叶片上下表面的光谱特性

绿色植物的光合作用、生产量及能量关系受叶片及整个群落的光学特性的强烈制约。叶片的光谱特性包括对光的吸收、反射和透过等几个方面。对光合作用有效辐射[400—700nm(纳诺米),可见光区域]的吸收是光合作用的第一个步骤。叶片对光的反射可以降低叶温、减少叶片的水分丧失,在一个植株或植物群落中,上部叶片对光的反射和透过通常可以调节群落中的光能利用。一般而言,绿色植物的上表面吸收太阳可见辐射能的80—85%,反射约10%,透过5—     

人体劳宫穴红外辐射光谱特性研究

目的:比较正常人及冠心病患者两侧劳宫穴(PC8)微弱红外辐射光谱的差异性。方法:对47名正常人和50名冠心病患者左右侧劳宫穴红外辐射进行检测,通过光谱形态分析和点值比较的方法对两侧红外辐射光谱的差异进行研究。结果:人体两侧劳宫穴红外辐射光谱形态基本一致,但在辐射峰处两侧劳宫穴红外辐射强度有显著差异(P<0.05),正常人两侧劳宫穴辐射强度差值和冠心病患者相比并无显著性差异P>0.05。结论:劳宫穴的红外辐射不能灵敏地反应冠心病心肌缺血缺氧的病理状态,人体穴位红外辐射光谱无刺激性探测和分析为经穴特异性研究提供了新的途径。     

聚乙二醇化黑色TiO2介导的光动力疗法灭活HL60细胞试验研究

为了探究聚乙二醇化黑色TiO2介导的光动力疗法体外灭活HL60细胞的潜力,先后采用水热还原法和表面修饰法制备不同质量比的聚乙二醇化黑色TiO2(PEG@B-TiO2)纳米复合材料.通过X射线衍射(XRD)、傅里叶红外光谱(FTIR)、紫外可见吸收光谱(UV-VIS)、荧光光谱(FS)、透射电子显微镜(TEM)及粒度仪研...     

长白山阔叶红松林太阳辐射分光谱特征

根据对林冠上方和林下太阳辐射的观测及气象站资料,分析了长白山阔叶红松林太阳辐射分光谱特征。结果表明,长白山阔叶红松林区太阳总辐射、直接辐射、散射辐射的光合有效辐射系数有一定的日变化和年变化,年平均值分别为０．４６、０．４３、０．５６。阔叶红松林中不同树种的单叶对于太阳总辐射的反射率、透射率、吸收率的平均值分别为２７．０％、２３．４％、４９．６％。单叶的分光谱反射、透射和吸收的特点是,单叶对紫外辐射     

森林冠层辐射的数值模拟

一、引言太阳辐射是树木和各种作物生长过程中所需能量的直接或间接源泉。一定强度的太阳辐射达到林冠层表面时,由于叶、枝等器官的吸收、反射和透射作用,使得冠层内的辐射分布有其独具的特征。本文综合考虑天空散射和叶片的内部散射作用,从辐射通量的角度在计算机上模拟了各向同性叶角分布的冠层中辐射通量的分布特征,讨论了单叶反射系数和透射系     

帽峰山常绿阔叶林辐射通量特征

常绿阔叶林作为南亚热带气候条件下森林的典型代表,在森林辐射研究中扮演着重要的角色.基于广州帽峰山常绿阔叶林1 a的辐射观测数据,分析了其时序变化和分配等规律.结果表明:太阳总辐射(K ↓)、反射辐射(K↑)和净辐射(Rn)通量日变化呈典型的单峰曲线,大气逆辐射(L↓)、森林长波辐射(L↑)呈余弦曲线,长波有效辐射(Ln)呈波浪形.各辐射总量均为雨季大于旱季,Ln除外;帽峰山常绿阔叶林K ↓年总量为4201.22 MJ/m2,Rn、K↑和Ln占其比例分别为63％、11％和26％.Rn通量分配率日变化呈倒“U”型曲线,Ln和K↑呈“U”型曲线.林冠上光合有效辐射(PARa)日平均值旱季小于雨季,林冠下(PARb)则相反;PARa变异系数旱雨季均小于PARb;PARa日变化呈典型的单峰曲线,PARb整体和PARa一致,仅在中午时刻出现微弱双峰.PAR透射率日峰值出现时间范围与K↓基本一致,尤其是在雨季,PAR透射率日平均值雨季大于旱季.帽峰山常绿阔叶林PAR/K↓比率为20％左右.     

UV-B辐射增强对陆地植物次生代谢的影响

平流层臭氧的减薄已导致地表中波紫外辐射(UV-B,280～320nm)增强,由于UV-B能被许多生物大分子如蛋白质和核酸吸收并引起分子构象的变化,因此可对植物的各方面产生影响。本文将近年来特别是近5年的UV-B辐射增强对植物次生代谢物影响的研究工作进行了综述。主要包括：UV-B辐射增强对植物紫外吸收物的影响和可能的机制;环境因子的复合作用对植物紫外吸收物的影响和可能的机制;UV-B辐射增强对次生代谢物影响的生态学意义。并对该领域未来的研究作了展望。     

葡萄糖氧化酶和柠檬汁对甘蔗汁保鲜效果的研究

为了研究甘蔗汁的保鲜,在鲜甘蔗汁中添加葡萄糖氧化酶和柠檬汁。利用单因素考察了葡萄糖氧化酶的量(A)、酶解温度(B)、酶解时间(C)和柠檬汁的量(D)对甘蔗汁保鲜效果的影响,在此基础上设计L9(34)正交实验,得出最优组合,并利用紫外光谱和红外光谱进行表征。实验结果表明在室温20℃下40 m L甘蔗汁保鲜的最优组合为:葡萄糖氧化酶的量为0.060 mg、酶解温度为30℃、酶解时间为10 min和柠檬汁的量为1 m L,因素的主次关系依次为柠檬汁的量、酶解温度、葡萄糖氧化酶的量和酶解时间,在最优组合条件下甘蔗汁能有效地保鲜12 d,保鲜12 d的样品和新鲜甘蔗汁的紫外光谱基本相同,红外光谱中都具有醌类物质吸收峰,而变质后的样品紫外发色基团C=C、C≡C和共轭多烯遭到了破坏,没有明显的醌类物质红外吸收峰。     

g-C3N4@C-TiO2纳米颗粒增强可见光驱动的体外光动力灭活HL60细胞的试验研究

通过化学气相沉积法制备了g-C3N4@C-TiO2纳米颗粒,利用X射线衍射(XRD)、荧光光谱(FS)、透射电子显微镜(TEM)、紫外-可见吸收光谱(UV-Vis)、能谱(EDS)等对纳米颗粒进行表征.分别研究了暗室条件及光照条件下g-C3N4@C-TiO2纳米颗粒对HL60细胞的作用效果.采用CCK-8法探究了一系列...     

芦丁与胰蛋白酶相互作用的光谱性质研究

利用紫外光谱和荧光光谱研究了芦丁和胰蛋白酶的相互作用机制。结果表明,生理pH 7.40条件下芦丁使胰蛋白酶的紫外吸收峰增强,特征荧光峰淬灭。并利用荧光淬灭反应测得芦丁和胰蛋白酶之间结合常数KA=6.8786×104(mol/L)-1,结合位点数n=1.0173。     

Ultraviolet B exposure of whole leaves of barley affects structure and functional organization of photosystem II

This study examines the effects of ecologically important levels of ultraviolet B radiation on protein D1 turnover and stability and lateral redistribution of photosystem II. It is shown that ultraviolet B light supported only limited synthesis of protein D1, one of the most important components of photosystem II, whereas it promoted significant degradation of proteins D1 and D2. Furthermore, dephosphorylation of photosystem II subunits was specifically elicited upon exposure to ultraviolet B light. Structural modifications of photosystem II and changes in its lateral distribution between granum membranes and stroma-exposed lamellae were found to be different from those observed after photoinhibition by strong visible light. In particular, more complete dismantling of photosystem II cores was observed. Altogether, the data reported here suggest that ultraviolet B radiation alone fails to activate the photosystem II repair cycle, as hypothesized for visible light. This failure may contribute to the toxic effect of ultraviolet B radiation, which is increasing as a consequence of depletion of stratospheric ozone.     

RecA Expression in Response to Solar UVR in the Marine Bacterium Vibrio natriegens

Solar ultraviolet radiation may produce daily stress on marine and estuarine communities as cells are damaged and repair that damage. Reduction in the earth's stratospheric ozone layer has increased awareness of the potential effects that ultraviolet radiation may have in the environment, including how marine bacteria respond to changes in solar radiation. We examined the use of the bacterial RecA protein as an indicator of the potential of bacteria to repair DNA damage caused by solar UV irradiation using the marine bacterium Vibrio natriegens as a model. RecA is universally present in bacteria and is a regulator protein for the so-called Dark Repair Systems, which include excision repair, postreplication recombinational repair, and mutagenic or SOS repair. Solar UVB and UVA both reduced V. natriegens viability in seawater microcosms. After exposure to unfiltered solar radiation or radiation in which UVB was blocked, survival dropped below 1%, whereas visible light from which UVA and UVB had been filtered had no effect on survival. Using a RecA-specific antibody for detection, RecA protein was induced by solar radiation in a diel pattern in marine microcosms conducted in the Gulf of Mexico. Peak induction was observed at dusk each day. Although RecA expression was correlated with the formation of UVB-induced cyclobutyl pyrimidine dimers, longer wavelength UVA radiation also induced recA gene expression. Our results demonstrate that RecA-regulated, light-independent repair is an important component in the ability of marine bacteria to survive exposure to solar ultraviolet radiation and that RecA expression is a useful monitor of bacterial repair after exposure to solar UVR.     

Photoreactivation in pigmented and non-pigmented extreme halophiles

The sensitivity to ultraviolet radiation (254 nm) and the photoreactivability of four pigmented and three colourless strains of the extremely halophilic bacteria Halobacterium cutirubrum and Halobacterium salinarium have been studied. The results with three pigmented/non-pigmented pairs show that the pigments play an accessory role in photoreactivation at low visible light intensities and confirm that they do not provide passive protection against ultraviolet light. Evidence is presented that photoreactivation plays an unexpected direct role in the resistance of extreme halophiles to ultraviolet radiation and that colourless mutants of H. cutirubrum NRC 34001 only arise in cultures that have been both ultraviolet-irradiated and photoreactivated. None of these extreme halophiles is capable of excision repair of ultraviolet damage to DNA.     

Visible and ultraviolet reflectance characteristics of arctic homeotherms

Reflectance characteristics of the epidermal coverings (hair, feathers) of several white birds and mammals were examined in the visible and ultraviolet regions of the solar spectrum. Non-white phases of the same species, and other non-white animals were examined for comparison. As expected, non-white animals exhibited lower reflectance values than white animals in the visible spectrum. Most species examined demonstrated reduced reflectance in the ultraviolet, reaching minimum values between 290 and 310 nm. In white animals, significant differences were found in the reflectance of UV-A (320–400 nm) and UV-B (280–320 nm) radiation. This accounts for the apparent differences in ultraviolet reflectance among various arctic mammals detected previously with ultraviolet photography. Reflectance patterns in the visible and ultraviolet were not obviously correlated with phylogenetic relationship, nor with the gross structure of hair or feathers.     

Spectral polymorphisms in angiosperm flowers determined by differential ultraviolet reflectance

The ultraviolet reflectance pattern of flowers from 54 species representing 22 families, many native or introduced to Japan, were surveyed. Their differential ultraviolet patterns, i.e. spectral polymorphisms, were recorded by paired photographs of fresh flowers: one taken in full sunlight and the other through a visible spectrum absorbing filter. The different types of polymorphisms observed varied from total absorption by the whole flower to limited absorption by selected floral parts, such as corolla bases (nectar guides) or anthers. Some visible spectrum polymorphisms, e.g. inAnemone andHepatica, were not associated with different ultraviolet patterns. In three species ofIris, a distinct ultraviolet absorbing landing spot and nectar, tunnel guide as well as reflecting anthers are reported. The downward exerted anthers ofSolanum nigrum which shed pollen through bee wing vibration were ultraviolet absorbent. The implications of these ultraviolet patterns for biochemical (flavonoid), taxonomic, pollination and eco-evolutionary research are discussed. Attention is drawn to the seasonal distribution of ultraviolet radiation in the northern hemisphere and its selective role on northern floras.     

The effects of gilvocarcin V and ultraviolet radiation on pBR322 DNA and lymphocytes

The antitumor antibiotic gilvocarcin (GV) when photoactivated with UV radiation induced single strand breaks in superhelical pBR322 DNA. The optimal wavelengths for nicking DNA correlated with the absorbance maximum of GV near the visible region (398 nm). The response of lymphocytes to stimulation by phytohemagglutinin was reduced to 10% of controls at 0.10 ng/ml GV in combination with 3 J/cm2 of ultraviolet A (UVA) radiation. The potency of gilvocarcin is attributed to two factors: its strong tendency to intercalate with DNA (K = 6.6 X 10(5) M-1) and its intense absorption of UVA radiation (E398 = 11971 M-1 cm-1).     

PHOTOSYNTHETIC INSENSITIVITY OF THE TERRESTRIAL CYANOBACTERIUM NOSTOC FLAGELLIFORME TO SOLAR UV RADIATION WHILE REHYDRATED OR DESICCATED1

Photosynthetic performance of the terrestrial cyanobacterium Nostoc flagelliforme (M. J. Berkeley et M. A. Curtis) Bornet et Flahault during rehydration and desiccation has been previously characterized, but little is known about the effects of solar UV radiation (280–400 nm) on this species. We investigated the photochemical activity during rehydration and subsequent desiccation while exposing the filamentous colonies to different solar radiation treatments. Photochemical activity could be reactivated by rehydration under full‐spectrum solar radiation, the species being insensitive to both ultraviolet‐A radiation (UVAR; 315–400 nm) and ultraviolet‐B radiation (UVBR). When the rehydrated colonies were exposed for desiccation, the effective PSII photochemical yield was inhibited by visible radiation (PAR) at the initial stage of water loss, then increased with further decrease in water content, and reached its highest value at the water content of 10%–30%. However, no significant difference was observed among the radiation treatments except for the moment when they were desiccated to critical water content of about 2%–3%. At such a critical water content, significant reduction by UVBR of the effective quantum yield was observed in the colonies that were previously rehydrated under indoor light [without ultraviolet radiation (UVR)], but not in those reactivated under scattered or direct solar radiation (with UVR), indicating that preexposure to UVR during rehydration led to higher resistance to UVR during desiccation. The photosynthetic CO₂ uptake by the desiccated colonies was enhanced by elevation of CO₂ but was not affected by both UVAR and UVBR. It increased with enhanced desiccation to reach the maximal values at water content of 40%–50%. The UV‐absorbing compounds and the colony sheath were suggested to play an important role in screening harmful UVR.     

Inactivation of carotenoid-producing and albino strains of Neurospora crassa by visible light, blacklight, and ultraviolet radiation.

Suspensions of Neurospora crassa conidia were inactivated by blacklight (BL) radiation (300 to 425 nm) in the absence of exogenous photosensitizing compounds. Carotenoid-containing wild-type conidia were less sensitive to BL radiation than albino conidia, showing a dose enhancement factor (DEF) of 1.2 for dose levels resulting in less than 10% survival. The same strains were about equally sensitive to shortwave ultraviolet (UV) inactivation. The kinetics of BL inactivation are similar to those of photodynamic inactivation by visible light in the presence of a photosensitizing dye (methylene blue). Only limited inactivation by visible light in the absence of exogenous photosensitizers was observed. BL and UV inactivations are probably caused by different mechanisms since wild-type conidia are only slightly more resistant to BL radiation (DEF = 1.2 at 1.0% survival) than are conidia from a UV-sensitive strain (upr-1, uvs-3). The BL-induced lethal lesions are probably no cyclobutyl pyrimidine dimers since BL-inactivated Haemophilus influenzae transforming deoxyribonucleic acid is not photoreactivated by N. crassa wild-type enzyme extracts, whereas UV-inactivated transforming deoxyribonucleic acid is photoreactivable with this treatment.     

Effects of visible and ultraviolet radiation on the ultrastructure of zooxanthellae (Symbiodinium sp.) in culture and in situ

Summary Quantitative ultrastructural studies on the effects of visible and ultraviolet radiation on zooxanthellae in culture and in situ showed an inverse relationship between the volume fraction of chloroplast and irridiance. An independent effect of ultraviolet radiation was detected in cultured zooxanthellae only. The volume fraction of chloroplasts in cultured zooxanthellae and zooxanthellae in situ were the same, while the surface density of thylakoid lamellae relative to chloroplast volume in cultured zooxanthellae was less than in zooxanthellae in situ for all irradiances. Additionally, zooxanthellae in situ showed an effect of ultraviolet radiation on surface density of thylakoid lamellae. The response to different irradiances suggests a limit to photoadaptation by means of changing chloroplast volume, and that changes in thylakoid density are responsible for the continued photoadaptive plasticity observed. Flow cytometry and stereological studies show that the volume fraction of accumulation bodies within zooxanthellae increases with irradiance and ultraviolet radiation. Ultrastructurally, accumulation bodies do not resemble plant peroxisomes or glyoxysomes, while other inclusions observed in this stydy are suggestive of peroxisomes. This evidence suggests that accumulation bodies are not peroxisomes, but does support the previous assumptions concerning their role in autophagic processes.