2 results for Ascaso, Carmen

  • Ecology of endolithic lichens colonizing granite in continental Antarctica

    de los Ríos, Asunción; Wierzchos, Jacek; Sancho, Leopoldo G.; Green, T.G. Allan; Ascaso, Carmen (2005)

    Journal article
    University of Waikato

    In this study, the symbiont cells of several endolithic lichens colonizing granite in continental Antarctica and the relationships they have with the abiotic environment were analyzed in situ, in order to characterize the microecosystems integrating these lichens, from a microecological perspective. Mycobiont and photobiont cells, the majority classified as living by fluorescent vitality testing, were observed distributed through the fissures of the granite. The fact that extracellular polymeric substances were commonly observed close to these cells and the features of these compounds, suggest a certain protective role for these substances against the harsh environmental conditions. Different chemical, physical and biological relationships take place within the endolithic biofilms where the lichens are found, possibly affecting the survival and distribution of these organisms. The alteration of bedrock minerals and synthesis of biominerals in the proximity of these lichens give rise to different chemical microenvironments and suggest their participation in mineral nutrient cycling.

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  • Anatomical, morphological and ecophysiological strategies in Placopsis pycnotheca (lichenized fungi, Ascomycota) allowing rapid colonization of recently deglaciated soils

    de los Ríos, Asunción; Raggio, José; Pérez-Ortega, Sergio; Vivas, Mercedes; Pintado, Ana; Green, T.G. Allan; Ascaso, Carmen; Sancho, Leopoldo G. (2011)

    Journal article
    University of Waikato

    The green algal lichen Placopsis pycnotheca was identified at Pia and Marinelli glaciers (Isla Grande of Tierra de Fuego, Chile) as a primary colonizer of bare soil in areas close to the front of the glacier or around small ponds created after glacier retreatment. Electron microscopy study showed that P. pycnotheca formed a thick hypothallus within which hyphae and their extracellular polymeric substances bind numerous soil particles. This structure augments water holding and soil stabilization capacities and constitutes an early stage in soil crust development. In addition, numerous cephalodia are formed within the hypothallus and subsequently develop upwards towards the thallus surface, sometimes before the formation of squamules with green algae. These anatomical and morphological strategies together with physiological properties such as the long photosynthetic activity period (measured in the laboratory) help explain its pioneering role as a colonizer and its apparently high growth rate.

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