Enhanced UV-B Radiation Research Articles

Effects of ultraviolet-B radiation on crop growth, development, yield and leaf pigment concentration of tartary buckwheat ( Fagopyrum tataricum) under field conditions

Tartary buckwheat ( Fagopyrum tataricum Gaertn.) crops were grown in sheltered field plots for two consecutive seasons under reduced, near-ambient and two supplemental levels of ultraviolet-B radiation (UV-B, 280–315 nm). The effects of different UV-B treatments on crop growth, development, yield and leaf pigment levels were determined. All four treatments were replicated three times in a randomized complete block design. Near-ambient solar UV-B (approximately 84–88% of solar UV-B) was provided by using a Teflon film, attenuated solar UV-B radiation (43–49% reduction in solar UV-B) by using a cellulose acetate film, and supplemental UV-B radiation by the use of UV fluorescent lamps (two levels: 5.30 and 8.50 kJ m −2 day −1). The prevailing ambient solar radiation caused a negative effect on plant growth and yield. The crop growth, total biomass, final seed yield, thousand-grain weight and the amount of photosynthetic pigments decreased under near-ambient and enhanced UV-B radiation, while crop development was promoted by enhanced UV-B radiation. Leaf rutin concentration and the amount of UV-B absorbing compounds were increased by UV-B with the exception of the 8.50 kJ m −2 day −1 supplemental levels. Our results showed that tartary buckwheat is a potentially UV-B sensitive species, and the crop response to UV-B radiation is associated with UV-B intensity, environmental factors and growing season.

Mediated Modeling of the Impacts of Enhanced UV‐B Radiation on Ecosystem Services

This article describes the use of group model building to facilitate interaction with stakeholders, synthesize research results and assist in the development of hypotheses about climate change at the global level in relation to UV-B radiation and ecosystem service valuation. The objective was to provide a platform for integration of the various research components within a multidisciplinary research project as a basis for interaction with stakeholders with backgrounds in areas other than science. An integrated summary of the scientific findings, along with stakeholder input, was intended to produce a bridge between science and policymaking. We used a mediated modeling approach that was implemented as a pilot project in Ushuaia, Argentina. The investigation was divided into two participatory workshops: data gathering and model evaluation. Scientists and the local stakeholders supported the valuation of ecosystem services as a useful common denominator for integrating the various scientific results. The concept of economic impacts in aquatic and marsh systems was represented by values for ecosystem services altered by UV-B radiation. In addition, direct local socioeconomic impacts of enhanced UV-B radiation were modeled, using data from Ushuaia. We worked with 5 global latitudinal regions, focusing on net primary production and biomass for the marine system and on 3 plant species for the marsh system. Ecosystem service values were calculated for both sectors. The synthesis model reflects the conclusions from the literature and from experimental research at the global level. UV-B is not a significant stress for the marshes, relative to the potential impact of increases in the sea level. Enhanced UV-B favors microbial dynamics in marine systems that could cause a significant shift from primary producers to bacteria at the community level. In addition, synergetic effects of UV-B and certain pollutants potentiate the shift to heterotrophs. This may impact the oceanic carbon cycle by increasing the ratio of respiratory to photosynthetic organisms in surface waters and, thus, the role of the ocean as a carbon sink for atmospheric CO2. In summary, although changes in the marine sector due to anthropogenic influences may affect global climate change, marshes are expected to primarily be affected by climate change.

Ecotoxicological Effects of Combined UVB and Organic Contaminants in Coastal Waters: A Review

ABSTRACTOrganisms living in coastal waters are exposed to anthropogenic contaminants from terrestrial drainage, ice melting and maritime traffic and to enhanced UVB radiation (UVBR; 280–320 nm) caused by decreased concentrations of ozone in the stratosphere. This article reviews available information about the combined effects of UVBR and selected hydrosoluble contaminants potentially present in surface waters on marine species and especially on plankton community structure in high‐latitude coastal zones. Effects of UVBR on three selected pesticides (Atrazine, carbaryl and Acifluorfen) and possible induction of phototoxicity are reviewed. Most toxicological studies have been conducted under laboratory conditions with questionable relevance for coastal marine ecosystems. Similarly, photoactivation of polycyclic aromatic hydrocarbons (PAHs) has been closely examined and reported effects on aquatic species summarized. Experiments with field‐sampled communities demonstrated the complexity and the difficulty in determining the impact of multiple stressors on an aquatic ecosystem, even for ecosystems simplified by eliminating large grazers and fish. Nutrient status, specific composition and light history have influenced the different responses of planktonic assemblages exposed to enhanced UVBR and water‐soluble fraction (WSF) from crude oil or to tributyltin. Plankton assemblages subjected to changes in the ozone hole were physiologically stressed and more susceptible to WSF tox‐icity than communities from less enhanced UVBR‐impacted sites. A close relationship between phytoplankton assemblages and bacteria was observed in all experiments in mesocosms. A contaminant‐induced phytoplankton crash after a bloom event may release important carbon and nutrient sources for bacteria. The magnitude of phytoplanktonic mortality induced by a contaminant probably influenced how rapidly bacteria grew over time. The transition from a herbivorous food web to a microbial food web has significant ecological implications for carbon cycling and energy flow in pelagic systems. A high phytoplankton mortality implies a situation in which the potential for downward carbon export from surface waters is high. In contrast, high bacterial enrichment implies that the phytoplankton carbon is largely recycled in surface waters through a microbial loop and does not contribute significantly to sinking particle flux. The most ecologically relevant results were obtained with mesocosm studies using field‐collected communities. The enhancement of hydrocarbon toxicity in the presence of a high level of UVBR cannot be described as being a synergistic or an additive effect, because the WSF alone is not toxic and may even be beneficial by increasing bacterial activity. This is a case in which one stressor has the ability to modify another stressor to cause it to be toxic to target organisms. These abiotically induced interactions may be important for biological communities exposed to extreme conditions when physical, chemical or photochemical reactions modify the nature of environmental stressors before they interact with biological functions. The need for models on the impacts of multiple stressors on biodiversity and ecosystem functioning is emphasized.

UV-B가 강낭콩(Phaseolus vulgaris L.)의 지방산 구성, 지질과산화 및 polyamine 함량에 미치는 영향

UV-B에 의한 강낭콩 식물의 피해양상, 지질과산화, 지질조성 변화와 UV-B에 대한 식물의 방어기작 등을 조사하기 위하여 3주간 UV-B 조사 실험을 수행하였다. UV-B 처리에 의해 초장이 약 22% 정도 감소하는 것으로 나타났다. MDA 함량은 UV-B 처리에 의해 약 50% 정도 증가하는 것으로 나타났다. Glutathione 및 ascorbate acid 함량은 UV-B 조사에 의해 산화형이 증가하고 환원형이 감소하는 것으로 나타났다. UV-B 조사에 의한 지방산 구성 변화를 조사한 결과 당지질 및 인지질 모두 UV-B조사에 의해 포화지방산이 증가하는 것에 반해, 불포화지방산이 감소하는 것으로 나타났다. 강낭콩 잎에는 주로 3종류의 polyamine이 존재하는 것으로 나타났으며, 3종류 모두 UV-B 조사에 의해 증가하는 것으로 나타났다. 본 실험 결과로 볼 때, UV-B 조사는 활성산소를 생성하여 생체막 지질에 직접적인 영향을 미치는 것으로 나타났으며, ascorbate acid, glutathione, polyamine 등의 항산화물질들이 이에 대한 피해를 최소화하기 위하여 작용하는 것으로 나타났다. To investigate the effects of UV-B on fatty acid composition, lipid peroxidation and biochemical defense responses of plant, kidney bean (Phaseolus vulgaris L.) was subjected to enhanced UV-B irradiation [daily dose : 0.02.(No UV-B) and 11.36 (enhanced UV-B) <TEX>$kJ\;m^{-2};UV-B_{BE}$</TEX>] for 3 weeks. UV-B drastically inhibited both height and dry weight of kidney bean. The content of malondialdehyde significantly increased by about 50% after 3 weeks of UV-B irradiation. The ratio of unsaturated to saturated fatty acids of kidney bean was increased by UV-B irradiation. Three major polyamines of kidney bean leaves : putrescine, spermidine and spermine, were observed. All of the polyamine contents were increased with UV-B irradiation. These results suggested that enhanced UV-B radiation caused oxidative stress on lipids and biochemical protection responses might be activated to prevent from damaging effects of oxidative stress generated by UV-B irradiation.

Photosynthesis and growth response of Calamagrostis arundinacea and C. villosa to enhanced UV-B radiation

Calamagrostis arundinacea L. (Roth.) and C. villosa (Chaix.) J.F. Gmel are two grass species substituting forest communities on deforested areas in Central Europe. They were exposed to enhanced ultraviolet-B (UV-B, λ = 290-320 nm) radiation during 22 weeks. A system of modulated lamps operating under field conditions was used to simulate a 25 % increase of incident UV-B radiation. CO2 assimilation seemed to be limited by a decrease of stomatal conductance (g s) in C. arundinacea, whereas carboxylation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) was not affected. On the contrary, g s and RuBPCO activity decreased in C. villosa. These physiological adjustments resulted in growth changes; above-ground biomass decreased in C. villosa (prevailing negative effect) and significantly increased in C. arundinacea (prevailing positive effect) in response to enhanced UV-B radiation.

Variable phytoplankton response to enhanced UV-B and nitrate addition in mesocosm experiments at three latitudes (Canada, Brazil and Argentina)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 313:57-72 (2006) - doi:10.3354/meps313057 Variable phytoplankton response to enhanced UV-B and nitrate addition in mesocosm experiments at three latitudes (Canada, Brazil and Argentina) Maria Lorena Longhi1,4, Gustavo Ferreyra1,2, Irene Schloss2,3, Suzanne Roy1,* 1Institut des Sciences de la Mer de Rimouski, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 2Instituto Antártico Argentino, Cerrito 1248, C1010AAZ, Buenos Aires, Argentina 3Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina 4Present address: Faculté des Sciences, Université du Québec à Montréal, succ. Centre-Ville, C.P. 8888, Montréal, Québec H3C 3P8, Canada *Corresponding author. Email: suzanne_roy@uqar.qc.ca ABSTRACT: The influence of nitrate enrichment on the response of natural phytoplankton populations to enhanced UV-B radiation was tested during a series of week-long mesocosm (1800 l) experiments carried out in Rimouski (Canada), Ubatuba (Brazil) and Ushuaia (southern Argentina). We set up 2 mesocosms at each site, one was submitted to ambient UV-B levels while the other received enhanced UV-B levels corresponding to a local 60% ozone-depletion scenario, and both were continuously mixed. Samples from the mesocosms were incubated in UV-transparent plastic bags (4 l) floating at the surface for 24 h. Half of these received nitrate, phosphate and silicate enrichments while for the other half nitrate was omitted. Responses in terms of photochemical yield (Fv/Fm, where Fv is variable fluorescence after dark relaxation and Fm is maximal fluorescence following short pulses of saturating white light, pulse amplitude-modulated [PAM] fluorescence) and high-performance liquid chromatography (HPLC) pigments, differed among sites and over time, particularly for Rimouski, where a large bloom took place in the mesocosms. Enhanced UV-B significantly increased photoinhibition in the surface bags, while nitrate addition partly relieved this inhibition only during the post-bloom period. The net growth of fucoxanthin was reduced by enhanced UV-B except during the post-bloom period, when it increased, probably because grazing pressure was reduced under enhanced UV-B (strong decrease in ciliates). In Ubatuba, cells were affected by the high ambient-light irradiances at the surface, and enhanced UV-B had no further effect, irrespective of the nutrient status. At Ushuaia, enhanced UV-B prevented all increases of fucoxanthin and chl a, with much less effect on chl b (green algae), and no nutrient response was observed. This strong and consistent negative response to enhanced UV-B is likely to be related to the cold temperature prevailing at Ushuaia at the time of the experiment (slowing repair) as well as the local community composition. In contrast, no effects of enhanced UV-B were observed in the stirred mesocosms at the 3 sites, indicating that mixing moderated the UV-B effects in all 3 experiments. KEY WORDS: UV-B radiation · Nutrient status · Phytoplankton · Fv/Fm · Pigments · Latitudinal variations · Nitrate availability Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 313. Online publication date: May 11, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Lensing effect on underwater levels of UV radiation

In the austral spring/summer the Antarctic ozone hole can cause enhanced UVB radiation events in the photic zone of the Southern Ocean. If these events coincide with rich shallow‐water algal blooms in the marginal ice zone, a high mortality rate can result. The contribution to the sub‐surface radiation field of UVB light flashes created through the focusing of collimated solar radiation by surface waves is sought. A three‐dimensional Monte Carlo model with cyclic boundaries was developed to investigate the intensity and temporal characteristics of UVB light flashes. The model accounts for reflection, refraction, absorption and scattering of photons, and is based on a data set of ocean optical properties from 280 to 700 nm. The model includes the effect of biogenic particles and covarying yellow substance. Model runs were performed with collimated light for both 350 and 300 nm. Runs for a flat ocean surface revealed a rapid increase of statistical fluctuations (noise) with depth. This increase was more pronounced at 300 nm. Model runs with sinusoidal surface waves showed significant light flashes which were stronger and penetrated more deeply at 350 nm. At 300 nm, the flashes could exceed the collimated part of surface irradiance for 25% of the time, but were negligible at depths greater than 3.7 m. Small sinusoidal waves produced a more intense focus at a shallower depth than larger sinusoidal waves of the same steepness. Model runs with a more complex ocean surface were less conclusive, as the light flashes were disguised by variations in the water elevation.

잎들깨 수량과 단백질체 발현에 미치는 UV-B의 영향

Plastichouse cultivation for crops and vegetables in the winter has been widely popularized in Korea. In the vinylhouse Ultraviolet B penetration is lower than in the field, and so some problems, as plant overgrowth and outbreak of disease, occurred frequently. The effect of artificial supplement ultraviolet B radiation on the physiological responses and yield of perilla (perilla frutescens) was investigated UV-B ray was radiated on perilla with the 10th leaf stage at the distance of 90, 120 and 150 cm from the plant canopy for 30 days after planting in the vinylhouse. The production of fresh perilla leaves was high in the order of plastic house, ambient+50% of supplemental UV-B, ambient ambient+100% of supplemental UV-B. Enhanced UV-B radiation affected the intensity of thirty-three proteins in 2-dimensional electrophoretic analysis of proteins and ten proteins out of them seemed to be responsive to UV-B : a protein was, ATP synthase CF1 alpha chain, down regulated and nine proteins (Chlorophyll a/b bindng protein type I, Chlorophyll a/b binding protein type II precursor, Photosystem I P700 chlorophyll a apoprotein A2, DNA recombination and repair protein recF, Galactinol synthase, S-adenosyl-L-methionine, Heat shock protein 21, Calcium-dependent protein kinase(CDPK)-like, Catalase) were up-regulated.

Long-term exposure to enhanced UV-B radiation has no significant effects on growth or secondary compounds of outdoor-grown Scots pine and Norway spruce seedlings

The effects of long-term enhanced UV-B radiation on growth and secondary compounds of two conifer species were studied in an outdoor experiment. Scots pine (Pinus sylvestris) seedlings were exposed for two growing seasons and Norway spruce (Picea abies) seedlings for three growing seasons to supplemental UV-B radiation, corresponding to a 30% increase in ambient UV-B radiation. The experiment also included appropriate controls for ambient and increased UV-A radiation. Enhanced UV-B did not affect the growth of the conifer seedlings. In addition, neither the concentrations of terpenes and phenolics in the needles nor the concentrations of terpenes in the wood were affected. However, in the UV-A control treatment the concentrations of diterpenes in the wood of Scots pine decreased significantly compared to the ambient control. Apparently, a small increase in UV-B radiation has no significant effects on the secondary compounds and growth of Scots pine and Norway spruce seedlings.

Effects of enhanced UV-B radiation on nitrogen fixation in arctic ecosystems

Recent global climate models predict a further significant loss of ozone in the next decades, with up to 50% depletion of the ozone layer over large parts of the Arctic resulting in an increase in ultraviolet-B radiation (UV-B) (280–315 nm) reaching the surface of the Earth. The percentage of total annual ecosystem N input due to biological nitrogen fixation by cyanobacteria might be as high as 80% and the contribution to total annual N uptake by plants up to 20%. A possible reduction of nitrogen fixation raises serious concerns about already nutrient impoverished plant communities. This review shows that nitrogen fixation by moss-associated cyanobacteria in arctic vegetation was dramatically reduced after six years of exposure to enhanced UV-B radiation. In subarctic vegetation, nitrogen fixation activity of moss-associated cyanobacteria was not affected by 6 years of enhanced UV-B radiation. However, a 50% increase of summer precipitation resulted in a 5- to 6-fold increase in activity. Long-term effects of UV-B radiation on nitrogen fixation activity have been examined only in two lichens, giving contrasting results. Peltigera aphthosa (L.) Willd., having external cephalodia, experienced a significant reduction, whereas Peltigera didactyla (With.) J.R. Laudon, having cyanobacteria in the photobiont layer below the upper cortex, did not experience any changes due to radiation regimes. The difference is probably related to the location of the cyanobacteria. While the Nostoc cells are protected by the fungal, melanized upper cortex in P. didactyla, they are exposed and unprotected in P. aphthosa, and their own synthesis of UV-B absorbing compounds appears to be low. Under certain environmental conditions, an increasing UV-B radiation will dramatically affect nitrogen fixation in arctic tundra vegetation, which in turn may have severe influence on the nitrogen budget in these environments. Further long-term studies are necessary to conclude if these effects are temporal and how concurrent climatic changes will influence the nitrogen balance of the ecosystem.

Effects of quercetin and enhanced UV-B radiation on the soybean (Glycine max) leaves

The possible ameliorative effects of quercetin on soybean [Glycine max (L.) Merr.] leaves exposed to UV-B radiation were conducted in greenhouse. The symmetrical leaves supplied with quercetin solution (0.2%, 1%) were exposed to UV-B radiation (0, 3.5, 6.5 kJ m−2 d−1). 0.2% quercetin ameliorated leaf photosynthesis, improved leaf water content (LWC), and decreased lipid oxidation. The unfavorable effect on photosynthetic parameter was displayed in 1% quercetin treatment. The effect of quercetin on phenylalanine ammonia lyase (PAL) activity varied with the quercetin concentration, UV-B radiation intensity and leaf development. In the later development polyphenol oxidase (PPO) activity was increased significantly by quercetin treatments. We suggested that quercetin with suitable concentration could serve as UV-B protective agent partly due to its antioxidant capacity.

Effects of enhanced ultraviolet-B radiation on water use efficiency, stomatal conductance, leaf nitrogen content and morphological characteristics of Spiraea pubescens in a warm-temperate deciduous broad-leaved forest

Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing, was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4 kJ/m2 for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ13C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency (WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular CO2 concentration/ air CO2 concentration (Ci/Ca) (4.0%), and an increase in leaf tissue δ13C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance, δ13C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation between soil water content and leaf water content, δ13C, Ci/Ca, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content. These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment, it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics.

EFFECTS OF ENHANCED UV_B RADIATION ON WATER USE EFFICIENCY, STOMATAL CONDUCTANCE, LEAF NITROGEN CONTENT AND MORPHOLOGICAL CHARACTERISTICS OF SPIRAEA PUBESCENS IN A WARM_TEMPERATE DECIDUOUS BROAD_LEAF FOREST

Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone, is distributed in the Dongling Mountain area of Beijing, was exposed to ambient and enhanced ultraviolet-B (UV-B, 280-320 nm) radiation by artificially supplying a daily dose of 9.4 kJ•m^(-2) for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ 13C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency (WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular CO2 concentration/air CO2 concentration (C(subscript i)/C(subscript a)) (4.0%), and an increase in leaf tissue δ 13C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%), and WUE (4.1%). The effects of UV-B on the plant were greatly affected by the water content of the deep soil (30-40 cm). During the dry season, differences in the stomatal conductance, δ 13C, and WUE between the control and UV-B treated shrubs were very small, whereas differences became much greater when soil water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation between soil water content and leaf water content, δ 13C, C(subscript i)/C(subscript a), stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content. These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment, it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics.

Modelled effects of ambient UV radiation on a natural Antarctic marine microbial community

Ozone depletion over Antarctica has enhanced ultraviolet-B radiation (UVBR, 280 to 320 nm wavelength). We measured the effect of ambient solar UV radiation on the biomass and species composition of phytoplankton, protozoa, bacteria and dissolved organic carbon (DOC) in natural microbial assemblages from Antarctic coastal waters. Results were modelled to determine the features of the irradiance responsible for changes in the biomass of these microbial components and responses of individual phytoplankton taxa. Model results showed that changes in phytoplankton biomass were primarily due to dose rate, indicating that their UV-induced mortality resulted from the equilibrium between damage and repair. However, there was considerable variability between individual species in their response to dose and dose rate. Changes in protozoan biomass were mainly due to dose and were likely due to community-level, trophodynamic interactions. UV radiation did not measurably affect bacterial biomass, but resulted in increasing concentrations of DOC. We found a threshold of erythemal irradiance of 28 mW m-2, approximating peak noon-time irradiance at 3.6 m depth near the summer solstice in Antarctic coastal waters, below which no change in the community structure was observed, but above which phytoplankton mortality and protozoan biomass increased. Our results indicate that enhanced UVB radiation in Antarctic waters increases phytoplankton mortality and causes changes in the structure, function and composition of the microbial community that are likely to return more photoassimilated carbon to the atmosphere. © Inter-Research 2006.

Stratospheric Ozone Depletion: High Arctic Tundra Plant Growth on Svalbard is not Affected by Enhanced UV-B after 7 years of UV-B Supplementation in the Field

The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78 degrees N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996 and 2002. After 7 years of exposure to enhanced UV-B radiation, plant cover, density, morphological (leaf fresh and dry weight, leaf thickness, leaf area, reproductive and ecophysiological parameters leaf UV-B absorbance, leaf phenolic content, leaf water content) were not affected by enhanced UV-B radiation. DNA damage in the leaves was not increased with enhanced UV-B in Salix polaris and Cassiope tetragona. DNA damage in Salix polaris leaves was higher than in leaves of C. tetragona. The length of male gametophyte moss plants of Polytrichum hyperboreum was reduced with elevated UV-B as well as the number of Pedicularis hirsuta plants per plot, but the inflorescence length of Bistorta vivipara was not significantly affected. We discuss the possible causes of tolerance of tundra plants to UV-B (absence of response to enhanced UV-B) in terms of methodology (supplementation versus exclusion), ecophysiological adaptations to UV-B and the biogeographical history of polar plants.

Microwave Treatment of Eight Seconds Protects Cells of Isatis indigotica from Enhanced UV-B Radiation Lesions

Microwave Treatment of Eight Seconds Protects Cells of Isatis indigotica from Enhanced UV-B Radiation Lesions

Ecotoxicological Effects of Combined UVB and Organic Contaminants in Coastal Waters: A Review

Organisms living in coastal waters are exposed to anthropogenic contaminants from terrestrial drainage, ice melting and maritime traffic and to enhanced UVB radiation (UVBR; 280-320 nm) caused by decreased concentrations of ozone in the stratosphere. This article reviews available information about the combined effects of UVBR and selected hydrosoluble contaminants potentially present in surface waters on marine species and especially on plankton community structure in high-latitude coastal zones. Effects of UVBR on three selected pesticides (Atrazine, carbaryl and Acifluorfen) and possible induction of phototoxicity are reviewed. Most toxicological studies have been conducted under laboratory conditions with questionable relevance for coastal marine ecosystems. Similarly, photoactivation of polycyclic aromatic hydrocarbons (PAHs) has been closely examined and reported effects on aquatic species summarized. Experiments with field-sampled communities demonstrated the complexity and the difficulty in determining the impact of multiple stressors on an aquatic ecosystem, even for ecosystems simplified by eliminating large grazers and fish. Nutrient status, specific composition and light history have influenced the different responses of planktonic assemblages exposed to enhanced UVBR and water-soluble fraction (WSF) from crude oil or to tributyltin. Plankton assemblages subjected to changes in the ozone hole were physiologically stressed and more susceptible to WSF toxicity than communities from less enhanced UVBR-impacted sites. A close relationship between phytoplankton assemblages and bacteria was observed in all experiments in mesocosms. A contaminant-induced phytoplankton crash after a bloom event may release important carbon and nutrient sources for bacteria. The magnitude of phytoplanktonic mortality induced by a contaminant probably influenced how rapidly bacteria grew over time. The transition from a herbivorous food web to a microbial food web has significant ecological implications for carbon cycling and energy flow in pelagic systems. A high phytoplankton mortality implies a situation in which the potential for downward carbon export from surface waters is high. In contrast, high bacterial enrichment implies that the phytoplankton carbon is largely recycled in surface waters through a microbial loop and does not contribute significantly to sinking particle flux. The most ecologically relevant results were obtained with mesocosm studies using field-collected communities. The enhancement of hydrocarbon toxicity in the presence of a high level of UVBR cannot be described as being a synergistic or an additive effect, because the WSF alone is not toxic and may even be beneficial by increasing bacterial activity. This is a case in which one stressor has the ability to modify another stressor to cause it to be toxic to target organisms. These abiotically induced interactions may be important for biological communities exposed to extreme conditions when physical, chemical or photochemical reactions modify the nature of environmental stressors before they interact with biological functions. The need for models on the impacts of multiple stressors on biodiversity and ecosystem functioning is emphasized.

Combined effects of elevated UV-B radiation and the addition of selenium on common (Fagopyrum esculentum Moench) and tartary [Fagopyrum tataricum (L.) Gaertn.] buckwheat

The combined effects of UV-B irradiation and foliar treatment with selenium on two buckwheat species, common (Fagopyrum esculentum Moench) and tartary [Fagopyrum tataricum (L.) Gaertn.] buckwheat, that underwent different intensity of breeding, were examined. Plants grown outdoors under three levels of UV-B radiation were studied for 9 weeks, from sowing to ripening. At week 7 they were sprayed with solution containing 1 g(Se) m-3 that presumably mitigates UV-B stress. Morphological, physiological, and biochemical parameters of the plants were monitored. Elevated UV-B radiation, corresponding to a 17 % reduction of the ozone layer, induced synthesis of UV absorbing compounds. In both buckwheat species it also caused a reduction in amounts of chlorophyll a during the time of intensive growth, an effect, which was increased in tartary buckwheat in the presence of selenium. The respiratory potential, measured as terminal electron transport system activity, was lower in plants subjected to enhanced UV-B radiation during the time of intensive growth. The effective quantum yield of photosystem 2 was also reduced due to UV-B radiation in both buckwheat species and was mitigated by the addition of Se. Se treatment also mitigated the stunting effect of UV-B radiation and the lowering of biomass in common buckwheat.

Tundra plants protect the soil surface from UV

In the Arctic, seasonal ozone depletion is resulting in periods of enhanced UV-B radiation at ground level while regional climate change is associated with increasing temperatures. These changes are likely to alter plant distribution, biodiversity and morphology, which may have knock-on effects for microbially driven biogeochemical cycling and other soil processes. Our study examined the transmission of solar UV radiation through arctic tundra plants using a portable UV radiometer and the DLR-biofilm biological UV dosimeter. A strong negative correlation was found between vegetation cover and UV transmission to the soil surface. Penetration of UV to the soil beneath tundra plants varied depending upon plant morphology, being greater through low creeping plants than cushion plants, grasses or mosses. UV transmission to the soil surface beyond the foliage edge also varied with plant morphology and the presence of flowers.

Red Clover Trifolium pratense L. Phytoestrogens: UV-B Radiation Increases Isoflavone Yield, and Postharvest Drying Methods Change the Glucoside Conjugate Profiles

Isoflavone extracts of red clover Trifolium pratense L. (cv. Pawera) with dissimilar glucoside conjugate profiles were obtained by employing different postharvest drying methods. The most prominent isoflavones found were formononetin and biochanin A and their corresponding glucosides and malonyl glucoside esters. Postharvest freeze drying inhibited the conversion of the glycosides to the aglycones, while vacuum drying allowed for maximum conversion of the glycosides to their corresponding aglycones. Air drying produced a low level of the aglycones formononetin and biochanin A, and oven drying promoted decarboxylation of the malonyl glucosides to the acetyl glucosides. Exposure to enhanced UV-B radiation resulted in an increase in total formononetin and biochanin A isoflavone levels, indicating that harvest during a period of high ambient UV-B radiation may be appropriate for maximum yield. The levels of caffeic acid and flavonols also increased by about 40 and 250%, respectively, on exposure to enhanced UV-B radiation.