Recursos de colección

Estudo Geral - Universidade de Coimbra (19.630 recursos)

ESTUDO GERAL é a designação do repositório digital da produção científica da Universidade de Coimbra, com o objectivo de divulgar conteúdos digitais de natureza científica de autores ligados à Universidade de Coimbra. A sua criação insere-se no movimento de Acesso Livre à Literatura científica (Open Access), ao qual o Conselho de Reitores das Universidades Portuguesas aderiu em 2006 e que a Universidade de Coimbra subscreveu. À semelhança de outras grandes universidades nacionais e internacionais, a UC tem o maior interesse em aumentar a sua presença na rede informática mundial, sendo cada vez mais - e também por essa via - um emissor de conhecimento e cultura.

FCTUC Botânica - Artigos em Revistas Internacionais

Mostrando recursos 1 - 20 de 55

  1. Identification of selected seaweed polysaccharides (phycocolloids) by vibrational spectroscopy (FTIR-ATR and FT-Raman)

    Pereira, Leonel; Amado, Ana M.; Critchley, Alan T.; Velde, Fred van de; Ribeiro-Claro, Paulo J. A.

  2. Improvement of plant growth and nickel uptake by nickel resistant-plant-growth promoting bacteria

    Ma, Ying; Rajkumar, Mani; Freitas, Helena

  3. Preparation, characterization, bioactive and metal uptake studies of alginate/phosphorylated chitin blend films

    Jayakumar, R.; Rajkumar, M.; Freitas, H.; Selvamurugan, N.; Nair, S.V.; Furuike, T.; Tamura, H.

  4. Ecophysiological tolerance of duckweeds exposed to copper

    Kanoun-Boulé, Myriam; Vicente, Joaquim A. F.; Nabais, Cristina; Prasad, M. N. V.; Freitas, Helena

  5. Above-ground biomass and productivity in the Montado: From herbaceous to shrub dominated communities

    Castro, H.; Freitas, H.

  6. Isolation and characterization of Ni mobilizing PGPB from serpentine soils and their potential in promoting plant growth and Ni accumulation by Brassica spp.

    Ma, Ying; Rajkumar, Mani; Freitas, Helena

  7. Micropropagation of Eucalyptus nitens maiden (Shining gum)

    Gomes, Filomena; Canhoto, Jorge
    Summary Eucalyptus nitens Maiden (shining gum) is a frost-tolerant species of Eucalyptus that can be used as an alternative species to Eucalyptus globulus in some regions of Portugal where winter temperatures are too low. Seedlings and 1-yr-old shoot tips and nodes were used for micropropagation of E. nitens. The best multiplication rate (2.25) was obtained when seedling shoots (<15 mm) were cultured on a medium containing the major nutrients (at half-strength) and minor elements of Murashige and Skoog (1962) medium, the organics of De Fossard medium (De Fossard et al., 1974) and a combination of benzyladenine (0.9 µM) and 1-naphthaleneacetic...

  8. Fungal biomass and decomposition in Spartina maritima leaves in the Mondego salt marsh (Portugal)

    Castro, Paula; Freitas, Helena
    Spartina maritima (Curtis) Fernald is a dominant species in the Mondego salt marsh on the western coast of Portugal, and it plays a significant role in estuarine productivity. In this work, leaf litter production dynamics and fungal importance for leaf decomposition processes in Spartina maritima were studied. Leaf fall was highly seasonal, being significantly higher during dry months. It ranged from 42 g m-2 in June to less than 6 g m-2 during the winter. Fungal biomass, measured as ergosterol content, did not differ significantly between standing-decaying leaves and naturally detached leaves. Fungal biomass increased in wet months, with a...

  9. Invasive plants and their escape from root herbivory: a worldwide comparison of the root-feeding nematode communities of the dune grass Ammophila arenaria in natural and introduced ranges

    Putten, W. H. van der; Yeates, G. W.; Duyts, H.; Reis, C. Schreck.; Karssen, G.
    Invasive plants generally have fewer aboveground pathogens and viruses in their introduced range than in their natural range, and they also have fewer pathogens than do similar plant species native to the introduced range. However, although plant abundance is strongly controlled by root herbivores and soil pathogens, there is very little knowledge on how invasive plants escape from belowground enemies. We therefore investigated if the general pattern for aboveground pathogens also applies to root-feeding nematodes and used the natural foredune grass Ammophila arenariaas a model. In the late 1800s, the European A. arenariawas introduced into southeast Australia (Tasmania), New Zealand,...

  10. Diversity of AMF associated with Ammophila arenaria ssp. arundinacea in Portuguese sand dunes

    Rodríguez-Echeverría, Susana; Freitas, Helena
    Abstract Dune vegetation is essential for the formation and preservation of sand dunes and the protection of the coast line. Coastal sand dunes are harsh environments where arbuscular mycorrhizal fungi (AMF) play an important role in promoting plant establishment and growth. We present a study of the diversity of AMF associated with A. arenaria ssp. arundinacea in two locations of the Portuguese coast under a Mediterranean climate. These two locations were selected to compare a well-preserved dune system from a protected area with a degraded dune system from a public beach. AMF diversity was assessed mainly by cloning and sequencing...

  11. Effects of nickel hyperaccumulation in Alyssum pintodasilvae on model arthropods representatives of two trophic levels

    Gonçalves, M.; Gonçalves, Susana; Portugal, António; Silva, Sandra; Sousa, José; Freitas, Helena
    Abstract An experimental assessment of the defence hypothesis of nickel (Ni) hyperaccumulation in Alyssum was lacking. Also, to date no study had investigated the effects of hyperaccumulator litter on a detritivore species. We performed several experiments with model arthropods representatives of two trophic levels: Tribolium castaneum (herbivore) and Porcellio dilatatus (detritivore). In no-choice trials using artificial food disks with different Ni concentrations, T. castaneum fed significantly less as Ni concentration increased and totally rejected disks with the highest Ni concentration. In choice tests, insects preferred disks without Ni. In the no-choice experiment, mortality was low and did not differ significantly...

  12. Soil recovery after removal of the N2-fixing invasive Acacia longifolia : consequences for ecosystem restoration

    Marchante, Elizabete; Kjøller, Annelise; Struwe, Sten; Freitas, Helena
    Abstract Invasion by Acacia longifolia alters soil characteristics and processes. The present study was conducted to determine if the changes in soil C and N pools and processes induced by A. longifolia persist after its removal, at the São Jacinto Dunes Nature Reserve (Portugal). Some areas had been invaded for a long time (>20 years) and others more recently (<10 years). For each type of invasion, (i.e., long-invaded and recently invaded), three treatments were used: (1) A. longifolia left intact; (2) A. longifolia was removed; and (3) both A. longifolia and litter layer were removed. Soil samples were collected once...

  13. Ultrastructural study of the relationship between generative and vegetative cells inMagnolia ×soulangeana Soul.-Bod. pollen grains

    Dinis, A. M.; Mesquita, J. F.
    Summary InMagnolia ×soulangeana pollen grains the generative cell (GC) does not become totally free within the vegetative cell (VC), at least until the pollen tube emergence. Due to a deviation in its detachment process from the sporoderm, the opposing ends of the VC plasmalemma do not fuse themselves when the GC moves away from the intine. Consequently, the interplasmalemmic space surrounding the GC does not become isolated but rather maintains continuity with the sporoderm through a complex formation that we have called plasmalemmic cord. The real existence of this formation was confirmed through serial sectioning showing the plasmalemmic cord to...

  14. Evaluating the Madeiran wheat germplasm for aluminum resistance using aluminium-induced callose formation in root apices as a marker

    Santos, Teresa dos; laski, Jan; Carvalho, Miguel Pinheiro de; Taylor, Gregory; Vieira, Maria Clemente
    Abstract Aluminum (Al) resistance of 57 Madeiran wheat cultivars was evaluated using callose content in root tips and root elongation as markers. Al induced callose formation was a very sensitive indicator of Al damage detecting wide range of genotypic differences existing in the Madeiran wheat germplasm. A weak, yet positive correlation (R2=0.285, P<0.05) between callose content and root elongation was found.

  15. Effect and analysis of phenolic compounds during somatic embryogenesis induction in Feijoa sellowiana Berg

    Reis, E.; Batista, M. T.; Canhoto, J. M.
    Summary. The effect of phenolic compounds on somatic embryogenesis in Feijoa sellowiana was analysed. The results showed that caffeic acid (140–560 µM) significantly increased somatic embryogenesis induction compared with the control. The presence of phloridzin, even at lower concentrations (11.5 µM), or caffeic acid or phloroglucinol at concentrations greater than 140.0 and 197.5 µM, respectively, inhibited somatic embryo development beyond the globular stage. When somatic embryos were transferred to the germination medium, the highest rates of germination (81.9%) were obtained with embryos induced in the presence of phloroglucinol (79.0 µM). At all concentrations tested, somatic embryos induced in medium containing...

  16. Salicornia ramosissima population dynamics and tolerance of salinity

    Silva, Helena; Caldeira, Gustavo; Freitas, Helena
    Abstract Field and greenhouse studies have been conducted to clarify aspects of population dynamics and NaCl tolerance of Salicornia ramosissima J. Woods. Two populations, Varela and Verdemilho, were monitored in the field during two consecutive life cycles and aspects of their morphology and density were recorded monthly. In the laboratory seedlings were exposed to different salinity for 10 weeks and growth and mortality rate were recorded weekly. The growth of the populations differed significantly, possibly because of the different salinities of the two sampling sites and/or genetic adaptations of the two populations to the environmental conditions. The absence of a...

  17. Occurrence of Plant-Uncoupling Mitochondrial Protein (PUMP) in Diverse Organs and Tissues of Several Plants

    Ježek, Petr; Žácková, Markéta; Košarová, Jana; Rodrigues, Elsa T. S.; Madeira, Vítor M. C.; Vicente, Joaquim A. F.
    The presence of plant-uncoupling mitochondrial protein (PUMP), previously described by Vercesi et al. (1995), was screened in mitochondria of various organs or tissues of several plant species. This was done functionally, by monitoring purine nucleotide-sensitive linoleic acid-induced uncoupling, or by Western blots. The following findings were established: (1) PUMP was found in most of the higher plants tested; (2) since ATP inhibition of linoleic acid-induced membrane potential decrease varied, PUMP content might differ in different plant tissues, as observed with mitochondria from maize roots, maize seeds, spinach leaves, wheat shoots, carrot roots, cauliflower, broccoli, maize shoots, turnip root, and potato...

  18. Genetic diversity and differential in vitro responses to Ni in Cenococcum geophilum isolates from serpentine soils in Portugal

    Gonçalves, Susana; Portugal, António; Gonçalves, M.; Vieira, Rita; Martins-Loução, M.; Freitas, Helena
    Abstract Amplified fragment length polymorphism (AFLP) analysis was used to investigate the genetic diversity in isolates of the ectomycorrhizal fungus Cenococcum geophilum from serpentine and non-serpentine soils in Portugal. A high degree of genetic diversity was found among C. geophilum isolates; AFLP fingerprints showed that all the isolates were genetically distinct. We also assessed the in vitro Ni sensitivity in three serpentine isolates and one non-serpentine isolate. Only the non-serpentine isolate was significantly affected by the addition of Ni to the growth medium. At 30 µg g-1 Ni, radial growth rate and biomass accumulation decreased to 73.3 and 71.6% of...

  19. Belowground mutualists and the invasive ability of Acacia longifolia in coastal dunes of Portugal

    Rodríguez-Echeverría, Susana; Crisóstomo, João; Nabais, Cristina; Freitas, Helena
    The ability to form symbiotic associations with soil microorganisms and the consequences for plant growth were studied for three woody legumes grown in five different soils of a Portuguese coastal dune system. Seedlings of the invasive Acacia longifolia and the natives Ulex europaeus and Cytisus grandiflorus were planted in the five soil types in which at least one of these species appear in the studied coastal dune system. We found significant differences between the three woody legumes in the number of nodules produced, final plant biomass and shoot 15N content. The number of nodules produced by A. longifolia was more...

  20. Population studies and carrageenan properties of Chondracanthus teedei var. lusitanicus (Gigartinaceae, Rhodophyta)

    Pereira, Leonel; Mesquita, José F.
    Features of an intertidal population of Chondracanthus teedei var. lusitanicus, which occurs in sandy basins on rocky shores of part of the Portuguese coast (Buarcos, Figueira da Foz), were studied over one year. Biomass and plant size showed a small increase in early spring (April), a marked increase in early summer (June/July) and were at a minimum in late summer. There was generally more tetrasporophytes (4–32.5%) than female gametophytes (3–29%), which contrasts with other geographical regions where C. teedei populations have been studied, such as Brazil and France. However, non-fructified thalli predominated throughout the year. Phycocolloid extracts were compared for...

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