ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    EFFECTS OF UV-B RADIATION ON TERRESTRIAL AND AQUATIC PRIMARY PRODUCERS* (2002)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 33 (2002), S. 371-396 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Ozone depletion by anthropogenic gases has increased the atmospheric transmission of solar ultraviolet-B radiation (UV-B, 280-315 nm). Our understanding of the consequencences of enhanced UV-B levels on primary producers has grown dramatically over the past 20 years, but it has been hampered by how realistically experimental UV-B exposures mimic ozone-depletion scenarios. Overcoming these shortcomings will require sophisticated and creative approaches. Biological weighting functions and solar spectral irradiance estimates are critical in evaluating effects and require more attention. Whereas UV screening compounds in terrestrial and aquatic producers commonly increase with UV-B exposure, the implications, while potentially far reaching, are unclear. Photosynthesis is more sensitive to UV-B in phytoplankton than in terrestrial plants, probably owing to less effective screening in phytoplankton. Productivity of terrestrial plants is usually unaffected by enhanced UV-B, although reduced growth has been observed and may increase in magnitude over successive years. Aquatic productivity is often compromised by short-term exposures to enhanced UV-B, and long-term assessments are complicated by the dynamic nature of aquatic systems and by nonlinear responses. Recent work examining UV-B effects on multiple trophic levels suggests that outcomes will be diverse and difficult to predict. Such effects may lead to feedbacks on primary producers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ecolsys.33.010802.150434
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Effect of springtime solar ultraviolet-B radiation on growth of Colobanthus quitensis at Palmer Station, Antarctica (2002)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 8 (2002), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We examined the influence of solar ultraviolet-B radiation (UV-B; 280–315 nm) on the growth of Colobanthus quitensis plants by placing them under contrasting UV-B filters at Palmer Station, along the Antarctic Peninsula. The filters reduced diurnal biologically effective UV-B (UV-BBE) either by 83% (‘reduced UV-B’) or by 12% (‘near-ambient UV-B’) over the 63 day experiment (7 November 1998–8 January 1999). Ozone column depletion averaged 17% during the experiment. Relative growth and net assimilation rates of plants exposed to near-ambient UV-B were 30 and 20% lower, respectively, than those of plants exposed to reduced UV-B. The former plants produced 29% less total biomass, as a result of containing 54% less aboveground biomass. These reductions in aboveground biomass were mainly the result of a 45% reduction in shoot biomass, and a 31% reduction in reproductive biomass. Reductions in shoot biomass were owing to an 18% reduction in branch production by main shoots, while reductions in reproductive biomass were the result of a 19% reduction in individual capsule mass. Total plant leaf area was reduced by 19% under near-ambient UV-B, although total leaf biomass was unaffected because leaves had a greater specific leaf mass. The reduction in plant leaf area under near-ambient UV-B was attributable to: (1) production of 11% fewer leaves per main shoot system and plant, which resulted from an 18% reduction in branch production by main shoots. Leaf production per individual main shoot or branch was not affected; (2) shorter leaf longevity—main shoots contained 14% fewer green leaves at a given time; and (3) smaller individual leaves—leaf elongation rates were 14% slower and mature leaves were 13% shorter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2002.00539.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Response of cotton and sorghum to several levels of subambient solar UV-B radiation: a test of the saturation hypothesis (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 122 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Some have proposed that plant responses to above-ambient or supplemented levels of solar ultraviolet-B radiation (UV-B; 280–315 nm) are typically subtle because targets or receptors in plants become saturated. If true, in solar UV-B filter exclusion experiments we would expect that plant responses would level off or ‘saturate’ as doses approached ambient levels. To test this so-called ‘saturation hypothesis’ we examined the response of Gossypium hirsutum (cotton) and Sorghum bicolor (sorghum) to filter exclusions that provided five levels of biologically effective UV-B, ranging from 36 to 91% of ambient solar levels in Arizona, USA. UV-B dose had no effect on biomass production of either species. As UV-B dose increased or approached ambient, individual leaves of S. bicolor were smaller, but plants produced more tillers and leaves. In G. hirsutum, individual leaves as well as total plant leaf area were smaller, but plants produced more branches. Bulk concentrations of soluble UV-B absorbing compounds increased with UV-B dose in both species. Leaf epidermal UV-B transmittance, assessed with the chlorophyll fluorescence technique, declined with increasing UV-B dose, and was well correlated with bulk concentrations of soluble UV-B screening compounds. Bulk concentrations of insoluble or wall-bound UV-B absorbing compounds were not affected by UV-B dose. The intensity of UV-induced blue fluorescence from leaf surfaces was strongly correlated with bulk concentrations of wall-bound UV-B absorbing compounds, and this signal has the potential to provide a rapid, non-invasive method to estimate concentrations of these compounds, which are time-consuming to extract. While both species were responsive to solar UV-B, responses did not appear to become saturated as doses approached ambient levels. Rather, responses required a threshold dose of 〉70% of solar ambient UV-B levels before they became apparent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.2004.00411.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Photosynthetic temperature response of the Antarctic vascular plants Colobanthus quitensis and Deschampsia antarctica (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 106 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The photosynthetic temperature response of the Antarctic vascular plants Colobanthus quitensis and Deschampsia antarctica was examined by measuring whole-canopy CO2 gas exchange and chlorophyll (Chl) a fluorescence of plants growing near Palmer Station along the Antarctic Peninsula. Both species had negligible midday net photosynthetic rates (Pn) on warm, usually sunny, days (canopy air temperature [Tc]〉 20°C), but had relatively high Pn on cool days (Tc〈10°C). Laboratory measurements of light and temperature responses of Pn showed that high temperature, not visible irradiance, was responsible for depressions in Pn on warm sunny days. The optimal leaf temperatures (Tl) for Pn in C. quitensis and D. antarctica were 14 and 10°C, respectively. Both species had substantial positive Pn at 0°C Tl, which were 28 (C. quitensis) and 32% (D. antarctica) of their maximal Pn, and we estimate that their low-temperature compensation points occurred at −2°C Tl (C. quitensis) and −3°C (D. antarctica). Because of the strong warming trend along the peninsula over recent decades and predictions that this will continue, we were particularly interested in the mechanisms responsible for their negligible rates of Pn on warm days and their unusually low high-temperature compensation points (i.e., 26°C in C. quitensis and 22°C in D. antarctica). Low Pn at supraoptimal temperature (25°C) appeared to be largely due to high rates of temperature-enhanced respiration. However, there was also evidence for direct impairment of the photosynthetic apparatus at supraoptimal temperature, based on Chl fluorescence and Pn/intercellular CO2 concentration (ci) response curve analyses. The breakpoint or critical temperature (Tcr) of minimal fluorescence (Fo) was ≈42°C in both species, which was well above the temperatures where reductions in Pn were evident, indicating that thylakoid membranes were structurally intact at supraoptimal temperatures for Pn. The optimal Tl for photochemical quenching (qp) and the quantum yield of photosystem II (PSII) electron transfer (φPSII) were 9 and 7°C in C. quitensis and D. antarctica, respectively. Supraoptimal temperatures resulted in lower qp and greater non-photochemical quenching (qNP), but had little effect on Fo, maximal fluorescence (Fm) or the ratio of variable to maximal fluorescence (Fv/Fm) in both species. In addition, carboxylation efficiencies or initial slopes of their Pn/ci response were lower at supraoptimal temperatures, suggesting reduced activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Although continued warming along the peninsula will increase the frequency of supraoptimal temperatures, Tc at our field site averaged 4.3°C and was below the temperature optima for Pn in these species for the majority of diurnal periods (86%) during the growing season, suggesting that continued warming will usually improve their rates of Pn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.106304.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Changes in leaf expansion and epidermal screening effectiveness in Liquidambar styraciflua and Pinus taeda in response to UV-B radiation (1996)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Absorption or screening of ultraviolet-B (UV-B) radiation by the epidermis may be an important protective method by which plants avoid damage upon exposure to potentially harmful UV-B radiation. In the present study we examined the relationships among epidermal screening effectiveness, concentration of UV-absorbing compounds, epidermal anatomy and growth responses in seedlings of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.). Seedlings of each species were grown in a greenhouse at the University of Maryland under either no UV-B radiation or daily supplemental UV-B radiation levels of 4, 8 or 11 kJ m−2 of biologically effective UV-B (UV-BBE) radiation. Loblolly pine seedlings were subsequently grown in the field under either ambient or supplemental levels of UV-B radiation. At the conclusion of the growing season, measurements of epidermal UV-B screening effectiveness were made with a fiber-optic microprobe. In loblolly pine, less than 0.5% of incident UV-B radiation was transmitted through the epidermis of fascicle needles and about 1% was transmitted in primary needles. In contrast, epidermal transmittance in sweetgum ranged from about 20% in leaves not preconditioned to UV-B exposure, to about 10% in leaves grown under UV-B radiation. The concentration of UV-absorbing compounds was unaffected by UV-B exposure, but generally increased with leaf age. Increases in epidermal thickness were observed in response to UV-B treatment in loblolly pine, and this accounted for over half of the variability in UV-B screening effectiveness. In spite of the low levels of UV-B penetration into the mesophyll, delays in leaf development (both species) and final needle size (loblolly pine) were observed. Seedling biomass was reduced by supplemental UV-B radiation in loblolly pine. We hypothesize that the UV-induced growth reductions were manifested by changes in either epidermal anatomy or epidermal secondary chemistry that might negatively impact cell elongation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1996.980217.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Enhancement of photosynthesis in Sorghum bicolor by ultraviolet radiation (2002)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 116 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We assessed the influence of ultraviolet radiation (UV) on net photosynthetic CO2 assimilation rate (Pn) in Sorghum bicolor, with particular attention to examining whether UV can enhance Pn via direct absorption of UV and absorption of UV-induced blue fluorescence by photosynthetic pigments. A polychromatic UV response spectrum of leaves was constructed by measuring Pn under different UV supplements using filters that had sharp transmission cut-offs from 280 to 382 nm, against a background of non-saturating visible light. When the abaxial surface was irradiated, Pn averaged 4.6% higher with the UV supplement that cut-off UV at 311 nm, compared to lower and higher UV wavelength supplements. This former supplement differed from higher wavelength supplements by primarily providing more UV between 320 and 350 nm. To assess the possibility of direct absorption of UV by photosynthetic pigments, we measured the absorbance of extracted chlorophylls. Chlorophyll a had absorbance peaks at 340 and 389 nm that were 49 and 72% of that at the sorét peak. Chlorophyll b had absorbance peaks at 315 and 346 nm that were both 35% of that at the sorét peak. Since the epidermis transmits some UV, the strong UV absorbance of chlorophyll implies a potential role for irradiance beyond the bounds of the conventionally defined photosynthetically active radiation waveband (400–700 nm). To assess the role of absorption of UV-induced blue fluorescence, we measured the UV-induced fluorescence excitation and emission spectra of leaves. Abaxial excitation peaked at 328 nm, while emission peaked at 446 nm. In this analysis, we used our abaxial fluorescence excitation spectrum and the UV photosynthetic inhibition spectrum of Caldwell et al. (1986) to weight the UV irradiance with each cut-off filter, thereby estimating the potential contribution of UV-induced blue fluorescence to photosynthesis and the inhibitory effects of UV irradiance on photosynthesis, respectively. With a non-saturating visible background, we estimate that the absorption of UV-induced blue fluorescence and the direct absorption of UV by photosynthetic pigments maximally enhanced photosynthesis by about 1% each with the UV supplement that cut-off UV at 311 nm. We suggest that a portion of the incident UV on the S. bicolor leaves was used to drive photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1160415.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Effects of ultraviolet-B radiation on leaf elongation, production and phenylpropanoid concentrations of Deschampsia antarctica and Colobanthus quitensis in Antarctica (2000)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 109 (2000), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Stratospheric ozone depletion by anthropogenic chlorofluorocarbons has lead to increases in ultraviolet-B radiation (UV-B; 280–320 nm) along the Antarctic Peninsula during the austral spring. We manipulated UV-B levels around plants of Antarctic hair grass (Deschampsia antarctica; Poaceae) and Antarctic pearlwort (Colobanthus quitensis; Caryophyllaceae) for one field season near Palmer Station along the west coast of the Antarctic Peninsula. Treatments involved placing frames over naturally growing plants that either (1) held filters that absorbed most biologically effective radiation (UV-BBE; ‘reduced UV-B’, 22% of ambient UV-BBE levels), (2) held filters that transmitted most UV-BBE (‘near-ambient UV-B’, 87% of ambient UV-BBE levels), or (3) lacked filters (‘ambient UV-B’). Leaves on D. antarctica exposed to near-ambient and ambient UV-B were 16–17% shorter than those exposed to reduced UV-B, and this was associated with shorter epidermal cells at the leaf base and tip. Leaves on C. quitensis exposed to near-ambient and ambient UV-B tended to be shorter (P=0.18) and epidermal cells at the leaf base tended to be smaller than those under reduced UV-B (P〈0.10). In order to further explain reductions in leaf length, we examined leaf concentrations of insoluble (cell-wall bound) phenylpropanoids, since it has been proposed that wall-bound phenylpropanoids such as ferulic acid may constrain cell expansion and leaf elongation. In both species, HPLC analysis revealed that ferulic and p-coumaric acid were major components of both insoluble and soluble phenylpropanoids. Although there were no significant differences in concentrations between UV-B treatments, concentrations of insoluble ferulic acid in D. antarctica tended to be higher under ambient and near-ambient UV-B than under reduced UV-B (P=0.17). We also examined bulk-leaf concentrations of soluble (methanol extractable) UV-B-absorbing compounds and found that concentrations were higher in plants exposed to near-ambient and ambient UV-B than in plants exposed to reduced UV-B. We also assessed the UV-B-screening effectiveness of leaves that had developed on plants at the field site with a fiber-optic microprobe. Leaf epidermal transmittance of 300-nm UV-B was 4.0 and 0.6% for D. antarctica and C. quitensis, respectively, which is low compared to grasses and herbaceous dicotyledonous plants found in more temperate climates. While the leaves of Antarctic vascular plants are relatively effective at screening UV-B, levels of UV-B in Antarctica are sufficient to reduce leaf epidermal cell size and leaf elongation in these species, although the mechanisms for these reductions remain unclear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.100304.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Photosynthetic symmetry of sun and shade leaves of different orientations (1991)
    Springer
    Oecologia 87 (1991), S. 51-57 
    Details
    ISSN: 1432-1939
    Keywords: Leaf anatomy ; Photosynthesis ; Functional symmetry ; Leaf orientation ; Optical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The photosynthetic responses to light of leaves irradiated on the adaxial or abaxial surfaces, were measured for plants with contrasting leaf orientations. For vertical-leaf species of open habitats (Eryngium yuccifolium and Silphium terebinthinaceum), photosynthetic rates were identical when irradiated on either surface. However, for horizontal-leaf species of open habitats (Ambrosia trifida and Solidago canadensis), light-saturated rates of photosynthesis for adaxial irradiation were 19 to 37% higher than rates for abaxial irradiation. Leaves of understory plants (Asarum canadense and Hydrophyllum canadense) were functionally symmetrical although they had horizontal orientation. Photosynthetic rates were measured at saturating CO2, thus differences in the response to incident irradiance presumably resulted from complex interactions of light and leaf optical properties rather than from stomatal effects. Differences in absorptance (400–700 nm) among leaf surfaces were evident for horizontal-leaf species but the primary determinant of functional symmetry was leaf anatomy. Functionally symmetrical leaves had upper and lower palisade layers of equal thickness (vertical leaves of open habitats) or were composed primarily of a single layer of photosynthetic cells (horizontal leaves of understory habitats). Photosynthetic symmetry of vertical-leaf species may be an adaptation to maximize daily integrated carbon gain and water-use efficiency, whereas asymmetry of horizontal-leaf species may be an adaptation to maximize daily integrated carbon gain and photosynthetic nutrient-use efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323779
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Influence of enhanced UV-B radiation on biomass allocation and pigment concentrations in leaves and reproductive structures of greenhouse-grown Brassica rapa (1996)
    Springer
    Plant ecology 127 (1996), S. 109-116 
    Details
    ISSN: 1573-5052
    Keywords: Chlorophyll ; Flavonoids ; Ovary ; Ozone depletion ; Pollen ; Reproduction ; Screening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We assessed the effects of enhanced ultraviolet-B radiation (UV-B; 280–320 nm) on biomass allocation to roots, shoots, leaves and flowers in the annual Brassica rapa. In addition, we investigated how concentrations of chlorophyll and UV-B-absorbing compounds in leaves, ovaries and pollen changed in response to enhanced UV-B. Plants were grown for 38 d in a greenhouse under lampbanks providing daily biologically effective UV-B doses equivalent to those under ambient mid-March stratospheric ozone levels or 16% (‘low-enhanced UV-B’) or 32% (‘high-enhanced UV-B’) ozone depletion levels for Morgantown, WV, USA. Total and aboveground biomass of plants was less under low-enhanced UV-B, but similar to ambient controls under high-enhanced UV-B. Concentrations of UV-B-absorbing compounds in leaves (area basis) increased under high-enhanced UV-B by about 20%, but were similar to ambient controls under low-enhanced UV-B. More effective protection due to higher screening-compound concentrations in plants under high-enhanced UV-B may explain why biomass production was not reduced. Plants under high-enhanced UV-B also had more reproductive biomass and produced more flowers, and had less root mass, than plants under ambient or low-enhanced UV-B. Concentrations of leaf total chlorophyll were not affected by UV-B treatment. While UV-B treatment had no affect on concentrations of UV-B-absorbing compounds in ovaries, concentrations in pollen from plants under both enhanced-UV-B treatments were 〉40% greater than ambient controls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044635
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    facet.materialart.
    Unknown
    Mixing of Aleppo pine and Holm oak litter increases biochemical diversity and alleviates N limitations of microbial activity (2017)
    Elsevier
    Details
    Publication Date: 2017-02-01
    Print ISSN: 0038-0717
    Electronic ISSN: 1879-3428
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Elsevier
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...