共查询到20条相似文献，搜索用时 46 毫秒
1.
Evidence for photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C(60), is reported. After photo-excitation of the conjugated polymer with light of energy greater than the pi-pi* gap, an electron transfer to the C(60) molecule is initiated. Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the separate components, consistent with photo-excited charge transfer. A photoinduced electron spin resonance signal exhibits signatures of both the conducting polymer cation and the C(60) anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C(60), the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-separated state in composite films is metastable at low temperatures. 相似文献
2.
缺锌胁迫对苹果叶片光合速率及叶绿素荧光特性的影响 总被引：4，自引：0，他引：4
【目的】研究不同程度的缺锌胁迫对大田苹果树叶片的叶绿素含量、光合速率、叶绿素荧光特性等的影响,进一步揭示缺锌对叶片光系统的伤害机理。【方法】以大田盛果期‘红富士/平邑甜茶’正常树和缺锌小叶病树为试材,对叶片锌含量、叶绿素含量、净光合速率、荧光参数等指标进行测定。【结果】缺锌胁迫下,苹果叶片叶绿素含量下降,单叶面积、比叶重显著减小;气孔导度降低,胞间CO2浓度升高,净光合速率和水分利用效率下降。随缺锌程度加重,叶片初始荧光Fo上升,PSⅡ潜在活性Fv/Fo 、PSⅡ实际光化学效率ΦPSⅡ、光化学淬灭系数qP及PSⅡ天线转化效率Fv’/Fm’显著下降;J点相对可变荧光VJ和K点的相对变化Wk上升,电子传递的量子产额ETo/ABS和单位面积有活性的反应中心数量RC/CSo下降,光合性能指数PIABS显著降低。【结论】缺锌时非气孔限制是导致苹果叶片光合速率降低的原因之一;缺锌时首先引起放氧复合体（OEC）的破坏,进而使PSⅡ反应中心受损,PSⅡ供体侧、受体侧电子传递受抑制,影响叶片对光能的吸收、传递与利用。 相似文献
3.
NN Kuzma P Khandelwal SE Barrett LN Pfeiffer KW West 《Science (New York, N.Y.)》1998,281(5377):686-690
Optically pumped nuclear magnetic resonance (OPNMR) measurements were performed in two different electron-doped multiple quantum well samples near the fractional quantum Hall effect ground state nu = 13. Below 0.5 kelvin, the spectra provide evidence that spin-reversed charged excitations of the nu = 13 ground state are localized over the NMR time scale of about 40 microseconds. Furthermore, by varying NMR pulse parameters, the electron spin temperature (as measured by the Knight shift) could be driven above the lattice temperature, which shows that the value of the electron spin-lattice relaxation time tau1s is between 100 microseconds and 500 milliseconds at nu = 13. 相似文献
4.
为了揭示毛竹Phyllostachys edulis快速生长期茎秆不同节间叶绿素荧光特征,以毛竹笋竹茎秆为材料,用YZQ-500型非调制式叶绿素荧光仪和JIP-test数据分析方法,研究了茎秆不同节间光合色素质量分数和叶绿素荧光参数的变化特征。结果显示:随着节间的升高,毛竹笋竹茎秆中叶绿素a,叶绿素b和类胡萝卜素质量分数显著下降（P < 0.05）;单位面积捕获的光能（TRo/CSo）,单位面积电子传递的量子产额（ETo/CSo）,PSⅡ反应中心吸收光能用于电子传递的量子产额（φEo）,PSⅡ最大光化学效率（φPo）,光合性能指数（PIABS）和反应中心数量（RC/CSo）显著下降（P < 0.05）;用于热耗散的量子比率（φDo）,单位面积热耗散（DIo/CSo）和单位反应中心耗散掉的能量（DIo/RC）显著上升（P < 0.05）,表明茎秆上下部节间的生长发育存在明显差异,中下部节间PSⅡ反应中心活性较强,光能转换效率较高,能量耗散较少,生长较快;上部节间光合功能相对较弱,生长比较缓慢。研究成果对明确毛竹快速生长机制具有参考价值。 相似文献
5.
光谱对水稻灌浆期剑叶光合及叶绿素荧光特性的影响 总被引：1，自引：0，他引：1
【目的】探讨光谱对水稻剑叶光合及叶绿素荧光特性的影响。【方法】以华粳5号为材料,采用660 nm（R660）和630 nm（R630）的红光及460 nm（B460）和440 nm（B440）的蓝光分别与专用植物灯（W）组成不同光谱,设R660+W、R630+W、B460+W及B440+W 4种光谱处理,于水稻灌浆期测定剑叶光合特性及叶绿素荧光特性。【结果】蓝光能提高水稻剑叶的最大光化学效率（Fv/Fm）、实际光化学效率（ΦPSⅡ）、电子传递速率（ETR）、非光化学猝灭系数（NPQ）和光化学猝灭系数（qP）;灌浆后期,B460+W处理水稻剑叶的净光合速率显著高于红光处理,R660+W处理的单位面积穗数最多,B460+W处理的千粒重和结实率高于其他处理。光响应曲线拟合表明,B460+W处理能提高水稻剑叶的最大净光合速率（Pnmax）、光响应曲线初始斜率（α）、暗呼吸量子效率、补偿点量子效率、捕光色素分子的本征光能吸收截面（σik）和捕光色素分子数（No）。【结论】B460+W处理能改善水稻剑叶光系统Ⅱ的性能,使其在灌浆后期维持一个较高的水平,进而促进干物质积累,最终提高千粒重和结实率,即在白光背景中添加460 nm蓝光是人工环境水稻栽培灌浆期的适宜光谱。 相似文献
6.
N Liang A G Mauk G J Pielak J A Johnson M Smith B M Hoffman 《Science (New York, N.Y.)》1988,240(4850):311-313
Yeast iso-1-cytochrome c (Cc) mutants have been constructed with Phe, Tyr, Gly, Ser, Leu, and Ile at position 82, each with Thr substituted for Cys at position 102. Their long-range electron transfer with zinc-substituted cytochrome c peroxidase (ZnCcP) has been studied by two kinetic techniques. The charge-separated complex, [(ZnCcP)+,FeIICc] converts to [ZnCcP,FeIIICc] by a single, intracomplex electron transfer step that is not governed by "gating" through possible rapid dissociation of the complex or isomerization (for example, heme-ligand) by FeIICc subsequent to its formation from FeIIICc. In every variant with an aliphatic residue at position 82 of Cc, the rate of this electron transfer process is approximately 10(4) slower at approximately 0 degrees C than for the two variants with aromatic residues. 相似文献
7.
模拟酸雨对大叶黄杨叶片叶绿素荧光参数的影响 总被引：1，自引：0，他引：1
为了明确酸雨对大叶黄杨叶片荧光参数的影响,在拱棚条件下,以2年生大叶黄杨(Euonymus japonicus)为试材,采用人工喷洒的方法,以pH为7.0的模拟雨水为对照,研究了不同pH值(1.0、2.0、3.0、4.0、5.0)的模拟酸雨对大叶黄杨叶片的叶绿素相对含量和叶绿素荧光特性的影响。结果表明:随着酸雨浓度pH值降低,大叶黄杨叶片的叶绿素含量呈现下降的趋势;叶绿素荧光参数非光化学猝灭系数(qN)呈先上升后下降趋势;光化学猝灭系数(qP)、PSⅡ最大光化学效率(Fv/Fm)、PSⅡ电子传递量子效率(ΦPSII)、表观光合电子传递速率(ETR)呈现下降趋势。当模拟酸雨pH≤2.0时,会对大叶黄杨的叶片造成严重的损伤,破坏叶绿体结构,直接影响了光合作用中的电子传递,导致光合电子传递过程中受到损害和抑制。 相似文献
8.
缺磷胁迫对温州蜜柑光合作用的光抑制研究（一） 总被引：3，自引：2，他引：3
经缺磷处理后,温州蜜柑叶片的表观量子效率（AQY）,最大荧光（Fm）,光化学效率（Fv/Fm）,光量子产量（Y）和电子传递速率（ETR）下降,而初始荧光（Fo）上升。净光合速率（Pn）和光呼吸速率（Pr）均下降。但Pr/Pn比值升高。表明缺磷处理后,温州蜜柑更易发生光合作用的光抑制。 相似文献
9.
以国外主推番茄品种好韦斯特(不抗TYLCV)为对照,比较了其与自育高抗TYLCV番茄品种——瓯秀806的叶绿素含量、植物学特性、光合特性等生理特性的差异,结果表明,Chla、Chlb、Chl (a+b)和Car含量均以瓯秀806较高(P＜005);而Chla / Chlb则以好韦斯特较高(P＜005);2个番茄品种的光合速率均随着CO2浓度的升高而增大,当CO2浓度大于450 μmol·mol-1,其光合速率增加不显著(P＞005)。在低CO2浓度(350 μmol·mol-1)下,好韦斯特的最大光合速率较高(P＜005);较高CO2浓度(450,550和650 μmol·mol-1)下,好韦斯特的光饱和点均较低(P＜005),分析认为主要由于其较低的叶绿素含量引起。而不同CO2浓度下,2个番茄品种表观量子效率(AQY)、暗呼吸速率(Rn)和光补偿点(LCP)差异较小。瓯秀806早期产量为1 4568 kg·667 m-2,低于好韦斯特(P＞005);而其总产量则高于好韦斯特,达7 245 kg,增产582% (P＜005),分析其原因主要是由于好韦斯特后期发病率较高。 相似文献
10.
采用盆栽试验,以西安91-2、甘啤3号和扬饲麦3号为材料,研究不同浓度PEG6000(5%、10%、15%、20%、25%和30%)渗透胁迫下大麦苗期叶片光能利用和能量耗散的影响。结果表明,随着PEG渗透胁迫的增加,3个大麦品种叶片叶绿素a含量、叶绿素b含量,最大荧光(Fm)、最大光化学效率(Fv/Fm)、实际光化学效率(PSⅡ)都有不同程度的降低,初始荧光(F0)、表观光合量子传递速率(ETR)、光化学淬灭系数(qP)、非光化学淬灭系数(NPQ)等则表现出增加的趋势。3个品种在低浓度的PEG处理下只是通过减少光能的利用和增加热耗散维持光合机构的稳定,但高浓度的PEG处理造成了光合机构的破坏,不同品种的表现不同。与甘啤3号相比,西安91-2各项生理参数值变化幅度小,与西安91-2相比,扬饲麦3号各项生理参数值变化幅度小。 相似文献
11.
On the prevalence of room-temperature protein phosphorescence 总被引：6，自引：0，他引：6
A large number of proteins were tested for the property of intrinsic phosphorescence in deoxygenated aqueous solution at room temperature. The majority of proteins exhibit phosphorescence under normal solution conditions. Phosphorescence lifetimes from 0.5 millisecond to 2 seconds were observed in three-fourths of the proteins tested. The lifetime appears to correlate with relative isolation of the tryptophan indole side chain from solvent. With few exceptions, proteins in general can be expected to display a phosphorescence lifetime greater than 30 microseconds. This widespread characteristic of proteins has been largely overlooked because long-lived phosphorescence is highly sensitive to quenching by low levels of dissolved oxygen in solution. Protein phosphorescence offers a new time domain and a far wider dynamic range than has been used before for photoluminescence experimentation. 相似文献
12.
Antibody-catalyzed porphyrin metallation 总被引：3，自引：0，他引：3
An antibody elicited to a distorted N-methyl porphyrin catalyzed metal ion chelation by the planar porphyrin. At fixed Zn2+ and Cu2+ concentrations, the antibody-catalyzed reaction showed saturation kinetics with respect to the substrate mesoporphyrin IX (2) and was inhibited by the hapten, N-methylmesoporphyrin IX (1). The turnover number of 80 hour-1 for antibody-catalyzed metallation of 2 with Zn2+ compares with an estimated value of 800 hour-1 for ferrochelatase. The antibody also catalyzed the insertion of Co2+ and Mn2+ into 2, but it did not catalyze the metallation of protoporphyrin IX (3) or deuteroporphyrin IX (4). The antibody has high affinity for several metalloporphyrins, suggesting an approach to developing antibody-heme catalysts for redox or electron transfer reactions. 相似文献
13.
为了解水分抑制条件下棉花光合生理和叶绿素荧光特性响应机理,为抗旱棉花品种的筛选和培育提供理论依据,试验以3个北疆主栽棉花品种为材料,利用叶绿素荧光分析技术,研究了渗透胁迫下棉花品种的叶绿素荧光猝灭特性的响应变化.结果表明,长时间(16 h)和高浓度(30;)渗透胁迫会降低棉花PSⅡ的原初光能转化效率(Fv/Fm),使PSⅡ反应中心开放部分的比例(qP)缩小,用于光合作用电子传递的份额(qP)减少,从而使光合器官受到损伤,非辐射能量耗散增加,抑制了棉花叶片的光合功能.响应的结果同时与品种自身的恢复能力差异性有密切的关系.各个品种对长时间、高浓度胁迫后恢复的Fv/Fm、qP和qN及其与对照之间差异分别达到了极显著水平,建议用长时间、高浓度渗透胁迫的荧光猝灭特性的恢复能力差异来作为辅助鉴定和筛选棉花品种抗旱性的依据. 相似文献
14.
Xiong P Nocek JM Vura-Weis J Lockard JV Wasielewski MR Hoffman BM 《Science (New York, N.Y.)》2010,330(6007):1075-1078
Direct measurements of electron transfer (ET) within a protein-protein complex with a redesigned interface formed by physiological partner proteins myoglobin (Mb) and cytochrome b(5) (b(5)) reveal interprotein ET rates comparable to those observed within the photosynthetic reaction center. Brownian dynamics simulations show that Mb in which three surface acid residues are mutated to lysine binds b(5) in an ensemble of configurations distributed around a reactive most-probable structure. Correspondingly, charge-separation ET from a photoexcited singlet zinc porphyrin incorporated within Mb to the heme of b(5) and the follow-up charge-recombination exhibit distributed kinetics, with median rate constants, k(f)(s) = 2.1 × 10(9) second(-1) and k(b)(s) = 4.3 × 10(10) second(-1), respectively. The latter approaches that for the initial step in photosynthetic charge separation, k = 3.3 × 10(11) second(-1). 相似文献
15.
Effects of silicon on photosynthetic parameters and antioxidant enzymes of chloroplast in cucumber seedlings under excess Mn were studied. Compared with the control, excess Mn significantly inhibited net photosynthetic rate （Pn）, stomatal conductance, as well as the maximum yield of the photosystem II photochemical reactions （Fv/Fm） and the quantum yield of photosysytem II electron transport （Φ PSII）, application of Si reversed the negative effects of excess Mn. In the further investigation, it was obtained that application of Si significantly increased the activities of enzymes related with ascorbate-glutathione cycle including ascorbate peroxidase （APX）, dehydroascorbate reductase （DHAR） and glutathione reductase （GR） in cucumber chloroplast under excess Mn, this could be responsible for the lower accumulation of H2O2 and lower lipid peroxidation of chloroplast induced by Mn, and resulted in keeping higher photosynthesis. 相似文献
16.
[目的]研究汉麻在重金属锌胁迫下的光合特性及叶绿素荧光参数的响应。[方法]通过温室水培试验,研究不同浓度锌胁迫对汉麻光合特性及叶绿素荧光参数的影响。[结果]与2μmol/L锌浓度处理(CK)相比,缺锌0μmol/L和高浓度锌处理(50、100、200μmol/L)的汉麻,其叶片的叶绿素a、叶绿素b和类胡萝卜素均下降,叶绿素a减少速率最快;高锌处理随着锌浓度的增加,净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)呈下降趋势,胞间二氧化碳浓度(Ci)缓慢上升。胁迫40 d后,高锌处理的PSⅡ原初光能转化效率(Fv/Fm)、实际光量子产量(Y)、光化学淬灭系数(q P)、光合电子传递速率(ETR)随锌浓度的升高呈下降趋势,非光化学荧光猝灭系数(NPQ)在200μmol/L锌浓度水平下胁迫10 d后取得最大值,而后随时间延长而迅速衰减,叶绿素b与非光化学荧光猝灭机制对汉麻的光合作用起重要保护作用。[结论]锌对汉麻光合机制有明显的影响,缺锌和高浓度锌对汉麻光合代谢过程有抑制和损害。 相似文献
17.
低温弱光胁迫对棉花幼苗叶绿素荧光特性及能量分配的影响 总被引：4，自引：1，他引：3
[目的]探讨低温弱光胁迫下不同基因型棉花幼苗叶绿素荧光特性及能量分配的响应机制,为棉花耐低温品种选育及筛选耐低温鉴定指标和方法提供理论依据.[方法]以6种不同基因型棉花幼苗为试材,通过5℃、100 μmol/( m2·s)低温弱光处理,测定12 h内叶绿素荧光相关参数.[结果]低温弱光胁迫提高了初始荧光Fo、光合功能相对限制值L(PFD),显著降低了PSⅡ最大光化学效率Fv/Fm、PSⅡ实际光化学效率φPSⅡ、光合电子传递速率ETR、光化学猝灭系数qP等指标,非光化学猝灭系数NPQ则呈现先升后降的趋势;同时,PSⅠ激发能分配系数σ、天线热耗散速率Drate增大,PSⅡ激发能分配系数β、光化学速率Prate降低.[结论]低温弱光胁迫导致棉花幼苗叶片PSⅡ光化学活性降低,光合电子传递过程受抑,更多的光能用于天线热耗散,且干扰了PSⅠ和PSⅡ间的激发能分配和传递.综合各指标分析,新陆中28号与中棉所50号在低温弱光胁迫下表现出良好的光能分配、利用能力,耐低温能力较强,新陆早42号与中棉所43号次之,新陆早33号和新陆早19号较差. 相似文献
18.
Yang H Luo G Karnchanaphanurach P Louie TM Rech I Cova S Xun L Xie XS 《Science (New York, N.Y.)》2003,302(5643):262-266
Electron transfer is used as a probe for angstrom-scale structural changes in single protein molecules. In a flavin reductase, the fluorescence of flavin is quenched by a nearby tyrosine residue by means of photo-induced electron transfer. By probing the fluorescence lifetime of the single flavin on a photon-by-photon basis, we were able to observe the variation of flavin-tyrosine distance over time. We could then determine the potential of mean force between the flavin and the tyrosine, and a correlation analysis revealed conformational fluctuation at multiple time scales spanning from hundreds of microseconds to seconds. This phenomenon suggests the existence of multiple interconverting conformers related to the fluctuating catalytic reactivity. 相似文献
19.
Photosynthetic Characteristics of a Super High Yield Cultivar of Winter Wheat During Late Growth Period 总被引：3，自引：0，他引：3
The mechanism of high yield of winter wheat in the field at late growth period was investigated by measuring the photosynthetic characteristics of photosystem Ⅱ （PSⅡ） and xanthophylls cycle, which could provide physiological reference for breeding. Weimai 8 （W8）, a super high yield cultivar, and Lumai 14 （L14）, a control cultivar were object. The photosynthetic rate （Pn）, parameters of chlorophyll fluorescence and chlorophyll content were measured. The Pn, maximum photochemical efficiency of PSII （Fv/Fm）, quantum yield of PSII electron transport （ΦPSⅡ）, efficiency of excitation energy capture by open PSII reaction centers （Fv＇/Fm＇）, and photochemical quenching coefficient （qP） were higher in Weimai 8 compared to that in Lumai 14, a commercial high yield cultivar. Furthermore, Weirnai 8 showed a lower non- photochemical quenching coefficient and a lower de-epoxidized ratio of the xanthophyll cycle pigments than of Lumai 14 at late growth period. At mature stage, chlorophyll content of different leaves decreased both in Weimai 8 and Lumai 14. Chlorophyll content in flag, second and third leaf from the top of plant decreased more in Lumai 14 than in Weimai 8. These results suggested that Weimai 8 had more antenna pigments to absorb light energy, and had higher photosynthetic capability and photochemical efficiency of PSⅡ. The yield of Weimai 8 was also higher than that of Lumai 14. 相似文献
20.
氨基酸肥料对大豆叶片光合作用与产量的影响 总被引：11，自引：0，他引：11
以泗洪县和兴化市两地区主栽的大豆品种‘高丰1号’和‘大豆王’为材料,研究了喷施氨基酸肥料对植株叶片光合特性、农艺性状、产量与品质的影响。结果表明:喷施氨基酸肥料能够显著提高大豆叶片SPAD值、净光合速率(Pn)、PSⅡ反应中心最大量子效率(φPo)和捕获的激子将电子传递到QA-以远其他电子受体的概率(ψo),减少PSⅡ反应中心吸收光能用于热耗散的量子比率(φDo)。其中泗洪‘高丰1号’的φPo值增加9.5%,兴化‘大豆王’的ψo值增加23%。氨基酸肥料处理还显著增加产量,‘高丰1号’的百粒质量增加10%,单株产量增加39%,每m2产量增加64%;‘大豆王’的百粒质量增加8.6%,单株产量增加22.6%,每m2产量增加22%。并且,氨基酸肥料处理提高了豆粒维生素C、可溶性糖、游离氨基酸以及蛋白质含量。 相似文献