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  • 1
    Electronic Resource
    Electronic Resource
    Effects of ozone depletion and increased ultraviolet-B radiation on northern vegetation (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 18 (1999), S. 0 
    Details
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: The stratospheric ozone layer has been depleted at high and mid-latitudes as a consequence of man's pollution of the atmosphere, and this results in increasing ultraviolet-B radiation at ground level. We investigate the effects of further radiation increases on plants and ecosystems by irradiating natural sub-Arctic and Arctic vegetation with artificial UV-B radiation in field experiments extending over several years. Our experimental sites are located at Abisko, in northern Sweden (68°N), and Adventdalen, on the island of Spitsbergen (78°N). Additional UV-B induced interspecific differences in plant response in terms of reduced (or, in one case, increased) growth, changed morphology and changed pigment content. In some cases effects seem to be accumulated from one year to another. Plant litter decomposition is retarded. We are also studying how UV-B enhancement may affect the interaction between species. In some experiments we combine UV-B enhancement with changes in other factors: carbon dioxide concentration, water availability, and temperature. In some cases the effect of radiation enhancement is modified, or even reversed, by such changes. Over a four year period we did not find any significant radiation induced change in species composition, but based on the effects on individual plant species, such changes can be expected to take place over a longer time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-8369.1999.tb00311.x
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  • 2
    Electronic Resource
    Electronic Resource
    Response of sugar beet plants to ultraviolet-B (280–320 nm) radiation and Cercospom leaf spot disease (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 84 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sugar beet (Beta vulgaris L.) plants injected with Cercospora beticota Sace. as well as non-infected plants were grown under visible light with or without ultraviolet-B (UV-B, 280–320 nm) radiation for 40 days. An interaction between UV-B radiation and Cercospora leaf spot disease was observed, resulting in a large reduction in leaf chlorophyll content, dry weight of leaf laminae, petioles and storage roots. Lipid peraxidation in leaves also increased the most under the combined treatments. This was also true for ultraweak luminescence from both adaxial and abaxial leaf surfaces. However, no correlation between lipid peroxidation and ultraweak luminescence was observed. Ultraviolet-B radiation given alone appeared to have either a stimulating effect, giving an increase in dry weight of laminae and reducing lipid peroxidation, or no effect. This lack of effect was seen in the absence of change in dry weight of storage roots and chlorophyll content relative to controls. The :study demonstrated a harmful interaction between UV-B radiation and Cercospom leaf spot disease on sugar beet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb08776.x
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  • 3
    Electronic Resource
    Electronic Resource
    Stomatal closure by ultraviolet radiation (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 66 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of ultraviolet radiation (UV) (255–325 nm) on stomatal closure was investigated on tef [Eragrostis tef (Zucc) Trotter] in the presence of white light (ca 50 ·mol m−2 s−1). The action spectrum showed that UV (ca 2 ·mol m−2 s−1, half band width about 10 nm) of 285 nm or shorter wavelengths was very efficient in causing stomatal closure. The effectiveness decreased sharply towards longer wavelengths. Radiation of 313 nm or longer wavelengths was practically without effect. Increasing UV intensity increased stomatal resistance. When stronger white light (5 to 9 times stronger than the one used during irradiation) was administered, stomates re-opened rapidly irrespective of whether the UV was on or off, although a subsequent gradual closing tendency was observed when the UV was on.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb05935.x
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  • 4
    Electronic Resource
    Electronic Resource
    Light-induced, dark-reversible colour shifts in petals of Phlox (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 64 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Flowers of some Phlox (Phlox x paniculata L.) varieties undergo daily colour shifts, being blue in the early morning, turning red during the day, and returning to blue in the evening. The colour shift, which occurs only in the upper (adaxial) petal surfaces, is due to the daily changes in ambient light. In the laboratory, colour shifts could be induced by 2.5 h of ultraviolet, visible or far-red light and recorded by reflectance spectrophotometry.There are indications that irradiations with different kinds of light cause qualitatively different colour shifts, and that thus more than one photoreceptor pigment and more than one primary light reaction may be involved. The presence of phytochrome was demonstrated in petals of white Phlox flowers by in vivo transmission spectrophotometry. It is therefore possible that colour shifts in coloured Phlox flowers are mediated by phytochrome. Possibly the movement of ions (e.g. hydrogen ions) into or out of the vacuole (where the visible pigments are located) is affected by light absorption in a pigment in the tonoplast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb08520.x
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  • 5
    Electronic Resource
    Electronic Resource
    Light-induced linear dichroism in photoreversibly photochromic sensor pigments. – IV. Lack of chromophore rotation in phycochrome b immobilized in vitro (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 60 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In photochromic pigments, immobilized on Sepharose beads to prevent reorientation of the molecules, linear absorption dichroism can be induced with plane-polarized light. This phenomenon was used to study the relation between the carrier protein and the chromophore in the photochromic cyanobacterial pigment, phycochrome b, from Tolypothrix distorta var. symplocoides Hansgirg, strain UTEX 424 (formerly IUCC 424). It was found that the transition moment of the chromophore has the same direction with respect to the protein in the long-wavelength and the short-wavelength forms of phycochrome b. This contrasts to earlier results for phytochrome in higher plants, in which the transition moment was found to rotate 32° (or 180°—32°) when the long-wavelength form was converted to the short-wavelength form or vice versa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb04573.x
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  • 6
    Electronic Resource
    Electronic Resource
    Response to directional light by leaves of a sun-tracking lupine (Lupinus succulentus) (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Experiments were done to examine the phototrophic response of sun-tracking leaves of Lupinus succulentus Dougl. to fixed beams of white and broad band light. Upon irradiation with 15 W m−2 white light that struck the laminae at an angle of 45°, there was a 45–60 min lag period prior to leaf movement. The greatest rate of movement was 15° h−1, and reorientation ceased when leaves attained a position within 15° of perpendicular to the light beam. Laminar movement was largely pulvinar, and a 60 min inductive light treatment was sufficient to activate a maximum pulvinar response in subsequent darkness. Light striking the lamina at angles between 20 and 70° induced similar maximum pulvinar responses and only light that struck the upper (adaxial) leaf surface was effective. Leaf tracking was fully activated by blue light but not by red or yellow light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb06276.x
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  • 7
    Electronic Resource
    Electronic Resource
    Photochromic pigments in akinetes and pigment characteristics of akinetes in comparison with vegetative cells of Anabaena variabilis (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Since akinete germination is triggered by light and the action spectrum for this process has features in common with the spectra of the two photochromic pigments, phycochromes b and d, a search was made for the presence of these phycochromes in akinetes of the blue-green alga. Anabaena variabilis Kützing. Allophycocyanin-B was also looked for, since the action spectrum for akinete germination points to a possible participation of this pigment too. Isoelectric focusing was used for purification of the pigments. The different fractions were investigated for phycochromes b and d by measuring the absorbance difference spectra: for phycochrome b. 500 nm irradiated minus 570 nm irradiated, and for phycochrome d, 650 nm irradiated minus 610 nm irradiated. For determination of allophycocyanin-B. fourth derivative analysis of absorption spectra was made for some of the fractions from the isoelectric focusing column. Phycochrome b was also assayed for by measuring in vivo absorption difference spectra. The assays were positive for all three pigments.The complete photosynthetic pigment systems were also studied by in vivo fluorescence measurements on both akinetes and vegetative cells of Anabaena variabilis. Fluorescence emission and excitation spectra at selected emission wavelengths were measured at room temperature and liquid nitrogen temperature. The energy transfer from phycoerythrocyanin to phycocyanin is very efficient under all conditions, as is the energy transfer from phycocyanin to allophycocyanin at room temperature. At low temperature, however, phycocyanin is partly decoupled from allophycocyanin, particularly in the akinetes; the energy transfer from allophycocyanin to chlorophyll a is less efficient at low temperature in both types of cells, but especially in akinetes. Delayed light emission was measured for both types of cells and found to be very weak in akinetes compared to vegetative cells. From this study it would seem that akinetes lack an active photosystem II, although the 691 nm peak in the 570 nm excited low temperature fluorescence emission spectrum proves the presence of photosystem II chlorophyll, and also its energetic connection to the phycobilisomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb04236.x
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  • 8
    Electronic Resource
    Electronic Resource
    The Influence of Red Light on the Growth of Pea Seedlings. An Attempt to Localize the Perception (1958)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 11 (1958), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1958.tb08471.x
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of ultraviolet radiation on accumulation and leakage of 86Rb+ in guard cells of Vicia faba (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 69 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of UV-C (254 nm), UV-A (365 nm) and broad-band UV (280–380 nm) on guard cells of Vicia faba L. cv. Long Pod were investigated in the presence of white light (450 μmol m−2 s−1). UV-C (7 μmol m−2 s−1) was found to cause leakage of 86Rb+ from guard cells, while UV-A (0.3 μmol m−2 s−1) stimulated increased uptake in these cells. A relatively small stimulatory effect was observed by broad-band UV (3 μmol m−2 s−1) during the first 30 min of irradiation with an apparent equilibration of influx and efflux thereafter. Leakage of 86Rb+ from guard cells continued despite the removal of UV-C and an increase in the amount of white light from 450 to 1500 μmol m−2 s−1, suggesting that membranes were irreversibly damaged. Irradiation of guard cells with UV-C for 30, 45 and 90 min indicated that these cells began to be affected already by 30 min UV-C irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb04276.x
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  • 10
    Electronic Resource
    Electronic Resource
    Light-induced linear dichroism in photoreversibly photochromic sensor pigments. – V. Reinterpretation of the experiments on in vivo action dichroism of phytochrome (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 60 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Experiments by several authors on the effects of polarized light on phytochromemediated responses in fern gametophytes and in the green alga Mougeotia have earlier been interpreted as showing that the transition moment of phytochrome in the Pr form is parallel to the plasmalemma, but perpendicular to the plasmalemma for the Pfr form of phytochrome. It is now shown that the experimental results can be interpreted differently, and that they are also consistent with a chromophore rotation of about 30° (instead of 90°), as found for immobilized phytochrome molecules in vitro. Thus there is no evidence for a rotation of the whole phytochrome protein. For the gametophyte of Adiantum it is calculated that the Pr transition moment is inclined 17° to the plasmalemma, and the Pfr transition moment ca 50°, corresponding to an in vivo chromophore rotation of ca 33°; however, these values are very approximate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb06077.x
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