UV-B增强后秸秆还田分解对土壤氮转化微生物及酶活性的影响

为明确UV-B辐射增强对水稻秸秆化学成分的影响,阐释UV-B辐射增强后秸秆还田分解特征及其对稻田土壤氮素转化的间接效应,本研究在元阳梯田(海拔1600 m)开展大田试验,以当地水稻品种白脚老粳为研究对象,研究UV-B辐射增强(5.00kJ·m^(-2))对水稻秸秆化学成分及其还田后秸秆降解、土壤氮素转化的影响。结果表明:UV-B辐射增强显著降低水稻秸秆纤维素含量,增加木质素含量,提高秸秆木质素/氮;并导致秸秆纤维素、木质素、总氮的降解速率总体降低,最大降幅分别达38.7%、18.1%、25.8%。与自然光照秸秆相比,UV-B辐射后的秸秆还田显著降低土壤固氮细菌、氨化细菌、硝化细菌和反硝化细菌数量,增加土壤蛋白酶、氨单加氧酶、硝酸还原酶活性,提高土壤硝化和反硝化速率。相关性分析表明,秸秆木质素/氮与秸秆降解速率呈极显著负相关;秸秆纤维素、木质素、总氮降解速率与硝酸还原酶活性呈显著正相关,后者又与N_(2)O排放通量呈显著正相关;硝化细菌数量与NO_(3)^(-)-N含量呈负相关。研究表明,UV-B辐射增强通过提高秸秆木质素/氮,抑制秸秆纤维素、木质素、总氮降解,减少土壤氨化细菌数量,增加氨单加氧酶和硝酸还原酶活性,从而促进土壤NH_(4)^(+)-N向NO_(3)^(-)-N转化,导致N2O排放通量增加。

Increasing Surface UV Radiation in the Tropics and Northern Mid-Latitudes due to Ozone Depletion after 2010

Excessive exposure to ultraviolet(UV)radiation harms humans and ecosystems.The level of surface UV radiation had increased due to declines in stratospheric ozone in the late 1970s in response to emissions of chlorofluorocarbons.Following the implementation of the Montreal Protocol,the stratospheric loading of chlorine/bromine peaked in the late 1990s and then decreased;subsequently,stratospheric ozone and surface UV radiation would be expected to recover and decrease,respectively.Here,we show,based on multiple data sources,that the May–September surface UV radiation in the tropics and Northern Hemisphere mid-latitudes has undergone a statistically significant increasing trend[about 60.0 J m^(–2)(10 yr)^(–1)]at the 2σlevel for the period 2010–20,due to the onset of total column ozone(TCO)depletion[about−3.5 DU(10 yr)^(–1)].Further analysis shows that the declines in stratospheric ozone after 2010 could be related to an increase in stratospheric nitrogen oxides due to increasing emissions of the source gas nitrous oxide(N_(2)O).

UV-LED辐射模式对表面消毒辐射场均匀度的影响

在使用紫外发光二极管(Ultraviolet light-emitting diodes,UV-LED)进行表面消毒时,物体表面会出现部分区域消毒剂量超出必要,部分区域消毒剂量不足的现象。理想的辐射场是物体表面各点的辐射照度相同。为了优化辐射场,建立了辐射场的通用公式,编写VBA程序,实现了对辐射场的数学模拟、分析和优化。对9种UV-LED辐射模式的辐射场进行了实际模拟分析。结果显示:对于由多颗UV-LED组成的光源板,辐射距离与UV-LED间距的比以及UV-LED的辐射模式是辐射场均匀性的决定因素。由于边缘效应,在光源板正下方投影的边长的80%范围内才有可能实现辐射场均匀。当辐射距离和UV-LED间距之比在3~15的范围内时,均匀性良好(最小和最大值的比≥81.8%)。较小的最大发光角的辐射模式在照射距离和UV-LED间距比例偏大的情况下更为适用,反之亦然。

UVRAG基因在索拉非尼诱导的K562细胞铁死亡中的作用

目的:探讨抗紫外线辐射相关基因(UVRAG)在索拉非尼(sorafenib)介导的白血病K562细胞铁死亡中的作用及机制。方法:用浓度为0、0.625、1.25、2.5、5、10、20μmol/L的索拉非尼分别处理K562细胞24、48 h后,采用CCK-8试剂检测细胞活力;浓度为0、5、10μmol/L的索拉非尼处理K562细胞24 h后,流式细胞术检测活性氧的变化情况;Western blot分别检测浓度为0、5、10μmol/L的索拉非尼干预处理及铁死亡抑制剂预处理K562细胞后GPX4蛋白的表达情况;采用重组慢病毒载体在K562细胞中构建UVRAG过表达稳株,应用q PCR及Western blot验证UVRAG过表达情况及其对索拉非尼干预处理后GPX4、HMGB1蛋白表达情况的影响。结果:不同浓度的索拉非尼均能显著抑制K562细胞增殖,且随着浓度增高细胞活力逐渐下降(r24 h=-0.9841,r48 h=-0.9970);浓度为0、5、10μmol/L的索拉非尼诱导K562细胞死亡过程中伴随着活性氧水平的增加(浓度为10μmol/L时,P<0.001)、GPX4蛋白的下降(P<0.05),铁死亡抑制剂预处理后可以部分逆转索拉非尼诱导的GPX4蛋白下降(P<0.05);与NC组及NC-sorafenib组相比,OE-sorafenib组GPX4蛋白表达明显下降(均P<0.05),HMGB1蛋白表达明显增加(均P<0.05)。结论:索拉非尼能诱导K562细胞铁死亡,UVRAG促进了索拉非尼诱导的K562细胞铁死亡过程。

UV⁃B辐射增强和氮添加及其互作对空心莲子草-马唐竞争的影响

【目的】以入侵种空心莲子草(Alternanthera philoxeroides)与本土伴生种马唐(Digitaria sanguinalis)为研究对象,探讨UV⁃B辐射、施氮及其交互效应对二者竞争的影响,以期为全球变化下的入侵植物防治提供科学依据。【方法】依据de Wit取代试验法,在单种、混种盆栽模式下分别设置处理方式(施氮、UV⁃B辐射、施氮×UV⁃B辐射)、物种属性(空心莲子草、马唐)2个因子,测定各处理组合下的植物总生物量、形态、色素及光合荧光等指标,并采用二因素方差分析和LSD多重比较法分析以上各指标差异。【结果】①单种模式中,施氮导致植物最大茎长和马唐叶面积显著增加207.154%和297.643%、空心莲子草总生物量及稳态光适应光化学猝灭系数(qp_Lss)显著降低40.612%和52.381%;UV⁃B辐射导致植物最大茎长、空心莲子草最大光量子产率(QY_max)及稳态光量子效率(QY_Lss)显著增加117.607%、404.459%和835.714%,导致马唐QY_Lss显著降低45.605%;施氮×UV⁃B辐射导致空心莲子草总生物量及马唐QY_max显著降低79.310%和18.984%,空心莲子草QY_max显著增加685.350%,施氮×UV⁃B辐射还使得空心莲子草暗适应后最小荧光(F_(0))下降而QY_Lss增加、马唐F_(0)增加而QY_Lss下降。②混种模式中,施氮导致马唐叶面积及其叶绿素a指数(Chla)显著增加254.259%和53.018%,导致空心莲子草根长及其Chla显著降低76.051%和12.084%;UV⁃B辐射导致空心莲子草Chla显著增加45.434%;施氮×UV⁃B辐射导致空心莲子草根长显著降低58.824%。【结论】施氮相对增加了马唐在生物量及形态上的优势,但UV⁃B辐射削弱马唐光合活性而增加空心莲子叶绿素含量;且UV⁃B辐射、施氮×UV⁃B辐射交互作用显著提升空心莲子草的实际光化学效率。全球变化下应加强空心莲子草入侵监控,以防多类因子交互效应加剧其对于本土植物的竞争替代。

UV-B辐射对滇黄精幼苗生长、抗性生理及代谢物的影响

为探究滇黄精幼苗对UV-B辐射的生理响应机制,以两年生药用植物滇黄精为材料,在540 mw/cm^(2)的UV-B辐射强度下,以5 d为一个周期,分别测定处理了0~25 d后的滇黄精幼苗的生物量、抗氧化酶活性、MDA、类黄酮的含量.结果表明:在UV-B辐射下,滇黄精幼苗的株高与叶绿素含量呈下降趋势,并随着辐射时间延长,影响效果更明显,UV-B辐射对POD、SOD活性的影响呈升高趋势,在UV-B辐射中期,相较于CK显著升高.对MDA含量的影响呈现先升高后降低的趋势.滇黄精叶片中类胡萝卜素含量及叶片和块茎中类黄酮含量也随着辐射时间的延长而增加.因此,UV-B辐射处理可抑制滇黄精幼苗的生长,使其抗氧化酶活性以及类黄酮含量显著增加,从而增强滇黄精对UV-B辐射的抗性,对植株起到保护作用.

Effect of UV-B radiation on the feeding behavior of the rotifer Brachionus plicatilis

Effect of UV - B radiation on the feeding behaviour of marine zooplankton is important to assessing the health harm of marine ecosystem due to the gradually enhanced UV - B radiation in air. However, there are a few studies on this topic. The feeding behavior of the rotifer, Brachionus plicatilis, under the treatment of UV - B radiation on five species of microalgae, i. e. , Chlorella sp. , Tetraselmis chuii, Isochrysis galbana Park 8701, Chaetoceros muelleri Lermumerman, and Nitzschia clostertum, was studied. The results showed that the filtering and feeding rates of the rotifer decreased significantly with the dose increase of UV - B radiation when fed with five species of microalgae respectively （ P 〈 0.05 ） which indicates UV - B radiation inhibits the feeding activities of the rotifer on microalage. The mixed culture experiments shows the rotifer preferred to feed Chlorella sp. , then C. muelleri, L galbana, N. clostertum and T. chuii in turn if without UV - B radiation. Under the highest dose of UV - B radiation treatment （2.70 kJ/m^2）, the rotifer preferred to feed C. muelleri, then Chlorella sp. , N. clostertum, L galbana and T. chuii in turn. Chlorella sp. , L galbana and C. muelleri became the more favorite foods of the rotifer while T. chuii and N. clostertum became less favorite foods. The change of feeding rate and feeding selectivity of zooplankton driven by the enhanced UV - B radiation will lead to the change in the structure of phytoplankton community.

Effects of ultraviolet(UV) radiation and litter layer thickness on litter decomposition of two tree species in a semi-arid site of Northeast China

Forests and grasslands in arid and semi-arid regions receive high-intensity ultraviolet（UV） radiation year-round. However, how the UV radiation affects the litter decomposition on the forest floor remains unclear. Here, we conducted a field-based experiment in 2011 in the southeastern Horqin Sandy Land, Northeast China, to investigate the effects of UV radiation, litter layer thickness, and their interaction on the mass loss and chemical properties of decomposing litter from Xiaozhuan poplar（Populus × xiaozhuanica） and Mongolian pine（Pinus sylvestris var. mongolica） plantation trees. We found that UV radiation accelerated the decomposition rates of both the Xiaozhuan poplar litter and Mongolian pine litter. For both species, the thick-layered litter had a lower mass loss than the thin-layered litter. The interaction between UV radiation and litter layer thickness significantly affected the litter mass loss of both tree species. However, the effects of UV radiation on the chemical properties of decomposing litter differed between the two species, which may be attributed to the contrasting initial leaf litter chemical properties and morphology. UV radiation mostly had positive effects on the lignin concentration and lignin/N ratio of Xiaozhuan poplar litter, while it had negative effects on the N concentration of Mongolian pine litter. Moreover, litter layer thickness and its interaction with UV radiation showed mostly positive effects on the N concentration and lignin/N ratio of Xiaozhuan poplar litter and the ratios of C/N and lignin/N of Mongolian pine litter, and mostly negative effects on the C/N ratio of Xiaozhuan poplar litter and the N concentration of Mongolian pine litter. Together, these results reveal the important roles played by UV radiation and litter layer thickness in the process of litter decomposition in this semi-arid region, and highlight how changes in the litter layer thickness can exert strong influences on the photodegradation of litter in tree plantations.

Enhanced electrochemical oxidation of phenol by introducing ferric ions and UV radiation

The mineralization of phenol in aerated electrochemical oxidation has been investigated.The results show that a cathodic Fenton process can occur when the Ti-0.3Mo-0.8Ni alloy material is used as cathode in solution containing ferric or ferrous ions; moreover,the reinforcement of cathodic Fenton process on the total organic carbon (TOC) removal rate of phenol is quite distinct.Among the metallic ions investigated,the ferric ion is the best catalyst for the electrochemical mineralization of phenol at initial...

Assessment of Long Term UV Radiation Measured by the Brewer Spectrophotometer in Hong Kong during 1995-2005

Time series of daily UV radiation measured by the ground-based Brewer spectrophotometer #115 in Hong Kong during 1995-2005 were studied through statistics analysis, with focus on the variability and long term changes in relation to total ozone, clouds and AOD (Aerosol Optical Depth). The 11-year mean UV daily dose is 2644±262 J/m2, with maxima(3311 J/m2) in 2000 and minima (2415 J/m2) in 2002. The data were compared with that from TOMS (Total Ozone Mapping Spectrometer) Version 8 and show general agreement between the two. However, the Brewer UV measurement is about 10% lower compared to TOMS data. Apart from the common-known strong seasonal cycle, 26 month periodical was resolved by use of wavelet analysis, which was believed to be associated with quasi-biennial oscillation (QBO) of general circulation. In cloudy days, the annual mean UV daily dose decrease 3.5% to 44.5% compared to clear days. It was also found that surface UV irradiance has close relation to air pollution. Under clear sky condition, 1% AOD increase will lead to 0.2% UV decrease. While global UV radiation increase due to the worldwide observed ozone depletion, investigations indicate that this trend is not significant in Hong Kong during the last 11 years. The possible causes can be attributed to the compensative effect from two aspects. One is the increase of UV resulting from the reduction of clouds with rate of 0.56/10 yr. The other is the decrease of UV due to the enhancement of total ozone and AOD with a rate of 4.23 DU/10 yr and 0.33/10 yr, respectively.

Strain H_2-419-4 of Haematococcus pluvialis induced by ethyl methanesulphonate and ultraviolet radiation

Two strains H2-410 and H2-419 were obtained from the chemically mutated survivors of wild Haematococcus pluvialis 2 by using ethyl methanesulphonate (EMS). Strains H2-410 and H2-419 showed a fast cell growth with 13% and 20% increase in biomass compared to wild type, respectively. Then H2-419-4, a fast cell growth and high astaxanthin accumulation strain, was obtained by exposing the strain H2-419 to ultraviolet radiation (UV) further. The total biomass, the astaxanthin content per cell, astaxanthin production of H2-419-4 showed 68%, 28%, and 120% increase compared to wild H. pluvialis 2, respectively. HPLC (High Performance Liquid Chromatography) data showed also an obvious proportional variation of different carotenoid compositions in the extracts of H2-419-4 and the wild type, although no peak of carotenoids appeared or disappeared. Therefore, the main compositions in strain H2-419-4, like its wild one, were free of astaxanthin, monoester, and diester of astaxanthin. The asexual reproduction in survivors after exposed to UV was not synchronous, and different from the normal synchronous asexual reproduction as the mother cells were motile instead of non-motile. Interestingly, some survivors from UV irradiation produced many mini-spores (or gamete?), the spores moved away from the mother cell gradually 4 or 5 days later. This is quite similar to sexual reproduction described by Elliot in 1934. However, whether this was sexual reproduction remains questionable, as no mating process has been observed.

The effect of UV-B radiation enhancement on the interspecific competition between Skeletonema costatum and Heterosigma akashiwo

The responses of the interspecific competition between Skeletonema costatum and Heterosigma akashiwo to UV-B radiation enhancement were studied by the co-culture method. The results showed that Heterosigma akashiwo exhibited inhibition on the growth of Skeletonema costatum, and with the increase of initial inoculation density of Heterosigma akashiwo, heavier inhibition on Skeletonema costatum appeared. Under different inoculation proportions, Heterosigma akashiwo could always be in predominance in competition with Skeletonema costatum. The UV-B radiation treatment could change the competition relationship between Skeletonema costatum and Heterosigma akashiwo, which could increase the competitive dominance of Skeletonema costatum and decrease the competitive dominance of Heterosigma akashiwo. When the inoculation proportions of Heterosigma akashiwo and Skeletonema costatum were H∶S=1∶4 and H∶S=1∶1,Skeletonema costatum was in predominance in this competition; however, Heterosigma akashiwo was in predominance when the inoculation proportion was H∶S=4∶1.

Effects of lanthanum(Ⅲ) on nitrogen metabolism of soybean seedlings under elevated UV-B radiation

The hydroponic culture experiments of soybean bean seedlings were conducted to investigate the effect of lanthanum （La） on nitrogen metabolism under two different levels of elevated UV-B radiation （UV-B, 280-320 nm）. The whole process of nitrogen metabolism involves uptake and transport of nitrate, nitrate assimilation, ammonium assimilation, amino acid biosynthesis, and protein synthesis. Compared with the control, UV-B radiation with the intensity of low level 0.15 W/m^2 and high level 0.45 W/m^2 significantly affected the whole nitrogen metabolism in soybean seedlings （p 〈 0.05）. It restricted uptake and transport of NO3^-, inhibited activity of some key nitrogen-metabolism-related enzymes, such as： nitrate reductase （NR） to the nitrate reduction, glutamine systhetase （GS） and glutamine synthase （GOGAT） to the ammonia assimilation, while it increased the content of free amino acids and decreased that of soluble protein as well. The damage effect of high level of UV-B radiation on nitrogen metabolism was greater than that of low level. And UV-B radiation promoted the activity of the anti-adversity enzyme glutamate dehydrogenase （GDH）, which reduced the toxicity of excess ammonia in plant. After pretreatment with the optimum concentration of La （20 mg/L）, La could increase the activity of NR, GS, GOGAT, and GDH, and ammonia assimilation, but decrease nitrate and ammonia accumulation. In conclusion, La could relieve the damage effect of UV-B radiation on plant by regulating nitrogen metabolism process, and its alleviating effect under low level was better than that under the high one.

Effects of UV-B radiation on the growth interaction of Ulva pertusa and Alexandrium tamarense

Enhanced UV-B(280-320 nm) radiation resulting from ozone depletion is one of global environmental problems. Not only marine organisms but also marine ecosystems can be affected by enhanced UV-B radiation. The effects of UV-B radiation on interaction of macro-algae and micro-algae were investigated using Ulva pertusa Kjellman and Alexandrium tamarense as the materials in this study. The results demonstrated that UV-B radiation could inhibit the growth of Ulva pertusa and Alexandrium tamarense when they were both mono-cultured, and the growth inhibition of algae was more significant with increasing doses of UV-B radiation. Alexandrium tamarense could inhibit the growth of Ulva pertusa in mixed culture, and the growth inhibition was more significant when increasing the initial cell density. However, Ulva pertusa could inhibit the growth of Alexandrium tamarense in early phase and stimulate the growth in latter phase when they were grown in mixed culture. Lower initial cell density(10~2 cell/ml) of Alexandrium tamarense could inhibit the growth of Ulva pertusa under UV-B radiation treatment,however, with the initial cell density increasing(10~3 and 10~4 cell/ml), the growth of Ulva pertusa was stimulated under lower dose of UV-B radiation and inhibited under higher dose of UV-B radiation by Alexandrium tamarense. Compared with that in mixed culture, Ulva pertusa showed more positive inhibition to the growth of Alexandrium tamarense under UV-B radiation treatment.

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Among biopolymers,thermoplastic starch(TPS)is a good candidate to obtain biomaterials because of its natural origin,biodegradable character,and processability.Exposure to ultraviolet(UV)radiation causes significant degradation of starch-based materials,inducing photooxidative reactions which result in breaking of polymer chains,production of free radical,and reduction of molar mass.These changes produce a deterioration of TPS mechanical properties,leading to useless materials after an unpredictable time.In this work,changes induced on TPS by UV radiation,analyzing structural properties and mechanical behavior,are studied.TPS was obtained through thermo-mechanical processing of native corn starch in the presence of water(45%w/w)and glycerol(30%w/w)as plasticizers.Films were obtained by thermocompression and,before testing,specimens were conditioned to reduce material fragility.Photodegradation process was performed by exposing TPS to 264 h UV radiation in a weathering test chamber.Specimen’s weight loss was determined gravimetrically.Chemical changes were studied by Fourier Transform Infrared Spectroscopy(FTIR)and morphological modifications were analyzed by Scanning Electron Microscopy(SEM).Reduction of weight average molar mass was measured by Static Light Scattering(SLS).Changes in mechanical properties were studied from tensile tests.After 96 h exposure,TPS specimens presented a weight reduction of 4-6%,mainly attributed to plasticizers lost by evaporation.SEM observations showed that UV radiation induced morphological changes on TPS,evidenced by an increment of specimens cracking.By FTIR,it was detected the presence of an additional band located at 1726 cm-1 in samples submitted to UV radiation,attributed to the formation of-C=O groups.Weight average molar mass of native starch was in the order of 107 g mol-1.TPS exposure to UV radiation decreased significantly its molar mass,confirming molecular degradation of the biopolymer.When TPS was exposed during 48 h,it was detected a considerable decrease in elongation at break values(~85%),indicating that TPS flexibility was reduced.On the other hand,after 48 h exposure,TPS elastic modulus was 55 times higher than those of the unexposed specimens,evidencing an increase in material rigidity.TPS maximum tensile strength was also increased by UV light,with an increment of^400%after 48 h exposure.Results revealed that starch-based materials can be degraded by exposure to UV radiation,modifying their microstructure and mechanical performance.

Effect of UV Radiation and Other Abiotic Stress Factors on DNA of Different Wild Plant Species Grown in Three Successive Seasons in Alpine and Subalpine Regions

Plants in natural ecosystems are exposed to a combination of UV radiation,ionizing radiation(IR)and other abiotic factors.These factors change with the altitude.We investigated DNA alterations of some wild plants of different plant families in natural ecosystems at three altitudes in Rila Mountain,Bulgaria(1500,1782,and 2925 m above sea level(a.s.l.)exposed to UV radiation,IR and other abiotic stresses,to assess the tolerance of plant species to the changing environmental conditions in three successive growth seasons.For this purpose,physicochemical,cytogenetic,and molecular methods were applied.DNA damage was assessed by micronucleus test and molecular method comet assay adapted and applied by us to wild plant species from Onagraceae,Rosaceae,Boraginaceae,Saxifragaceae,Orobanchaceae,Asteraceae and Poaceae families,growing at three different altitudes.Variability in the DNA sensitivity and the level of tolerance was observed among the plant species in response to combined abiotic factors assessed by induced DNA damage and gross beta activity.The studied representatives of Poaceae were less susceptible than the other studied species at all three altitudes and showed close level of DNA injuries to that of unaffected control plant grown in laboratory conditions.The lower levels of DNA damage of these wild plant species corresponded to their lower ability to accumulate radionuclides.There was a particularly pronounced low level of DNA injuries in the plant species at the highest altitude.The level of DNA damage showed correlation with the values of some abiotic environmental factors.The results would contribute to the elucidation of the extent of adaptation of plant species to the continuously changing environment and would be useful in selecting sensitive herbaceous monitor species for environmental impact assessment at mountain and alpine sites.

Effects of UV-B radiation on tetraspores of Chondrus ocellatus Holm(Rhodophyta),and effects of red and blue light on repair of UV-B-induced damage

We evaluated the effects of red and blue light on the repair of UV-B radiation-induced damage in tetraspores of Chondrus ocellatus Holm. Tetraspores of C. ocellatus were treated with different UV-B radiation levels(0,36,72,108,144 and 180 J/m2),and thereafter subjected to PAR,darkness,or red or blue light during a 2-h repair stage,each day for 48 days. The diameters and cellular contents of cyclobutane pyrimidine dimmers(CPDs),chlorophyll a(Chl a),phycoerythrin,and UV-B-absorbing mycosporinelike amino acids(MAAs) contents of the tetraspores were determined. Our results show that low doses of UV-B radiation(36 and 72 J/m 2) promoted the growth of C. ocellatus; however,increased UV-B radiation gradually reduced the C. ocellatus growth(greater than 72 J/m2). The MAAs(palythine and asterina-330) in C. ocellatus were detected and analyzed by LC/MS. Our results suggest that moderate red light could induce the growth of this alga in aquaculture. In addition,photorepair was inhibited by red light,so there may be some other DNA repair mechanism activated by red light. Blue light promoted the activity of DNA photolyase,greatly improving remediation efficiency. Red and blue lights were found to reduce the capacity of C. ocellatus to form MAAs. Therefore,PAR,red light,and blue light play different roles during the repair processes for damage induced by UV-B radiation.

Saponin synthesis and cotton growth is antagonistically regulated by solar UV-B radiation

Background: Earlier we have reported that the exclusion of solar UV-B increased the growth and yield of cotton plants as compared with ambient UV-B. The UV-B radiation effects on the saponins and the impact of ambient and reduced UV-B on the accumulation of saponins has not been investigated yet. Thus a field experiment was conducted to study the influence of solar UV-B on the growth response and saponin synthesis in cotton(Gossypium hirsutum) var. Vikram plants by the exclusion of UV-B. The cotton plants were grown in specially designed iron chambers, wrapped with filters that excluded UV-B(<315 nm), or transmitted ambient UV-B.Results: Exclusion of ambient UV-B enhanced the growth of cotton plants in terms of plant height and leaf area.Greater plant height in UV-B excluded plants was due to elongated internode and more number of nodes.Enhancement in growth was accompanied by a decrease in the accumulation of saponins, which was quantified by the spectrophotometric, TLC and HPLC methods. Solvent extraction of saponins from the internodes and leaves were used for the bioassay of Amaranthus hypocotyl growth and expansion of cucumber cotyledons. Extracts obtained from the UV-B excluded plants(leaves and internodes) promoted the growth to a larger extent as compared with the extracts obtained from ambient grown plants.Conclusions: The result indicates that solar UV-B may possibly suppress the plant growth by regulating the synthesis of natural growth inhibitor's like saponin.

Effect of UV-B Radiation on Ingesting and Nutritional Selecting Behavior of Rotifer Brachionus urceus

Effect of UV-B radiation on ingesting and nutritional selecting behavior of the roifer Brachionus urceus on 5 species of microlgae were studied under controlled laboratory conditions. Restdts showed that enhanced UV-B radiation significantly inhibited ingesting of the rotifer B. urceus when it was fed with 5 species of micro-algae （p〈0.05）. The ingesting selectivity rate varied with the UV-B radiation enhancement when it was fed with 5 species micro-algal mixture. Results indicated that the enhanced UV-B radiation could affect ingesting and nutritional selectivity of B. urceus.

The Effect of Inorganic Nanoadditives on the Thermal, Mechanical and UV Radiation Barrier Properties of Polypropylene Fibres

The objective of this study of modified polypropylene (PP) fibres using nanoadditives (nano-CaCO3 and Cloisite 30B) was to determine the influence of these additives on thermal and mechanical properties, but especially on the barrier properties of the nanocomposite fibres against UV radiation. The DSC data obtained from measurements of PP/CaCO3 or PP/C30B nanocomposite fibres were used for determination of the constants n and K of the Avrami equation and in the estimation of other thermal properties of the fibres, such as their crystallization half-time t1/2, rate of crystallization t1/2, the necessary time for maximum crystallization tmax and free energy per unit area of surface in the lamella perpen-dicular to the axis of a high-molecular chain se. The nano-CaCO3 or Closite 30B fillers (pre-treated separately in three different solvents: glycerine, acetone and water) did not influence the melting temperatures but caused an increase in PP crystallization temperatures in comparison with the pure PP fibres. The pre-treatments of nanoadditives resulted in increase of n, K, t1/2 values and decrease of t1/2, tmax as well as the values of free surface energies per unit area of the modified PP fibres. There was also observed a decrease in the mechanical properties, however, there was an increase of barrier properties against UV radiation of nanocomposite PP fibres in comparison with neat PP fibres, which was one of the main objectives of the study.