UV—B对高等植物生长和产量及某些生理代谢过程的影响

本文介绍ＵＶ－Ｂ实验的方法和ＵＶ－Ｂ对高等植物生长发育、作物产量及代谢过程影响的研究进展。     

亚热带植物叶片UV-B吸收化合物的积累

供试的５７种亚热带植物在自然条件下,其叶片ＵＶ－Ｂ吸收化合物在２８０ｎｍ～３３０ｎｍ有１个或２个吸收峰。以单位面积为基数表示的ＵＶ－Ｂ吸收化合物吸收率为乔木＞灌木＞草本;阳生植物＞阴生植物。降低生长光强至自然光的４０％和１６％,荷木,黧蒴,黄果厚壳桂和马尾松叶片的ＵＶ－Ｂ吸收化合物减少８％～４８％。化工厂和电厂附近生长的植物叶片ＵＶ－Ｂ吸收化合物吸收率呈现增高或降低两种变化类型。结果表明叶片具有抵御ＵＶ－Ｂ辐射损伤作用的ＵＶ－Ｂ吸收化合物的积累受植物基因型、生活型、生态型的控制和环境因子的调节。     

不同海拔地区紫外线B辐射状况及植物叶片紫外线吸收物质含量的分析

对不同海拔地区的太阳ＵＶ－Ｂ辐射和植物叶片的光学特性进行了比较研究。结果表明：位于高海拔地区的海北高寒草甸生态系统定位站，太阳ＵＶ－Ｂ辐射明显高于相近纬度的西宁、兰州和南京地区。ＵＶ－Ｂ辐射与总辐射和ＰＡＲ的日变化规律相似，都受太阳高度角的直接影响，在当地太阳正午时最高。ＵＶ－Ｂ／Ｑ的日变化也为单峰曲线，海北部地区的ＵＶ－Ｂ／Ｑ高于西宁的同期测定结果。对蛛芽蓼等植物的研究表明，生长于海北部地区的蛛     

紫外线—B辐射与3种植物幼苗的光合作用：光合作用对紫外线—B敏 …

紫外线－Ｂ辐射降低豌豆、大豆和黄瓜３种植物幼苗的净光合作用速率（Ｐｎ）和表观量子效率（ＡＱＥ）,Ｐｎ和ＡＱＥ的减少幅度随紫外线－Ｂ辐射时间的延长逐渐增大。３种植物的光合作用对此外线－Ｂ辐射的敏感性依为：豌豆〉黄瓜〉大豆,光合作用光抑制的发生程度与光合作用对ＵＶ－Ｂ辐射敏感性有内在联系。定量分析显示,光合作用光抑制的发生程度随ＵＶ－Ｂ辐射时间增加,是ＵＶ－Ｂ辐射剂量的累积效应。     

增强UV-B辐射对小麦叶片内源ABA和游离脯氨酸的影响

研究温室种植的小麦在０（ＣＫ）、８．８２ＫＪ／ｍ＾２（Ｔ１）和１２．６ＫＪ／ｍ＾２（Ｔ２）３种剂量的ＵＶ－Ｂ辐射下其内源ＡＢＡ和游离脯氨酸含量的变化。ＵＶ－Ｂ辐射导致叶绿体膜脂脂肪酸配比改变和ＩＵＦＡ降低,叶片ＭＤＡ含量升高及ＡＢＡ和游离脯脯氨酸积累。分析表明,ＵＶ－Ｂ辐射对膜系统的损坏也许是内源ＡＢＡ和游离脯氨酸含量增加的原因之一,而后者也是植物抵抗ＵＶ－Ｂ胁迫所做出的适应性反应。     

亚热带植物叶片UV—B呼吸化合物的积累

供试的５７种亚热带在自然条件下,其叶片ＵＶ－Ｂ吸收化合物在２８０ｎｍ￣３３０ｎｍ有１个或２个吸收峰。以单位面积为基数表示的ＵＶ－Ｂ吸收化合物吸收率为乔木〉灌木〉草本;阳生植物〉阴生植物。降低生长光强至自然光的４０％和１６％,荷木,黧蒴,黄果厚壳桂和马尾松叶片的ＵＶ－Ｂ吸收光化合物减少８％￣４８％。化工厂和电厂附近生长的植物叶片ＵＶ－Ｂ吸收化合物吸收率呈现增高或降低两种变化类型。结果表明叶片具有抵御     

增强的UV—B辐射对麦田生态系统Mg和Zn累积和循环的影响

近 2 0多年以来 ,ＵＶ Ｂ辐射增加对植物个体的影响受到了广泛的关注 ,而对植物群体和生态系统的影响仍然知道的很少[2 ] 。仅见ＵＶ Ｂ辐射对副极地石南灌丛和沙丘草地生态系统物种结构、生长、物候和叶分解等方面有报道[3,4 ] 。ＵＶ Ｂ辐射影响植物Ｍｇ和Ｚｎ吸收和运转[5～ 7] ,但对营养累积和物质循环的影响了解甚少[3] 。因此 ,大田条件下 ,植物群体和生态系统水平的营养累积和物质循环对ＵＶ Ｂ辐射的响应与反馈的研究 ,对于真实评估ＵＶ Ｂ辐射对生态系统的影响是必不可少的[2 ] 。ＵＶ Ｂ辐射对春小麦生长、生理、群体结构、植物营…     

增强的ＵＶ—Ｂ辐射对麦田生态系统中杂草、大型土壤动物和麦蚜种群数量动态

研究了大田栽培和自然光条件下,模拟ＵＶ－Ｂ辐射（ＵＶ－Ｂ,２８０－３１５nm)增强对麦田生态系统杂草、大型土壤动物和麦蚜种群数量动态的影响,在ＵＶ－Ｂ辐射下,杂草和大型土壤动物的种类和数量降低,种物多样性改变,杂草总生物量也降低。ＵＶ－Ｂ辐射降低牙复合种群数量,并与麦叶粗纤维、可溶性蛋白、可溶性糖、Ｍg和Ｚn含量有显著的相关性。ＵＶ－Ｂ辐射还导致麦蚜与麦叶Ｍg、Fe和Ｚn含量均显著增加。     

ＵＶ—Ｂ辐射对８个大豆品种种子萌发率和幼苗生长的影响

在生长房５种（暗处、可见光、低、中、高强度紫外线－Ｂ）处理下,研究了８个大豆品种的种子萌发率和萌发后幼苗的生长状况。结果表明,暗处种子萌发率高于自然当和ＵＶ－Ｂ辐射的种子。ＵＶ－Ｂ辐射增强对大豆种子的萌发率没有显著影响,仅使部分 品种的最大萌发率降低和导致部分品种达到最大萌发率的时间延长。幼苗的生长对增强的ＵＶ－Ｂ辐射非常敏感,使大部分品种的胚根变短增粗,这可能是植物激素作用的结果,大豆的叶绿素a、叶绿素b和总叶绿素含量明显受到ＵＶ－Ｂ辐射的抑制。ＵＶ－Ｂ作用能促进类黄酮在幼苗中的积累,紫外吸收色素的增设有利于提高对ＵＶ－Ｂ的抵抗力,ＵＶ－Ｂ辐射的这种效应及大豆种间的差异在自然情况下会产生深远的生物学和生态学意义。     

紫外线辐射增加对生物的影响

因大气臭氧层的破坏引起了地表紫外线－Ｂ（ＵＶ－Ｂ）辐射增加,从而导致对各种生物产生不良影响。过量的ＵＶ－Ｂ辐射能增加人类患皮肤癌及白内障等多种疾病的机会,改变自然界某些昆虫的生活习性。同时,ＵＶ－Ｂ辐射还能抑制和破坏许多陆生和水生植物的生长,引起全球生态平衡的改变和作用生产的下降。     

Differences in the Sensitivity to UVB Radiation of Two Cultivars of Rice (Oryza sativa L.)

The effects of UVB radiation on the growth of two cultivarsof Japanese lowland rice (Oryza sativa L.), Sasanishiki andNorin 1, were examined in a phytotron. Supplementation of visibleradiation with UVB radiation reduced plant length, tiller number,the fresh and dry weights of the aboveground parts of plants,and the amounts of total leaf nitrogen, chlorophyll, solubleprotein and ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) in the eighth leaf, the youngest fully expanded leaf.By contrast, UVB radiation significantly increased the accumulationof UV-absorbing compounds. There was a difference between thetwo cultivars in the resistance to the effects of UVB radiation.The reduction in the amounts of Rubisco was smaller in Sasanishiki,while the increase in the accumulation of UV-absorbing compoundswas greater in Sasanishiki. Parameters of plant growth, withthe exception of the amount of Rubisco, decreased in directproportion to decreases in total leaf nitrogen in plants grownunder lower or higher doses of UVB radiation. However, the decreasein the Rubisco content of Norin 1 grown under a high dose ofUVB radiation was exceptionally marked, and was not observedsimilarly in Sasanishiki. These results suggest that the remarkablereduction in Rubisco content in Norin 1 might have been dueto the specific effects of UVB radiation. It is also suggestedthat the difference between cultivars in the resistance to UVBradiation might be due to the differences in the levels of Rubiscoand in UV-absorbing compounds that are induced by UVB radiation. (Received January 29, 1996; Accepted May 31, 1996)     

Increase in CPD photolyase activity functions effectively to prevent growth inhibition caused by UVB radiation

Rice cultivars vary widely in their sensitivity to ultraviolet B (UVB) and this has been correlated with cyclobutane pyrimidine dimer (CPD) photolyase mutations that alter the structure/function of this photorepair enzyme. Here, we tested whether CPD photolyase function determines the UVB sensitivity of rice (Oryza sativa) by generating transgenic rice plants bearing the CPD photolyase gene of the UV-resistant rice cultivar Sasanishiki in the sense orientation (S-B and S-C lines) or the antisense orientation (AS-D line). The S-B and S-C plants had 5.1- and 45.7-fold higher CPD photolyase activities than the wild-type, respectively, were significantly more resistant to UVB-induced growth damage, and maintained significantly lower CPD levels in their leaves during growth under elevated UVB radiation. Conversely, the AS-D plant had little photolyase activity, was severely damaged by elevated UVB radiation, and maintained higher CPD levels in its leaves during growth under UVB radiation. Notably, the S-C plant was not more resistant to UVB-induced growth inhibition than the S-B plant, even though it had much higher CPD photolyase activity. These results strongly indicate that UVB-induced CPDs are one of principal causes of UVB-induced growth inhibition in rice plants grown under supplementary UVB radiation, and that increasing CPD photolyase activity can significantly alleviate UVB-caused growth inhibition in rice. However, further protection from UVB-induced damage may require the genetic enhancement of other systems as well.     

SCREENING OF ULTRAVIOLET‐A AND ULTRAVIOLET‐B RADIATION IN MARINE GREEN MACROALGAE (CHLOROPHYTA)1

Ultraviolet‐screening capacity of macrothalli from marine chlorophytes was analyzed using an in vivo technique based on chl fluorescence. The method, originally introduced to assess epidermal UV transmittance in leaves from higher plants, is extended to macroalgae. Validation of the method was obtained by measuring unprotected samples (i.e., isolated chloroplasts from six algal species). It is shown that in a total of 71 investigated green macroalgae, including cultured and field‐collected material from six systematic orders, only 40% or 60% displayed significant screening of ultraviolet‐A (UVA) or ultraviolet‐B (UVB) radiation, respectively. Generally, the extent of screening was low in most of these species. Data analysis resulted in a clear phylogenetic pattern with minor influence of climatic origin of a given species. For some species, comparison between field‐collected and culture‐grown samples was possible. Only in 11 of 25 species field collected algae had appreciably higher screening than those grown in the absence of UVB radiation. For the first time, very efficient UVA and UVB screening is demonstrated for the order of the Cladophorales. Their UVB‐screening potential varied between 40% and 85% of incoming UVB radiation. However, the nature and localization of the detected UV‐absorbing compounds are still unknown. Long‐term UV‐exposure experiments pointed to a negative correlation of UVB‐screening capacity and UV‐induced inhibition of photosynthetic efficiency. Thus, species with pronounced screening were more UV resistant than species with lower screening.     

Sensitivity of rice to ultraviolet-B radiation

BACKGROUND: Depletion of the stratospheric ozone layer leads to an increase in ultraviolet-B (UVB: 280-320 nm) radiation reaching the earth's surface, and the enhanced solar UVB radiation predicted by atmospheric models will result in reduction of growth and yield of crops in the future. Over the last two decades, extensive studies of the physiological, biochemical and morphological effects of UVB in plants, as well as the mechanisms of UVB resistance, have been carried out. SCOPE: In this review, we describe recent research into the mechanisms of UVB resistance in higher plants, with an emphasis on rice (Oryza sativa), one of the world's most important staple food crops. Recent studies have brought to light the following remarkable findings. UV-absorbing compounds accumulating in the epidermal cell layers have traditionally been considered to function as UV filters, and to play an important role in countering the damaging effects of UVB radiation. Although these compounds are effective in reducing cyclobutane pyrimidine dimer (CPD) induction in plants exposed to a challenge exposure to UVB, certain levels of CPD are maintained constitutively in light conditions containing UVB, regardless of the quantity or presence of visible light. These findings imply that the systems for repairing DNA damage and scavenging reactive oxygen species (ROS) are essential for plants to grow in light conditions containing UVB. CONCLUSION: CPD photolyase activity is a crucial factor determining the differences in UVB sensitivity between rice cultivars. The substitution of one or two bases in the CPD photolyase gene can alter the activity of the enzyme, and the associated resistance of the plant to UVB radiation. These findings open up the possibility, in the near future, of increasing the resistance of rice to UVB radiation, by selective breeding or bioengineering of the genes encoding CPD photolyase.     

UVB radiation and 17‐hydroxygeranyllinalool diterpene glycosides provide durable resistance against mirid (Tupiocoris notatus) attack in field‐grown Nicotiana attenuata plants

Depending on geographical location, plants are exposed to variable amounts of UVB radiation and herbivore attack. Because the role(s) of UVB in the priming and/or accumulation of plant defence metabolites against herbivores are not well understood, we used field‐grown Nicotiana attenuata plants to explore the effects of UVB on herbivore performance. Consistent with previous reports, UVB‐exposed plants accumulated higher levels of ultraviolet (UV)‐absorbing compounds (rutin, chlorogenic acid, crypto‐chlorogenic acid and dicaffeoylspermidine). Furthermore, UVB increased the accumulation of jasmonic acid, jasmonoyl‐L‐isoleucine and abscisic acid, all phytohormones which regulate plant defence against biotic and abiotic stress. In herbivore bioassays, N. attenuata plants experimentally protected from UVB were more infested by mirids in three consecutive field seasons. Among defence metabolites measured, 17‐hydroxygeranyllinalool diterpene glycosides (HGL‐DTGs) showed strongly altered accumulation patterns. While constitutive HGL‐DTGs levels were higher under UVB, N. attenuata plants exposed to mirid bugs (Tupiocoris notatus) had still more HGL‐DTGs under UVB, and mirids preferred to feed on HGL‐DTGs‐silenced plants when other UVB protecting factors were eliminated by UVB filters. We conclude that UVB exposure not only stimulates UV protective screens but also affects plant defence mechanisms, such as HGL‐DTGs accumulation, and modulates ecological interactions of N. attenuata with its herbivores in nature.     

Effects of UVB Radiation on Stomatal Density and Opening in Rice (Oryza sativa L.)

Ultraviolet-B (UVB, wavelength 280-320 nm) radiation has beendemonstrated to affect growth and development of many plants.This study was conducted to determine the effect of UVB radiationon stomatal density and opening of Oryza sativa and to testif the stomatal response to UVB was associated with differentsensitivity of growth to UVB in four cultivars. Ten-day-oldseedlings of IR45 and IR74 (UVB sensitive), and IR64 and IR30(UVB less sensitive), were subjected to UVB radiation in a glasshousefor 6 h d^-1 for 4 weeks. The unweighted UVB radiation was 1·94W m^-2 for UVB treatment and 0·15 W m^-2 for control. Leafarea and plant dry mass were determined every 2 weeks whilestomatal density and opening were recorded weekly. Results showedthat a 2-week UVB treatment had no effect on the leaf area orplant dry mass of any test cultivar, but significantly reducedstomatal density and opening in IR45 and IR74. Under 4-weekUVB exposure, leaf area and plant dry mass of IR45 and IR74were significantly reduced. Stomatal density decreased in allcultivars, except in IR64. Greater reduction of stomata on theadaxial surface than on the abaxial surface under 3 and 4 weeksof UVB exposure suggests a direct effect of UVB radiation onstomata. IR45 and IR74 showed significant reductions in stomatalopening after 2 weeks of exposure to UVB, while stomatal openingin IR30 and IR64 decreased significantly after only 4 weeksof UVB treatment. Difference in plant dry mass between UVB treatedand control plants was significantly correlated with the reductionsin stomatal opening and density on adaxial surface under UVBtreatment. Thus, reduction in dry mass of rice plants underUVB in the glasshouse could be attributed to decrease in stomataldensity and opening.Copyright 1995, 1999 Academic Press Oryza sativa, UVB radiation, stomatal density, stomatal opening     

Plant-mediated effects of elevated ultraviolet-B radiation on peat microbial communities of a subarctic mire

Elevated ultraviolet‐B (UVB) radiation has been reported to have few effects on plants but to alter the soil microbial community composition. However, the effects on soil microorganisms have to be mediated via plants, because direct radiation effects are only plausible on the uppermost millimeters of soil. Here, we assessed secondary effects of UVB on soil microbes. The responses in the dominant plant Eriophorum russeolum, peat pore water and microbial communities in the peat were recorded at a subarctic mire in the middle of the third growing season under field exposure simulating 20% depletion in the ozone layer. The UVB treatment significantly reduced the sucrose and the total soluble sugar (sucrose+glucose+fructose) concentration of the plant leaves while increasing the sucrose concentration in the belowground storage organ rhizome. The starch concentration of the leaves was also slightly reduced by elevated UVB. In the plant roots, carbohydrate concentrations remained unaffected but the total phenolics concentration increased under elevated UVB. We suggest that the simultaneously observed decrease in bacterial growth rate and the altered bacterial community composition are due to UVB‐induced changes in the plant photosynthate allocation and potential changes in root exudation. There were no effects of elevated UVB on microbial biomass, peat pore water or nutrient concentrations in the peat. The observed responses are in line with the previously reported lower ecosystem dark respiration under elevated UVB, and they signify that the changed plant tissue quality and lower bacterial activity are likely to reduce decomposition.     

The greater lethality of UVB radiation to cultured human cells is associated with the specific activation of a DNA damage-independent signaling pathway

UV radiation causes cell death through the activation of various intracellular signaling molecules in both DNA damage-dependent and -independent manners. The ability of middle-wavelength UV (UVB) radiation to form DNA photoproducts is less than that of short-wavelength UV (UVC) radiation; however, the differences between UVB and UVC radiation in the extent of DNA damage-independent signaling and its contribution to cell death have not been well characterized. When cells were irradiated with UVB or UVC radiation at doses that generated equivalent amounts of DNA photoproducts, UVB radiation induced more clonogenic cell death, apoptotic cells, mitochondrial cytochrome C release, and intracellular oxidative stress. Among the signaling molecules examined, levels of p53 phosphorylated at Ser-392 and p38 were higher in UVB-irradiated cells than in UVC-irradiated cells. Both phosphorylations were reduced by treating cells with an antioxidant. Furthermore, an inhibitor of p38 also blocked the phosphorylation of p53 at Ser-392. These results suggest that UVB radiation activates the p38 pathway through the generation of oxidative stress, which merges with the DNA p53 pathway by phosphorylation of p53 at ser392. This greater contribution of the DNA damage-independent pathway in UVB-irradiated cells may explain the greater lethality of UVB radiation.     

Responses of plants in polar regions to UVB exposure: a meta-analysis

We report a meta‐analysis of data from 34 field studies into the effects of ultraviolet B (UVB) radiation on Arctic and Antarctic bryophytes and angiosperms. The studies measured plant responses to decreases in UVB radiation under screens, natural fluctuations in UVB irradiance or increases in UVB radiation applied from fluorescent UV lamps. Exposure to UVB radiation was found to increase the concentrations of UVB absorbing compounds in leaves or thalli by 7% and 25% (expressed on a mass or area basis, respectively). UVB exposure also reduced aboveground biomass and plant height by 15% and 10%, respectively, and increased DNA damage by 90%. No effects of UVB exposure were found on carotenoid or chlorophyll concentrations, net photosynthesis, F_v/F_m or Φ_PSII, belowground or total biomass, leaf mass, leaf area or specific leaf area (SLA). The methodology adopted influenced the concentration of UVB absorbing compounds, with screens and natural fluctuations promoting significant changes in the concentrations of these pigments, but lamps failing to elicit a response. Greater reductions in leaf area and SLA, and greater increases in concentrations of carotenoids, were found in experiments based in Antarctica than in those in the Arctic. Bryophytes typically responded in the same way as angiosperms to UVB exposure. Regression analyses indicated that the percentage difference in UVB dose between treatment and control plots was positively associated with concentrations of UVB absorbing compounds and carotenoids, and negatively so with aboveground biomass and leaf area. We conclude that, despite being dominated by bryophytes, the vegetation of polar regions responds to UVB exposure in a similar way to higher plant‐dominated vegetation at lower latitudes. In broad terms, the exposure of plants in these regions to UVB radiation elicits the synthesis of UVB absorbing compounds, reduces aboveground biomass and height, and increases DNA damage.