but larger flowers than tetraploids. Butterfly attack rates were higher in tetraploid than in octoploid populations, whereas the gall midge attacked only octoploids. These differences were associated with higher abundance of butterflies in sunny habitats and gall midges in shaded habitats. In contrast to the pattern at the population level, octoploid flower shoots were more likely to be attacked by the butterfly in sympatric populations. Also trait selection differed between ploidy levels, both in the absence and in the presence of herbivores. In a field experiment, butterfly preference did not alter the trait selection in tetraploids. In octoploids, the two herbivores did not change selection considered separately. However, their joint effect resulted in significant selection for smaller flower shoots and reduced selection on number of flowers. This thesis demonstrates that differences in habitat preference and phenotypic plant traits between polyploid cytotypes can lead to altered interactions with herbivores. Such differences in interactions with animals may alter not only the relative fitness of cytotypes but also trait selection within the respective ploidy type.

  • 19.
    Arvanitis, Leena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Wiklund, Christer
    Ehrlén, Johan
    Butterfly seed predation: effects of landscape characteristics, plant ploidy level and population structure2007Inngår i: Oecologia, ISSN 0029-8549, Vol. 152, nr 2, 275-285 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 20.
    Arvanitis, Leena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Ekologi.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Butterfly seed predation: effects of landscape characteristics, plant ploidy level and population structure2007Inngår i: Oecologia, ISSN 0029-8549, Vol. 152, nr 2, 275-285 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyploidization has been suggested as one of the most common mechanisms for plant diversification. It is often associated with changes in several morphological, phenological and ecological plant traits, and therefore has the potential to alter insect–plant interactions. Nevertheless, studies evaluating the effect of plant polyploidy on interspecific interactions are still few. We investigated pre-dispersal seed predation by the butterfly Anthocharis cardamines in 195 populations of two ploidy levels of the herb Cardamine pratensis (tetraploid ssp. pratensis, 2n = 30 vs. octoploid ssp. paludosa, 2n = 56–64). We asked if differences in incidence and intensity of predation among populations were related to landscape characteristics, plant ploidy level and population structure. The incidence of the seed predator increased with increasing plant population size and decreasing distance to nearest population occupied by A. cardamines. The intensity of predation decreased with increasing plant population size and was not affected by isolation. Probability of attack decreased with increasing shading, and intensity of predation was higher in grazed than in non-grazed habitats. The attack intensity increased with increasing mean flower number of plant population, but was not affected by flowering phenology. Individuals in tetraploid populations suffered on average from higher levels of seed predation, had higher mean flower number, were less shaded and occurred more often in grazed habitats than octoploid populations. When accounting for differences in habitat preferences between ploidy levels there was no longer a difference in intensity of predation, suggesting that the observed differences in attack rates among populations of the two ploidy levels are mediated by the habitat. Overall, our results suggest that polyploidization is associated with differentiation in habitat preferences and phenotypic traits leading to differences in interspecific interaction among plant populations. This, in turn, may facilitate further divergence of ploidy levels.

  • 21.
    Arvanitis, Leena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Wiklund, Christer
    Zoologiska institutionen. Ekologi.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Plant ploidy level influences selection by butterfly seed predators2008Inngår i: Oikos, Vol. 117, 1020-1025 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyploidization is a common route to plant diversification. Polyploids often differ from their progenitors in size, flower number, flower size and flowering phenology. Such differences may translate into differences in the intensity of interactions with animals. Here we investigated the impact of the ploidy-related differences in tetraploids and octoploids of the perennial herb Cardamine pratensis on pre-dispersal seed predation by the butterfly Anthocharis cardamines. The probability of escaping attack was lower for octoploids than for tetraploids, even after accounting for the fact that octoploids were larger and had fewer flowers than tetraploids. Flower shoot size was correlated with probability of attack in tetraploids but not in octoploids. Differences in plant traits associated with polyploidization can alter interactions with animals, and animal-mediated differences in trait selection between ploidy types can contribute to their further divergence.

  • 22. Ashihara, H
    et al.
    Sano, H
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Crozier, A
    Caffeine and relatedpurine alkaloids: Biosynthesis, catabolism, function and genetic engineering2008Inngår i: Phytochemistry, Vol. 69, 841-856 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 23.
    Asplund-Samuelsson, Johannes
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Bergman, Birgitta
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Larsson, John
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Prokaryotic Caspase Homologs: Phylogenetic Patterns and Functional Characteristics Reveal Considerable Diversity2012Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 11, e49888- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Caspases accomplish initiation and execution of apoptosis, a programmed cell death process specific to metazoans. The existence of prokaryotic caspase homologs, termed metacaspases, has been known for slightly more than a decade. Despite their potential connection to the evolution of programmed cell death in eukaryotes, the phylogenetic distribution and functions of these prokaryotic metacaspase sequences are largely uncharted, while a few experiments imply involvement in programmed cell death. Aiming at providing a more detailed picture of prokaryotic caspase homologs, we applied a computational approach based on Hidden Markov Model search profiles to identify and functionally characterize putative metacaspases in bacterial and archaeal genomes. Out of the total of 1463 analyzed genomes, merely 267 (18%) were identified to contain putative metacaspases, but their taxonomic distribution included most prokaryotic phyla and a few archaea (Euryarchaeota). Metacaspases were particularly abundant in Alphaproteobacteria, Deltaproteobacteria and Cyanobacteria, which harbor many morphologically and developmentally complex organisms, and a distinct correlation was found between abundance and phenotypic complexity in Cyanobacteria. Notably, Bacillus subtilis and Escherichia coli, known to undergo genetically regulated autolysis, lacked metacaspases. Pfam domain architecture analysis combined with operon identification revealed rich and varied configurations among the metacaspase sequences. These imply roles in programmed cell death, but also e.g. in signaling, various enzymatic activities and protein modification. Together our data show a wide and scattered distribution of caspase homologs in prokaryotes with structurally and functionally diverse subgroups, and with a potentially intriguing evolutionary role. These features will help delineate future characterizations of death pathways in prokaryotes.

  • 24.
    Axemar, Hanna
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    An experimental study of plant habitat choices by macroinvertebrates in brackish soft-bottom bays2007Bok (Annet vitenskapelig)
  • 25. Backlund, Maria
    et al.
    Bremer, Birgitta
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Bergianska botaniska trädgården (tills m Kungl. Vet. Ak.).
    Thulin, Mats
    Paraphyly of Paederieae, recognition of Putorieae and expansion of Plocama (Rubiaceae-Rubioideae)2007Inngår i: TAXON, ISSN 0040-0262, Vol. 56, nr 2, 315-328 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Phylogenctic analyses of taxa that have been included in the tribe Paederieae are performed on the basis of a molecular dataset of plastid DNA sequences (the rbcL gene, rps16 intron, and the regions trnT-F). The paraphyly of Paederieae as currently circumscribed is confirmed. A clade comprising Paederia, Spermadietyon, Leptodermis, and Serissa is retrieved and the circumscription of Paederieae is proposed to be restricted to this clade. Paederia is sister to a clade with Spermadiclyon, Leptodermis, and Serissa. Paederia is subdivided into an Asian and an African clade, and within the African clade seven species endemic to Madagascar are sister to P. pospischilii in north-eastern Africa. The position of Kelloggia as sister to Rubieae is confirmed and a position of Saprosma in the Spermacoceae alliance is supported. The genera Putoria, Gaillonia (with segregates), Plocama, and Aitchisonia form a clade that is sister to Theligoneae/Ke//oggia/Rubieae. The name Putoricae is resurrected for the members of this clade. A synopsis of Putorieae is provided, where all species are placed in an expanded Plocama with 34 species. Thirty-one new combinations in Plocama are proposed. Plocama pendula on the Canary Islands is strongly supported as sister to a clade with P. crocyllis (former Crocyllis) in southern Africa and P. yemenensis and P. tinctoria (former Gaillonia) in southern Arabia/Horn of Africa.

  • 26. Barreda, V. D.
    et al.
    Palazzesi, L.
    Telleria, M. C.
    Katinas, L.
    Crisci, J. V.
    Bremer, Kåre
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Passalia, M. G.
    Corsolini, R.
    Rodriguez Brizuela, R.
    Bechis, F.
    Eocene Patagonia Fossils of the Daisy Family2010Inngår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 329, nr 5999, 1621-1621 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 27.
    Bauer, Karolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Diazotrophy and diversity of benthic cyanobacteria in tropical coastal zones2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Discoveries in recent years have disclosed the importance of marine cyano-bacteria in the context of primary production and global nitrogen cycling. It is hypothesized here that microbial mats in tropical coastal habitats harbour a rich diversity of previously uncharacterized cyanobacteria and that benthic marine nitrogen fixation in coastal zones is substantial.

    A polyphasic approach was used to investigate cyanobacterial diversity in three tropical benthic marine habitats of different characters; an intertidal sand flat and a mangrove forest floor in the Indian Ocean, and a beach rock in the Pacific Ocean. In addition, nitrogenase activity was measured over diel cycles at all sites. The results revealed high cyanobacterial diversity, both morphologically and genetically. Substantial nitrogenase activity was observed, with highest rates at daytime where heterocystous species were present. However, the three habitats were dominated by non-heterocystous and unicellular genera such as Microcoleus, Lyngbya, Cyanothece and a large group of thin filamentous species, identified as members of the Pseudanabaenaceae family. In these consortia nocturnal nitrogenase activities were highest and nifH sequencing also revealed presence of non-cyanobacterial potential diazotrophs. A conclusive phylogenetic analysis of partial nifH sequences from the three sites and sequences from geographi-cally distant microbial mats revealed new clusters of benthic potentially ni-trogen-fixing cyanobacteria. Further, the non-heterocystous cyanobacterium Lyngbya majuscula was subjected to a physiological characterization to gain insights into regulatory aspects of its nitrogen fixation. The data demon-strated that nitrogenase activity is restricted to darkness, which called upon a re-evaluation of its diazotrophic behaviour.

  • 28.
    Bauer, Karolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Nitorgen fixation and diversity of benthic cyanobacteria in tropical coastal zones2004Licentiatavhandling, monografi (Annet vitenskapelig)
  • 29.
    Bauer, Karolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Bergman, Birgitta
    Díez, Beatriz
    New nitrogen-fixing tropical marine cyanobacteria; a case-study of microbial mats in a mangrove habitatManuskript (Annet vitenskapelig)
  • 30.
    Bauer, Karolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Díez, Beatriz
    Lugomela, Charles
    Seppälä, Susanna
    Borg, Agneta Julia
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Bergman, Birgitta
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Variability in benthic diazotrophy and cyanobacterial diversity in a tropical intertidal lagoon.2008Inngår i: FEMS Microbiol Ecol, ISSN 0168-6496, Vol. 63, nr 2, 205-21 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 31.
    Bauer, Karolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Díez, Beatriz
    Lugomela, Charles
    Seppälä, Susanna
    Borg, Agneta Julia
    Bergman, Birgitta
    Variability in diazotrophy and cyanobacterial diversity in a tropical intertidal lagoonManuskript (Annet vitenskapelig)
  • 32.
    Bengtson, Annika
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Anderberg, A. A.
    Karis, Per Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Three new species of metalasia (asteraceae gnaphalieae) from the western cape and an updated key to the genus2013Inngår i: South African Journal of Botany, ISSN 0254-6299, E-ISSN 1727-9321, Vol. 84, 72-82 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three new species of Metalasia from the Western Cape of South Africa are described; Metalasia tristis A.Bengtson & P.O.Karis, a small shrublet from the Groot Winterhoek Mountains, and Metalasia formosa A.Bengtson & P.O.Karis and Metalasia eburnea A.Bengtson & P.O.Karis both found in the Langeberg Mountains. The morphology and relationships of the three new species are discussed, and an updated key to the genus is provided.

  • 33.
    Bengtson, Annika
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Anderberg, Arne A.
    Karis, Per Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    PHYLOGENY AND GENERIC DELIMITATION OF THE METALASIA CLADE (ASTERACEAE-GNAPHALIEAE)2011Inngår i: International journal of plant sciences, ISSN 1058-5893, E-ISSN 1537-5315, Vol. 172, nr 8, 1067-1075 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Metalasia clade, which consists of the genus Metalasia and a number of much smaller satellite genera, is a South African group in the tribe Gnaphalieae (Asteraceae). This study scrutinizes the phylogenetic relationships of the Metalasia clade by means of chloroplast (trnL-trnF, psbA-trnH) and nuclear (external transcribed spacer, internal transcribed spacer) sequence data. The Metalasia clade is confirmed to be a monophyletic group, and the phylogenetic positions of the included genera are determined. The genus Metalasia may be monophyletic if the monotypic Planea is included, but the node has very poor support and further studies are needed. The Metalasia species fall into two well-supported groups, distinguishing the members of Karis's Metalasia densa group from the others. Lachnospermum is shown to be monophyletic and is placed as a possible sister group to Metalasia. Phaenocoma is placed as sister to the branch consisting of Metalasia and Lachnospermum. Calotesta, Hydroidea, and Atrichantha form a clade, with the monotypic Dolichothrix as their sister group.

  • 34.
    Bergman, Birgitta
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Ran, Liang
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Adams, David G
    Cyanobacterial-plant symbiosis: signaling and development2008Inngår i: The Cyanobacteria: Molecular Biology, Genomics and evolution, Caister Academic Press, Norfolk, UK , 2008, 447-473 s.Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 35.
    Bergman, Birgitta
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Rasmussen, Ulla
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Rai, Amar N
    Cyanobacterial Associations2007Inngår i: Associative and Endophytic Nitrogen-fixing Bacteria and Cyanobacterial Associations., Kluwer Academic Publishers, Dordrecht , 2007, 257-301 s.Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 36.
    Bergman, Birgitta
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Sandh, Gustaf
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Lin, Senjie
    Larsson, John
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Carpenter, Edward J.
    Trichodesmium - a widespread marine cyanobacterium with unusual nitrogen fixation properties2013Inngår i: FEMS Microbiology Reviews, ISSN 0168-6445, E-ISSN 1574-6976, Vol. 37, nr 3, 286-302 s.Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The last several decades have witnessed dramatic advances in unfolding the diversity and commonality of oceanic diazotrophs and their N2-fixing potential. More recently, substantial progress in diazotrophic cell biology has provided a wealth of information on processes and mechanisms involved. The substantial contribution by the diazotrophic cyanobacterial genus Trichodesmium to the nitrogen influx of the global marine ecosystem is by now undisputable and of paramount ecological importance, while the underlying cellular and molecular regulatory physiology has only recently started to unfold. Here, we explore and summarize current knowledge, related to the optimization of its diazotrophic capacity, from genomics to ecophysiological processes, via, for example, cellular differentiation (diazocytes) and temporal regulations, and suggest cellular research avenues that now ought to be explored.

  • 37.
    Bergman, Birgitta
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Zheng, Weiwen
    Ekman, Martin
    Ran, Liang
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    The cyanobacterium–Azolla symbiosis: Interactions and cell differentiation2007Inngår i: Abstracts of the Annual Main Meeting of the Society for Experimental Biology, Glasgow, Scotland, 31st March - 4th April, 2007, 2007Konferansepaper (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Selected cyanobacteria form stable nitrogen-fixing symbioses with diverse eukaryotes. The water-fern Azolla carries a nitrogen-fixing cyanobacterium (cyanobiont) in its leaves and shows a pronounced intimacy between its partners. It is the only perpetual N2-fixing symbiosis, i.e. the cyanobiont is vertically transmitted in sporocarps between plant generations. The cyanobiont also seems incapable of independent growth which may suggest gene loss and that the symbiosis is on its way to evolve into a N2-fixing plant. Proteomic analyses of the cyanobiont (2-D coupled to MS) resulted in an identification of about 79% of proteins analysed. Processes upregulated were related to energy production, nitrogen and carbon metabolism and stress, while photosynthesis and metabolic turnover rates were downregulated, stressing a slow heterotrophic mode of growth, high heterocyst frequencies and nitrogen-fixing capacities. Peptide mass spectra of NifH demonstrated the presence of a 300–400 Da protein modification localized to a 13 amino acid sequence. Additionally, a short phylogenetic distance between the cyanobiont and some sequenced cyanobacteria (Section IV) and the database hits of the proteins identified by proteomics, together suggest that the Azolla cyanobiont may represent a novel cyanobacterial genus. The genome of the cyanobiont will be sequenced in 2007 (DOE/JGI, USA).

  • 38.
    Bergman, Birgitta
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Zheng, Wei-Wen
    Klint, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Ran, Liang
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    On the origin of plants and relations to contemporary cyanobacterial-plant symbioses.2008Inngår i: Plant Biotechnology, Vol. 25, nr 3, 213-220 s.Artikkel, forskningsoversikt (Annet (populærvitenskap, debatt, mm))
  • 39.
    Bergqvist, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Arsenic accumulation in various plant types2011Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 40.
    Bergqvist, Claes
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Greger, Maria
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Arsenic accumulation and speciation in plants from different habitats2012Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 27, nr 3, 615-622 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding As accumulation in plants is necessary in order to alleviate problems with As in the environment and to improve sustainable As phytotechnologies. To find suitable candidates for phytoremediation purposes and to investigate specific accumulation patterns due to growth habitat and plant groups, As accumulation in 124 plant species collected from different habitats and speciation in 6 of these plant species, was determined. The data show that submerged plants have a higher accumulation than emergent and terrestrial plants. The As concentration in terrestrial and emergent plants were correlated with the [As](soil), while the accumulation factor correlated negatively with [As](soil). Gymnosperms had a high [As](shoot):[As](root) ratio. The inorganic As species, arsenate and arsenite were found in plants from all habitats and methylarsonic acid (MMA) in all but one plant species. Arsenate predominated in submerged plants. The results suggest that the habitat and the [As](soil) have a strong influence on the As accumulation in plants and that submerged plants and/or gymnosperms might be suitable for phytoremediation of As.

  • 41.
    Bergqvist, Claes
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Greger, Maria
    Phytostabilization of arsenic2015Inngår i: In-Situ Remediation of Arsenic-Contaminated Sites / [ed] Jochen Bundschuh, Hartmut M. Holländer, Lena Qiying Ma, Boca Raton: CRC Press, 2015, Vol. 6, 53-67 s.Kapittel i bok, del av antologi (Fagfellevurdert)
  • 42. Berry, Alison M.
    et al.
    Mendoza-Herrera, Alberto
    Guo, Ying-Yi
    Hayashi, Jennifer
    Persson, Tomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Barabote, Ravi
    Demchenko, Kirill
    Zhang, Shuxiao
    Pawlowski, Katharina
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    New perspectives on nodule nitrogen assimilation in actinorhizal symbioses2011Inngår i: Functional Plant Biology, ISSN 1445-4408, E-ISSN 1445-4416, Vol. 38, nr 8-9, 645-652 s.Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Nitrogen-fixing root nodules are plant organs specialised for symbiotic transfer of nitrogen and carbon between microsymbiont and host. The organisation of nitrogen assimilation, storage and transport processes is partitioned at the subcellular and tissue levels, in distinctive patterns depending on the symbiotic partners. In this review, recent advances in understanding of actinorhizal nodule nitrogen assimilation are presented. New findings indicate that Frankia within nodules of Datisca glomerata (Presl.) Baill. carries out both primary nitrogen assimilation and biosynthesis of arginine, rather than exporting ammonium. Arginine is a typical storage form of nitrogen in plant tissues, but is a novel nitrogen carrier molecule in root nodule symbioses. Thus Frankia within D. glomerata nodules exhibits considerable metabolic independence. Furthermore, nitrogen reassimilation is likely to take place in the host in the uninfected nodule cortical cells of this root nodule symbiosis, before amino acid export to host sink tissues via the xylem. The role of an augmented pericycle in carbon and nitrogen exchange in root nodules deserves further attention in actinorhizal symbiosis, and further highlights the importance of a comprehensive, structure-function approach to understanding function in root nodules. Moreover, the multiple patterns of compartmentalisation in relation to nitrogen flux within root nodules demonstrate the diversity of possible functional interactions between host and microsymbiont that have evolved in the nitrogen-fixing clade.

  • 43.
    Beste, Lisa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Nahar, Nurun
    Dalman, Kerstin
    Fujioka, Shozo
    Jonsson, Lisbeth
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Dutta, Paresh C.
    Sitbon, Folke
    Synthesis of Hydroxylated Sterols in Transgenic Arabidopsis Plants Alters Growth and Steroid Metabolism2011Inngår i: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 157, nr 1, 426-440 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To explore mechanisms in plant sterol homeostasis, we have here increased the turnover of sterols in Arabidopsis (Arabidopsis thaliana) and potato (Solanum tuberosum) plants by overexpressing four mouse cDNA encoding cholesterol hydroxylases (CHs), hydroxylating cholesterol at the C-7, C-24, C-25, or C-27 positions. Compared to the wild type, the four types of Arabidopsis transformant showed varying degrees of phenotypic alteration, the strongest one being in CH25 lines, which were dark-green dwarfs resembling brassinosteroid-related mutants. Gas chromatography-mass spectrometry analysis of extracts from wild-type Arabidopsis plants revealed trace levels of alpha and beta forms of 7-hydroxycholesterol, 7-hydroxycampesterol, and 7-hydroxysitosterol. The expected hydroxycholesterol metabolites in CH7-, CH24-, and CH25 transformants were identified and quantified using gas chromatography-mass spectrometry. Additional hydroxysterol forms were also observed, particularly in CH25 plants. In CH24 and CH25 lines, but not in CH7 ones, the presence of hydroxysterols was correlated with a considerable alteration of the sterol profile and an increased sterol methyltransferase activity in microsomes. Moreover, CH25 lines contained clearly reduced levels of brassinosteroids, and displayed an enhanced drought tolerance. Equivalent transformations of potato plants with the CH25 construct increased hydroxysterol levels, but without the concomitant alteration of growth and sterol profiles observed in Arabidopsis. The results suggest that an increased hydroxylation of cholesterol and/or other sterols in Arabidopsis triggers compensatory processes, acting to maintain sterols at adequate levels.

  • 44. Bisang,
    et al.
    Ehrlén,
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Hedenäs,
    Are annual growth intervals independent units in the moss Pseudocalligeron trifarium (Amblystegiaceae)2008Inngår i: BryologistArtikkel i tidsskrift (Fagfellevurdert)
  • 45. Björk, Mats
    et al.
    Kangwe, Juma W.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Mtolera, Matern S. P.
    Temperature effects on photosynthesis and calcification at varying light levels in rhodoliths from a tropical lagoonManuskript (Annet vitenskapelig)
  • 46.
    Björk, Mats
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Fysiologi.
    Short, Fred
    Mcleod, Elisabeth
    Beer, Sven
    Managing Seagrasses for Resilience to Climate Change2008Bok (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    There is growing evidence that seagrasses are experiencing

    declines globally due to anthropogenic

    threats (Short and Wyllie-Echeverria 1996, Duarte

    2002, Orth et al. 2006). Runoff of nutrients and

    sediments that affect water quality is the greatest

    anthropogenic threat to seagrass meadows,

    although other stressors include aquaculture, pollution,

    boating, construction, dredging and landfill

    activities, and destructive fishing practices. Natural

    disturbances such as storms and floods can

    also cause adverse effects. Potential threats from

    climate change include rising sea levels, changing

    tidal regimes, UV radiation damage, sediment

    hypoxia and anoxia, increases in sea temperatures

    and increased storm and flooding events.

    Thus, seagrass meadows, the ecosystems that

    they support and the ecosystem services that they

    provide are threatened by a multitude of environmental

    factors that are currently changing or will

    change in the future.

    Seagrasses are flowering plants that thrive in shallow

    oceanic and estuarine waters around the world.

    Descendants of terrestrial plants that re-entered

    the ocean between 100 and 65 million years ago,

    seagrasses have leaves, stems, rhizomes (horizontal

    underground runners) and roots. Although

    there are only about 60 species of seagrassesworldwide, these plants play an important role in

    many shallow, near-shore, marine ecosystems.

    Seagrass meadows provide ecosystem services

    that rank among the highest of all ecosystems on

    earth. The direct monetary outputs are substantial

    since highly valued commercial catches such

    as prawns and fish are dependent on these systems.

    Seagrasses provide protective shelter for

    many animals, including fish, and can also be a

    direct food source for manatees and dugongs,

    turtles, water fowl, some herbivorous fish and sea

    urchins. The roots and rhizomes of seagrasses

    also stabilise sediments and prevent erosion while

    the leaves filter suspended sediments and nutrients

    from the water column. Seagrass meadows

    are thus linked to other important marine habitats

    such as coral reefs, mangroves, salt marshes and

    oyster reefs.

    This paper presents an overview of seagrasses,

    the impacts of climate change and other threats to

    seagrass habitats, as well as tools and strategies

    for managers to help support seagrass resilience.

  • 47. Björkman, Maria
    et al.
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Hopkins, Richard J.
    Ramert, Birgitta
    Evaluating the enemies hypothesis in a clover-cabbage intercrop: effects of generalist and specialist natural enemies on the turnip root fly (Delia floralis)2010Inngår i: Agricultural and Forest Entomology, ISSN 1461-9555, E-ISSN 1461-9563, Vol. 12, nr 2, 123-132 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relative importance of the resource concentration hypothesis and the enemies hypothesis was investigated for the turnip root fly Delia floralis in a cabbage-red clover intercropping system compared with a cabbage monoculture. Delia floralis egg densities were measured as well as the activity-densities of generalist predators in a field experiment during two growing seasons. In the second year, a study of egg predation with artificially placed eggs was conducted, in addition to a predator exclusion experiment, to estimate total predation during the season. Parasitization rates were estimated from samples of pupae. Delia floralis oviposition was greater in the monoculture during both years. The predator activity-densities differed between treatments and study years. The known natural enemies of Delia spp., Bembidion spp. and Aleochara bipustulata showed a strong response to a cultivation system with higher activity-densities in the monoculture. The response, however, appeared to be caused primarily by habitat preferences and not by D. floralis egg densities. The reduction in the number of D. floralis pupae in the intercropping may be explained by a disruption in oviposition behaviour caused by the presence of clover because neither predation, nor parasitization rates differed between cultivation systems.

  • 48. Björkman, Maria
    et al.
    Hambäck, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Rämert, Birgitta
    Neighboring monocultures enhance the effect of intercropping in turnip root flies (Delia floralis).2007Inngår i: Entomologia Experimentalis et Applicata, Vol. 124, 319-326 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Knowledge of insect behaviour is essential for accurately interpreting studies of diversification and to develop diversified agroecosystems that have a reliable pest-suppressive effect. In this study, we investigated the egg-laying behaviour of the turnip root fly, Delia floralis (Fall.) (Diptera: Anthomyiidae), in an intercrop-monoculture system. We examined both the main effect of intercropping and the effect on oviposition in the border zone between a cabbage monoculture [Brassica oleracea L. var. capitata (Brassicaceae)] and a cabbage-red clover intercropping system [Trifolium pratense L. (Fabaceae)]. To investigate the border-effect, oviposition was measured along a transect from the border between the treatments to the centre of experimental plots. Intercropping reduced the total egg-laying of D. floralis with 42% in 2003 and 55% in 2004. In 2004, it was also found that the spatial distribution of eggs within the experimental plots was affected by distance from the adjoining treatment. The difference in egg-laying between monoculture and intercropping was most pronounced close to the border, where egg-laying was 68% lower on intercropped plants. This difference in egg numbers decreased gradually up to a distance of 3.5 m from the border, where intercropped plants had 43% fewer eggs than the corresponding monocultured plants. The reason behind this oviposition pattern is most likely that flies in intercropped plots have a higher probability of entering the monoculture if they are close to the border than if they are in the centre of a plot. When entering the monoculture, flies can pursue their egg-laying behaviour without being disrupted by the clover. As the final decision to land is visually stimulated, flies could also be attracted to fly from the intercropped plots into the monoculture, where host plants are more visually apparent. Visual cues could also hinder flies in a monoculture from entering an intercropped plot. Other possible patterns of insect attack due to differences in insect behaviour are discussed, as well as the practical application of the results of this study.

  • 49. Björkman, Maria
    et al.
    Hopkins, Richard
    Hambäck, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Rämert, Birgitta
    Effects of plant competition and herbivore density on the development of the turnip root fly (Delia floralis) in an intercropping system2009Inngår i: Arthropod-plant interactions, ISSN 1872-8855, Vol. 3, 55-62 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, interactive effects of plant competition and herbivory on plant quality and herbivore development were examined in a greenhouse experiment where cabbage plants [Brassica oleracea L. var. capitata (Brassicaceae)] were intercropped with red clover [Trifolium pratense L. (Fabaceae)]. Cabbages were grown with two red clover densities and attack rates by the root feeding herbivore the turnip root fly, Delia floralis Fall. (Diptera: Anthomyiidae). Above ground and below ground cabbage biomass was reduced through intercropping and larval damage. Intercropping also resulted in lower nitrogen and higher carbon root levels compared with levels in the roots of monocultured cabbage. Furthermore, both root nitrogen and carbon levels increased with herbivory. Root neutral detergent fibre (NDF) and lignin content increased in response to both increased plant competition and higher egg densities. For lignin, an interaction effect was observed in the form of elevated levels in intercropped plants subjected to larval damage, while levels in roots of monocultured cabbage remained unchanged. The quality changes brought about by clover competition affected D. floralis development negatively, which resulted in reduced pupal weight. In addition, increased egg density also decreased larval growth. The effects on the development of D. floralis in relation to host plant quality are discussed.

  • 50. Blackmore, Stephen
    et al.
    Wortley, Alexandra H.
    Skvarla, John J.
    Gabarayeva, Nina I.
    Rowley, John R.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Developmental origins of structural diversity in pollen walls of Compositae2010Inngår i: Plant Systematics and Evolution, ISSN 0378-2697, E-ISSN 1615-6110, Vol. 284, nr 02-jan, 17-32 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Compositae exhibit some of the most complex and diverse pollen grains in flowering plants. This paper reviews the evolutionary and developmental origins of this diversity in pollen structure using recent models based on the behaviour of colloids and formation of micelles in the differentiating microspore glycocalyx and primexine. The developmental model is consistent with observations of structures recovered by pollen wall dissolution. Pollen wall diversity in Compositae is inferred to result from small changes in the glycocalyx, for example ionic concentration, which trigger the self-assembly of highly diverse structures. Whilst the fine details of exine substructure are, therefore, not under direct genetic control, it is likely that genes establish differences in the glycocalyx which define the conditions for self-assembly. Because the processes described here for Compositae can account for some of the most complex exine structures known, it is likely that they also operate in pollen walls with much simpler organisation.

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