| 1. |
- Demmig-Adams, Barbara, et al.
(författare)
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Modulation of PsbS and flexible vs sustained energy dissipation by light environment in different species
- 2006
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 127, s. 670-80
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Tidskriftsartikel (refereegranskat)abstract
- Contrasting acclimation strategies of photosynthesis and photoprotection were identified for annual mesophytes (spinach, pumpkin, and Arabidopsis) vs the tropical evergreen Monstera deliciosa. The annual species utilized full sunlight for photosynthesis to a much greater extent than the evergreen species. Conversely, the evergreen species exhibited a greater capacity for photoprotective thermal energy dissipation as well as a greater expression of the PsbS protein in full sun than the annual species. In all species, the majority of thermal energy dissipation [assessed as non-photochemical fluorescence quenching (NPQ)] was the flexible, ΔpH-dependent form of NPQ over the entire range of growth light environments. However, in response to a transfer of shade-grown plants to high light, the evergreen species exhibited a high level of sustained thermal dissipation (qI), but the annual species did not. This sustained energy dissipation in the evergreen species was not ΔpH-dependent nor did the low level of PsbS in shade leaves increase upon transfer to high light for several days. Sustained ΔpH-independent NPQ was correlated (a) initially, with sustained D1 protein phosphorylation and xanthophyll cycle arrest and (b) subsequently, with an accumulation over several days of PsbS-related one-helix proteins and newly synthesized zeaxanthin and lutein.
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| 2. |
- Björn, G S, et al.
(författare)
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Action spectra for conversions of phycochrome c from Nostoc-muscorum
- 1978
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 43:3, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- The reversibly photochromic pigment, phycochrome c, was extracted from the blue-green alga Nostoc muscorum strain A. Action spectra were determined for in vitro conversions of the pigment from the short wavelength to the long wavelength form and vice versa. The action peak for the absorbance decrease at 650 nm is at 630 nm. During this decrease there is only a slight increase of the absorbance in the green region. Green and yellow light (maximum efficiency at 580 nm) completely restores absorbance at 650 nm. The observations are explained by the existence of three spectrally different forms of phycochrome c: Pc630 and Pc650 which equilibrate in darkness and Pc580 which is reversibly photoconvertible to Pc630. We have also measured the absorbance changes brought about by saturating irradiations with light of various wavelengths ("photostationary state spectrum"). Extreme photostationary states were obtained with about 650 nm and 500 nm light.
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| 3. |
- Björn, G S, et al.
(författare)
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Light-induced, dark-reversible color shifts in petals of Phlox
- 1985
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 64:4, s. 445-448
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Björn, G S, et al.
(författare)
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Photochromic pigments from blue-green algae - phycochrome-A, phycochrome-B and phycochrome-C
- 1976
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 36:4, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous extracts of blue-green algae were fractionated by electrofocusing. In all algae investigated, fractions with isoelectric points at or near 4.6 showed photochromic behavior analogous to that of phytochrome, although they were sensitive to light of shorter wavelength. Three main types of photochromic pigments were found. Phycochrome a (in Tolypothrix distorta, Phormidium luridium, Nostoc muscorum 1453/12 and Anacystis nidulans) had 1 form absorbing maximally at about 590 nm (formed under red light) and 1 absorbing maximally at about 630 nm (formed under green light). Phycochrome b (in T. distorta) had 1 form absorbing maximally near 510 nm and 1 form absorbing maximally at 570 nm (formed in yellow-green and blue-green light, respectively). Phycochrome c (in N. muscorum A and probably in T. tenuis) had 1 form absorbing maximally at 650 nm (formed under green light) and 1 absorbing very weakly in the green region (formed under red light). The conversion of Phormidium phycochrome a from its red-absorbing form to its green-absorbing form caused the same spectral change as if an f-chromophore of phycocyanin were transformed into an s-chromophore. The quantum yield for this conversion was estimated to be 0.1, while the quantum yield for the reversion was estimated to be 0.4 on the assumption that the absorption coefficients were those of f- and s-chromophores. Phycochrome c was less light-sensitive than phycochromes a and b.
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| 5. |
- Björn, G S, et al.
(författare)
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Photochromic pigments in akinetes and pigment characteristics of akinetes in comparison with vegetative cells of Anabaena-Variabilis
- 1983
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 59:3, s. 493-500
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Björn, Lars Olof, et al.
(författare)
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Imaging by delayed light-emission (phytoluminography) as a method for detecting damage to the photosynthetic system
- 1979
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 47:4, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- An improved apparatus for obtaining luminescence (delayed light emission) images of plants is described. It consists of a phosphoroscope equipped with an imaging lens and an electronic image intensifier. It is also equipped with light-sources for obtaining images with reflected light and fluorescence light. Damage to the photosynthetic system caused by virus, insects, high or low temperature, UV radiation, or herbicide, and also chloroplast senescence as part of a normal developmental process, can be followed by this non-destructive method. In many cases changes which are not visible in fluorescence images are clearly seen in luminescence images. (Leaves of Hibiscus sp., Oxalis tetraphylla, Nicotiana glutinosa with a tobacco mosaic virus infection, Fagus sylvatica with midge gall and Polypodium vulgare were used.).
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| 7. |
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| 8. |
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| 9. |
- Brodelius, M, et al.
(författare)
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Immunolocalization of the saposin-like insert of plant aspartic proteinases exhibiting saposin C activity. Expression in young flower tissues and in barley seeds
- 2005
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 125:4, s. 405-418
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Tidskriftsartikel (refereegranskat)abstract
- The plant- specific insert ( PSI) of cypro11 gene- encoding cyprosin, an aspartic proteinase from Cynara cardunculus, has been cloned by polymerase chain reaction ( PCR) into a bacterial expression vector. A rearranged form of this PSI in which the N- and C- terminal sequences were permutated to make it more similar to the structural arrangement observed in saposins was also cloned and expressed in the same system. The biological activities of the two purified recombinant proteins were compared to those of human saposins B and C. The proteins showed similar activity to saposin C, i. e. capacity to activate human glucosylceramidase. At a concentration of 5 mu M, wild- type PSI, saposin C, and rearranged PSI activated human glucosylceramidase two-, three-, and five- fold, respectively. The K-m for 4- methylumbelliferyl beta-glucopyranoside was around 7 mM in the presence of any of the three activators ( 5 mM). The neurotropic activity using NS20Y cells and lipid- binding properties of the plant recombinant proteins were tested. The two plant proteins showed lipid- binding properties similar to those of saposins but did not have any effect on neurite outgrowth. Immunolocalization of PSI showed its expression in protective tissues in flower meristem - protodermis, in C. cardunculus and embryonic root cap and coleorhiza in mature barley grains - as well as husk, pericarp, and the aleurone layer. Possible biological functions suggested for the plant homologue to saposins besides the general activation of enzymes involved in lipid metabolism would be involvement in plant defence.
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| 10. |
- Christensen, Anna, et al.
(författare)
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Overexpression of the Ca2+-binding protein calreticulin in the endoplasmic reticulum improves growth of tobacco cell suspensions (Nicotiana tabacum) in high-Ca2+ medium
- 2005
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 123:1, s. 92-99
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Tidskriftsartikel (refereegranskat)abstract
- Calreticulin (CRT) is a eukaryotic, highly conserved, Ca2+-binding protein predominantly located in the endoplasmic reticulum (ER) lumen. In addition to being involved in the regulation of cellular Ca2+, calreticulin is a key quality control element during protein folding in the ER lumen. Tobacco (Nicotiana tabacum L.) suspension cells overexpressing a maize CRT (CRT1a) were used here to examine the properties of CRT in growing plant cells with respect to stress exposure. The endogenous CRT gene was induced rapidly after subculturing of the cells to new medium. In accordance, the CRT protein levels increased, peaking at days 3-4. At day 5, when the CRT transcript levels had levelled off, a further increase in endogenous CRT expression was obtained when the cells were treated with excess Ca2+ or the N-linked glycosylation inhibitor tunicamycin. Whereas the response to Ca2+ occurred within 30 min, the induction by tunicamycin took several hours to be established. Transforming tobacco cells with maize CRT1a, under a constitutive mannopine synthase promoter, resulted in a stable level of expressed CRT1a during the growth cycle compared with endogenous CRT. The CRTs showed differences in attached glycans, but both contained the high mannose-rich-type glycans characteristic of ER proteins. In agreement with an ER location, both tobacco CRT and the transgene product CRT1a codistributed with the ER marker NADH cytochrome c reductase after density gradient centrifugation of microsomal fractions from tobacco cells. Increased production of CRT, as was obtained in the transgenic tobacco cell lines, made cells more tolerant than wild-type cells to high Ca2+ during growth. These data suggest that overexpression of CRT1a in plant cells results in a more efficient calcium buffering capacity in the ER.
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| 11. |
- Ekelund, Nils, 1956-, et al.
(författare)
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Photophobic stop-response in a dinoflagellate - modulation by preirridation
- 1987
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 70:3, s. 394-398
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Tidskriftsartikel (refereegranskat)abstract
- Gyrodinium dorsum Kofoid responds photophobically to flashes of blue light. The photophobic response consists of a cessation of movement (stop-response). Without background light and after a flash fluence above 10 J m-2, 75-85% of the cells show a stop-response, only only 50% of the cells show this response at 5 J m-2. With a flash fluence of 5 J m-2, background light of different wavelengths either increases (614 nm, 5.5-18.2 .mu.mol m-2 s-1) or decreases (700 nm, 18.4-36.0 .mu.mol m-2 s-1) the stop-response. Two hypotheses for the mechanism of the modulation by background light of the photophobic response are discussed: an effect of light on the balance of the photosynthetic system (PS I/PS II) or an effect on a phytochrome-like pigment (Pr /Pfr). This study supports the idea that a phytochrome-like pigment works in combination with a blue light-absorbing pigment. It was also found that cells of Gyrodinium dorsum cultured in red light (39.8 .mu.mol m-2) had a higher absorption in the red region of the absorption spectra than those cultured in white light (92.7 .mu.mol m-2).
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| 12. |
- Eskling, Marie, et al.
(författare)
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The xanthophyll cycle, its regulation and components
- 1997
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 100:4, s. 806-816
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Forskningsöversikt (refereegranskat)abstract
- During the last few years much interest has been focused on the photoprotective role of zeaxanthin. In excessive light zeaxanthin is rapidly formed in the xanthophyll cycle from violaxanthin, via the intermediate antheraxanthin, a reaction reversed in the dark. The role of zeaxanthin and the xanthophyll cycle in photoprotection, is based on fluorescence quenching measurements, and in many studies a good correlation to the amount of zeaxanthin (and antheraxanthin) has been found. Other suggested roles for the xanthophylls involve, protection against oxidative stress of lipids, participation in the blue light response, modulation of the membrane fluidity and regulation of abscisic acid synthesis. The enzyme violaxanthin de-epoxidase has recently been purified from spinach and lettuce as a 43-kDa protein. It was found as 1 molecule per 20-100 electron-transport chains. The gene has been cloned and sequenced from Lactuca sativa, Nicotiana tabacum and Arabidopsis thaliana. The transit peptide was characteristic of nuclear-encoded and lumen-localized proteins. The activity of violaxanthin de-epoxidase is controlled by the lumen pH. Thus, below pH 6.6 the enzyme binds to the thylakoid membrane. In addition ascorbate becomes protonated to ascorbic acid (pKa= 4.2) the true substrate (Km= 0.1 mM) for the violaxanthin de-epoxidase. We present arguments for an ascorbate transporter in the thylakoid membrane. The enzyme zeaxanthin epoxidase requires FAD as a cofactor and appears to use ferredoxin rather than NADPH as a reductant. The zeaxanthin epoxidase has not been isolated but the gene has been sequenced and a functional protein of 72.5 kDa has been expressed. The xanthophyll cycle pigments are almost evenly distributed in the thylakoid membrane and at least part of the pigments appears to be free in the lipid matrix where we conclude that the conversion by violaxanthin de-epoxidase occurs.
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| 13. |
- Forsberg, Jens, et al.
(författare)
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Protease activities in the chloroplast capable of cleaving an LHCII N-terminal peptide
- 2005
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 123:1, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- Two protease activities of pea chloroplasts, one located in the stroma and the other associated to the thylakoid membrane, are described. Both proteases catalyse the endo-proteolytic cleavage of a peptide corresponding to the N-terminal loop and the first turn in helix-B of light-harvesting complex II (Lhcb1 from pea). The stromal protease cleaves preferentially on the carboxy-side of glutamic acid residues. Inhibitor studies indicate that this protease is a serine-type protease. The protease was partially purified and could be correlated to a 95-kDa polypeptide band on SDS-polyacrylamide gels. The 95 kDa protein was partially sequenced and showed similarity to an to an 'unknown protein' from A. thaliana (in the NCBI public database) as well as to a glutamyl endopeptidase purified from crude extract of cucumber leaves. It is concluded that the stromal protease is a chloroplast glutamyl endopeptidase (cGEP). The protease localized in the thylakoid membrane, cleaved the peptide at only one site, close to its N terminus. The activity of the thylakoid-associated protease was found to be drastically increased in the presence of the reducing agent 1,4-dithiothreitol. Inhibitor studies suggest that this protease is a cysteine- or serine-type protease. The possible roles of these proteases in the regulation of photosynthetic electron transport and in the chloroplast homeostasis are discussed.
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| 14. |
- Fredrikson, Karin, et al.
(författare)
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Isolation and polypeptide composition of 1,3-ß-glucan synthase from plasma membranes of Brassica oleracea
- 1991
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 81:3, s. 289-294
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Tidskriftsartikel (refereegranskat)abstract
- The l,3‐ß‐glucan synthase (callose synthase, EC 2.4.1.34) was solubilized from cauliflower (Brassica oleracea L.) plasma membranes with digitonin, and partially purified by ion exchange chromatography and gel filtration [fast protein liquid chromatography (FPLC)] using 3‐[(cholamidopropyl)dimethylammonio]‐1‐propane‐sulfonate (CHAPS) in the elution buffers. These initial steps were necessary to obtain specific precipitation of the enzyme during product entrapment, the final purification step. Five polypeptides of 32, 35, 57, 65 and 66 kDa were highly enriched in the final preparation and are thus likely components of the callose synthase complex. The purified enzyme was activated by Ca2+, spermine and cellobiose in the same way as the enzyme in situ, indicating that no essential subunits were missing. The polyglucan produced by the purified enzyme contained mainly 1,3‐linked glucose.
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| 15. |
- Gisselsson, A, et al.
(författare)
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Role of histidines in the binding of violaxanthin de-epoxidase to the thylakoid membrane as studied by site-directed mutagenesis
- 2004
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 122:3, s. 337-343
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Tidskriftsartikel (refereegranskat)abstract
- Regulation of violaxanthin de-epoxidase (VDE) involves a conformational change at low lumenal pH, followed by binding of the enzyme to the thylakoid membrane. The role of histidine residues in this process was studied by release of unbound enzyme from thylakoids upon sonication, on a pH scale from 4.7 to 7.1. The co-operativity for binding of spinach VDE (four histidines) to the membrane was found to be 3.8, with respect to protons, and had an inflexion point at pH 6.6, whereas VDE from wheat (three histidines) showed a co-operativity of 2.9 and had an inflexion point at pH 6.2. Mutant forms of VDE were constructed and probed for their binding to the outside of thylakoid membranes. With one or two histidines substituted for alanine or arginine, a lower co-operativity (1.6-2.3) was found, compared with the wild type. Based on these findings, and that the pKa value for histidine is within the range where the VDE binding takes place, we propose that protonation of the histidine residues at low pH induces the conformational change of VDE, and hence indirectly regulates binding of the enzyme to the thylakoid membrane.
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| 16. |
- Hideg, Éva, et al.
(författare)
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Ultraweak light emission, free radicals, chilling and light sensitivity
- 1996
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 98:2, s. 223-228
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Tidskriftsartikel (refereegranskat)abstract
- Ultraweak light emission (UWLE) was measured from leaves of various chillingsensitive (Lycopersicon esculentum, Cucumis sativus and Phaseolus vulgaris) and tolerant (Pisum sativum and Vicia faba) plants after exposure to low (47C) temperature in the light. UWLE increased upon chilling treatment combined with illumination with 200 mol m2 s1 PAR in all plants, by about 30 in tolerant and by more than 100 in sensitive plants. It increased more when applied together with 400 mol m2 s1 PAR: by 90100 and by 250280 in chillingtolerant and sensitive plants, respectively. Free radical production was detected by spintrapping EPR spectroscopy in thylakoid membranes isolated from the chillingtreated Lycopersicon esculentum and Vicia faba leaves. After 12 h chilling at 200 mol m2 s1 PAR, free radical production was approximately 3 times greater in the former than in the latter species. The same ratio was approximately 6 if chilling was carried out at 400 mol m2 s1 PAR, indicating the role of photooxidative stress in chilling injury.Our results also confirm that the stressinduced increase in UWLE is an indicator of free radical production and offers the possibility of using UWLE for monitoring the effect of chilling on temperaturesensitive plants in an early stage.
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| 17. |
- Hsiao, K C, et al.
(författare)
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Aspects of photoinduction of carotenogenesis in the fungus Verticillium-Agricinum
- 1982
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 54:3, s. 235-238
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Tidskriftsartikel (refereegranskat)abstract
- An action spectrum for light induced carotenogenesis in V. agaricinum (Link) Corda (ATCC 24668) was obtained by exposing mycelial pads to monochromatic radiation. Action maxima occurred at 290 (main peak) and 390 nm and there was a minor peak at 483 nm. An interaction between the blue and UV light occurred. Blue light partly reversed the UV light induction of carotenogenesis when given after, but not when given before UV light. This implies that there are at least 2 photoreceptors involved in carotenogenesis in Verticillium, but phytochrome is not likely to be one of them.
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| 18. |
- Hsiao, K C, et al.
(författare)
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Light-induced absorbance changes in the fungus Verticillium-Agricinum
- 1982
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 55:2, s. 73-75
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Tidskriftsartikel (refereegranskat)abstract
- Light-induced absorbance changes were investigated in vivo in the fungus V. agaricinum (Link) Corda. There was a broad light-induced absorbance decrease in the blue and near UV with a maximum at 384 nm. An action spectrum indicated that the absorbance changes were due to photo-bleaching of a pigment with an absorption spectrum that was similar to the action spectrum. Neither redox reactions nor energy metabolism were involved in the photo-bleaching process. A direct comparison of action spectra for light-induced absorbance changes and photo-induction of carotenogenesis suggests that the photo-bleaching may not be related to photo-induction of carotenogenesis.
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| 19. |
- Kjell, Jonas, et al.
(författare)
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Protein complexes of the plant plasma membrane resolved by Blue Native PAGE
- 2004
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 121:4, s. 546-555
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Tidskriftsartikel (refereegranskat)abstract
- With the characterization of the total genomes of Arabidopsis thaliana and Oryza sativa, several putative plasma membrane components have been identified. However, a lack of knowledge at the protein level, especially for hydrophobic proteins, have hampered analyses of physiological changes. To address whether protein complexes may be present in the native membrane, we subjected plasma membranes isolated from Spinacia oleracea leaves to blue-native polyacrylamide gel electrophoresis (BN-PAGE). BN-PAGE is well established in the separation of functional membrane protein complexes from mitochondria and chloroplasts, but a resolved protein complex pattern from PM of eukaryotic cells has previously not been reported. Using this method, protein complexes from Spinacia oleracea PM could be efficiently solubilized and separated, including the highly hydrophobic aquaporin (apparent molecular mass 230 kDa), a putative tetramer of H+-ATPase, and several less abundant complexes with apparent masses around or above 750 kDa. After denaturation and separation of the complexes into their subunits in a second dimension (SDS-PAGE), several of the complexes were identified as hydrophobic membrane proteins. Large amounts of protein (up to 1 mg) can be resolved in each lane, which suggests that the method could be used to study also low-abundance protein complexes, e.g. under different physiological conditions.
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| 20. |
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| 21. |
- Kumagai, T, et al.
(författare)
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Light-induced linear dichroism in photoreversibly photocromic sensor pigments 6. Relation between the 2 pigments of the mycochrome system in Alternaria-Chichorii
- 1984
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 60:4, s. 449-452
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Tidskriftsartikel (refereegranskat)abstract
- Conidiation in A. cichorii Nattras is reversibly stimulated by near UV radiation (NUV .apprx. 313 nm) and inhibited by blue light (.apprx. 450 nm) and apparently is a mycochrome-mediated process. After induction with plane-polarized NUV, blue light polarized perpendicularly to the NUV was more effective in counteracting the induction than was blue light polarized parallel to the NUV. Both the blue-absorbing component (presumably a flavo-protein) and the PNUV (NUV absorbing moiety) of the mycochrome system are membrane-bound. The transition moment associated with blue light absorption in the presumed flavoprotein forms an angle of at least 53.degree. with the transition moment associated with NUV absorption in PNUV.
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| 22. |
- Negash, L, et al.
(författare)
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Effect of ultraviolet-radiation and leakage of RB-86+ in guard-cells of Vicia-Faba
- 1987
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 69:2, s. 200-204
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Tidskriftsartikel (refereegranskat)abstract
- 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 .mu.mol m-2 s-1). UV-C (7 .mu.mol m-2 s-1) was found to cause leakage of 86Rb+ from guard cells, while UV-A (0.3 .mu.mol m-2 s-1) stimulated increased uptake in these cells. A relatively small stimulatory effect was observed by broad-band UV (3 .mu.mol 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 .mu.mol m-2 s-1, suggesting that membranes were irreversibly damaged. Irradiation of guard cells UV-C for 30, 45 and 90 min indicated that these cells began to be affected already by 30 min UV-C irradiation.
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| 23. |
- Negash, L, et al.
(författare)
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Stomatal closure by ultraviolet-radiation
- 1986
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 66:3, s. 360-364
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Tidskriftsartikel (refereegranskat)abstract
- 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 .mu.mol m-2 s-1). The action spectrum showed that UV (ca 2 .mu.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.
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| 24. |
- Panagopoulos, Ioannis, et al.
(författare)
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Response of sugar beet plants to ultraviolet-B (280-320 nm) radiation and Cercospora leaf spot disease
- 1992
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 84:1, s. 140-145
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Tidskriftsartikel (refereegranskat)abstract
- Sugar beet (Beta vulgaris L.) plants injected with Cercospora beticola Sacc. 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 peroxidation 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 Cercospora leaf spot disease on sugar beet.
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| 25. |
- Panagopoulos, Ioannis, et al.
(författare)
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The effect of UV-B and UV-C radiation on hibiscus leaves determined by ultraweak luminescence and fluorecence induction
- 1989
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 76:4, s. 461-465
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Tidskriftsartikel (refereegranskat)abstract
- The effects of UV-C (254 nm) and UV-B (280-320 nm) on chlorophyll fluorescence induction and ultraweak luminescence (UL) in detached leaves of Hibiscus rosa-sinensis L. were investigated. UL from leaves exposed to UV-B and UV-C radiation reached a maximum 72 h after irradiation. In both cases most of the light was of a wavelength over 600 nm. An increase in the percentage of long wavelength light with time was detected. UV radiation increased peroxidase activity, which also reached a maximum 72 h after irradiation. UV-B and UV-C both reduced variable chlorophyll fluorescence. No effect on the amount of chlorophyll or UV screening pigments was observed with the short-term irradiation used in this investigation.
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