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  • 11
    Electronic Resource
    Electronic Resource
    The ability of abaxial and adaxial epidermis of sun and shade leaves to attenuate UV-A and UV-B radiation in relation to the UV absorbing capacity of the whole leaf methanolic extracts (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 117 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The UV-absorbing capacity (measured as A310 cm−2 and A365 cm−2 or AUVR cm−2) of the shade leaves of four representative evergreen sclerophylls of the Mediterranean region (Quercus coccifera, Q. ilex, Arbutus andrachne and A. unedo) was considerably lower than the corresponding one of sun leaves of the same species. However, fibre optic microprobe measurements showed that adaxial as well as abaxial epidermis of shade leaves of all examined plants, except abaxial epidermis of A. andrachne, were almost as effective as the corresponding ones of the sun leaves in screening out most of the incident UV-B radiation. There is probably a threshold, under which the concentration of the UV-B absorbing compounds in the protective tissues is not furthermore reduced, in spite of the low levels of the stress factor (UV-B radiation) in the environment. On the other hand, the ability of both abaxial and adaxial epidermis to attenuate UV-A radiation, except of adaxial leaf epidermis of Quercus species, depended on the UV absorbing capacity of the whole-leaf extracts, with different correlation patterns between the two Quercus species and the two Arbutus species. This could be explained by the fact that shade leaves showed not only quantitative, but also qualitative differences (higher A310/A365 ratio) in the absorbance of their methanolic extracts compared to these of sun leaves. The results of the present study showed that we should not always correlate the depth of penetration of UV radiation into sun and shade leaves according to the corresponding UV absorbing capacity of the whole leaf methanolic extracts, without taking into account all the anatomical, developmental and biochemical (such as different composition and distribution of the UV-absorbing compounds among the different protective tissues) peculiarities of the leaves of each species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.1170104.x
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  • 12
    Electronic Resource
    Electronic Resource
    Phenylpropanoid compounds in primary leaf tissues of rye (Secale cereale). Light response of their metabolism and the possible role in UV-B protection (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 97 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The present study was undertaken in order to investigate the suitability of certain markers for UV plant response. In addition, we attempted to link the internal tissue distribution of specific UV-absorbing compounds to profiles of radiation gradients within intact primary rye leaves (Secale cereale L. cv. Kustro). Etiolated rye seedlings irradiated with low visible light (LL) and/or UV radiation were used to study enzyme activities of the two key enzymes, phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS), together with the tissue-specific accumulation of soluble phenylpropanoid products. Plants grown under relatively high visible light (HL) with or without supplementary UV-B radiation were used for further characterization. Apparent quantum yield and fluorescence quenching parameters were monitored to assess potential physiological changes due to UV-B exposure in HL-grown seedlings. A quartz fibreoptic microprobe was used to characterize the internal UV-B gradient of the leaf. The response of the phenylpropanoid metabolism to UV radiation was similar in primary leaves of both etiolated and HL-treated green plants. The epidermis-specific flavonoids together with CHS activity turned out to be suitable markers for assessing the effect of UV on the phenolic metabolism. The functional role of phenylpropanoid compounds was strongly implicated in protecting rye from UV-B radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00492.x
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  • 13
    Electronic Resource
    Electronic Resource
    Selection in vitro for UV-tolerant sugar beet (Beta vulgaris) somaclones (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 88 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: With a reduced stratospheric ozone concentration, the generation of UV-tolerant plants may be of particular importance. Among different crop plants there is large variation in sensitivity to UV-B radiation. This study was undertaken to investigate the possibilities of using somaclonal variation and selection in vitro for improving UV-B tolerance in sugar beet (Beta vulgaris L.).Sugar beet callus was exposed to UV radiation (280–320 nm, 0.863–5.28 kJ m-2 day-1, unweighted) and resultant shoots were selected from surviving cells. After establishment of the plants, they were grown under either visible radiation (114 μmol m-2 s-1 PAR) or with the addition of UV radiation (6.3 kJ m-2 day-1 biologically effective UV-B). Screening of regenerants in vivo for tolerance to UV radiation was undertaken 10 months after termination of the UV selection pressure. Screening was done visually and by using a number of physiological parameters, including chlorophyll fluorescence induction, ultraweak luminescence, pigment analysis and total content of UV-screening pigments. A clear difference between the unselected and the UV-selected somaclones was observed when visually studying the UV damage and other leaf injury. The observations were supported by the ultraweak luminescence measurements. Unselected plants showed significantly greater damage when subjected to subsequent UV radiation as compared to the selected plants. The clones subjected to UV selection pressure displayed a significantly higher concentration of UV-screening pigments under subsequent UV radiation. The unselected plants under subsequent UV treatment showed a lower carotenoid concentration when compared to selected plants. However, no significant difference between treatments was found for chlorophyll a/b, or F/Fmax, a measure of photosynthetic quantum yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb01757.x
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  • 14
    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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  • 15
    Electronic Resource
    Electronic Resource
    Differential response of a sensitive and tolerant sugarbeet line to Cercospora beticola infection and UV-B radiation (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: Increased ultraviolet-B (UV-B, 280–320 nm) radiation, due to depletion of stratospheric ozone, is an increasing threat to living organisms. Furthermore, increased ground level temperatures as a consequence of global warming may favour development of pathogens, such as Cercospora beticola, that thrive at high temperatures. This study evaluates the effect of combined UV stress and Cercospora leaf-spot disease on young sugarbeet plants (Beta vulgaris L.). An inoculum consisting of twelve European isolates of C. beticola Sacc. was used in the experiments. One Cercospora-sensitive and one Cercospora-tolerant sugarbeet line were analysed from growth regimes where plants were grown either under visible radiation alone or with supplemental UV-B. Photosynthetic pigments and partial reactions of photosynthesis, including potential yield and quantum yield under illumination, non-photochemical quenching (qNPQ) and photochemical quenching (qP), were measured to assess plant response. The combination of Cercospora and supplemental UV-B radiation in the sensitive line resulted in a decreased photosynthetic efficiency, shown by qNPQ and quantum yield under illumination as compared with that for either stress applied alone. The Fv/Fm was unchanged for plants subjected to UV-B radiation without infection, although the qNPQ decreased. The Cercospora-tolerant line showed no significant differences under the different treatments. Thus, the line tolerant to Cercospora infection also proved to be tolerant to UV-B radiation alone and in combination with the infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.100104.x
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  • 16
    Electronic Resource
    Electronic Resource
    Epidermal transmittance and phenolic composition in leaves of atrazine-tolerant and atrazine-sensitive cultivars of Brassica napus grown under enhanced UV-B radiation (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 107 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Experiments were conducted on the atrazine-tolerant mutant Stallion and the atrazine-sensitive cv. Paroll of Brassica napus L., which were grown under either visible light or with the addition of UV-B radiation (280–320 nm) for 15 days. The mutant has been shown to be sensitive to high levels of visible light as compared to the atrazine-sensitive cultivar and therefore we wished to determine plant response to UV-B radiation with respect to potential pigment changes, certain anatomical features, radiation penetration and partial photosynthesis. With regard to pigment changes, we were particularly interested in whether the compositional shift in flavonol pigments under enhanced UV-B radiation, previously suggested to favour increased antioxidant activity, is confined to the adaxial epidermis, which generally receives most UV-B radiation or whether the pigment shift is also inducible in the abaxial epidermis.As was to be expected, the penetration of UV-B radiation (310 nm) was lower in the UV-B-exposed plants, which was correlated with an increased amount of UV-screening pigments in the adaxial and abaxial epidermal layers. The main flavonoid glycosides showed the largest shift from kaempferol to quercetin as aglycone moiety in the adaxial epidermal layer. However, in the abaxial epidermal layer the hydroxycinnamic acid (HCA) derivatives and kaempferol glycosides were predominant. Penetration of 430 nm light was higher after UV-B exposure, and probably contributed to the fact that photosynthetic efficiency of photosystem II was unchanged or higher after UV-B exposure. UV-B radiation decreased leaf area in the atrazine-tolerant mutant only. Both cultivars showed an increased leaf thickness after UV-B exposure due to cell elongation mainly of the palisade tissue. This was especially evident in the mutant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.100302.x
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  • 17
    Electronic Resource
    Electronic Resource
    Penetration of UV-A, UV-B and blue light through the leaf trichome layers of two xeromorphic plants, olive and oak, measured by optical fibre microprobes (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 105 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Quartz fibre-optic microprobes were used to monitor the light microenvironment beneath trichome layers of the xeromorphic leaves of two Mediterranean evergreen sclerophylls, Olea europaea and Quercus ilex. Young developing leaves of both plants were densely pubescent on both surfaces of the lamina, whereas the mature leaves were pubescent only on the abaxial side. Trichome layers of young as well as of mature leaves of both plants attenuated almost all incident ultraviolet (UV)-B (310 nm) and UV-A (360 nm) radiation and a considerable portion of blue light (430 nm). Abaxial trichome layers of young leaves were more effective in screening out the incident radiation compared to the adaxial ones of the same leaves and also compared to the abaxial layer of the mature leaves. The abaxial epidermis of dehaired mature leaves of O. europaea was ineffective in absorbing most of the incident UV-B and UV-A radiation. UV and visible spectra beneath trichome layers of O. europaea in mature leaves confirmed that the light microenvironment on the epidermis was deprived in the UV-B, UV-A and partly in the blue spectral regions. It is proposed that the occurrence of a dense trichome layer, especially in young leaves, may play a protective role against not only UV-B radiation damage, but also against high visible irradiance. This function is performed irrespective of the differing anatomy of individual hairs of both plants. The protection provided by the trichomes could afford advantages under stress conditions, especially during leaf development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.105409.x
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  • 18
    Electronic Resource
    Electronic Resource
    Epidermal focussing and effects on light utilization in Oxalis acetosella (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 91 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: lmage analysis was used to quantify the lateral heterogeneity of the radiation field within the palisade of Oxialis acetosella L. leaves. Oxalis acetosella epidermal cells focus light up to four times incident irradiance, resulting in regions of high and low internal fluenec rate within the palisade. Chlorophyll fluorescence from leaves irradiated with directional light was found to originate primarily from palisade cell chloroplasts located within focal zones. When the internal radiation field was made more homogeneous by using diffuse light or by coating the leaf with a layer of mineral oil to eliminate epidermal focussing, the characteristics of the chlorophyll fluorescence signal were altered: non-photochemical quenching (qN) increased, while relaxation of qN was slowed. This indicates that upper palisade chloroplasts may fine-tune their light utilization to the intra leaf light microenvironment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb03001.x
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  • 19
    Electronic Resource
    Electronic Resource
    The effect of exposure to enhanced UV-B radiation on the penetration of monochromatic and polychromatic UV-B radiation in leaves of Brassica napus (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Using quartz optical fibres, penetration of both monochromatic (310 nm) and polychromatic UV-B (280–320 nm) radiation in leaves of Brassica napus L. (cv. Ceres) was measured. Plants were grown under either visible light (750 μmol m−2 s−1 photosynthetically active radiation) or with the addition of 8. 9 KJ m−2 day−1 biologically effective UV-B (UV-BBE) radiation. Results showed that of the 310 nm radiation that penetreated the leaf, 90% was within the intial one third of the leaf with high attenuation in the leaf epidermis, especially in UV-treated plants. Polychromatic UV-B radiation, relative to incident radiation, showed a relatively uniform spectral distribution within the leaf, except for collimated radiation. Over 30% of the UV-screening pigments in the leaf, including flavonoids, were found in the adaxial epidermal layer, making this layer less transparent to UV-B radiation than the abaxial epidermis, which contained less than 12% of the UV-screening pigments. UV-screening pigments increased by 20% in UV-treated leaves relative to control leaves. Densely arranged epicuticular wax on the adaxial leaf surface of UV-treated plants may have further decreased penetration of UV-B radiation by reflectance. An increased leaf thickness, and decreases in leaf area and leaf dry weight were also found for UV-treated plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb01727.x
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  • 20
    Electronic Resource
    Electronic Resource
    Ultraviolet-B radiation causes shade-type ultrastructural changes in Brassica napus (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cell and chloroplast structural changes in palisade cells from mature leaves of Brassica napus L. cv. Paroll were quantified following exposure of plants to enhanced ultraviolet-B (280–320 nm; 13 kJ m−2 day−1 biologically effective UV-B) radiation at two different levels of photosynthetically active radiation (PAR, 400–700 nm; 200 and 700 μmol m−2 s−1). Short-term changes in leaf ultrastructure after 30 min and longer term changes after one day and one week were analyzed using stereological techniques incorporating light and electron microscopy and mathematical reconstruction of a mean cell for each sample.Ultraviolet-B together with either relatively high or low PAR resulted in cell structural changes resembling those typical of plants under shade conditions, with the most marked response occurring after 30 min of UV-B radiation. The ultrastructural changes at the cellular level were generally similar in both the relatively high and low PAR plus UV-B radiation treatments. The surface areas of all three thylakoid types, the appressed, non-appressed and margin thylakoids increased in the palisade tissue under supplemental UV-B irradiation.Although the appressed and non-appressed thylakoids increased in surface area, they did not increase equally, leaving open the possibility that the two thylakoid types have independent regulatory systems or different sensitivity to UV-B radiation. Increased thylakoid packing (mm2 thylakoid membrane per mm2 leaf surface) in UV-B-exposed plants may increase the statistical probability of photon interception. An increased level of UV-absorbing pigments after one week of supplemental UV-B radiation did not prevent or significantly ameliorate UV effects. Our data supported the assumption that UV-B radiation may have a regulatory role besides damaging effects and that an increased UV-B environment will likely increase this regulatory influence of UV-B radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01071.x
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