Effects Of Elevated ultraviolet-B Radiation Research Articles

Accumulation of phenolics and growth of dioecious Populus tremula (L.) seedlings over three growing seasons under elevated temperature and UVB radiation

Accumulation of secondary metabolites may exhibit developmentally regulated variation in different plant organs. Moreover, prevailing environmental conditions may interact with development-related variations in plant traits. In this study, we examined developmentally regulated variation in phenolic accumulation in the twigs of dioecious Populus tremula (L.) and how the effects of elevated temperature and ultraviolet B (UVB) radiation on growth and phenolics accumulation varied as the plants get older. In an open-field experiment, six female and six male genotypes were exposed to single and combined elevated temperature and UVB radiation treatments for three consecutive growing seasons. The concentrations of low molecular weight phenolics and condensed tannins did not show age-dependent variation in the twigs. In temperature-treated plants, diameter growth rate decreased, and concentration of condensed tannins increased as plants aged; there were no cumulative effects of elevated UVB radiation on growth and phenolic accumulation. Females maintained a higher concentration of low molecular weight phenolics throughout the experimental period; however, growth and phenolic concentration did not vary over time in females and males. Our results suggest that phenolic accumulation in perennial plants may not necessarily always exhibit age-dependent variation and the effects of elevated temperature on growth and phenolic may diminish as plants get older.

Effects of elevated UV-B radiation and N deposition on the decomposition of coarse woody debris

Increases in nitrogen (N) deposition and ultraviolet-B (UV-B) radiation play an important role in global climate change. Because coarse woody debris (CWD) represents a sizeable proportion of total carbon (C) pool in forest ecosystems, understanding the response of CWD decomposition to increased UV-B and N deposition become necessary for evaluating forest C storage under global climate change. In this study, we investigated the respiration of CWD (RCWD) in response to increased UV-B and N deposition over a two-year period for two tree species in subtropical Chinese forests: Cunninghamia lanceolata (Lamb.) Hook. (CL) and Cinnamomum camphora (L.) Presl (CC). We found that N and UV-B treatment, alone or in combination, significantly promoted RCWD, which was further magnified by increased temperature. Moreover, the combined treatment (UV-B + N) far exceeded the sum of the individual effects of N and UV-B treatments. Our results indicated that the three components of global climate change (increased UV-B, N deposition, and warming) worked interactively to accelerate CWD decomposition in forest ecosystems, suggesting that the biogeochemical cycling of subtropical forests could be altered greatly in the future, and this alteration must be considered in modelling the effects of global climate change.

Effects of elevated ultraviolet-B radiation on root growth and chemical signaling molecules in plants

Ozone layer depletion leads to elevated ultraviolet-B (UV-B) radiation, which affects plant growth; however, little is known about the relationship between root growth and signaling molecules in roots. Therefore, in this work, simulated UV-B radiation was used to study the effects of elevated UV-B radiation on root growth of soybean seedlings and changes in the content of signaling molecules in roots. The results showed that compared with the control, the 2.63 kJ m−2 d−1 and 6.17 kJ m−2 d−1 elevated UV-B radiation treatments inhibited root growth, and root growth parameters (total root length, root surface area, root volume, average diameter, root tip number, and root dry weight) all decreased. For root signaling molecules, the content of nitric oxide, reactive oxygen species, abscisic acid, salicylic acid, and jasmonic acid increased, and the content of auxin, cytokinin, and gibberellin decreased. The above indices changed more significantly under the 6.17 kJ m−2 d−1 treatment. After withdrawal of the exposure, the above indices could be restored to a certain extent. These data indicated that UV-B radiation interfered with root growth by affecting the content of signaling molecules in roots, and the degree of the effects was related to the intensity of UV-B radiation. The results from this study provide a theoretical basis for studying the preliminary mechanism of elevated UV-B radiation on root growth and possible pathways that can mitigate UV-B radiation damage for root growth. One sentence summaryThe effects of elevated UV-B on root growth of soybean seedlings were regulated by signaling molecules, and the degree of the effects was related to the intensity of UV-B radiation.

Effect of Elevated UV-B Radiation on Microbial Biomass C and Soil Respiration in Different Barley Cultivars Under Field Conditions

Elevated ultraviolet-B (UV-B) radiation effect on soil carbon (C) cycling has been regarded as one of the important issues in global change. Field simulating experiment was conducted to investigate the effects of elevated UV-B radiation on the content of microbial biomass C in rhizosphere and non-rhizosphere soils as well as soil respiration in three barley cultivars. The UV-B radiation was set at two levels, i.e., reference (A, ambient UV-B radiation), and elevated by 20% (E, elevated UV-B radiation, 14.4 kJ m−2 day−1). Three barley cultivars were tested including Dan 2, Supi 3, and Supi 4, respectively. The results indicated that elevated UV-B radiation obviously decreased the content of microbial biomass C in rhizosphere and non-rhizosphere soil, but had no effect on the tendency of microbial biomass C in rhizosphere and non-rhizosphere soil during the entire barley growing season. Compared with control (ambient UV-B radiation), elevated UV-B radiation depressed soil respiration rate and its temperature sensitivity coefficients (Q10), especially in barley cultivar Dan 2 and cultivar Supi 3. It is suggested that the different responses of three barley cultivars to elevated UV-B radiation were related to the changes of microbial biomass C and soil respiration.

Combined effects of Lanthanum(III) and elevated Ultraviolet-B radiation on root nitrogen nutrient in soybean seedlings.

Rare earth element pollution and elevated ultraviolet-B (UV-B) radiation occur simultaneously in some regions, but the combined effects of these two factors on plants have not attracted enough attention. Nitrogen nutrient is vital to plant growth. In this study, the combined effects of lanthanum(III) and elevated UV-B radiation on nitrate reduction and ammonia assimilation in soybean (Glycine max L.) roots were investigated. Treatment with 0.08mmolL(-1) La(III) did not change the effects of elevated UV-B radiation on nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), nitrate, ammonium, amino acids, or soluble protein in the roots. Treatment with 0.24mmolL(-1) La(III) and elevated UV-B radiation synergistically decreased the NR, NiR, GS, and GOGAT activities as well as the nitrate, amino acid, and soluble protein levels, except for the GDH activity and ammonium content. Combined treatment with 1.20mmolL(-1) La(III) and elevated UV-B radiation produced severely deleterious effects on all test indices, and these effects were stronger than those induced by La(III) or elevated UV-B radiation treatment alone. Following the withdrawal of La(III) and elevated UV-B radiation, all test indices for the combined treatments with 0.08/0.24mmolL(-1) La(III) and elevated UV-B radiation recovered to a certain extent, but they could not recover for treatments with 1.20mmolL(-1) La(III) and elevated UV-B radiation. In summary, combined treatment with La(III) and elevated UV-B radiation seriously affected nitrogen nutrition in soybean roots through the inhibition of nitrate reduction and ammonia assimilation.

Interactive effects of elevated UV-B radiation and N deposition on decomposition of Moso bamboo litter

Being two important agents of global environmental change, elevated ultraviolet-B (UV-B) radiation derived from anthropogenic driven ozone depletion and enhanced nitrogen (N) deposition may strongly affect litter decomposition, a crucial factor in biogeochemical cycling. However, the interactive effects of both agents together on litter decomposition are still unclear even though each has been well-documented independently. We conducted a field-based experiment in subtropical China to investigate the combined effects UV-B radiation and N deposition on the decomposition of Moso bamboo (Phyllostachys pubescens) leaf litter over a 20 months period. It was found that the combined effect significantly accelerated litter decomposition, C loss, and lignin degradation as well as facilitating phosphorous (P) release, although it had no measurable effect on N release. Moreover, the interactive effects of both agents together far exceeded the effects of each separately. Results indicated that the positive combined effect of UV-B radiation and N deposition on litter decomposition and C loss could potentially impact Moso bamboo forest ecosystem C cycling. These findings provide a new perspective to further understand the interactive effects of global environmental changes on terrestrial ecosystem processes.

Effect of elevated UV-B radiation on CH4 emissions from the stands of Spartina alterniflora and Phragmites australis in a coastal salt marsh

It has been estimated that solar ultraviolet-B (UV-B) radiation reaching the Earth's surface will continue increasing until 2050s. To investigate the effect of elevated UV-B radiation on CH4 emission from the coastal marsh, mesocosm experiments were conducted to monitor CH4 emissions in stands of invasive plant Spartina alterniflora and native plant Phragmites australis from a coastal salt marsh exposed to ambient and elevated UV-B radiation, respectively. Enhanced UV-B radiation dramatically decreased aboveground, belowground biomass and plant height of P. australis by 16%, 24% and 16%, respectively, and did not affect those of S. alterniflora. This suggests that P. australis was much more sensitive to elevated UV-B than S. alterniflora. The seasonal variation patterns of CH4 fluxes from the S. alterniflora and P. australis mesocosms were very similar, and were hardly affected by exposure to elevated UV-B. Mean CH4 emission rates were higher in S. alterniflora than P. australis mesocosms under both ambient and enhanced UV-B radiation due to the higher biomass of S. alterniflora, which could fix and allocate more photosynthetic carbon to the soil. Seasonal average CH4 flux from the P. australis mesocosms under elevated UV-B radiation was 0.51mgCH4m−2h−1, which was 25% lower than the value under ambient radiation. In contrast, there was no notable effect of elevated UV-B on CH4 emission from the S. alterniflora mesocosms. Enhanced UV-B remarkably decreased porewater DOC and CH4 concentrations by 17% and 23%, respectively, in the P. australis mesocosms during the growing season. This indicates that CH4 emission from the P. australis mesocosms under elevated UV-B was primarily reduced by the reduction of porewater CH4 concentration due to the decrease in plant biomass. Thus, our results suggest that CH4 fluxes in the coastal marshes would be increased by the invasion of S. alterniflora, and the effect of elevated UV-B radiation on CH4 emission from the coastal salt marsh is strongly correlated with plant characteristics.

Suspended Sediment as an Attenuating Factor of Ultraviolet-B Radiation Effects on the Growth and DNA Damage of <i>Chlorella</i> Sp.

Effects of enhanced ultraviolet-B (UV-B) radiation and suspended sediment (SS) separately as well as in combination on the growth and DNA damage of Chlorella sp. were studied under controlled laboratory conditions. The Chlorella sp. was exposed to UV-B of 17 µW cm-2 for 0, 1 and 5 minutes in 0, 500 and 5000 mg L-1 defined SS. The results showed that SS attenuated light penetration and suppressed the growth of Chlorella sp.. It also attenuated UV-B induced DNA damage and promoted the cell growth. The suppression and promotion of cell growth depended on the concentration of SS and dose of UV-B radiation. These results are important in understanding of the effects of elevated UV-B radiation on microalgae in sediments-dominate coastal waters.

Elevated UV-B radiation did not affect decomposition rates of needles of two coniferous species in subtropical China

The increased level of ultraviolet-B (UV-B) radiation reaching the earth’s surface has profound implications for altering terrestrial ecosystem processes such as litter decomposition and nutrient cycling. Here we report on a field experiment that investigated the direct effect of elevated UV-B radiation on the rate of decomposition, lignin degradation, and N and P release from needle litter of two native coniferous species, Cunninghamia lanceolata and Pinus massoniana, in humid subtropical China. Elevated UV-B irradiation did not significantly accelerate litter mass loss and lignin photodegradation of the two species. Elevated UV-B irradiation accelerated the release of N and P from the litter of C. lanceolata, but not from that of P. massoniana. Our data indicated that elevated UV-B irradiation would accelerate N and P turnover in C. lanceolata forest. Our findings will contribute to the better understanding of the role of UV-B radiation in moist subtropical region.

Minor long-term effects of ultraviolet-B radiation on methane dynamics of a subarctic fen in Northern Finland

The effects of elevated ultraviolet-B (UV-B) radiation on methane dynamics was studied in a natural fen in Northern Finland for three growing seasons (2003–2005). This is the first in situ study on the effects of elevated UV-B radiation on methane dynamics in a natural fen. The experimental setup consisted of 30 study plots (120 × 120 cm) that were randomly divided into three treatments: ambient control, UV-A control and elevated UV-B. The UV-B enhancements were 63, 37 and 21% above ambient during the growing seasons 2003, 2004 and 2005, respectively. Elevated UV-B did not affect net methane emission. Stable isotope composition of methane indicated that methane was produced by the acetate fermentation. Under elevated UV-B there was a slight increase in the concentrations of acetate and propionate but decrease in the oxalate concentration suggesting UV-B-induced changes in the belowground processes. The results emphasize the need for long-term field studies under moderately enhanced exposures to estimate whether the function and feedbacks of mire ecosystems change under increased UV-B radiation.

Effect of Elevated Ultraviolet-B Radiation on Microbial Biomass Carbon and Nitrogen in Barley Rhizosphere Soil

As one of the important problems in global change, elevated ultraviolet-B (UV-B) radiation induced by the depletion of stratospheric ozone layer has received more and more attentions around the world. Field experiment with barley was conducted to investigate the effects of elevated UV-B radiation on microbial biomass carbon and nitrogen in rhizosphere and nonrhizosphere soil. The experiment was designed with two UV-B radiation levels, i.e., elevated (E, simulating 25% stratospheric ozone depletion) and ambient (A, control), and performed at the Station of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing, China. Compared with the control, elevated UV-B radiation significantly depressed shoot biomass by 13.2–42.6% and root biomass by approximately 50% from jointing to ripening stage. Elevated UV-B radiation significantly increased microbial biomass C and N in nonrhizosphere soil in most cases, but significantly decreased microbial biomass C and N in rhizosphere soil. Further researches are needed to elucidate whether the above findings are connected with the changes in composition and amount of root exudates induced by elevated UV-B radiation, which can mainly affect the dynamics of soil microbial biomass.

Effects of elevated ultraviolet-B radiation on a plant–herbivore interaction

Enhanced ultraviolet-B (UV-B) radiation may have multiple effects on both plants and animals and affect plant-herbivore interactions directly and indirectly by inducing changes in host plant quality. In this study, we examined combined effects of UV-B and herbivory on the defence of the mountain birch (Betula pubescens ssp. czerepanovii) and also the effects of enhanced UV-B radiation on a geometrid with an outbreak cycle: the autumnal moth (Epirrita autumnata). We established an experiment mimicking ozone depletion of 30% (a relevant level when simulating ozone depletion above Northern Lapland). Both arctic species responded only slightly to the enhanced level of UV-B radiation, which may indicate that these species are already adapted to a broader range of UV-B radiation. UV-B exposure slightly induced the accumulation of myricetin glycosides but had no significant effect on the contents of quercetin or kaempferol derivatives. Mountain birch seedlings responded more efficiently to herbivory wounding than to enhanced UV-B exposure. Herbivory induced the activities of foliar oxidases that had earlier been shown to impair both feeding and growth of moth larvae. In contrast, the contents of foliar phenolics did not show the same response in different clones, except for a decrease in the contents of tannin precursors. The induction of foliar phenoloxidase activities is a specific defence response of mountain birches against insect herbivory. To conclude, our results do not support the hypothesis that the outbreak cycle of the autumnal moth can be explained by the cycles of solar activity and UV-B.

Research advances on the biological effects of elevated ultraviolet-B radiation on terrestrial plants

This review describes the effects of ultraviolet-B (UV-B) radiation on plant growth and development, photosynthesis and photosynthetic pigments and UV-B absorbing compounds. Moreover, plant ecosystem level responses to elevated UV-B radiation and interactions of UV-B radiation with abiotic and biotic factors were also involved. Results collected in this review suggest that approximately two-thirds terrestrial plant species are significantly affected by increase in UV-B radiation. The majority of evidences indicate that elevated UV-B radiation is usually detrimental but there exists tremendous variability in the sensitivity of species to UV-B radiation, and sensitivity also differs among cultivars of the same species.

Effects of Elevated Ultraviolet‐B Radiation on Productive Tillers, Spikelet Sterility and Grain Characteristics of Southern US Rice (Oryza sativa L.) Cultivars

AbstractDepletion of the stratospheric ozone layer is leading to an increase in ultraviolet‐B (UVB) radiation (280–320 nm) reaching the Earth’s surface, which can alter crop productivity. The objective of this study was to determine the effects of elevated UVB radiation on rice production with special emphasis on grain characteristics in southern US rice cultivars (six inbred cultivars and three hybrids). Due to the spectral characteristics of the greenhouse glass, plants received no natural UVB radiation; hence, plants were provided with supplemental UVB lighting. Plants were exposed to UVB radiation of 0, 8 (ambient) or 16 (twice ambient) kJ m−2 day−1. There was no significant effect of elevated UVB radiation on the number of productive tillers in any cultivar except ‘Sierra’. All the cultivars except ‘Sierra’ showed increased spikelet sterility with an increase in UVB radiation. There were decreases in main‐stem panicle length, number of primary branches per panicle, and grain width with an increase in UVB radiation in most of the inbred cultivars. Elevated UVB radiation decreased plant grain yield in all the cultivars, however the per cent decrease in plant grain yield varied among the cultivars (31–79 %). The hybrid ‘Clearfield XL729’ performed best among the selected southern US rice cultivars under an elevated UVB environment.

05/00981 Viscosity correlations for minor constituent fluids in natural gas: n-octane, n-nonane and n-decane

The increased level of ultraviolet-B (UV-B) radiation reaching the earth’s surface has profound implications for altering terrestrial ecosystem processes such as litter decomposition and nutrient cycling. Here we report on a field experiment that investigated the direct effect of elevated UV-B radiation on the rate of decomposition, lignin degradation, and N and P release from needle litter of two native coniferous species, Cunninghamia lanceolata and Pinus massoniana, in humid subtropical China. Elevated UV-B irradiation did not significantly accelerate litter mass loss and lignin photodegradation of the two species. Elevated UV-B irradiation accelerated the release of N and P from the litter of C. lanceolata, but not from that of P. massoniana. Our data indicated that elevated UV-B irradiation would accelerate N and P turnover in C. lanceolata forest. Our findings will contribute to the better understanding of the role of UV-B radiation in moist subtropical region.

Interactions between willows and insect herbivores under enhanced ultraviolet-B radiation.

We studied the effects of elevated ultraviolet-B radiation on interactions between insect herbivores and their host plants by exposing two species of phytochemically different willows, Salix myrsinifolia and S. phylicifolia, to a modulated increase in ultraviolet radiation in an outdoor experiment and monitoring the colonisation of insect herbivores on these willows. We examined the effect of increased ultraviolet-B (UV-B) radiation on (1) the quality of willow leaves, (2) the distribution and abundance of insect herbivores feeding on these willows, (3) the resulting amount of damage, and (4) the performance of insect larvae feeding on the exposed plant tissue. Six clones of each of the two willow species were grown in eight blocks for 12 weeks in the UV-B irradiation field. The clones were exposed to a constant 50% increase in UV-B radiation (simulating 20-25% ozone depletion), to a small increase in UV-A radiation or to ambient solar irradiation. We allowed colonisation on the willows by naturally occurring insects, but also introduced adults of a leaf beetle, Phratora vitellinae, a specialist herbivore on S. myrsinifolia. Increased UV-B radiation did not affect any of the measured indices of plant quality. However, numbers of P. vitellinae on S. myrsinifolia were higher in plants with UV-B treatment compared with UV-A and shade controls. In laboratory tests, growth of the second-instar larva of P. vitellinae was not affected by UV-B treatment of S. myrsinifolia, but was retarded on UV-B treated leaves of S. phylicifolia. In addition, naturally occurring insect herbivores were more abundant on willows exposed to elevated UV-B radiation compared to those grown under control treatments. In spite of the increased abundance of insect herbivores, willows treated with elevated UV-B did not suffer more herbivore damage than willows exposed to ambient solar radiation (shade control). The observed effects of UV-B on herbivore abundance, feeding and growth varied significantly due to spatial variation in environment quality, as indicated by the UV-treatment x block interaction. The results suggest that (1) environmental variation modifies the effects of UV-B radiation on plant-insect interactions and (2) specialist herbivores might be more sensitive to chemical changes in their secondary host plants (S. phylicifolia) than to changes in their primary hosts (S. myrsinifolia).

Population differences in Trifolium repens L. response to ultraviolet-B radiation: foliar chemistry and consequences for two lepidopteran herbivores.

White clover growing in New Zealand is experiencing increasing levels of ultraviolet-B (UV-B) radiation as a result of ozone depletion. We evaluated the effects of UV-B radiation on the foliar chemistry of two populations of white clover (Trifolium repens L.), 'Huia' and 'Tienshan,' and the consequences for the performance of armyworms (Spodoptera litura) and cutworms (Graphania mutans). Plants were grown in controlled environment rooms with and without supplemental UV-B radiation at a dose of 13.3 kJ m-2 day-1, corresponding to a 25% mid-summer ozone depletion above Palmerston North, New Zealand. In both white clover populations, UV-B radiation elicited changes in foliar chemistry, including slight increases in nitrogen concentrations and decreases in carbohydrate concentrations. In addition, the 'Huia' population showed decreases in fiber concentrations and marked increases in cyanogenic activity. No change in UV-absorbing compounds was detected in either population. Long- and short-term feeding trials were conducted to assess dietary effects on insect growth, consumption, and food utilization. Changes in the performance of both insect species were generally small. The most pronounced effect was a 36% reduction in weight of S. litura after 2 weeks of feeding on Huia grown at high UV, but larval development times were only slightly prolonged and pupal weights were unaffected. S. litura short-term performance was affected by differences in white clover population. The long-term performance of G. mutans was not affected and its short-term performance (stadium duration and consumption rate) was only marginally affected by the high-UV treatment. We conclude that the effects of elevated UV-B radiation on white clover plant chemistry can be specific to certain plant populations. The differences in sensitivity of the two generalist insect species suggest that effects may also be specific to certain plant-herbivore associations. These results indicate that future UV-B herbivory studies should examine genotypic effects in both plants and animals.

Effect of elevated ultraviolet-B radiation on abscisic acid and indoleacetic acid content of rice leaves

Effect of elevated ultraviolet-B radiation on abscisic acid and indoleacetic acid content of rice leaves