Effects Of Elevated UV-B Radiation Research Articles

Effects of silicon application on diurnal variations of physiological properties of rice leaves of plants at the heading stage under elevated UV-B radiation.

We investigated the effects of silicon (Si) application on diurnal variations of photosynthetic and transpiration physiological parameters in potted rice (Oryza sativa L. cv Nanjing 45) at the heading stage. The plants were subjected to two UV-B radiation levels, i.e., reference UV-B (A, ambient, 12.0 kJ m(-2) day(-1)) and elevated UV-B radiation (E, a 20% higher dose of UV-B than the reference, 14.4 kJ m(-2) day(-1)), and four Si application levels, i.e., Si0 (no silicon supplementation, 0 kg SiO2 ha(-1)), Si1 (sodium silicate, 100 kg SiO2 ha(-1)), Si2 (sodium silicate, 200 kg SiO2 ha(-1)), and Si3 (slag silicon fertilizer, 200 kg SiO2 ha(-1)). Compared with the reference, elevated UV-B radiation decreased the diurnal mean values of the net photosynthetic rate (Pn), intercellular carbon dioxide (CO2) concentration (Ci), transpiration rate (Tr), stomatal conductivity (Gs), and water use efficiency (WUE) by 11.3, 5.5, 10.4, 20.3, and 6.3%, respectively, in plants not supplemented with silicon (Si0), and decreased the above parameters by 3.8-5.5, 0.7-4.8, 4.0-8.7, 7.4-20.2, and 0.7-5.9%, respectively, in plants treated with silicon (Si1, Si2, and Si3), indicating that silicon application mitigates the negative effects of elevated UV-B radiation. Under elevated UV-B radiation, silicon application (Si1, Si2, and Si3) increased the diurnal mean values of Pn, Ci, Gs, and WUE by 16.9-28.0, 3.5-14.3, 16.8-38.7, and 29.0-51.2%, respectively, but decreased Tr by 1.9-10.8%, compared with plants not treated with silicon (E+Si0), indicating that silicon application mitigates the negative effects of elevated UV-B radiation by significantly increasing the P n, C i, G s, and WUE and decreasing the T r of rice. Evident differences existed in mitigating the depressive effects of elevated UV-B radiation on diurnal variations of physiological parameters among different silicon application treatments, exhibiting as Si3>Si2>Si1>Si0. In addition to recycling steel industrial wastes, the application of slag silicon fertilizer mitigates the negative effects of elevated UV-B radiation on photosynthesis and transpiration in rice.

The combined effect of water limitation and UV-B radiation on common and tartary buckwheat

The effects of elevated UV-B radiation and water limitation have been evaluated in terms of the biochemical, physiological, morphological and productivity responses of common buckwheat (Fagopyrum esculentum Moench) and tartary buckwheat (Fagopyrum tataricum Gaertn.). Research was carried out under semi-controlled conditions. Common and tartary buckwheat were exposed to UV-B radiation and water limitation in different combinations. Photosynthetic pigments, UV-absorbing compounds, potential and effective photochemical efficiency, stomatal conductance, plant morphology and biomass production were monitored. The negative effect of elevated UV-B radiation on growth parameters in common buckwheat was highly significant in watered plants but less pronounced in plants exposed to water limitation. However, in tartary buckwheat UV-B radiation mitigated the negative effects of water limitation, resulting in increased biomass production.

ALTERATION IN THE MINERAL NUTRITION OF PURELY SYMBIOTIC AND NITRATE-FED NODULATED LEGUMES EXPOSED TO ELEVATED UV-B RADIATION

The effects of elevated UV-B radiation and two nitrogen (N) sources on mineral nutrition of Cyclopia maculata, a UV-B-sensitive species, was assessed together with UV-B-tolerant symbiotic legumes Vigna unguiculata, Glycine max, Lupinus luteus, Vicia atropurpurea, Podalyria calyptrata and Virgilia oroboides. Plants were grown outdoors on tables under moderately or highly elevated UV-B exposures which simulated 15% and 25% ozone depletion above Cape Town in South Africa. Exposing purely symbiotic plants of V. unguiculata to elevated UV-B132 radiation decreased the tissue concentration of calcium (Ca) in leaves, phosphorus (P) in stems and roots, potassium (K) in roots, and boron (B) in roots and nodules relative to UV-B162 or ambient control. In contrast, seedlings of C. maculata, V. oroboides, L. luteus, and V. atropurpurea plants exposed to elevated UV-B radiation increased the concentration of several nutrients in leaves, stems and roots whereas P. calyptrata showed no changes in the mineral nutrition. The reported reduction in plant dry matter yield in C. maculata was accompanied with increased concentrations of P, K, Ca, magnesium (Mg), copper (Cu), and manganese (Mn) in photosynthetic leaves and stems, suggesting that the reported decrease in biomass yield could not be attributed to limitations associated with nutrient uptake. Our results suggest that factors other than limitations of nutrient uptake contributed to the reduced biomass accumulation of purely symbiotic and nitrate (NO3 −)-fed nodulated seedlings of C. maculata.

Effects of elevated UV-B radiation on ecosystem and soil respiration in a winter wheat farmland

O 3 concentration in the stratosphere is decreasing, resulting in higher solar ultraviolet-B radiation (UV-B, 280–320 nm) to the Earth’s surface. Enhanced levels of UV-B radiation may, in turn, alter ecosystem processes such as respiration. In this study, daily changes of ecosystem and soil respiration rates under modulated 20% supplementation of UV-B and ambient UV-B conditions (CK) were investigated in the 2007–08 winter wheat ( Triticum aestivum L.) season in a farmland nearing Nanjing city, south-east China, in order to determine the effects of elevated UV-B radiation on these processes. A paired t-test indicated that the effects of elevated UV-B radiation on ecosystem respiration varied across different measuring periods. Significantly lower ecosystem respiration rates in the elevated UV-B plots were found at the later growth (anthesis and beginning grain filling) stages. Elevated UV-B radiation significantly reduced soil respiration rates during each development stages. As far as the whole measuring period is concerned, elevated UV-B radiation significantly ( p < 0.05) reduced both ecosystem respiration and soil respiration. The seasonal mean ecosystem respiration rates for the CK and UV-B treatments were 1144.1 and 1008.3 mg CO 2 m −2 h −1, respectively, and the seasonal mean soil respiration rates for the two treatments were 286.0 and 249.3 mg CO 2 m −2 h −1, respectively. Regression analysis showed that elevated UV-B radiation significantly reduced temperature sensitivity of ecosystem respiration, with the Q 10 decreasing from 1.73 in the CK plots to 1.63 in the elevated UV-B plots. The Q 10 of soil respiration was not significantly affected by enhanced UV-B radiation. The exponential response curve (ecosystem respiration VS temperature) might be constructed with less-damaged plants at the lower temperature and more-damaged plants at the higher temperature, which yielded a lower temperature sensitivity of ecosystem respiration in the UV-B treatment.

Long-term effects of elevated UV-B radiation on photosynthesis and ultrastructure of Eriophorum russeolum and Warnstorfia exannulata

The depletion of stratospheric ozone above the Arctic regions may increase the amount of UV-B radiation to which the northern ecosystems are exposed. In this paper, we examine the hypothesis that supplemental UV-B radiation may affect the growth rate and photosynthesis of boreal peatland plants and could thereby affect the carbon uptake of these ecosystems. In this study, we report the effects of 3-year exposure to elevated UV-B radiation (46% above ambient) on the photosynthetic performance and ultrastructure of a boreal sedge Eriophorum russeolum and a moss Warnstorfia exannulata. The experiment was conducted on a natural fen ecosystem at Sodankylä in northern Finland. The effects of UV-B radiation on the light response of E. russeolum CO 2 assimilation and the maximal photochemical efficiency of photosystem II in a dark-adapted state ( F v/ F m) were measured in the field. In addition, the effect of supplemental UV-B radiation on organelles of photosynthetic cells was studied by electron microscopy. The UV-B treatment had no effect on the CO 2 assimilation rate of either species, nor did it affect the structure of the cell organelles. On chlorophyll fluorescence, the UV-B exposure had only a temporary effect during the third exposure year. Our results suggested that in a natural ecosystem, even long-term exposure to reasonably elevated UV-B radiation levels does not affect the photosynthesis of peatland plants.

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.

Changes in Grain Size and Grain Storage Protein of Rice (Oryza Sativa L.) in Response to Elevated UV-B Radiation under Outdoor Conditions

Variation in growth, grain size and grain storage protein content of rice (Oryza sativa L.) in response to elevated UV-B radiation under sunlight was examined in a cool rice-growing region of Miyagi Prefecture, Japan, in 1999, 2001 and 2002. Tiller number, dry mass, panicle number, grain yield and grain size significantly decreased under elevated UV-B radiation in 2001 and 2002. The effects of elevated UV-B radiation on the reduction of each growth parameter were greatly enhanced by daily lower temperature during the ripening stage in those two years. On the contrary, total grain nitrogen content and grain storage protein content significantly increased under elevated UV-B radiation in 2001 and 2002. Among grain storage proteins, glutelin content significantly increased but albumin-globulin and prolamin contents did not. It was thus evident that not only grain size but also grain storage protein of rice was markedly influenced due to elevated UV-B radiation.

Effects of elevated solar UV-B radiation from ozone depletion on terrestrial ecosystems

In the last three decades much research has been carried out to investigate the biological effects of a thinning stratospheric ozone layer accompanied by an enhanced level of solar ultraviolet-B radiation at the Earth’s surface. Enhanced UV-B radiation affects ecosystems in many ways directly and indirectly. The responses can be biochemical, physiological, morphological or anatomical, and the direction of the response can vary between different species, communities and ecosystems. In this paper we firstly introduce general concepts, and methods for measuring the ecological effects of UV-B radiation. Secondly, we provide an overview interpretation of the effects of enhanced UV-B on terrestrial ecosystems from recent studies. These studies include effects of UV-B on growth and reproduction, composition of communities, competitive balance, decomposition of litter, and interactions with other factors etc. Finally, we recommend future research directions to identify the effects of elevated UV-B radiation on ecosystems in China.

Response of purely symbiotic and NO3-fed nodulated plants of Lupinus luteus and Vicia atropurpurea to ultraviolet-B radiation.

The effects of elevated UV-B radiation on growth, symbiotic function and concentration of metabolites were assessed in purely symbiotic and NO3-fed nodulated plants of Lupinus luteus and Vicia atropurpurea grown outdoors either on tables under supplemental UV-B radiation or in chambers covered with different types of plexi-glass to attenuate solar ultraviolet radiation. Moderately and highly elevated UV-B exposures simulating 15% and 25% ozone depletion as well as sub- ambient UV-B did not alter organ growth, plant total dry matter and N content per plant in both L. luteus and V. atropurpurea. In contrast, elevated UV-B increased (P <0.05) flavonoid and anthocyanin concentrations in roots and leaves of L. luteus, but not of V. atropurpurea. Feeding nodulated plants of L. luteus under elevated UV-B radiation with 2 mM NO3 increased (P <0.05) nodule, leaf and total dry matter, and whole plant N content. With V. atropurpurea, NO3 reduced (P <0.05) nodule activity, root %N and concentrations of flavonoids, anthocyanins in roots and leaves and soluble sugars in roots, in contrast to an observed increase (P <0.05) in nodule dry matter per plant. Similarly, supplying 2 mM NO3 to L. luteus plants exposed to sub-ambient UV-B radiation significantly reduced individual organ growth, plant total biomass, nodule dry matter, nodule %N, and whole plant N content, as well as root concentrations of flavonoids, anthocyanins, soluble sugars, and starch of L. luteus, but not V. atropurpurea plants. These results show no adverse effect of elevated UV-B radiation on growth and symbiotic function of L. luteus and V. atropurpurea plants. However, NO3 supply promoted growth in L. luteus plants exposed to the highly elevated UV-B radiation.

紫外線B（UVB）およびCO2大気の増大がイネの生育・収量に及ぼす影響についての野外試験の結果

紫外線B（UVB）およびCO2大気の増大がイネの生育・収量に及ぼす影響についての野外試験の結果

The direct effects of UV-B radiation on Betula pubescens litter decomposing at four European field sites

A co-ordinated series of field experiments were conducted to consider the effects of elevated UV-B radiation applied directly to decomposing plant litter. Betula pubescens was decomposed under ambient and elevated UV-B (simulating a 15% ozone depletion) using outdoor irradiation facilities at Adventdalen, Norway (78° N), Abisko, Sweden (68° N), Amsterdam, The Netherlands (52° N,) and Patras, Greece (38° N). There was no significant effect of treatment on mass loss for samples collected after 2, 12 and 14 months decomposition at Amsterdam, or after 4 months decomposition at Adventdalen. Significant reductions in the mass loss of litter decomposing under elevated UV-B compared to ambient were found at the other 2 sites. The only effect of treatment on litter chemistry during decomposition was a significant reduction in the N concentration of material at Abisko and a significant increase in C:N at Patras for litter decomposing under elevated UV-B. Significant differences were found in the structure of the fungal community decomposing litter in Sweden, the only site to be tested. These data, and the few published studies of the response of decomposition to UV-B incident on litter suggest that, in the ecosystems and climates that have been studied, such direct effects are typically confined to the initial stages of decomposition, and are rather small in magnitude.

Effects of increased solar ultraviolet radiation on terrestrial ecosystems

Elevated solar UV-B radiation associated with stratospheric ozone reduction may exert effects on terrestrial ecosystems through actions on plants, microbes, and perhaps on some animals. At the ecosystem level, the effects are less well understood than at the molecular and organismal levels. Many of the most important, yet less predictable, consequences will be indirect effects of elevated UV-B acting through changes in the chemical composition and form of plants and through changes in the abiotic environment. These indirect effects include changes in the susceptibility of plants to attack by insects and pathogens in both agricultural and natural ecosystems; the direction of these changes can result in either a decrease or an increase in susceptibility. Other indirect effects of elevated UV-B include changes in competitive balance of plants and nutrient cycling. The direct UV-B action on plants that results in changes in form or function of plants appears to occur more often through altered gene activity rather than damage. The yield of some crop varieties can be decreased by elevated UV-B, but other varieties are not affected. Plant breeding and genetic engineering efforts should be able to cope with the potential threats to crop productivity due to elevated UV-B. For forest trees, this may be more difficult if effects of elevated UV-B accumulate over several years. All effects of elevated UV-B radiation must be considered in the context of other climate changes such as increased temperature and levels of carbon dioxide, which may alter the UV-B responses, especially for plants. The actions of elevated carbon dioxide and UV-B appear to be largely independent, but interactions occur between changes in UV-B and other factors. Other ecosystem-level consequences of elevated UV-B radiation are emerging and their magnitude and direction will not be easily predicted.

Direct Effects of Elevated UV-B Radiation on the Decomposition of Quercus robur Leaf Litter

Decomposing Quercus robur L. leaf litter was exposed for 64 weeks at an outdoor facility to supplemental levels of UV-B radiation (280-315 nm) under treatment arrays of cellulose diacetate-filtered fluorescent lamps which also produce UV-A radiation (315-400 nm). Litter was also exposed to UV-A radiation alone under control arrays of polyester-filtered lamps and to ambient levels of solar radiation under arrays of unenergised lamps. The treatment corresponded to a 30% elevation above the ambient erythemally-weighted level of UV-B radiation. Litter was sampled after 11, 39 and 64 weeks and was examined for differences in mass loss, decomposition constants (k), chemical composition and the abundances of saprotrophic fungi. No effects of UV radiation on k values were recorded, but after 11 weeks, percentage mass loss of litter exposed to UV-B radiation under treatment arrays was 3% lower than under control arrays and 2% lower than under ambient arrays. After 39 weeks, litters exposed to UV-A radiation under control arrays had 10% lower total nitrogen contents and 13% higher C:N ratios than those litters exposed beneath ambient arrays. At the last sampling, litters exposed to supplemental UV-B radiation had 5% higher carbon contents than those under ambient arrays. A 2.4-fold increase in the frequency of lamina particles of litter that were uncolonised by fungi was recorded in litter exposed to UV-B radiation under treatment arrays, compared to ambient arrays. The abundances of the saprotrophic fungi Cladosporium spp. and Acremonium persicinum (Nicot) W. Gams were decreased by 50% and 91%, respectively, under UV-B treatment arrays compared to ambient arrays, and the abundance of coelomycete conidiomata recorded on leaves was increased by 12% under treatment arrays, compared to ambient. Dactylella spp. were not recorded on litter exposed to UV-A radiation under control arrays and UV-A radiation applied under control and treatment arrays apparently increased the abundance of Polyscytalum fecundissimum Riess. on litter. UV radiation had fewer effects on the abundances of decomposer fungi that develop in leaf tissues than it did on those that develop on leaf litter surfaces. We conclude that increased fluxes of UV-B radiation as a result of stratospheric ozone depletion will have subtle but wide-ranging impacts on the decomposition of litters in oak woodlands.