Effects Of Solar UV-B Radiation Research Articles

Interactive Effect of Solar UV-B Radiation and Planting Density on Sucker Development and Physiology of Enset (Ensete ventricosum) Variety-Entada

Interactive Effect of Solar UV-B Radiation and Planting Density on Sucker Development and Physiology of Enset (Ensete ventricosum) Variety-Entada

Effects of UV radiation on aquatic ecosystems and interactions with other environmental factors.

Interactions between climate change and UV radiation are having strong effects on aquatic ecosystems due to feedback between temperature, UV radiation, and greenhouse gas concentration. Higher air temperatures and incoming solar radiation are increasing the surface water temperatures of lakes and oceans, with many large lakes warming at twice the rate of regional air temperatures. Warmer oceans are changing habitats and the species composition of many marine ecosystems. For some, such as corals, the temperatures may become too high. Temperature differences between surface and deep waters are becoming greater. This increase in thermal stratification makes the surface layers shallower and leads to stronger barriers to upward mixing of nutrients necessary for photosynthesis. This also results in exposure to higher levels of UV radiation of surface-dwelling organisms. In polar and alpine regions decreases in the duration and amount of snow and ice cover on lakes and oceans are also increasing exposure to UV radiation. In contrast, in lakes and coastal oceans the concentration and colour of UV-absorbing dissolved organic matter (DOM) from terrestrial ecosystems is increasing with greater runoff from higher precipitation and more frequent extreme storms. DOM thus creates a refuge from UV radiation that can enable UV-sensitive species to become established. At the same time, decreased UV radiation in such surface waters reduces the capacity of solar UV radiation to inactivate viruses and other pathogens and parasites, and increases the difficulty and price of purifying drinking water for municipal supplies. Solar UV radiation breaks down the DOM, making it more available for microbial processing, resulting in the release of greenhouse gases into the atmosphere. In addition to screening solar irradiance, DOM, when sunlit in surface water, can lead to the formation of reactive oxygen species (ROS). Increases in carbon dioxide are in turn acidifying the oceans and inhibiting the ability of many marine organisms to form UV-absorbing exoskeletons. Many aquatic organisms use adaptive strategies to mitigate the effects of solar UV-B radiation (280-315 nm), including vertical migration, crust formation, synthesis of UV-absorbing substances, and enzymatic and non-enzymatic quenching of ROS. Whether or not genetic adaptation to changes in the abiotic factors plays a role in mitigating stress and damage has not been determined. This assessment addresses how our knowledge of the interactive effects of UV radiation and climate change factors on aquatic ecosystems has advanced in the past four years.

Beneficial effects of solar UV‐B radiation on soybean yield mediated by reduced insect herbivory under field conditions

Ultraviolet-B radiation (UV-B: 280-315 nm) has damaging effects on cellular components and macromolecules. In plants, natural levels of UV-B can reduce leaf area expansion and growth, which can lead to reduced productivity and yield. UV-B can also have important effects on herbivorous insects. Owing to the successful implementation of the Montreal Protocol, current models predict that clear-sky levels of UV-B radiation will decline during this century in response to ozone recovery. However, because of climate change and changes in land use practices, future trends in UV doses are difficult to predict. In the experiments reported here, we used an exclusion approach to study the effects of solar UV-B radiation on soybean crops, which are extensively grown in many areas of the world that may be affected by future variations in UV-B radiation. In a first experiment, performed under normal management practices (which included chemical pest control), we found that natural levels of UV-B radiation reduced soybean yield. In a second experiment, where no pesticides were applied, we found that solar UV-B significantly reduced insect herbivory and, surprisingly, caused a concomitant increase in crop yield. Our data support the idea that UV-B effects on agroecosystems are the result of complex interactions involving multiple trophic levels. A better understanding of the mechanisms that mediate the anti-herbivore effect of UV-B radiation may be used to design crop varieties with improved adaptation to the cropping systems that are likely to prevail in the coming decades in response to agricultural intensification.

Effects of solar UV-B radiation on the efficiency of PSII photochemistry in the alpine plant <I>Saussurea superba</I> under different weather conditions in the Qinghai-Tibet Plateau of China

Effects of solar UV-B radiation on the efficiency of PSII photochemistry in the alpine plant <I>Saussurea superba</I> under different weather conditions in the Qinghai-Tibet Plateau of China

Does Enhanced Solar UV‐B Radiation Affect Marine Primary Producers in Their Natural Habitats?

This article is a highlight of the paper by Li et al. in this issue of Photochemistry and Photobiology as well as a short summary of the research on the effects of solar UV-B radiation on primary production in the oceans. Laboratory experiments under controlled conditions using artificial light sources indicate species-specific damage of many phytoplankton groups. Mesocosm studies in enclosures of limited volume allow analyzing UV effects in multigeneration monitoring of natural assemblages. Field studies to determine the effects of short-wavelength solar radiation require sensitive instrumentation and measurements over extended areas of the open ocean to yield significant results. Results from a cruise described in the paper by Li et al. indicate clear effects of UV-B and UV-A on the photosynthetic carbon fixation of phytoplankton communities with spatial differences between coastal and open-ocean waters. Increasing temperatures and acidification in the ocean due to global climate change may exacerbate the detrimental effects of solar UV-B radiation.

Cutaneous vitamin D synthesis versus skin cancer development: The Janus faces of solar UV-radiation.

In scientific and public communities, there is an ongoing discussion how to balance between positive and negative effects of solar UV-exposure. On the one hand, solar UV-radiation represents the most important environmental risk factor for the development of non-melanoma skin cancer. Consequently, UV protection is an important measure to prevent these malignancies, especially in risk groups. Otherwise, approximately 90% of all vitamin D needed by the human body has to be formed in the skin through the action of UV-radiation. This dilemma represents a serious problem, for an association of vitamin D-deficiency and multiple independent diseases including various types of cancer, bone diseases, autoimmune diseases, infectious diseases, cardiovascular diseases and hypertension has now been reported in a large number of investigative and epidemiologic studies. As a consequence, it has been assumed that for the general population in the US, Europe and other countries, the net effects of solar UV B-radiation on human health are beneficial at or near current levels. We and others have shown that strict sun protection causes vitamin D-deficiency/insufficiency and that detection and treatment of vitamin D-deficiency in sun deprived risk groups is of high importance. Although further work is necessary to define an adequate vitamin D-status and adequate guidelines for solar and artificial UV-exposure, it is at present mandatory that public health campaigns and sun protection recommendations to prevent skin cancer consider these facts. In this review, we analyze the present literature to help developing well-balanced recommendations on sun protection that ensure an adequate vitamin D-status. These recommendations will hopefully protect us against adverse effects of UV protection without significantly increasing the risk to develop UV-induced skin cancer.

Specific effects of solar UV-B radiation on plant defense mediated by the jasmonate signaling pathway

Specific effects of solar UV-B radiation on plant defense mediated by the jasmonate signaling pathway

Leaves of Citrus aurantifolia exhibit a different sensibility to solar UV-B radiation according to development stage in relation to photosynthetic pigments and UV-B absorbing compounds production

Plants of Citrus aurantifolia grown in a greenhouse without solar UV radiation (UVR) were transferred outdoors to evaluate the effect of solar UV-B radiation (UVBR, 280–315 nm) in prior-developed leaves, constituted by apical bud and those fully expanded before being taken outdoors, and post-developed leaves, formed by those expanded outdoors. Results demonstrated that over a 40 d outdoor period leaf chlorophyll content and distribution pattern were different with and without solar UVBR. Chlorophyll a, chlorophyll b and total chlorophyll contents in both treatments were higher in prior-developed leaves than in post-developed ones. However, highest values were observed in prior-developed leaves under solar UVBR, whereas in post-developed leaves an opposite trend was observed. Carotenoids content in prior-developed leaves was higher with solar UVBR, whereas in post-developed leaves there were no significant differences in both with and without solar UVBR. In addition, prior-developed leaves under solar UVBR accumulated flavonoids, but not anthocyanins. Growth parameters (e.g. DW, DW/FW ratio, LMA, plant height, length and width of foliar lamina) did not show significant differences between plants grown with and without solar UVBR. Thus, our results demonstrated that C. aurantifolia leaves exhibited a different sensibility to solar UVBR according to development stage in relation to photosynthetic pigments and UV-B absorbing compounds production. In addition, the solar UVBR was not necessary as inductor of photosynthetic protection mechanisms in a short-time growth period. On the other hand, our results also demonstrated that solar UVBR acted as an effective feeding deterrent against citrus leafminer.

太陽紫外線がイネの生育・収量に及ぼす影響評価に関する野外環境試験－部分置換系統を用いた解析

太陽紫外線がイネの生育・収量に及ぼす影響評価に関する野外環境試験－部分置換系統を用いた解析

太陽紫外線がイネの生育・収量に及ぼす影響評価に関する宮城・鹿児島での野外環境試験

太陽紫外線がイネの生育・収量に及ぼす影響評価に関する宮城・鹿児島での野外環境試験

Ecological impact of solar ultraviolet-B (UV-B: 320?290�nm) radiation on Corynebacterium aquaticum and Xanthomonas sp. colonization on tea phyllosphere in relation to blister blight disease incidence in the field

To assess the effects of solar UV-B radiation on phyllosphere bacteria of tea leaves in relation to blister blight disease in the field. The effects of UV-B radiation on the phyllosphere microbiology of tea (Camellia sinensis) were studied in contrasting wet and dry seasons at a tropical site. Wavelength-selective filters were used to separate the effects of UV-B from those of other factors. Bacterial populations were quantified in relation to the incidence of blister blight disease. Attenuation of UV-B increased the survival of Xanthomonas sp. when populations were not water limited, and increased the incidence of blister blight, but had no effect on Corynebacterium aquaticum. The effects of solar UV-B on phyllosphere bacteria were substantial but depended on both species and interactions with other environmental variables. Xanthomonas sp. was more sensitive to UV-B than C. aquaticum, but this did not result in differences in population density under high radiation conditions (dry season), but only in the wet season when other factors were not limiting. The role of UV-B on leaf surface microbiology in the tropics is marked but depends on other conditions, and the contrasting UV-B responses of different organisms can be masked by other limiting factors.

Sudden exposure to solar UV-B radiation reduces net CO(2) uptake and photosystem I efficiency in shade-acclimated tropical tree seedlings.

Tree seedlings developing in the understory of the tropical forest have to endure short periods of high-light stress when tree-fall gaps are formed, and direct solar radiation, including substantial UV light, reaches the leaves. In experiments simulating the opening of a tree-fall gap, the response of photosynthesis in leaves of shade-acclimated seedlings (Anacardium excelsum, Virola surinamensis, and Calophyllum longifolium) to exposure to direct sunlight (for 20-50 min) was investigated in Panama (9 degrees N). To assess the effects of solar UV-B radiation (280-320 nm), the sunlight was filtered through plastic films that selectively absorbed UV-B or transmitted the complete spectrum. The results document a strong inhibition of CO(2) assimilation by sun exposure. Light-limited and light-saturated rates of photosynthetic CO(2) uptake by the leaves were affected, which apparently occurred independently of a simultaneous inhibition of potential photosystem (PS) II efficiency. The ambient UV-B light substantially contributed to these effects. The photochemical capacity of PSI, measured as absorbance change at 810 nm in saturating far-red light, was not significantly affected by sun exposure of the seedlings. However, a decrease in the efficiency of P700 photooxidation by far-red light was observed, which was strongly promoted by solar UV-B radiation. The decrease in PSI efficiency may result from enhanced charge recombination in the reaction center, which might represent an incipient inactivation of PSI, but contributes to thermal dissipation of excessive light energy and thereby to photoprotection.

Effects of solar UV-B radiation on canopy structure of Ulva communities from southern Spain.

Within the sheltered creeks of Cádiz bay, Ulva thalli form extended mat-like canopies. The effect of solar ultraviolet radiation on photosynthetic activity, the composition of photosynthetic and xanthophyll cycle pigments, and the amount of RubisCO, chaperonin 60 (CPN 60), and the induction of DNA damage in Ulva aff. rotundata Bliding from southern Spain was assessed in the field. Samples collected from the natural community were covered by screening filters, generating different radiation conditions. During daily cycles, individual thalli showed photoinhibitory effects of the natural solar radiation. This inhibition was even more pronounced in samples only exposed to photosynthetically active radiation (PAR). Strongly increased heat dissipation in these samples indicated the activity of regulatory mechanisms involved in dynamic photoinhibition. Adverse effects of UV-B radiation on photosynthesis were only observed in combination with high levels of PAR, indicating the synergistic effects of the two wavelength ranges. In samples exposed either to PAR+UV-A or to UV-B+UV-A without PAR, no inhibition of photosynthetic quantum yield was found in the course of the day. At the natural site, the top layer of the mat-like canopies is generally completely bleached. Artificially designed Ulva canopies exhibited fast bleaching of the top layer under the natural solar radiation conditions, while this was not observed in canopies either shielded from UV or from PAR. The bleached first layer of the canopies acts as a selective UV-B filter, and thus prevents subcanopy thalli from exposure to harmful radiation. This was confirmed by the differences in photosynthetic activity, pigment composition, and the concentration of RubisCO in thalli with different positions within the canopy. In addition, the induction of the stress protein CPN 60 under UV exposure and the low accumulation of DNA damage indicate the presence of physiological protection mechanisms against harmful UV-B. A mechanism of UV-B-induced inhibition of photosynthesis under field conditions is proposed.

The effect of solar UV-B radiation on terpenes and biomass production in Grindelia chiloensis (Asteraceae), a woody perennial of Patagonia, Argentina

UV-B radiation is absorbed effectively by nucleic acids and other sensitive targets, potentially causing harmful photochemical effects. Protection against UV-B radiation may be afforded by flavonoids and other phenolics, which absorb strongly in the UV region, but little is known about the role played by other compounds, such as terpenes. Grindelia chiloensis, native of Patagonia (Argentina), can accumulate as much as 25% resin (terpenes) in its leaves. The present investigation was carried out to test the effect of solar UV-B radiation on the allocation of photoassimilates to biomass and terpenes. Exposure to UV-B radiation reduced whole plant biomass, plant height and leaf area, and increased leaf thickness and resin accumulation in Grindelia chiloensis. Higher absorbance was found for refined resin in the UV-B waveband from plants grown under solar UV-B radiation than plants without UV-B radiation. These chemical and structural changes could protect the plant from UV radiation, and may help elucidate the importance of epicuticular resins for a species as G. chiloensis native to an environment with maximum daily integrated values of solar UV-B irradiance.

Effect of solar UV-B radiation on a phyllosphere bacterial community.

The effect of solar UV-B radiation on the population dynamics and composition of the culturable bacterial community from peanut (Arachis hypogeae L.) was examined in field studies using plants grown under UV-B-transmitting (UV-B+) or UV-B-excluding (UV-B-) plastic filters. Our data demonstrate that solar UV-B selection alters phyllosphere bacterial community composition and that UV tolerance is a prevalent phenotype late in the season. The total bacterial population size was not affected by either UV-B treatment. However, isolates from the UV-B+ plots (n = 368) were significantly more UV tolerant than those from the UV-B- (n = 363) plots. UV sensitivity was determined as the minimal inhibitory dose of UV that resulted in an inhibition of growth compared to the growth of a nonirradiated control. The difference in minimal inhibitory doses among bacterial isolates from UV-B+ and UV-B- treatments was mainly partitioned among nonpigmented isolates, with pigmented isolates as a group being characterized as UV tolerant. A large increase in UV tolerance was observed within isolate groups collected late (89 and 96 days after planting) in the season. Identification of 200 late-season isolates indicated that the predominant UV-tolerant members of this group were Bacillus coagulans, Clavibacter michiganensis, and Curtobacterium flaccumfaciens. We selected C. michiganensis as a model UV-tolerant epiphyte to study if cell survival on UV-irradiated peanut leaves was increased relative to UV survival in vitro. The results showed an enhancement in the survival of C. michiganensis G7.1, especially following high UV-C doses (300 and 375 J m(-2)), that was evident between 24 and 96 h after inoculation. A dramatic increase in the in planta/in vitro survival ratio was observed over the entire 96-h experiment period for C. michiganensis T5.1.

The effects of solar UV-B radiation on embryonic mortality and development in three boreal anurans ( Rana temporaria, Rana arvalis and Bufo bufo)

Many species of amphibians have experienced population and range reductions. It has been hypothesized that sensitivity to UV-B may contribute to the population declines of some amphibian species. We performed field experiments to measure the effects of solar UV-B on the hatching success of three Finnish anuran species, the common frog ( Rana temporaria), moor frog ( Rana arvalis) and common toad ( Bufo bufo). Further, the effects of natural UV-B radiation on survival of the tadpoles of the same three species of anurans were tested. A significant percentage of R. temporaria and B. bufo embryos survived when exposed to and protected from solar UV-B and hatching success was not affected by solar radiation. Elimination of solar UV-B significantly increased the hatching success of R. arvalis, but embryonic mortality was high in both treatments. The data indicates that under natural conditions, solar UV-B radiation influences embryo survival in R. arvalis, but has no effect on R. temporaria and B. bufo. Solar UV-B radiation had no effect on R. temporaria and R. arvalis tadpoles, but elimination of UV-B significantly increased survival of B. bufo tadpoles. It seems that ambient UV-radiation levels have no effect on R. temporaria but may affect R. arvalis and B. bufo at different developmental stages.

Effects of solar UV-B radiation on aquatic ecosystems.

Solar UV degrades dissolved organic carbon photolytically so that they can readily be taken up by bacterioplankton. On the other hand solar UV radiation inhibits bacterioplankton activity. Bacterioplankton productivity is far greater than previously thought and is comparable to phytoplankton primary productivity. According to the "microbial loop hypothesis," bacterioplankton is seen in the center of a food web, having a similar function to phytoplankton and protists. The penetration of UV and PAR into the water column can be measured. Marine waters show large temporal and regional differences in their concentrations of dissolved and particulate absorbing substances. A network of dosimeters (ELDONET) has been installed in Europe ranging from Abisko in Northern Sweden to Gran Canaria. Cyanobacteria are capable of fixing atmospheric nitrogen which is then made available to higher plants. The agricultural potential of cyanobacteria has been recognized as a biological fertilizer for wet soils such as in rice paddies. UV-B is known to impair processes such as growth, survival, pigmentation, motility, as well as the enzymes of nitrogen metabolism and CO2 fixation. The marine phytoplankton represents the single most important ecosystem on our planet and produces about the same biomass as all terrestrial ecosystems taken together. It is the base of the aquatic food chain and any changes in the size and composition of phytoplankton communities will directly affect food production for humans from marine sources. Another important role of marine phytoplankton is to serve as a sink for atmospheric carbon dioxide. Recent investigations have shown a large sensitivity of most phytoplankton organisms toward solar short-wavelength ultraviolet radiation (UV-B); even at ambient levels of UV-B radiation many organisms seem to be under UV stress. Because of their requirement for solar energy, the phytoplankton dwell in the top layers of the water column. In this near-surface position phytoplankton will be exposed to solar ultraviolet radiation. This radiation has been shown to affect growth, photosynthesis, nitrogen incorporation and enzyme activity. Other targets of solar UV irradiation are proteins and pigments involved in photosynthesis. Whether or not screening pigments can be induced in phytoplankton to effectively shield the organisms from excessive UV irradiation needs to be determined. Macroalgae show a distinct pattern of vertical distribution in their habitat. They have developed mechanisms to regulate their photosynthetic activity to adapt to the changing light regime and protect themselves from excessive radiation. A broad survey was carried out to understand photosynthesis in aquatic ecosystems and the different adaptation strategies to solar radiation of ecologically important species of green, red and brown algae from the North Sea, Baltic Sea, Mediterranean, Atlantic, polar and tropical oceans. Photoinhibition was quantified by oxygen exchange and by PAM (pulse amplitude modulated) fluorescence measurements based on transient changes of chlorophyll fluorescence.

Effects of solar UV-B radiation on growth, flowering and yield of central and southern European bush bean cultivars (Phaseolus vulgaris L.)

Different cultivars of bush beans (Phaseolus vulgaris L.) originating from Central and Southern Europe were grown from July to August/September 1993 up to 7 and 8 weeks, respectively, in two greenhouses covered by different UV-B-absorbing (280–320nm) plastic foils. By using the ambient UV-B radiation of the southern location (Portugal, 38.7°N, 9.1°W) in one of the greenhouses as intense UV-B radiation compared to the reduced radiation in the second greenhouse at the same place, a difference in UV-B of about 8–10% was simulated. All cultivars examined showed significant reductions in height of up to 31, 8% in most growth phases under intense UV-B. Also fresh and dry weight as well as leaf area were reduced under intense UV-B in the cultivars Purple Teepee, Cropper Teepee and Goldstrahl, and in early growth phases also in Coco bianco, but with ongoing development this cultivar caught up. Cultivars Hilds Maja, Primel, Manata and Cannellino exhibited no UV-B effects on weight and leaf area. A flowering delay of up to 1 day was observed under intense UV-B in several cultivars. Probably due to this delay the yield (fresh weight of fruits) decreased in all cultivars up to 55% under intense UV-B at harvest time, while the potential yield (sum of buds, opened flowers and fruits) was reduced only in the cultivars Cropper Teepee, Purple Teepee, Cannellino and Goldstrahl. The UV-sensitivity index (UVSI) calculated according to the UV induced changes in growth, dry weight and yield at the second harvest date has shown that all cultivars are UV-sensitive, however the index was numerically higher for Southern European cultivars (average = 2.5) than for Central European ones (average = 2.3) which means that the first group was slightly less UV-sensitive than the second.

An in situ enclosure experiment to test the solar UVB impact on plankton in a high-altitude mountain lake. I. Lack of effect on phytoplankton species composition and growth

The effect of solar UVB radiation on the growth and species composition of phytoplankton from a high-mountain lake (2417 m a.s.l.) was studied in situ for 16 days in two enclosures of 1 m- receiving either full sunlight or sunlight without UVB. A total of 20 species were identified in both enclosures, consisting mainly of dinoflagellates, chrysophytes and diatoms. During the experiment, there were no significant differences in phytoplankton species composition between the two enclos- ures. In both treatments, the abundance of phytoplankton increased continuously, and chlorophyll a changed by -5-fold. We observed high fluctuations in the abundance of several species. However, these fluctuations occurred in both enclosures, and hence they were not related to UVB radiation. Some species were affected by daily fluctuations of radiation (UVA + photosynthetically active radi- ation). Cyclotella aff. gordonensis showed a robust positive correlation, whereas species of Gymno- dimum were negatively correlated. For most species, the sensitivity to radiation found during the experiment was consistent with their diurnal vertical distribution in the lake. Our findings suggest that the phytoplankton from this very clear lake (10% of the surface UVB radiation at 305 nm reached 9.6 m depth) were well adapted to the high UVB radiation characteristic of high-elevation sites.

Effects of Solar UVB Radiation on Growth, Flowering and Yield of Central and Southern European Maize Cultivars (Zea mays L.)

Abstract— Different cultivars of maize (Zea mays L.) originating from Central and South Europe were grown from June to September 1994 for 16 weeks in two greenhouses covered with different UVB‐absorbing (280–320 nm) plastic foils. Using the ambient UVB radiation level of a southern location (Portugal, 38.7°N) in one of the greenhouses as an enhanced radiation compared to the reduced radiation in the second greenhouse, an increase of about 12% of UVB was simulated. Six of the eight cultivars examined showed significant reductions in height of up to 18.9% at all developmental stages under increased UVB. In contrast to this, the fresh and dry weight as well as the leaf area was reduced under UVB only at early developmental stages, but with ongoing development the UVB stressed plants caught up. The total content of absorbing compounds of the maize cultivars was completely unaffected by UVB. A flowering delay up to a maximum of 5 days was observed under higher UVB in several cultivars. Probably due to this delay in the cob development the yield decreased to 27.7% under higher UVB at the first harvest after 12 and 14 weeks, whereas at the second harvest after 14 and 16 weeks yield reduction levelled off.