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The Science of Nature - 相似文献
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Manuela Baumgarten Christian Huber Patrick Büker Hans-Peter Dietrich Christian Heerdt Rainer Matyssek 《Environmental pollution (Barking, Essex : 1987)》2009,157(7):2091-2107
Exposure and flux-based indices of O3 risk were compared, at 19 forest locations across Bavaria in southern Germany from 2002 to 2005; leaf symptoms on mature beech trees found at these locations were also examined for O3 injury. O3 flux modelling was performed using continuously recorded O3 concentrations in combination with meteorological and soil moisture data collected from Level II forest sites. O3 measurements at nearby rural open-field sites proved appropriate as surrogates in cases where O3 data were lacking at forest sites (with altitude-dependent average differences of about 10% between O3 concentrations). Operational thresholds of biomass loss for both O3 indices were exceeded at the majority of the forest locations, suggesting similar risk under long-term average climate conditions. However, exposure-based indices estimated higher O3 risk during dry years as compared to the flux-based approach. In comparison, minor O3-like leaf injury symptoms were detected only at a few of the forest sites investigated. Relationships between flux-based risk thresholds and tree response need to be established for mature forest stands for validation of predicted growth reductions under the prevailing O3 regimes. 相似文献
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The optical properties (reflectance and transmittance) of selected leaves from a tropical mountain rainforest in southern Ecuador are determined to parametrize optical traits of plant functional types (PFT) of a state of the art land model (Community Land Model, CLM). 46 spatially dominating species are selected from 4 different forest types, the subpáramo and a succession stage of pasture areas representing ecologically predefined functional types within the study area. Measurements are conducted under a standardized experimental setup with a field spectrometer covering the radiation between 305 and 1305 nm. The results of the optical properties of all species are checked for similarity by cluster analysis and are compared to the composition of species of the predefined PFTs. Furthermore the results are compared to other studies, the default values for the globally defined PFT of tropical evergreen trees in the CLM and another forest growth model operated in the same study area. The results show that the clusters aggregated by the reflectance, transmittance or combined properties do not represent the predefined PFTs. The values of the other studies suggest a reassessment of the experimental setup for the transmittance measurements. Nevertheless, new reflectance values for the regionalized PFTs can be determined. The optical values differ from the CLM-PFT of tropical evergreen trees, and new values for the reflectance are recommended. 相似文献
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The ormer, Haliotis tuberculata Linnaeus, 1758, is able to accumulate paralytic shellfish toxins (PST) in the foot side skin. Epidermal and secretory cells are described
separately for the pedal side and sole epithelia, as notable differences have been observed. Melanin and photosynthetic pigment
granules in the epidermal cells of the foot side epithelium give this skin its appearance and characteristic color. This epidermis
also has abundant secretory cells containing at least three kinds of secretory granules. Conversely, the epidermal cells of
foot sole epithelium do not have pigment granules, and the secretory cells are mostly subepithelial. Immunohistochemical reaction
against PST (saxitoxin and its derivatives) showed that the toxins are located in specific cells of the foot side epithelium,
which are distinct from the epidermal cells. Immunofluorescence also reveals toxins throughout many areas of the mucilage
covering the epithelium, suggesting the secretory nature of the cells containing the toxins. These results do not show any
apparent relationship between melanin or photosynthetic pigment granules and PST content. PST were not detected in the foot
sole epithelium either immunohistochemically or by HPLC. Considering the toxic characteristics of ormers described in previous
studies and the results presented here, the authors discuss the role of toxins retained or produced by the foot side epithelium
Received: 25 July 2000 / Accepted: 7 November 2000 相似文献