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1.
Wolfram R. Ullrich 《Planta》1971,100(1):18-30
Summary Manometric measurements show that oxygen evolution proceeds in synchronised cells of Ankistrodesmus braunii even in an atmosphere of pure nitrogen. In this case the slow oxygen evolution is dependent on the presence of nitrate (Table 1). Light saturation is found at a low light intensity at pH 5.6, at a higher light intensity at pH 8.0 (Fig. 1). The light saturation curves are in good agreement with those of 32P-labelling in Ankistrodesmus under the same conditions (Fig. 2).DCMU inhibition in N2 of both O2-evolution and 32P-labelling begins only at a DCMU concentration of 5×10-7M or more. Complete inhibition of O2-evolution is reached only at 10-5M (Fig.3). In 32P-labelling a variable percentage is still left uninhibited at 10-5 M DCMU (Fig. 4, Table 2), which is at least partly due to cyclic photophsphorylation. Nitrate starvation for several hours causes a considerable decrease in O2-evolution and also in the sensitivity to those high concentrations of DCMU (Fig. 5), but it leads to a sensitivity to antimycin A not observed under normal conditions (Table 3). The effects of nitrate starvation thus become comparable to those of far-red light, under which noncyclic electron transport is slow or completely prevented.The inhibition by DCMU of electron transport in photosystem II is also estimated by measuring the increase in fluorescence at 684 nm in air containing additional CO2. This fluorescence is saturated only at 10-5M DCMU and shows that a certain percentage of photosystem II remains uninhibited at 5×10-7M (Fig. 6), a concentration found to be almost ineffective in inhibiting O2-evolution and 32P-labelling in an N2-atmosphere.The results indicate that in synchronised cells of Ankistrodesmus noncyclic electron flow and noncyclic photophosphorylation can proceed in an atmosphere of pure nitrogen if nitrate is available as the electron acceptor. In this case noncyclic photophosphorylation, inspite of its low rates, still dominates over cyclic photphosphorylation. At low pH, when nitrate reduction is slow, cyclic photophosphorylation accounts for a greater part of the total phosphorylation than at high pH. Thus in the absence of CO2 and O2 cyclic photophosphorylation can be regarded as the main process of ATP formation only after nitrate starvation, in far-red light or in the presence of high concentrations of DCMU.Inhibition by DCMU, though very efficient under conditions of high photosynthetic activity, becomes rate-limiting only if the electron transport is so far reduced by DCMU that the remaining rate is of the same order as the low rate of the control or less. Therefore high concentrations of DCMU are required for the inhibition of low rates of noncyclic photophosphorylation. 相似文献
2.
Die nitrat- und nitritabhängige photosynthetische O2-Entwicklung in N2 bei Ankistrodesmus braunii 总被引:1,自引:1,他引:0
Wolfram R. Ullrich 《Planta》1974,116(2):143-152
3.
Summary Carbon dioxide and oxygen gas exchange of illuminated Amaranthus and Phaseolus leaves was measured from 0–600 ppm of CO2 in an open system.At low oxygen concentration (2% O2) the ratio of CO2 uptake to O2 evolution came close to 1.At high oxygen partial pressure (42% O2) the O2 compensation point of an Amaranthus leaf was increased and oxygen evolution was depressed. Accordingly the CO2/O2 quotients were variable; the lowest value of 1,9 differed significantly from 1,0.The oxygen and carbon dioxide compensation points of a Phaseolus leaf were increased at high oxygen concentration (42% O2) and oxygen evolution as well as carbon dioxide uptake were reduced. Therefore the ratios CO2 over O2 varied and differed greatly from 1,0.It was concluded that the nature of photosynthates is regulated by the gas composition around the leaves. 相似文献
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5.
《Inorganica chimica acta》1986,117(1):45-48
The resonance Raman spectra of K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O2), with C2ν symmetry. The ν(OO), νs(TiO) and νas(TiO) are observed around 890, 610 and 535 cm−1, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O22− → Ti(IV) charge-transfer transition. The calculated force constant values for the O22− and TiO bonds are 320 and 275 N m−1, respectively. 相似文献
6.
Guduru Moulika Sannapureddy Sailaja Jillela Santhosh Vijitha Putluru Bayapu Reddy Kondala Shanthi Latha Gasthi Venkata Chalapathi Busireddy Sudhakar Reddy 《Luminescence》2022,37(7):1073-1077
Calcium boro fluoro zinc phosphate glasses modified using alkali oxide and doped with Nd3+ and Er3+ ions with the chemical composition of 69.5 (B2O3) + 10 (P2O5) + 10 (CaF2) + 5 (ZnO) + 5 (Na2O/Li2O/K2O) + 0.5 (Er2O3/Nd2O3) were prepared using a conventional melt quenching technique. The results of X-ray diffraction patterns indicated the amorphous nature of all the prepared glasses. The visible–near-infrared red (NIR) absorption spectra of these glasses were analyzed systematically. The NIR emission spectra of Er3+ and Nd3+:calcium boro fluoro zinc phosphate glasses showed prominent emission bands at 1536 nm (4I13/2→4I15/2) and 1069 nm (4F3/2→4I11/2) respectively with λexci = 514.5 nm (Ar+ laser) as the excitation source. 相似文献
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Fe2 -H2O2体系能够有效地降解壳聚糖,反应介质的pH值、反应时间、反应温度、Fe2 浓度及H2O2浓度等实验因素对壳聚糖的降解效果都有程度不同的影响,其中以反应介质的pH值和H2O2浓度对降解反应的影响为最大.在pH值为3~5时Fe2 -H2O2体系降解壳聚糖的活性最高.适当增大H2O2的用量可以增大壳聚糖的降解程度,但当其用量增大至一定程度后,壳聚糖降解产物分子量的下降趋势明显变缓.合理的Fe2 -H2O2体系降解壳聚糖的实验条件为:介质pH值3~5;温度,室温;时间60~90 min;壳聚糖:H2O2:Fe2 =240:12~24:1~2(摩尔比). 相似文献
9.
The synthesis of several 2-azido-2-deoxy-D-gluco- and -D-galactopyranosyl halides is described. With tetraethylammonium chloride, α-pyranosyl bromides react to give β-pyranosyl chlorides. This provides a facile method for obtaining selectively blocked halides for the synthesis of α-linked, amino sugar of oligosaccharides. The inversion reaction at the anomeric centre is shown to be of second order, corresponding to an SN2 mechanism. The rates of the inversion reactions were correlated to the 13C-n.m.r. data of C-1 of α-bromides. Within the gluco series, the 13C-n.m.r. shift of C-1 proves to be proportional to the natural logarithm of the rate constant. An analogous correlation in the galacto series could not be observed. 相似文献
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1血液中队和CO2的运输形式1.1O2的运输形式血液中O2有2种运输形式:(1)物理溶解的形式。(2)化学结合的形式,即O2在红细胞中和Hb(血红蛋白)结合成HbO2(表示氧合血红蛋白)。1.2CO2的运输形式血液中CO2的运输有3种形式:物理溶解的形式;(2)HCO的形式,这种形式大部分在血浆中;(3)氨基甲酸血红蛋白的形式,即CO。在红细胞中与Hb结合成HbNHCOOH(表示氨基甲酸血红蛋白)。后2种统称为化学结合形式。血液中以各种形式存在的O。和CO。的量大致如下表1所示:由表1可见,安静时,血液中98%以上的OZ和94%以上的COZ是… 相似文献
12.
植物中的H2O2信号及其功能 总被引:3,自引:0,他引:3
H2O2是植物细胞的信号分子,是细胞正常代谢的产物,生物和非生物胁迫促使植物细胞产生H2O2,通过H2O2信号应答胁迫.H2O2信号调控一系列重要的植物生理生化过程,如系统获得抗性(SAR)和高度敏感抗性(HR)、细胞衰老与程序化细胞死亡(PCD)、气孔关闭、根的向地性、根的生长和不定根形成、细胞壁的发育、柱头与花粉的发育及相互关系等.Ca2+流动和可逆蛋白磷酸化作用是H2O2下游信号,通过MAPK级联作用于转录因子,最终调控基因的表达.H2O2调控多种基因的表达,包括编码抗氧化酶基因、调控程序化细胞死亡相关蛋白基因、生物与非生物胁迫应答蛋白基因等. 相似文献
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植物体内重要的信号分子--H2O2 总被引:3,自引:3,他引:0
越来越多的证据表明,植物体内的H2O2作为信号分子发挥作用.在病原、诱发因子和激素应答中是调节细胞程序性死亡的关键因子.H2O2在环境胁迫防御反应中的信号作用也得到证实.已知H2O2直接调节无数基因的表达,其中有些基因与植物防御和超敏反应有关.H2O2还与其它信号系统特别是激素信号相互作用,是激素介导的信号传导通路上的上游或下游组分;更重要的是H2O2还影响和修饰其它第二信使如钙信号的作用,在H2O2信号和钙信号之间发生众多的交互作用且这两种信号分子都调节植物对多种胁迫的交互耐性.此外,现已广泛地认识到与H2O2相关的氧还状态调节是调整细胞活动的关键因子.本文主要概括和讨论了H2O2在不同生物过程中的信号作用. 相似文献
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H2O2诱导Neuro—2a细胞死亡机理的研究 总被引:1,自引:0,他引:1
Reactive oxygen species (ROS), such as H2O2, can be produced by enzymes involved in electron leakage of respiration chain in mitochondria, and by neurochemical enzymes such as monoamine oxidase in neural cells. ROS are toxic to cells, and can result in cell death. ROS also play an important role in some diseases, especially in neurodegenerative diseases by yet unknown mechanisms. In the current research, the N-2a neuroblastoma cell was treated with H2O2, and the morphological changes of cell death were characterized. Our results show that N-2a cell death is different from classical apoptosis, but belongs type II nerve cell programmed death, which shows condensed chromatin within intact nuclear envelope and no apoptotic body. The chromatin DNA of dead cells shows no internucleosomal cleavage, as well as no requirement for caspase-3, 1 activity. However, the H2O2-induced N-2a cell death can be inhibited by Bcl-XL. It can be concluded that type II nerve cell death is the result of cell toxicity mediated by ROS. The results pave the way for further research of type II nerve cell death. 相似文献
17.
A modified mass spectrometer was used to determine whether the higher oxidation states of the photosynthetic O2-evolving system contain substrate water that is not freely exchangeable with the external medium. Our data indicated that the higher oxidation states contain no appreciable bound, non-exchangeable H2O. This suggests that H2O oxidation takes place via a rapid, concerted, all-or-none mechanism rather than by a mechanism involving stable, partially oxidized, H2O-derived intermediates. These findings set definite constraints on possible mechanisms of O2 evolution. 相似文献
18.
Equipment was devised which permitted the addition of specific gaseous ions to the atmosphere of plastic chambers in which seedlings of HORDEUM VULGARIS were grown in sand culture supplied with chemically defined nutrient solutions. Moderate densities of O2
– or O2
+ ions (1.8×104/cm3)in air containing an added 8% of O2 accelerated the growth rate. A like number of CO2
– or CO2
+ ions in air containing 8% of CO2 inhibited growth, impeded the production of chlorophyll and devitalized the young seedlings. Evidence is presented that O2
– and O2
+ stimulate the production of cytochromes and other Fe-containing enzymes through their action on the plant regulatory system responsible for the control of Fe metabolism. The toxic effect of CO2
– and CO2
+ cannot be explained as yet.
Zusammenfassung Eine Apparatur wurde entwickelt, die die Zufuhr von ionisiertem Gas der AtmosphÄre in Kammern gestattet. Darin wurden Keimlinge von HORDEUM VULGARIS in Sand mit chemisch definierten NÄhrlösungen gezüchtet. Konzentrationen von 1,8×104/cm3 O2 – und O2 + in Luft mit zusÄtzlich 8% O2 beschleunigten die Wachstumsrate. Die gleiche Menge CO2 – und CO2 + in Luft mit zusÄtzlich 8% CO2 hemmte die Wachstumsrate, die Bildung von Chlorophyll und entkrÄftigte die Keimlinge. Es wird gezeigt,dass O2 – und O2 + die Bildung von Cytochrom und anderen eisenhaltigen Enzymen anregen durcn ihre Wirkung auf das den Fe-Stoffwechsel regulierende System der Pflanze. Die toxische Wirkung von CO2 – und CO2 + lÄsst sich noch nicht erklÄren.
Resume On a construit un appareil permettant d'introduire dans 1'atmosphères des ions de gaz déterminés. On a alors effectué de telles adjonctions à l'air contenu dans des cellules de plastique dans lesquelles on cultivait HORDEUM VULGARIS sur du sable et dans une solution nutritive chimiquement définie. Des densités modérées d'ions O2 – ou O2 + (1,8×104/cm3) dans de l'air additionné de 8% d'O2 accélèrent la croissance. La meme concentration de CO2 – et CO2 + additionnée de 8% de CO2 a ralenti la croissance et la formation de chlorophylle et a diminué la vitalite des plantes nouvellement germées. On démontre que O2 – et O2 + active la formation de cytochrome et d'autres enzymes ferreuses par suite de l'action de ces ions sur le système régularisant le métabolisme du fer dans la plante. L'effet toxique du CO2 – et CO2 + reste encore inexpliqué.相似文献
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外源H2O2对小麦幼苗耐盐性的调节作用 总被引:2,自引:0,他引:2
以高原448小麦品种为材料,分别测定了4个处理(Hoagland营养液、Hoagland营养液 150 mmol/LNaCl、Hoagland营养液 150 mmol/L NaCl 10μmol/L H2O2和Hoagland营养液 10μmol/L H2O2)的小麦幼苗在第2、4、6、8天叶片叶绿素、丙二醛、可溶性糖和还原性谷胱甘肽含量.结果显示:外源H2O2提高了NaCl胁迫下4个时段小麦幼苗的叶绿素含量(8.27%、32.57%、10.19%、4.86%)及还原性谷胱甘肽含量(3.09%、23.97%、5.85%、2.11%),显著提高了可溶性糖含量(14.58%、8.43%、16.68%、5.8%,P<0.05),而显著降低了其丙二醛含量(17.53%、14.04%、4.75%、8.47%,P<0.05).外源H2O2(10μmol/L)使NaCl胁迫下叶绿素含量和还原性谷胱甘肽含量峰值提前,同时推迟了丙二醛峰值出现的时间.研究表明,外源H2O2通过提高叶片叶绿素、可溶性糖和还原性谷胱甘肽含量以有效地增强小麦幼苗的耐盐性. 相似文献
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在常温下用不同浓度的外源H2O2(0~20 mmol·L-1)预处理水稻幼苗,再进行12 h 6℃低温胁迫,根据幼苗相对含水量和质膜相对透性筛选最佳外源H2O2处理浓度,并分析最佳外源H2O2浓度下幼苗的渗透调节物质和活性氧相关指标的变化.结果表明:(1)0~8 mmol·L-1 H2O2预处理可以增加水稻幼苗的相对含水量,降低其质膜相对透性,并以4 mmol·L-1 H2O2的效果最佳.(2)低温胁迫后,与对照组相比,4 mmol·L-1外源H2O2预处理降低了水稻幼苗萎蔫程度,并使其总呼吸速率、交替途径容量都有增加,同时还抑制了丙二醛的含量,增加了可溶性糖、可溶性蛋白质和脯氨酸的含量.(3)外源H2O2预处理对水稻幼苗的内源H2O2含量以及O(-)/(·)2产生速率没有显著影响.研究发现,外源H2O2可以通过提高呼吸速率、降低脂质过氧化程度、增加碳氮代谢来有效增强水稻幼苗的抗寒性,它可能以一种独立于内源活性氧系统之外的方式发挥作用. 相似文献