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  • 201.
    Forslund, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Reproduction and reproductive isolation in Fucus radicans (Phaeophyceae)2013In: Marine Biology Research, ISSN 1745-1000, E-ISSN 1745-1019, Vol. 9, no 3, p. 262-267Article in journal (Refereed)
    Abstract [en]

    Recent morphological and genetic studies show that Fucus radicans is a separate species from the sympatric F. vesiculosus. Fucus radicans recently diverged from F. vesiculosus in the Baltic Sea where populations grow in mixed stands. Thus, strong reproductive barriers are expected to be in place to prevent introgression. The seasonal timing of reproduction of the two species in Estonia was shown to be different, likely forming an effective pre-zygotic reproductive barrier. In Sweden, however, no such temporal difference was found. We artificially crossed Swedish F. radicans and F. vesiculosus to identify other potential reproductive barriers. Fertilization success and survival was equally high within and between species in the artificial crossings, suggesting no early post-zygote barriers. Both species recruit new thalli both sexually and asexually, but F. radicans is generally more asexual than F. vesiculosus. By studying their reproductive efforts we found that Swedish F. radicans allocates more resources to adventitious branches than to gamete production compared to F. radicans in Estonia and F. vesiculosus in both Sweden and Estonia. This indicates that Swedish F. radicans has an asexual reproductive strategy while Estonian F. radicans and F. vesiculosus have sexual reproductive strategies.

  • 202.
    Forslund, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Reproduction and reproductive isolation in Fucus radicans (Phaeophyceae)In: Marine Biology Research, ISSN 1745-1000, E-ISSN 1745-1019Article in journal (Refereed)
    Abstract [en]

    Recent morphological and genetic studies show that Fucus radicans is a separate species from the sympatric F. vesiculosus. Fucus radicans recently diverged from F. vesiculosus in the Baltic Sea where populations grow in mixed stands. Thus, strong reproductive barriers are expected to be in place to prevent introgression. The seasonal timing of reproduction of the two species in Estonia was shown to be different, likely forming an effective pre-zygotic reproductive barrier. In Sweden, however, no such temporal difference was found. We artificially crossed Swedish F. radicans and F. vesiculosus to identify other potential reproductive barriers. Fertilization success and survival was equally high within and between species in the artificial crossings, suggesting no early post-zygote barriers. Both species recruit new thalli both sexually and asexually, but F. radicans is generally more asexual than F. vesiculosus. By studying their reproductive efforts we found that Swedish F. radicans allocates more resources to adventitious branches than to gamete production compared to F. radicans in Estonia and F. vesiculosus in both Sweden and Estonia. This indicates that Swedish F. radicans has an asexual reproductive strategy while Estonian F. radicans and F. vesiculosus have sexual reproductive strategies.

  • 203.
    Forslund, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Pavia, Henrik
    Higher resistance to herbivory in introduced compared to native populations of a seaweed2010In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 164, no 3, p. 833-840Article in journal (Refereed)
    Abstract [en]

    Non-indigenous species (NIS) are important components of global change, and in order to manage such species it is important to understand which factors affect their success. Interactions with enemies in the new range have been shown to be important for the outcome of introductions, but thus far most studies on NIS-enemy interactions have considered only specialist herbivores in terrestrial systems. Here we present the results from the first biogeographic study that compares herbivore resistance between populations in the native and new region of a non-indigenous seaweed. We show that low consumption of the non-indigenous seaweed by a generalist herbivore is caused by higher chemical defence levels and herbivore resistance in the new range-and not by the failure of the herbivore to recognise the non-indigenous seaweed as a suitable host. Since most seaweed-herbivore interactions are dominated by generalist herbivores, this pattern could be common in marine communities. Our results also reveal that traits used to predict the invasive potential of species, such as their resistance to enemies, can change during the invasion process, but not always in the way predicted by dominant theories.

  • 204. Fortunato, Ana
    et al.
    Santos, Patricia
    Graca, Ines
    Gouveiva, Maria Manuela
    Martins, Sandra Marina
    Pinto Ricardo, Candido Pereira
    Pawlowski, Katharina
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Ribeiro, Ana Isabel
    Isolation and characterization of cgchi3, a nodule-specific gene from Casuarina glauca encoding a class III chitinase2007In: Physiologia Plantarum, ISSN 0031-9317, Vol. 130, no 3, p. 418-426Article in journal (Refereed)
    Abstract [en]

    Chitinases (EC 3.2.1.14) catalyse the hydrolysis of chitin, a homopolymer of beta-1,4-linked N-acetyl-D-glucosamine residues. Plant chitinases are involved in a wide variety of processes; in particular, their expression has been found to be enhanced in symbiotic and pathogenic plant-microbe interactions. During this work we have cloned and characterized a gene encoding a class III chitinase from actinorhizal nodules of Casuarina glauca (cgchi3). CGCHI3 was found to be encoded by a single gene that was specifically activated in nodules as compared with uninoculated control roots and leaves. The expression of this gene was further enhanced in nodules after salicylic acid treatment and completely repressed after wounding. In situ hybridisation analysis revealed that cgchi3 is an early nodulin gene, being expressed in the meristem and in the uninfected cortical cells of young nodules. Based on the obtained results we suggest that this gene is involved in nodule development. This is the first report on a class III chitinase coding gene that is specifically activated during actinorhizal symbiosis.

  • 205. Fortunel, Claire
    et al.
    Garnier, Eric
    Joffre, R
    Kazakou, E
    Quested, Helen
    Stockholm University, Faculty of Science, Department of Botany.
    Grigulis,
    Lavorel, S
    Ansquer, P
    Castro, H
    Cruz, P
    Dolezal, J
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Botany.
    Freitas, H
    Golodets, C
    Jouany, C
    Kigel, J
    Kleyer, M
    Lehsten, V
    Leps, J
    Meier, T
    Pakeman, R
    Papadimitriou, M
    Papanastasis, V P
    Quétier, F
    Robson, M
    Sternberg, M
    Theau, J-P
    Thébault, A
    Zarovali, M
    Leaf traits capture the effects of land use changes and climate on litter decomposability of grasslands across Europe2009In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, p. 598-611Article in journal (Refereed)
  • 206.
    Fredriksson, Charlotta
    Stockholm University, Faculty of Science, Department of Botany.
    Nitrogenase localisation reveals cell differentiation in filamentous, non-heterocystous cyanobacteria1996Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with detecting and interpreting natural and anthropogenic changes in the composition of the Arctic troposphere. It also covers quantifications of regional climate change due to the activities of mankind. By comparing observed temperature trends and calculated sulfate burdens over the globe, it was found that the two regions affected by a substantial increase in atmospheric loading of anthropogenic sulfate - Europe and China - displayed a decrease in summer temperatures between the 1940s and the 1980s. The cooling is consistent with recent studies indicating a negative radiative forcing by anthropogenic sulfate particles. The second part of the thesis concentrates on the interpretation of day-to-day variations in atmospheric carbon dioxide (CO2) mixing ratio measured at a monitoring station on Spitsbergen. Studies using three-dimensional back trajectories covering several spring-periods show that recent oceanic CO2 uptake was discernable in the Spitsbergen data. These findings were supported by complementary calculations from a simple Lagrangian model, using realistic CO2-saturations in the northern North Atlantic. In order to further interpret these and similar short-term variations in the atmospheric composition on Spitsbergen, a high-resolution regional transport model was developed. This model is driven by observed meteorology, with a parameterised boundary layer, and utilizes a mass conserving advection scheme with only small phase and amplitude errors. Tests showed that the model was able to simulate realistic seasonal and spatial variations of radon-222 in the lower troposphere. The model was next applied to a spring period in the Arctic. By comparing calculated CO2 mixing ratios with measurements taken on Spitsbergen it was possible to discriminate between oceanic and terrestrial CO2 uptake. These findings are encouraging for the further use of this model in detecting and quantifying CO2 fluxes in the high latitude northern hemisphere. In a final study the transport model was used to compare different estimates of fossil fuel CO2 emissions in Eurasia. The calculations showed that the Arctic troposphere is efficiently ventilated in winter, with an e-folding time on the order of 10 days. It was also shown that anthropogenic CO2 emissions in Siberia can not be distributed in proportion to population density, which has previously been done. There is, strong evidence of large combustion sources near the gas-fields around the Gulf of Ob, and in the interior of Eastern Siberia. The model results suggest that these emission regions are a dominating source for the formation of Arctic haze in winter.

  • 207.
    Fritioff, Åsa
    Stockholm University, Faculty of Science, Department of Botany.
    Metal accumulation by plants: evaluation of the use of plants in stormwater treatment2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Metal contaminated stormwater, i.e. surface runoff in urban areas, can be treated in percolation systems, ponds, or wetlands to prevent the release of metals into receiving waters. Plants in such systems can, for example, attenuate water flow, bind sediment, and directly accumulate metals. By these actions plants affect metal mobility. This study aimed to examine the accumulation of Zn, Cu, Cd, and Pb in roots and shoots of plant species common in stormwater areas. Furthermore, submersed plants were used to examine the fate of metals: uptake, translocation, and leakage. Factors known to influence metal accumulation, such as metal ion competition, water salinity, and temperature, were also examined. The following plant species were collected in the field: terrestrial plants – Impatiens parviflora, Filipendula ulmaria, and Urtica dioica; emergent plants – Alisma-plantago aquatica, Juncus effusus, Lythrum salicaria, Sagittaria sagittifolia, and Phalaris arundinacea; free-floating plants – Lemna gibba and Lemna minor; and submersed plants – Elodea canadensis and Potamogeton natans. Furthermore, the two submersed plants, E. canadensis and P. natans, were used in climate chamber experiments to study the fate of the metals in the plant–water system.

    Emergent and terrestrial plant species accumulated high concentrations of metals in their roots under natural conditions but much less so in their shoots, and the accumulation increased further with increased external concentration. The submersed and free-floating species accumulated high levels of metals in both their roots and shoots. Metals accumulated in the shoots of E. canadensis and P. natans derived mostly from direct metal uptake from the water column.

    The accumulation of Zn, Cu, Cd, and Pb in submersed species was in general high, the highest concentrations being measured in the roots, followed by the leaves and stems, E. canadensis having higher accumulation capacity than P. natans. In E. canadensis the Cd uptake was passive, and the accumulation in dead plants exceeded the of living with time. The capacity to quickly accumulate Cd in the apoplast decreased with successive treatments. Some of the Cd accumulated was readily available for leakage. In P. natans, the presence of mixtures of metal ions, common in stormwater, did not alter the accumulation of the individual metals compared to when presented separately. It is therefore, proposed that the site of uptake is specific for each metal ion. In addition cell wall-bound fraction increased with increasing external concentration. Further, decreasing the temperature from 20ºC to 5ºC and increasing the salinity from 0‰ to 5‰ S reduced Zn and Cd uptake by a factor of two.

    In P. natans the metals were not translocated within the plant, while in E. canadensis Cd moved between roots and shoots. Thus, E. canadensis as opposed to P. natans may increase the dispersion of metals from sediment via acropetal translocation. The low basipetal translocation implies that neither E. canadensis nor P. natans will directly mediate the immobilisation of metal to the sediment via translocation.

    To conclude, emergent and terrestrial plant species seem to enhance metal stabilization in the soil/sediment. The submersed plants, when present, slightly increase the retention of metals via shoot accumulation.

  • 208.
    Fritioff, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Greger, M
    Aquatic and terrestrial plant species with potential to remove heavy metals from stormwater2003In: International Journal of Phytoremediation, ISSN 1522-6514, Vol. 5, no 3, p. 211-224Article in journal (Refereed)
  • 209.
    Fritioff, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany.
    Fate of Cadmium in Elodea canadensis2007In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 67, no 2, p. 365-375Article in journal (Refereed)
    Abstract [en]

    Elodea canadensis is a submersed macrophytes, widely distributed in stormwater treatment ponds and able to remove heavy metals from water. This study examines the Cd uptake, translocation, and efflux patterns in Elodea. Several experiments were set up in a climate chamber. To study the root and shoot Cd uptake, living and dead roots and shoots were treated with 109Cd in one- and two-compartment systems. Furthermore, to examine Cd translocation and distribution, either roots or shoots were treated with 109Cd. Finally, the efflux of Cd from roots and shoots, respectively, to the external solution was studied after loading whole plants with 109Cd. Results from the two compartment studies show that Cd is accumulated via direct uptake by both roots and shoots of Elodea. The Cd accumulation proved not to be metabolically dependent in Elodea, and the apoplastic uptake in particular was decreased by Cd pretreatment. In one week, up to 23% of the root uptake was translocated to the shoots, while about 2% of the Cd accumulated by shoots was translocated to the roots. Thus, slight dispersion of Cd is possible, while metal immobilization will not be directly mediated via the Elodea plant. The efflux experiment proved that both shoots of dead plants and roots of living plants had a faster efflux than did shoots of living plants. This information is relevant for an understanding of the fate of Cd in stormwater treatment ponds with Elodea

    .

  • 210.
    Fritioff, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Fate of cadmium in Elodea canadensis2007In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Chemosphere, Vol. 67, no 2, p. 365-375Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Elodea canadensis is a submersed macrophytes, widely distributed in stormwater treatment ponds and able to remove heavy metals

    from water. This study examines the Cd uptake, translocation, and efflux patterns in Elodea. Several experiments were set up in a climate

    chamber. To study the root and shoot Cd uptake, living and dead roots and shoots were treated with 109Cd in one- and two-compartment

    systems. Furthermore, to examine Cd translocation and distribution, either roots or shoots were treated with 109Cd. Finally, the efflux of

    Cd from roots and shoots, respectively, to the external solution was studied after loading whole plants with 109Cd. Results from the two

    compartment studies show that Cd is accumulated via direct uptake by both roots and shoots of Elodea. The Cd accumulation proved

    not to be metabolically dependent in Elodea, and the apoplastic uptake in particular was decreased by Cd pretreatment. In one week, up

    to 23% of the root uptake was translocated to the shoots, while about 2% of the Cd accumulated by shoots was translocated to the roots.

    Thus, slight dispersion of Cd is possible, while metal immobilization will not be directly mediated via the Elodea plant. The efflux experiment

    proved that both shoots of dead plants and roots of living plants had a faster efflux than did shoots of living plants. This information

    is relevant for an understanding of the fate of Cd in stormwater treatment ponds with Elodea.

  • 211.
    Fritioff, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany.
    Uptake and distribution of Zn, Cu, Cd, and Pb in an aquatic plant Potamogeton natans2006In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 63, no 2, p. 220-227Article in journal (Refereed)
    Abstract [en]

    A better understanding of metal uptake and translocation by aquatic plants can be used to enhance the performance of constructed wetland systems for stormwater treatment. Specifically, this study examines whether the uptake of Zn, Cu, Cd, and Pb by Potamogeton natans is via the leaves, stems, or roots, and whether there is translocation from organs of uptake to other plant parts. Competition between the metals at uptake and at the level of the cell wall-bound part of the metals accumulated in stem and leaf tissue was also examined. The results show that Zn, Cu, Cd, and Pb were taken up by the leaves, stems, and roots, with the highest accumulation found in the roots. At the elevated metal concentrations common in stormwater the uptake of Cu, but not of Zn, Cd, or Pb, by the roots was somewhat limited at uptake due to competition with other metals. Between 24% and 59% of the metal content was bound to the cell walls of the plant. Except in the case of Pb, the cell wall-bound fraction was generally smaller in stems than in leaves. No translocation of the metals to other parts of the plant was found, except for Cd which was translocated from leaf to stem and vice versa. Dispersion of metals from sediment to water through P. natans is therefore unlikely.

  • 212.
    Fritioff, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Kautsky, L
    Greger, M
    Influence of temperature and salinity on heavy metal uptake by submersed plants2005In: Environmental Pollution, ISSN 0269-7491, Vol. 133, no 2, p. 265-274Article in journal (Refereed)
  • 213.
    Fröborg, Heléne
    Stockholm University, Faculty of Science, Department of Botany.
    Recruitment and understorey herb dynamics in deciduous and mixed coniferous forest2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The distribution and abundance of plant species is determined by the ability to disperse, recruit and persist in a suitable habitat. Plant-animal interactions influence recruitment by reducing seeds and seedlings through predation and herbivory. This thesis examines and quantifies the impact of pre-dispersal seed predation by Eupithecia immundata (Geometridae) on population dynamics of the perennial herb Actaea spicata (Ranunculaceae). The seed predator E. immundata consumed between 21 and 49% of A. spicata seeds produced in the decuduous forest, and between 24 and 80% in the mixed coniferous forest. Analysis of demographic information from seven years and two populations by transition matrix models resulted in population growth rates ranging from 0.84 to 1.14 in the deciduous forest, and from 0.78 to 1.08 in the mixed coniferous forest. Elasticity analysis indicated that survivorship of reproductive individuals contributed most to population growth rate, as is often found in long-lived perennials. Experimental seed addition intended to compensate for seed predation, increased seedling emergence significantly in the deciduous forest. Population growth rate shifted from negative to positive values in two more transition years when seed predation was excluded from matrices.

    Understorey forest perennials were subjected to treatments in seed sowing experiments in the field to examine effects of post-dispersal seed predation, seedling herbivory, density, litter and seed size on seedling recruitment. Reduced rodent seed predation increased seedling emergence in A. spicata, but seed density did not affect predation rates, although there was a density-dependent seed and seedling mortality in the high density. Seedling herbivory by slugs did not affect seedling emergence of e.g. A. spicata, Convallaria majalis, Paris quadrifolia or Ranunculus acris. Seedling emergence was significantly higher in species with large seeds (>3mg) than in those with small seeds (<2mg), irrespective of predation. Litter removal improved seedling emergence occasionally.

    Inventory data on 45 understorey species in a deciduous forest were used to investigate life history features, colonization and extinction. Local colonization was positively related to seed size and seed dispersal features, whereas local extinction rate was negatively related to seed size. In conclusion, several biotic interactions, seed predation in particular, causes significant reductions in recruitment. Although the effect on population dynamics is generally small, it is likely to translate to significant effects if viewed over a long time period.

  • 214.
    Funk, Vicki A
    et al.
    Smithsonian Institution, Washington, DC, .
    Karis, Per Ola
    Stockholm University, Faculty of Science, Department of Botany.
    Heterolepis: an unplaced genus2009In: Systematics, evolution and biogeography of compositae / [ed] Vicki A Funk, Vienna: International Association for Plant Taxonomy, University of Vienna , 2009, p. 483-486Chapter in book (Other academic)
  • 215. Gabarayeva, Nina
    et al.
    Grigorjeva, Valentina
    Rowley, John R
    Stockholm University, Faculty of Science, Department of Botany.
    Hemsley, Alan R
    Sporoderm development in Trevesia burckii (Araliaceae). I. Tetrad period: Further evidence for the participation of self-assembly processes2009In: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 156, no 1-2, p. 211-232Article in journal (Refereed)
    Abstract [en]

    The developmental events in the periplasmic space and cytoplasm of microspores, and in the tapetum of Trevesia burckii during the tetrad period have been traced in detail during microspore ontogeny from the sporogenous cell stage to the late tetrad stage and the initiation of the foot layer. The data obtained provide support to two of our previously proposed hypotheses: (1) the glycocalyx (scaffolding primexine matrix) is a colloidal system: (2) the involvement of processes of self-assembly of a number of colloidal micellar systems to the exine development. The main structures of the reticulate ectexine up to the establishment of the foot layer are columellae and tectum which evidently form on a base of spherical and cylindrical transitive micelle mesophases after sporopollenin accumulation. The importance of the callose envelope surrounding microspores; for exine development is discussed in the light of recent findings. Two possible pathways of pattern determination are possible. One suggests the role of the plasma membrane in pattern imprinting and the corresponding necessity of the transfer of 2-D information to 3-D. Our current supposition is that the other, self-assembly physical phenomena, cellular tensegrity, also participate in the process of the establishment of a wide-spread reticulate exine pattern which appears as the result of an interplay of the microspore cytoskeletal prestress and the resistance from the ECM (exocellular matrix = glycocalyx) adhesive sites. More and more information is appearing that provides evidence for the importance of mechanical forces and physico-chemical regularities in the living world.

  • 216. Gabarayeva, Nina
    et al.
    Grigorjeva, Valentina
    Rowley, John R
    Stockholm University, Faculty of Science, Department of Botany.
    Hemsley, Alan R
    Sporoderm development in Trevesia burckii (Araliaceae) II. Post-tetrad period: Further evidence for the participation of self-assembly processes2009In: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 156, no 1-2, p. 233-247Article in journal (Refereed)
    Abstract [en]

    The developmental events in the periplasmic space, the cytoplasm of microspores and in the tapetum of Trevesia burckii have been traced in detail during microspore ontogeny from the late tetrad stage, through the post-tetrad period, to intine formation (following on from our study of the tetrad period also published herein). The data obtained give further support to our previously proposed hypothesis regarding self-assembly of a number of colloidal micellar systems during exine (and possibly intine) development. The main structures of the mature exine are columellae, granules and tripartite lamellae with central white lines which evidently form on a base of cylindrical, spherical and lamellar transitive micelle mesophases after sporopollenin accumulation. Further information provides evidence for the importance of physico-chemical regularities in pollen wall development.

  • 217. Gabarayeva, Nina I.
    et al.
    Grigorjeva, Valentina V.
    Rowley, John R.
    Stockholm University, Faculty of Science, Department of Botany.
    A new look at sporoderm ontogeny in Persea americana and the hidden side of development2010In: Annals of Botany, ISSN 0305-7364, E-ISSN 1095-8290, Vol. 105, no 6, p. 939-955Article in journal (Refereed)
    Abstract [en]

    The phenomenon of self-assembly, widespread in both the living and the non-living world, is a key mechanism in sporoderm pattern formation. Observations in developmental palynology appear in a new light if they are regarded as aspects of a sequence of micellar colloidal mesophases at genomically controlled initial parameters. The exine of Persea is reduced to ornamentaion (spines and gemmae with underlying skin-like ectexine); there is no endexine. Development of Persea exine was analysed based on the idea that ornamentation of pollen occurs largely by self-assembly. Flower buds were collected from trees grown in greenhouses over 11 years in order to examine all the main developmental stages, including the very short tetrad period. After fixing, sections were examined using transmission electron microscopy. The locations of future spines are determined by lipid droplets in invaginations of the microspore plasma membrane. The addition of new sporopollenin monomers into these invaginations leads to the appearance of chimeric polymersomes, which, after splitting into two individual assemblies, give rise to both liquid-crystal conical 'skeletons' of spines and spherical micelles. After autopolymerization of sporopollenin, spines emerge around their skeletons, nested into clusters of globules. These clusters and single globules between spines appear on a base of spherical micelles. The intine also develops on the base of micellar mesophases. Colloidal chemistry helps to provide a more general understanding of the processes and explains recurrent features of pollen walls from remote taxa.

  • 218. Gabarayeva, Nina I.
    et al.
    Grigorjeva, Valentina V.
    Rowley, John R.
    Stockholm University, Faculty of Science, Department of Botany.
    Sporoderm development in Acer tataricum (Aceraceae): an interpretation2010In: Protoplasma, ISSN 0033-183X, E-ISSN 1615-6102, Vol. 247, no 1-2, p. 65-81Article in journal (Refereed)
    Abstract [en]

    For the first time, the developmental events in the course of complicated exine structure establishment have been traced in detail with transmission electron microscope in the representative of Acer. A new look at unfolding events is suggested using the knowledge of a boundary field, colloid science. Our purpose was to find out whether the sequence of sporoderm developmental events represents, in essence, the sequence of self-assembling micellar mesophases, initiated by genomically given physicochemical parameters and induced by surfactant glycoproteins at increasing concentration. Indeed, the first units observed in the periplasmic space are globular ones (=spherical micelles) which become arranged into rod-like units (=cylindrical micelles). Then, twisted clusters of rodlets form a layer of procolumellae (middle micellar mesophase). The tectum emerges as an untwisting and merging of distal ends of procolumellae (distal untwist of micelle clusters). In the end of tetrad period, when a hydrophilic-hydrophobic switch occurs in the periplasmic space, the contrast reversal of the columellae corresponds to the change of normal micelles to reverse ones. The initiation of the foot layer and the endexine lamellae, with their typical central "white lines", corresponds to the next-"neat"aEuro"mesophase, with its typical central gaps between layers. Aperture sites during development show all the main micellar mesophases and their transitional forms. The data received have supported our previous hypothesis.

  • 219. Gabriëls, Suzan H E J
    et al.
    Vossen, Jack H
    Ekengren, Sophia K
    Stockholm University, Faculty of Science, Department of Botany.
    van Ooijen, Gerben
    Abd-El-Haliem, Ahmed M
    van den Berg, Grardy C M
    Rainey, Daphne Y
    Martin, Gregory B
    Takken, Frank L W
    de Wit, Pierre J G M
    Joosten, Matthieu H A J
    An NB-LRR protein required for HR signalling mediated by both extra- and intracellular resistance proteins.2007In: Plant J, ISSN 0960-7412, Vol. 50, no 1, p. 14-28Article in journal (Refereed)
  • 220. Garcia,
    et al.
    Pico,
    Ehrlén,
    Stockholm University, Faculty of Science, Department of Botany.
    Life span correlates with population dynamics in perennial herbaceous plants2008In: American Journal of BotanyArticle in journal (Refereed)
  • 221. Garcia, Maria B.
    et al.
    Dahlgren, Johan P.
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlen, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    No evidence of senescence in a 300-year-old mountain herb2011In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 99, no 6, p. 1424-1430Article in journal (Refereed)
    Abstract [en]

    1. Understanding how vital rates and reproductive value change with age is fundamental to demography, life history evolution and population genetics. The universality of organism senescence has been questioned on both theoretical and empirical grounds, and the prevalence and strength of senescence remain a controversial issue. Plants are particularly interesting for studies of senescence since individuals of many species have been reported to reach very high ages. 2. In this study, we examined whether the herb Borderea pyrenaica, known to reach ages of more than 300 years, experiences senescence. We collected detailed demographic information from male and female individuals in two populations over 5 years. An unusual morphological feature in this species enabled us to obtain exact age estimates for each of the individuals at the end of the demographic study. 3. We used restricted cubic regression splines and generalized linear models to determine nonlinear effects of age and size on vital rates. We then incorporated the effects of age and size in integral projection models of demography for determining the relationship between age and reproductive value. As the species is dioecious, we performed analyses separately for males and females and examined also the hypothesis that a larger reproductive effort in females comes at a senescence cost. 4. We found no evidence for senescence. Recorded individuals reached 260 years, but growth and fecundity of female and male individuals did not decrease at high ages, and survival and reproductive value increased with age. The results were qualitatively similar also when accounting for size and among-individual vital rate heterogeneity, with the exception that male flowering probability decreased with age when accounting for size increases. 5. Synthesis. Overall, our results show that performance of both male and female plants of B. pyrenaica may increase rather than decrease at ages up to several centuries, and they support the notion that senescence may be negligible in long-lived modular organisms. This highlights the need to explore mechanisms that enable some species to maintain high reproductive values also at very high ages and to identify the evolutionary reasons why some organisms appear to experience no or negligible senescence.

  • 222. Garnier, Eric
    et al.
    Lavorel, Sandra
    Ansquer, P
    Castro, H
    Cruz, P
    Dolezal, J
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Fortunel, C
    Freitas, H
    Golodets, C
    Grigulis, K
    Jouany, C
    Kazakou, E
    Kigel, J
    Kleyer, M
    Lehsten, V
    Leps, J
    Meier, T
    Pakeman, R
    Papadimitriou, M
    Papanastasis, V
    Quested, Helen
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Quetier, F
    Robson, M
    Roumet, C
    Rusch, G
    Skarpe, C
    Sternberg, M
    Theau, J-P
    Thebault, A
    Vile, D
    Zarovali, M
    Assessing the effects of land use change on plant traits, communities and ecosystem functioning in grasslands: A standardized methodology and lessons from an application to 11 European sites2007In: Annals of Botany, Vol. 99, p. 967-985Article in journal (Refereed)
  • 223.
    Gehrke, Berit
    et al.
    University of Zurich, Institute for Systematic Botany.
    Bräuchler, Christian
    Department Biologie I, Systematische Botanik, LMU Munich.
    Romoleroux, Katia
    Herbario QCA, Pontificia Universidad Católica del Ecuador.
    Lundberg, Magnus
    Stockholm University, Faculty of Science, Department of Botany.
    Heubl, G
    Department Biologie I, Systematische Botanik, LMU Munich.
    Eriksson, Torsten
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Molecular phylogenetics of Alchemilla, Aphanes and Lachemilla (Rosaceae) inferred from plastid and nuclear intron and spacer DNA sequences, with comments on generic classification2008In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 47, p. 1030-1044Article in journal (Refereed)
    Abstract [en]

    Alchemilla (the lady’s mantles) is a well known but inconspicuous group in the Rosaceae, notable for its ornamental leaves and pharmaceutical properties. The systematics of Alchemilla has remained poorly understood, most likely due to confusion resulting from apomixis, polyploidisation and hybridisation, which are frequently observed in the group, and which have led to the description of a large number of (micro-) species. A molecular phylogeny of the genus, including all sections of Alchemilla and Lachemilla as well as five representatives of Aphanes, based on the analysis of the chloroplast trnL–trnF and the nuclear ITS regions is presented here. Gene phylogenies reconstructed from the nuclear and chloroplast sequence data were largely congruent. Limited conflict between the data partitions was observed with respect to a small number of taxa. This is likely to be the result of hybridisation/introgression or incomplete lineage sorting. Four distinct clades were resolved, corresponding to major geographical division and life forms: Eurasian Alchemilla, annual Aphanes, South American Lachemilla and African Alchemilla. We argue for a wider circumscription of the genus Alchemilla, including Lachemilla and Aphanes, based on the morphology and the phylogenetic relationships between the different clades.

  • 224. Ghai, Rohit
    et al.
    Mella Hernandez, Claudia
    Picazo, Antonio
    Megumi Mizuno, Carolina
    Ininbergs, Karolina
    Stockholm University, Faculty of Science, Department of Botany.
    Diez, Beatriz
    Valas, Ruben
    DuPont, Christopher L.
    McMahon, Katherine D.
    Camacho, Antonio
    Rodriguez-Valera, Francisco
    Metagenomes of Mediterranean Coastal Lagoons2012In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 2, article id 490Article in journal (Refereed)
    Abstract [en]

    Coastal lagoons, both hypersaline and freshwater, are common, but still understudied ecosystems. We describe, for the first time, using high throughput sequencing, the extant microbiota of two large and representative Mediterranean coastal lagoons, the hypersaline Mar Menor, and the freshwater Albufera de Valencia, both located on the south eastern coast of Spain. We show there are considerable differences in the microbiota of both lagoons, in comparison to other marine and freshwater habitats. Importantly, a novel uncultured sulfur oxidizing Alphaproteobacteria was found to dominate bacterioplankton in the hypersaline Mar Menor. Also, in the latter prokaryotic cyanobacteria were almost exclusively comprised by Synechococcus and no Prochlorococcus was found. Remarkably, the microbial community in the freshwaters of the hypertrophic Albufera was completely in contrast to known freshwater systems, in that there was a near absence of well known and cosmopolitan groups of ultramicrobacteria namely Low GC Actinobacteria and the LD12 lineage of Alphaproteobacteria.

  • 225. Gorelova, O. A.
    et al.
    Baulina, O. I.
    Rasmussen, Ulla
    Stockholm University, Faculty of Science, Department of Botany.
    Koksharova, O. A.
    The pleiotropic effects of ftn2 and ftn6 mutations in cyanobacterium Synechococcus sp PCC 79422013In: Protoplasma, ISSN 0033-183X, E-ISSN 1615-6102, Vol. 250, no 4, p. 931-942Article in journal (Refereed)
    Abstract [en]

    Two cell division mutants (Ftn2 and Ftn6) of the cyanobacterium Synechococcus sp. PCC 7942 were studied using scanning electron microscopy and transmission electron microscopy methods. This included negative staining and ultrathin section analysis. Different morphological and ultrastructural features of mutant cells were identified. Ftn2 and Ftn6 mutants exhibited particularly elongated cells characterized by significantly changed shape in comparison with the wild type. There was irregular bending, curving, spiralization, and bulges as well as cell branching. Elongated mutant cells were able to initiate cytokinesis simultaneously in several division sites which were localized irregularly along the cell. Damaged rigidity of the cell wall was typical of many cells for both mutants. Thylakoids of mutants showed modified arrangement and ultrastructural organization. Carboxysome-like structures without a shell and/or without accurate polyhedral packing protein particles were often detected in the mutants. However, in the case of Ftn2 and Ftn6, the average number of carboxysomes per section was less than in the wild type by a factor of 4 and 2, respectively. These multiple morphological and ultrastructural changes in mutant cells evinced pleiotropic responses which were induced by mutations in cell division genes ftn2 and ftn6. Ultrastructural abnormalities of Ftn2 and Ftn6 mutants were consistent with differences in their proteomes. These results could support the significance of FTN2 and FTN6 proteins for both cyanobacterial cell division and cellular physiology.

  • 226.
    Gove, Aaron D.
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Dunn, Robert R.
    Majer, Jonathan D.
    The importance of species range attributes and reserve configuration for the conservation of angiosperm diversity in Western Australia2008In: Biodiversity and Conservation, ISSN 0960-3115, E-ISSN 1572-9710, Vol. 17, no 4, p. 817-831Article in journal (Refereed)
    Abstract [en]

    In order to better understand the relationship between reserve design and the species represented by such designs, we examined the effectiveness of the Western Australian reserve system for conserving angiosperm diversity, and examined the characteristics of those species conserved. We overlayed species distribution data for 14 plant lineages with the distribution of the reserve system (8.5% of the State's area) and identified the species that remained unprotected. We found that, depending upon the method employed, between 174 (5.7%) and 570 (18.7%) of species were not included within the reserve system. Two main unprotected regions were identified, one of which was also a centre of high diversity. Geographical range sizes of unprotected species were six times smaller than those species that were protected, while species richness of small-ranged endemic species coincided with general patterns of species richness. At the level of Western Australia's bioregions we found that conservation effectiveness was most dependent on characteristics of the reserve system rather than characteristics (size and positioning) of species ranges. At this scale, the most effective way to conserve more species in Western Australia would be to conserve more land, while conservation would be most successful in a uniformly dispersed reserve system. Our results highlight the fact that reserve systems may take on two design approaches based on scale--at continental scales, reserves should be clustered around the hotspots of endemic species, while within regions, an evenly distributed reserve system will most adequately sample species.

  • 227.
    Gove, Aaron D.
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Botany.
    Nemomissa, Sileshi
    Shimelis, Anteneh
    Enkossa, Woldeyohannes
    Structurally complex farms support high avian functional diversity in tropical montane Ethiopia2013In: Journal of Tropical Ecology, ISSN 0266-4674, E-ISSN 1469-7831, Vol. 29, p. 87-97Article in journal (Refereed)
    Abstract [en]

    Of all feeding guilds, understorey insectivores are thought to be most sensitive to disturbance and forest conversion. We compared the composition of bird feeding guilds in tropical forest fragments with adjacent agro-ecosystems in a montane region of south-west Ethiopia. We used a series of point counts to survey birds in 19 agriculture and 19 forest sites and recorded tree species within each farm across an area of 40 x 35 km. Insectivores (similar to 17 spp. per plot), frugivores (similar to 3 spp. per plot) and omnivores (similar to 5 spp. per plot) maintained species density across habitats, while granivores and nectarivores increased in the agricultural sites by factors of 7 and 3 respectively. Species accumulation curves of each guild were equal or steeper in agriculture, suggesting that agricultural and forest landscapes were equally heterogeneous for all bird guilds. Counter to most published studies, we found no decline in insectivore species richness with forest conversion. However, species composition differed between the two habitats, with certain forest specialists replaced by other species within each feeding guild. We suggest that the lack of difference in insectivorous species numbers between forest and agriculture in this region is due to the benign nature of the agricultural habitat, but also due to a regional species pool which contains many bird species which are adapted to open habitats.

  • 228. Gove, A.D.
    et al.
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Nemomissa, Sileshi
    Shimelis, A.
    Ethiopian coffee cultivation: Implications for bird conservation and environmental certification2008In: Conservation Letters, Vol. 1, p. 208-216Article in journal (Refereed)
  • 229.
    Granbom, Malena
    Stockholm University, Faculty of Science, Department of Botany.
    Circadian rhythms and carbon acquisition in the red algae Kappaphycus alvarezii and Eucheuma denticulatum2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Aspects of carbon and nitrogen metabolism have been studied in two closely related tropical red macroalgae (Rhodophyta) that belong to the commercially important genera Kappaphycus and Eucheuma. These algae are cultivated around the world for their carrageenan content.

    Circadian rhythms are controlled by endogenous clocks and express a rhythm with a period of approximately 24 h. They can be studied in constant conditions. Circadian regulation of photosynthesis (measured as O2 evolution) was found in Kappaphycus alvarezii. The rhythm was expressed in all spectral ranges tested, white, blue, green and red light. In blue light the period of the free-running rhythm became shorter, and in red light longer, with higher irradiance. In contrast, in white and green light the period did not change with irradiance. These results suggest that at least two photoreceptors are involved in the light transduction pathway, controlling the circadian rhythm of photosynthesis in K. alvarezii, one sensitive to red light and another one sensitive to blue light.

    The enzyme nitrate reductase (NR) is very important in the nitrogen assimilation process. Measurements of NR activity in K. alvarezii were performed in vitro on crude extracts and protein levels estimated by probing Western blots with monoclonal antibodies against NR. Diurnal oscillation of both protein levels and activity of NR was found in K. alvarezii. The data also suggest a circadian regulation of NR which is expressed at a high irradiance (100 µmol photons m-2 s-1) but not at lower irradiances (25 and 55 µmol photons m-2 s-1). Characterization of the NR of K. alvarezii showed that the enzyme is composed of two 100 kDa subunits with a holoenzyme mass of 210 kDa. The enzyme was NADH specific and had high affinity both for nitrate and NADH. Furthermore, the enzyme was characterised by broad pH and temperature optima and high stability. A highly regulated, stable enzyme with high affinity for its substrates is likely to be important for growth in dense algal populations in nutrient-poor tropical waters.

    One important constraint of the marine environment on algae is the limited access to inorganic carbon (Ci). The major system that ensures sufficient Ci supply in Eucheuma denticulatum and K. alvarezii was found to be mediated by an external carbonic anhydrase (CA). The suggested function of this enzyme is to speed up the dehydration of HCO3- (the major form of inorganic carbon in natural seawater) to CO2, which can freely diffuse across the algal cellular membrane. Both E. denticulatum and K. alvarezii were also able to make direct use of the HCO3- in seawater via an anion exchange transport protein. This mechanism was found to be a major component of their carbon concentrating system at pH above 8.9 while the external CA was active in a wide pH range from pH 6.5 (start pH of our measurements) to pH 9.3, the pH compensation point. 

  • 230.
    Granbom, Malena
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lopes, Patricia F.
    Pedersen, Marianne
    Stockholm University, Faculty of Science, Department of Botany.
    Colepicolo, Pio
    Nitrate reductase in the marine macroalga Kappaphycus alvarezii (Rhodophyta): oscillation due to the protein level2007In: Botanica Marina, ISSN 0006-8055, E-ISSN 1437-4323, Vol. 50, no 2, p. 106-112Article in journal (Refereed)
    Abstract [en]

    Nitrate reductase, (NR; EC 1.6.6.1) of the marine red macroalga Kappaphycus alvarezii was examined in algae maintained under L:D and constant light conditions. Undenaturated protein had a molecular mass of about 210 kD (+/- 23 kD); based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting techniques, the enzyme appears to be composed of two possibly identical subunits of 100 kD. The NR of K alvarezii was recognized by 10 out of 17 monoclonal antibodies raised against the NR from the red alga Porphyra yezoensis. Basal parts of the algal thallus had higher NR protein content, although the highest activity of NR has been located previously in the apical thallus parts, suggesting a post-translational regulation. The cellular expression of NR exhibits a daily rhythm. In extracts of algae grown under either constant light or a light:dark cycle, staining with antibodies NR 6 and NR 10 showed that the amount of protein varied by a factor of about 2, with the maximum occurring in the early day phase.

  • 231.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Trace elements and radionuclides in edible plants.2008In: Trace elements as contaminants and nutrients: consequences to ecosystems and human health.(, Wiley, New Jersey , 2008, p. 121-136Chapter in book (Other academic)
  • 232.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Växter i askvägbeläggning2007Report (Other academic)
  • 233.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Dabrowska, Beata
    Stockholm University, Faculty of Science, Department of Botany.
    INFLUENCE OF NUTRIENT LEVEL ON METHYLMERCURY CONTENT IN WATER SPINACH2010In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 29, no 8, p. 1735-1739Article in journal (Refereed)
    Abstract [en]

    Widely consumed vegetables are often cultivated in sewage waters with high nutrient levels. They can contain high levels of methylmercury (MeHg), because they can form MeHg from inorganic Hg in their young shoots. We determined whether the MeHg uptake and the MeHg formation in the shoots of water spinach (Ipomoea aquatica) were affected by the presence of a high nutrient level in the growth medium. Water spinach shoots were rooted and pretreated in growth medium containing 7% (low) or 70% (high) Hoagland nutrient solution; thereafter, the plants were treated with either 0.02 mu M MeHg or 0.2 mu M HgCl2 for 3 d. Half the plants were then analyzed for total Hg and MeHg. The remaining plants were transferred to mercury-free medium with low or high nutrient levels and posttreated for 3 clays before analysis of total Hg and MeHg in order to measure MeHg formation in the absence of external Hg. The results indicate that nutrient level did not influence MeHg uptake, but that a high nutrient level reduced the distribution of MeHg to the shoots 2.7-fold versus low nutrient level. After treatment with HgCl2, MeHg was found in roots and new shoots but not in old shoots. The MeHg:total-Hg ratio was higher in new shoots than in roots, being 13 times higher at high versus low nutrient levels. Thus, MeHg formation was the same in new shoots independent of inorganic Hg concentration, since the total Hg level decreased at a high nutrient level.

  • 234.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Influence of Si on Cd in wheat.2008In: Scientific workshop on Contaminants and nutrients: availability, accumulation/exclusion and plant-microbia-soil interactions, COST Action 859 workshop, Smolenice, May 2008, 2008, p. 1-Conference paper (Other (popular science, discussion, etc.))
  • 235.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Rhizosphere interaction at Cd uptake by various wheat cultivars2007In: Scientific workshop on Phytotechnologies to promote sustainable land use and improve food safety, COST Action 859 workshop, Vilnius, June 2007, 2007Conference paper (Other (popular science, discussion, etc.))
  • 236.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Rhizosphere interaction at Cd uptake by various wheat cultivars2007In: Abstract. Rhizosphere 2 Int. Conference, Montpellier, August 2007., 2007Conference paper (Other (popular science, discussion, etc.))
  • 237.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Role of rhizosphere mechanisms in Cd uptake by various wheat cultivars2008In: Plant and Soil, Vol. 312, p. 195-205Article in journal (Refereed)
  • 238.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Malm, Torleif
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Heavy metal transfer from composted macroalgae to crops2007In: European journal of Agronomy, Vol. 26, p. 257-265Article in journal (Refereed)
  • 239.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Neuschütz, Clara
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Göthberg, Agneta
    Department of Applied Environmental Science (ITM).
    Nyquist, Johanna
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Dabrowska, Beata
    Stockholm University, Faculty of Science, Department of Botany. Växtfysiologi.
    Phytoremediation and metal uptake in food plants2007In: ECO-TECH 2007, 2007, p. 513-522Conference paper (Other academic)
    Abstract [en]

    This paper reviews some of our resent findings on metal uptake in phytotechnology and food plants. The Cd concentration in wheat grains can be decreased by pytoextraction by Salix prior to wheat cultivation. Water spinach commonly grown in nutrient rich waste water are able to form methyl-Hg in new leaves, but high nutrient level in cultivation medium decreases the metal concentration in the plant. Wetland plants grown on mine tailings are able to decrease the formation of acid mine drainage from the tailings. Submerged plants can increase the retention of metals in wetlands treating metal polluted water, but the efficiency depends on the quality of the inlet water. Plants can be used to prevent leakage of metals and nutrients from dry covers containing sewage sludge on mine tailing impoundments. If the sealing layer below the cover layer consists of fly ash root penetration can be prevented while if it contains a mixture of sewage sludge and fly ash roots will grow into the sealing layer. Macro algae as fertilizers in agriculture increase the biomass production but also transfer Cd to the crop. Therefore, algae should be used in production of non food crops, however, not suitable for hemp cultivation.

  • 240.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Wang, Yaodong
    Stockholm University, Faculty of Science, Department of Botany.
    Neuschütz, Clara
    Absence of Hg transpiration by shoot after Hg uptake by roots of six terrestrial plant species2005In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 134, no 2, p. 201-208Article in journal (Refereed)
    Abstract [en]

    In this paper we investigated if, and to what extent, six different plant species accumulate, translocate and emit mercury (Hg) into the air. The Hg uptake by roots, distribution of Hg to the shoot and release of Hg via shoots of garden pea, spring wheat, sugar beet, oil-seed rape, white clover and willow were investigated in a transpiration chamber. The airborne Hg was trapped in a Hopcalite trap or a gold trap. Traps and plant materials were analysed for content of Hg by CVAAS. The results show that all plant species were able to take up Hg to a large extent from a nutrient solution containing 200 μg L−1 Hg. However, the Hg translocation to the shoot was low (0.17–2.5%) and the Hg that reached the leaves was trapped and no release of the absorbed Hg to the air was detected.

    Mercury translocation to shoots was low.

  • 241. Groeninckx, Inge
    et al.
    Dessein, Steven
    Ochoterena, Helga
    Persson, Claes
    Motley, Timothy
    Kårehed, Jesper
    Stockholm University, Faculty of Science, Department of Botany. Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum.
    Bremer, Birgitta
    Stockholm University, Faculty of Science, The Bergius Botanical Garden Museum. Stockholm University, Faculty of Science, Department of Botany.
    Huysmans, Suzy
    Smets, Erik
    Phylogeny of the herbaceous tribe Spermacoceae (Rubiaceae) based on plastid DNA data2009In: Annals of the Missouri Botanical Garden, ISSN 0026-6493, E-ISSN 2162-4372, Vol. 96, p. 109-132Article in journal (Refereed)
    Abstract [en]

    In its current circumscription, the herbaceous tribe Spermacoceae s.l. (Rubiaceae, Rubioideae) unites the former tribes Spermacoceae s. str., Manettieae, and the Hedyotis–Oldenlandia group. Within Spermacoceae, and particularly within the Hedyotis–Oldenlandia group, the generic delimitations are problematic. Up until now, molecular studies have focused on specific taxonomic problems within the tribe. This study is the first to address phylogenetic relationships within Spermacoceae from a tribal perspective. Sequences of three plastid markers (atpB-rbcL, rps16, and trnL-trnF) were analyzed separately as well as combined using parsimony and Bayesian approaches. Our results support the expanded tribe Spermacoceae as monophyletic. The former tribe Spermacoceae s. str. forms a monophyletic clade nested within the Hedyotis–Oldenlandia group. Several genera formerly recognized within the Hedyotis–Oldenlandia group are supported as monophyletic (Amphiasma Bremek., Arcytophyllum Willd. ex Schult. & Schult. f., Dentella J. R. Forst. & G. Forst., Kadua Cham. & Schltdl., and Phylohydrax Puff), while others appear to be paraphyletic (e.g., Agathisanthemum Klotzsch), biphyletic (Kohautia Cham. & Schltdl.), or polyphyletic (Hedyotis L. and Oldenlandia L. sensu Bremekamp). Morphological investigations of the taxa are ongoing in order to find support for the many new clades and relationships detected. This study provides a phylogenetic hypothesis with broad sampling across the major lineages of Spermacoceae that can be used to guide future species-level and generic studies.

  • 242. Guerriero, Gea
    et al.
    Avino, Mariano
    Zhou, Qi
    Fugelstad, Johanna
    Clergeot, Pierre-Henri
    Stockholm University, Faculty of Science, Department of Botany.
    Bulone, Vincent
    Chitin Synthases from Saprolegnia Are Involved in Tip Growth and Represent a Potential Target for Anti-Oomycete Drugs2010In: PLoS Pathogens, ISSN 1553-7366, Vol. 6, no 8, p. e1001070-Article in journal (Refereed)
    Abstract [en]

    Oomycetes represent some of the most devastating plant and animal pathogens. Typical examples are Phytophthora infestans, which causes potato and tomato late blight, and Saprolegnia parasitica, responsible for fish diseases. Despite the economical and environmental importance of oomycete diseases, their control is difficult, particularly in the aquaculture industry. Carbohydrate synthases are vital for hyphal growth and represent interesting targets for tackling the pathogens. The existence of 2 different chitin synthase genes (SmChs1 and SmChs2) in Saprolegnia monoica was demonstrated using bioinformatics and molecular biology approaches. The function of SmCHS2 was unequivocally demonstrated by showing its catalytic activity in vitro after expression in Pichia pastoris. The recombinant SmCHS1 protein did not exhibit any activity in vitro, suggesting that it requires other partners or effectors to be active, or that it is involved in a different process than chitin biosynthesis. Both proteins contained N-terminal Microtubule Interacting and Trafficking domains, which have never been reported in any other known carbohydrate synthases. These domains are involved in protein recycling by endocytosis. Enzyme kinetics revealed that Saprolegnia chitin synthases are competitively inhibited by nikkomycin Z and quantitative PCR showed that their expression is higher in presence of the inhibitor. The use of nikkomycin Z combined with microscopy showed that chitin synthases are active essentially at the hyphal tips, which burst in the presence of the inhibitor, leading to cell death. S. parasitica was more sensitive to nikkomycin Z than S. monoica. In conclusion, chitin synthases with species-specific characteristics are involved in tip growth in Saprolegnia species and chitin is vital for the micro-organisms despite its very low abundance in the cell walls. Chitin is most likely synthesized transiently at the apex of the cells before cellulose, the major cell wall component in oomycetes. Our results provide important fundamental information on cell wall biogenesis in economically important species, and demonstrate the potential of targeting oomycete chitin synthases for disease control.

  • 243. Gullström, Martin
    et al.
    Lundén, Bengt
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bodin, Maria
    Kangwe, Juma W.
    Stockholm University, Faculty of Science, Department of Botany.
    Öhman, Marcus C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mtolera, Matern S. P.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Assessment of vegetation changes in seagrass communities of tropical Chwaka Bay (Zanzibar) using satellite remote sensing2006In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 67, no 3, p. 399-408Article in journal (Refereed)
    Abstract [en]

    Spatial and temporal dynamics of submerged aquatic vegetation (SAV) cover were studied in the relatively pristine and seagrass-dominated area of Chwaka Bay, Zanzibar (Tanzania) by using satellite remote sensing. Through complementary field work the potential of the technique for change detection was verified. The general changes in SAV cover were examined using Landsat images from 1986, 1987, 1998, 2001 and 2003. Two of these images, from 1987 (Landsat TM) and 2003 (Landsat ETM+), were specifically analysed to create a map of the change in SAV cover. Overall, the general distribution of SAV stayed fairly stable over the period investigated, but the result also showed regions where significant alterations, both losses and gains, had occurred between the two years. Based on our findings and anecdotal information from local fishermen and seaweed farmers potential causative factors are discussed. It was concluded that a repeated mapping with satellite remote sensing is a suitable tool to monitor changes of seagrass and seaweed distribution in shallow tropical environments.

  • 244.
    Gunnarsson, Karl
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Berglund, Anders
    The brown alga Fucus radicans suffers heavy grazing by the isopod Idotea baltica2012In: Marine Biology Research, ISSN 1745-1000, E-ISSN 1745-1019, Vol. 8, no 1, p. 87-89Article in journal (Refereed)
    Abstract [en]

    In 2005, a perennial brown alga in the Baltic Sea was recognized as a species on its own and named Fucus radicans (Bergstrom & Kautsky). This fucoid forms belts like does bladderwrack, Fucus vesiculosus L., its closest relative. These seaweeds are inhabited by many small animals, for example the isopod Idotea baltica (Pallas, 1772). Along the Swedish coasts of the Baltic Sea, F. radicans is found primarily in the northern half, i.e. the Gulf of Bothnia. I. baltica is common in the seaweeds of the southern half of the Baltic Sea, the Baltic proper, but is uncommon further north in the Bothnian Sea and nonexistent in the northernmost Bay of Bothnia. I. baltica is well able to graze down seaweeds in an area. In a field experiment, we here show that I. baltica, given a choice between the two algae species, prefers to graze on F. radicans rather than on F. vesiculosus. This may be one of the most important factors restricting F. radicans to the northern areas of the Baltic, where I. baltica is uncommon.

  • 245. Habayeb, Mazen S
    et al.
    Ekengren, Sophia K
    Stockholm University, Faculty of Science, Department of Botany.
    Hultmark, Dan
    Nora virus, a persistent virus in Drosophila, defines a new picorna-like virus family.2007In: J Gen Virol, ISSN 0022-1317, Vol. 88, no Pt 12, p. 3493-Article in journal (Refereed)
  • 246. Haglund, Peter
    et al.
    Malmvärn, Anna
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Bergek, Sture
    Bignert, Anders
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Nakano, Takeshi
    Wiberg, Karin
    Asplund, Lillemor
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brominated dibenzo-p-dioxins - A new class of marine toxins?2007In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 41, no 9, p. 3069-3074Article in journal (Refereed)
    Abstract [en]

    Levels of polybrominated dibenzo-p-dioxins (PBDDs) were measured in marine fish, mussels, and shellfish. PBDDs were nondetectable in samples from freshwater environments, and their levels were successively higher in samples from the marine environments of the Bothnian Bay and Bothnian Sea, the West Coast of Sweden, and the Baltic Proper. In Baltic Proper littoral fish the levels of PBDDs generally exceeded those of their chlorinated analogues (PCDDs). This is alarming as some Baltic fish species already are contaminated by chlorinated dioxins to such an extent that they cannot be sold on the European market. By comparing spatial trends in PBDD and PCDD distributions, and PBDD patterns in fish, mussels, and algae, we show that the PBDDs are probably produced naturally, and we propose a route for their biosynthesis. We further show that the levels of PBDDs are high (ng/g wet weight) in mussels, and that the levels increase over time. Finally, we discuss the possibility that the PBDDs have adverse biological effects, and that the levels are increasing as a result of global warming and eutrophication.

  • 247.
    Hamback, Per A
    Stockholm University, Faculty of Science, Department of Botany.
    Density-dependent processes in leaf beetles feeding on purple loosestrife: aggregative behaviour affecting individual growth rates2010In: Bulletin of entomological research, ISSN 0007-4853, E-ISSN 1475-2670, Vol. 100, no 5, p. 605-611Article in journal (Refereed)
    Abstract [en]

    Aggregative responses are commonly observed in insects, including chrysomelids, affecting both individual and population growth rates. In two closely related chrysomelid beetles (Galerucella calmariensis and G. pusilla) feeding on purple loosestrife (Lythrum salicaria), recent studies suggest that male-produced pheromones may cause both inter- and intraspecific attraction. This paper further examines the causes and consequences of feeding aggregations in these species. Olfactometer studies confirm previous findings, showing cross-species attraction to damaged plants, but suggest that also damaged induced plant volatiles may be involved. In addition, the studies suggest that the cross-species attraction observed in previous studies have asymmetric effects on the two beetles. Galerucella pusilla was more attracted to damage by G. calmariensis than to damage by conspecifics. Laboratory and field data suggest that feeding aggregations in these species increase pupal mass, at least at low to intermediate larval densities. This positive feedback may have important consequences for the spatiotemporal dynamics and as a consequence on the role of the two chrysomelid beetles on biological control of purple loosestrife.

  • 248.
    Hamback, Peter A.
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Björkman, Maria
    Stockholm University, Faculty of Science, Department of Botany.
    Hopkins, Richard J.
    Patch size effects are more important than genetic diversity for plant-herbivore interactions in Brassica crops2010In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 35, no 3, p. 299-306Article in journal (Refereed)
    Abstract [en]

    2. This paper examines the effect of intraspecific genetic diversity within Brassica fields on two Brassica specialists, cabbage root fly, and diamondback moth, and on a parasitoid attacking diamondback moths. Genetic diversity was manipulated both in a replacement and an additive design. 3. Both herbivore densities and parasitism rates were higher in smaller plots, with limited responses to increased within-plot diversity. All species showed variable densities across genotypes, and preference hierarchies were species specific. 4. Responses to plot size in root flies scaled with the diameter-to-area ratio, suggesting that patch detectability affected local density, whereas responses by diamondback moths and parasitoids deviated from this ratio. These species differences could be traced to differences in the residence time within patches, where diamondback moths typically spend longer and more variable time periods in patches than root flies. 5. The lack of response to genetic diversity by both herbivores suggests that egg-laying rates are affected by decisions on the plant and not by attraction from a distance, neither to the plant itself nor the patch. Patterns of differential attack may then be due to different acceptability for studied genotypes. 6. Future theories on insect responses to spatial heterogeneity should focus on species traits and how traits interact with information landscapes in the field.

  • 249.
    Hambäck, Peter
    Stockholm University, Faculty of Science, Department of Botany.
    A green or a prickly world?2010In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 327, p. 1583-1584Article in journal (Refereed)
    Abstract [en]

    Is the world a green place where plant biomass abounds for herbivores to devour, or a prickly place where herbivores struggle to locate the few edible plant pieces? The answer to this question has crucial consequences for broad ecological and evolutionary questions. On page 1642 of this issue, Mooney et al. (1) show how evolutionary trade-offs among plant traits affect responses to herbivores and higher trophic levels.

  • 250.
    Hambäck, Peter
    Stockholm University, Faculty of Science, Department of Botany.
    Flying the nest: Effects of cormorants on island communities2011Other (Other (popular science, discussion, etc.))
2345678 201 - 250 of 818
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