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  • 1
    Electronic Resource
    Electronic Resource
    Contrasting patterns of photosynthetic acclimation and photoinhibition in two evergreen herbs from a winter deciduous forest (1996)
    Springer
    Oecologia 107 (1996), S. 446-455 
    Details
    ISSN: 1432-1939
    Keywords: Forest understory ; Photosynthetic acclimation ; Photoinhibition ; Leaf longevity ; Nitrogen allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the microclimate within an Oak-Hickory forest and photosynthetic characters of two resident evergreen herbs with contrasting leaf phenologies was investigated on a monthly basis for 1 full year. Heuchera americana has leaf flushes in the spring and fall, with average leaf life spans of 6–7 months. Hexastylis arifolia produces a single cohort of leaves each spring with a leaf life span of 12–13 months. We predicted that among evergreen plants inhabiting a seasonal habitat, a species for which the frequency of leaf turnover is greater than the frequency of seasonal extremes would have a greater annual range in photosynthetic capacity than a species that only produced a single flush of leaves during the year. Photosynthetic parameters, including apparent quantum yield, maximum photosynthetic capacity (Pmax), temperature of maximum photosynthesis, photochemical efficiency of PSII and leaf nitrogen (N) and chlorophyll concentrations, were periodically measured under laboratory conditions in leaves sampled from natural populations of both species. Mature leaves of both species acclimated to changing understory conditions with the mean seasonal differences being significantly greater for Heuchera than for Hexastylis. Area based maximum photosynthetic rates at 25°C were approximately 250% and 100% greater in winter leaves than summer leaves for Heuchera and Hexastylis respectively. Nitrogen concentrations were highest in winter leaves. Chlorophyll concentrations were highest in summer leaves. Low Pmax/N values for these species suggest preferential allocation of leaf nitrogen into non-photosynthetic pools and/or light-harvesting function at the expense of photosynthetic enzymes and electron transport components. Despite the increase in photosynthetic capacity, there was evidence of chronic winter photoinhibition in Hexastylis, but not in Heuchera. Among these ecologically similar species, there appears to be a trade-off between the frequency of leaf production and the balance of photosynthetic acclimation and photoinhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333934
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthetic responses of Miconia species to canopy openings in a lowland tropical rainforest (1993)
    Springer
    Oecologia 94 (1993), S. 49-56 
    Details
    ISSN: 1432-1939
    Keywords: Miconia ; Tropics ; Rainforest ; Photosynthetic acclimation ; Canopy gaps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the photosynthetic acclimation of three tropical species of Miconia to canopy openings in a Costa Rican rainforest. The response of photosynthesis to canopy opening was very similar in Miconia affinis, M. gracilis, and M. nervosa, despite differences in growth form (trees and shrubs) and local distributions of plants (understory and gap). Four months after the canopy was opened by a treefall, photosynthetic capacity in all three species had approximately doubled from closed canopy levels. There were no obvious signs of high light damage after treefall but acclimation to the gap environment was not immediate. Two weeks after treefall, Amax, stomatal conductance, apprarent quantum efficiency, and dark respiration rates had not changed significantly from understory values. The production of new leaves appears to be an important component of light acclimation in these species. The only variables to differ significantly among species were stomatal conductance at Amax and the light level at which assimilation was saturated. M. affinis had a higher stomatal conductance which may reduce its water use efficiency in gap environments. Photosynthesis in the more shade-tolerant M. gracilis saturated at lower light levels than in the other two species. Individual plant light environments were assessed after treefall with canopy photography but they explained only a small fraction of plant variation in most measures of photosynthesis and growth. In conclusion, we speculate that species differences in local distribution and in light requirements for reproduction may be more strongly related to species differences in carbon allocation than in carbon assimilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317300
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  • 3
    Electronic Resource
    Electronic Resource
    The seasonal distribution of anionic binding sites in the basement membrane of the kidney glomerulus of the winter flounder Pseudopleuronectes americanus (1983)
    Springer
    Cell & tissue research 234 (1983), S. 271-277 
    Details
    ISSN: 1432-0878
    Keywords: Anionic binding sites ; Glomerular basement membrane ; Cationized ferritin ; Winter flounder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The blood of the winter flounder, Pseudopleuronectes americanus, contains small (3000–8000 daltons) anionic peptides (pI 〈 5) with antifreeze properties. They are present only in the winter and are retained in the circulatory system even though inulin and polyethylene glycol, of comparable molecular size, are filtered by the glomerular kidney. Electron micrographs of flounder-kidney glomeruli revealed that their structure is similar to that of mammals and that cationized ferritin binds at regular 60 nm intervals in the lamina rara interna of the basement membrane as it does in mammals. The binding of cationized ferritin, in conjunction with the previous observation that cationized antifreeze peptides exhibit a marked increase in renal clearance, suggests that an anionic repulsion barrier within the glomerular basement membrane of the winter flounder is responsible for the conservation of the anionic antifreeze peptide molecules found in their blood during the winter. This barrier also appears to be present in summer specimens of the flounder which lack the antifreeze peptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213768
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The secondary lamellae of the gills of cold water (high latitude) teleosts (1980)
    Springer
    Cell & tissue research 213 (1980), S. 361-367 
    Details
    ISSN: 1432-0878
    Keywords: Gills ; Chloride cells ; Mucous cells ; Winter flounder ; Secondary lamellae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the secondary lamellae of gills was examined in two cold-water marine teleosts, the winter flounder, Pseudopleuronectes americanus, and the antarctic cod, Trematomus borchgrevinki. In both species the overall lamellar fine structure is similar to that of other marine teleosts. The major variations in cellular organization involve the distribution of both the “chloride cells” and the mucous cells on the secondary lamellae of P. americanus. At winter water temperatures of +2.5° C, significantly more chloride and mucous cells are present than in summer with water temperatures of +15.2° C. Both cell types are routinely present throughout the length of a secondary lamella as far as the lamellar tip. The chloride cells on the secondary lamellae are always situated in the inner layer of epithelium deep to the outer pavement cells. T. borchgrevinki shows no apparent difference in the distribution of mucous cells either at its normal water temperature of -1.9° C or at a temperature of +4° C, the upper limit of its thermal tolerance to which some specimens were adapted in the aquarium. Chloride cells were never observed on the secondary lamellae of T. borchgrevinki. This suggests that low environmental water temperatures may be related to the distribution of mucous cells and chloride cells on the secondary lamella of the teleost gill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237884
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    Paper (German National Licenses)
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