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1.
Osman, M. E-A. H. and El-Shentenawy, F. 1988. Photosyntheticelectron transport under phosphorylating conditions as influencedby different concentrations of various salts.J. exp.Bot. 39: 859863. The rate of light-induced electron transport by isolated spinachthylakoids under phosphorylating conditions, as affected bydifferent concentrations of Br, Cl, NO3,HCO3, SO42 and CO32 has been investigated.The results show that both low and high concentrations of HCO32stimulated the oxygen evolution capacity under phosphorylatingconditions, whereas only low concentrations of CO32,SO42 and Cl stimulated the oxygen evolution capacity.However, irrespective of concentration, both Br and NO3reduced this capacity. The rate of photosynthetic electron transportwas generally stimulated by addition of ADP, even in cases whereelectron transport was inhibited by addition of bromide andnitrate. The different concentrations of these anions also causedreduction of the power generated by proton pumping and usedfor phosphorylation. The greatest level of reduction was observedin the presence of high concentrations of Cl and HCO3. Key words: Spinach thylakoids, photosynthetic electron transport, phosphorylation 相似文献
2.
Fujiki Tetsuichi; Suzue Takahiko; Kimoto Hideshi; Saino Toshiro 《Journal of plankton research》2007,29(2):199-208
A comparison of photosynthesis-irradiance response curves (PEresponse curves) obtained through fast repetition rate (FRR)fluorometry and radiocarbon (14C) tracer method was made inthe chlorophyte, Dunaliella tertiolecta, grown under differentirradiance conditions. In FRR-based PE response curveexperiments, actinic light provided by white light-emittingdiodes (LEDs) was increased gradually from 0 to 1500 µmolquanta m2 s1 and the rate of photosyntheticelectron transport was determined at each light level. Short-termexperiments (20 min) of 14C-based PE response curvewere carried out with an improved photosynthetron, which containswhite LEDs as the light source. Irrespective of growth irradiance,the ratios of FRR to 14C-based initial slopes were almost uniform.The ratios of FRR- to 14C-based maximum rates were 2536%higher than those of FRR- to 14C-based initial slopes. The relationshipbetween electron transport and carbon assimilation was non-linearwith increasing discrepancy towards high actinic light. Thisnon-linear relationship between FRR- and 14C-based estimatesis primarily due to the effect of physiological processes stimulatedat high levels of light, such as cyclic electron flow and theMehler reaction. The results of this study indicate that theFRR fluorometry can be used as a good indicator of photosyntheticrates from low to middle light levels, but becomes increasinglyquestionable as the maximum photosynthetic rate is approached.The degree to which this relationship is further affected bynutrient-status warrants investigation. 相似文献
3.
We grew water hyacinth [Eichhornia crassipes (Mart.) Solms]for 60 days in a greenhouse under natural light and in a controlledenvironment room at 31/25?C day/night temperatures and 90, 320and 750/µEm2sec1. We then determined maximumphotosynthetic rates in 21% and 1% oxygen, stomatal diffusionresistances, contents of chlorophyll and soluble protein, andthe size and density of the photosynthetic units (PSU) in representativeleaves from the four treatments. In air containing 21% oxygen,maximum photosynthetic rates were 14, 27 and 29 mg CO2 dm2hr1for plants grown in artificial light at 90, 320 and 750µEm2sec1,respectively. Plants grown in natural light (maximum of 2000µEm2sec1) had maximum photosynthetic ratesof 34 mg CO2 dm2hr1. In all treatments, photosyntheticrates in 1% oxygen were about 50% greater than rates in normalair, indicating the presence of photorespiration in water hyacinth.There was no apparent relationship between maximum photosyntheticrate per unit leaf area and stomatal conductance, chlorophyllcontent per unit area, or PSU density per unit area. However,the higher maximum photosynthetic rates were associated withgreater mesophyll conductances, specific leaf weights and proteincontents per unit area. When plants grown at 90µEm2sec1for 120 days were transferred to 750µEm2sec1for 5 days, only young leaves that were just beginning to expandat the time of transfer exhibited adaptation to the higher irradiance.The 40% increase in light-saturated photosynthetic rate in theseyoung leaves was associated with increases in mesophyll conductance,soluble protein content per unit area, and specific leaf weight.
1 Mississippi Agricultural and Forestry Experiment Station cooperating. (Received July 19, 1978; ) 相似文献
4.
The Relationship Between the Rates of Carbon Transport and of Photosynthesis in Tomato Leaves 总被引:6,自引:1,他引:5
The rate of carbon transport based on the carbon balance overa 6-h period from a mature tomato leaf was measured overa rangeof net photosynthetic rates from 0.1 to 4.9 mg C dm2h1 under light flux densities from 4 to 140 W m2.A proportional relationship was demonstrated between the rateof carbon transport and carbon fixation when the carbon fixationrate was higher than 2 mg C dm2 h1.Below a carbonfixation rate of 1 mg C dm2 h1, the rate of carbonexport was maintained at 1 mg C dm2 h1 at theexpense of the breakdown of starch. A highly significant correlationwas observed between sucrose concentration and the rate of carbontransport. The sucrose concentration in the leaf appears tobe the factor controlling carbon export. 相似文献
5.
Effects of Leaf Chilling on Thylakoid Functions, Measured at Room Temperature, in Cucumis sativus L. and Oryza sativa L. 总被引:5,自引:0,他引:5
Photosynthetic functions in leaves of cucumber (Cucumis sativusL.) and rice (Oryza sativa L.) were examined before and aftervarious chilling treatments. Cucumber leaves lost the capacityfor the photosynthetic oxygen evolution after chilling at 0°Cin the dark for 48 h. Thyla-koids isolated from such leaveswere not able to reduce dichloroindophenol (DCIP), but the additionof diphenylcarbazide (DPC), an electron donor to PS II, restoredthe ability to reduce DCIP, indicating that the site of damageis in the water-splitting machinery of PS II. In moderate light (500 jumol quanta m2s1), chillingof cucumber leaves at 5°C for 5 h was sufficient to inducethe complete loss of the capacity for photosynthetic oxygenevolution. Electron transport rates measured in thylakoids wereunaltered, but thylakoids were totally permeable to protons.Since the addition of dicyclohexylcarbodiimide (DCCD) restoredcoupling and the capacity for proton uptake, the primary siteof damage was deduced to be in the ATPase. In rice, both chilling treatments had barely any effect on thylakoidfunctions, although some negative effects was apparent in photosynthesisin leaves.
1Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113 Japan.
2Present address: Department of Botany, Duke University, Durham,NC 27706, U.S.A. (Received January 11, 1989; Accepted June 12, 1989) 相似文献
6.
Respiratory rates in the cladoceran Ceriodaphnia dubia in Lake Rotongaio, a monomictic lake 总被引:2,自引:0,他引:2
The experimentally measured oxygen consumption rate by the cladoceran,Ceriodaphnia dubia, showed a linear increase between 5 and 20°C.Oxygen consumption rates of C. dubia were estimated in situfrom respiratory electron transport system (ETS) activity inLake Rotongaio during summer stratification and winter mixing.Oxygen consumption was 0.002 µl O2 animal1 h1in the hypolimnion and 0.076 µl O2 animal1 h1in the epilimnion during stratification. Implications of respiredoxygen for metabolic carbon requirements are discussed. 相似文献
7.
Ichimura Toshiaki; Miyairi Sachio; Satoh Kazuhiko; Katoh Sakae 《Plant & cell physiology》1992,33(3):299-305
Very active and heat-stable oxygen-evolving photosystem II particleswere isolated from the thermophilic cyanobacterium Synechococcuselongatus by treatment of thylakoid membranes with a non-ionicdetergent, sucrose monolaurate (SML). The particles were analyzedin a comparison with photosystem II particles prepared withß-octylglucoside (OG). The two preparations had similarpolypeptide compositions, which were caracterized by high levelsof polypeptides from phycobilisomes. The ratio of chlorophylla to QA was 45 and there were four Mn atoms and one tightlybound Ca2+ ion per QA in the particles prepared with SML. Thepreparations were thermophilic, showing substantial rates ofoxygen evolution at temperatures up to 60°C. The maximumrates attained at 45°C were as high as 6.0 mmoles O2 mg1Chl h1. PS II particles prepared with OG were similarlythermostable but were less active in oxygen evolution at alltemperatures examined. Kinetic analysis of flash-induced absorptiontransients revealed that about 22% and 28% of photosystem IIreaction centers were not associated with the functional QBsite in the SML- and OG-particles, respectively. When correctedfor the inactive reaction centers, the maximum rates of oxygenevolution by SML- and OG-particles were 7.7 and 7.0 mmoles O2mg1 Chl h1, which correspond to half times of1.9 and 2.1 ms for the first-order electron transfer, respectively.Comparison of these half times with those of the S-state transitionand the release of oxygen indicates that the overall photosystemII electron transport is limited by the reduction of added electronacceptors and not by release of oxygen.
3On leave from National Chemical Laboratory for Industry, Higashi1-1, Tsukuba, Ibaraki 305 相似文献
8.
Photosynthetic characteristics of detached green barley leavesafter 72 h of treatment with 0·2 mol m3 of thepyridazinone herbicides SAN 6706, SAN 9785 and SAN 9789 werestudied. For comparison, the effects of 0·01 mol m3diuron were also investigated. Pyridazinone herbicides causedonly a slight reduction of the total carotene content of thebarley leaves. The total chlorophyll content, as well as thelinolenic to linoleic acid ratio of chloroplast glycerolipids,however, remained unchanged. Diuron treatment caused total inhibitionof electron transport, as revealed by fast fluorescence inductionof leaves and the Hill reaction activity of chloroplasts. The14CO2-nxation by the leaves and the light-induced fluorescencequenching were also completely inhibited in vivo by diuron.Pyridazinone herbicides left 2040% of the 14CO2-fixationfound in the control, in spite of the fact that their fast fluorescenceinduction tracings showed inhibition in the electron transport.Chloroplasts isolated from the leaves treated with pyridazinoneswere found to be highly active in mediating the ferricyanide-dependentHill reaction. In order to test the ability of pyridazinonesto inhibit photosynthetic electron transport in vivo, theirprompt effect on fluorescence was also investigated.It is concluded that pyridazinone herbicides can readily andrapidly enter the chloroplasts and inhibit the photosyntheticelectron transport in vivo. The differences between the long-termeffects of pyridazinones and those of diuron suggest differencesin the inhibitory effectiveness on the various photosyntheticparameters between the two herbicide groups. It is suggestedthat pyridazinones can leave the chloroplasts during isolationowing to the loose binding onto the thylakoid membranes. Key words: Pyridazinone herbicides, electron transport, fluorescence induction 相似文献
9.
Takahashi Mikio; Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko 《Journal of plankton research》1995,17(5):1017-1025
Measurement of the photosynthetic production rate in Lake Biwawas camed out from May 1985 to September 1987. In the light-saturatedlayer, the seasonal variation in the photosynthesis rate perchlorophyll a was regulated by water temperature. The depth-integratedphotosynthetic production rate was 0.21-1.48 g C m2 day1and the maximum value was observed in midsummer when the watertemperature of the mixed surface layer was highesL The criticalnutrient for photosynthesis may be dissolved reactive phosphorus,which was generally <1 µg P 11 throughout theobservation period. In the trophogenic layer, respiratory organiccarbon consumption, estimated from measurement of respiratoiyelectron transport system activity, was 0.35-1.07 (mean 0.66)g C m1 day1 and corresponded, on average, to 79%of the photosynthetic carbon production rate. This implies thatthe major part of photosynthetic fixed organic matter mightbe recycled in the trophogenic layer. The estimated settlingorganic carbon flux at 20 m depth, from calculation of theseparameters and changes in the particulate organic carbon concentration,was 0.01 (-0.09 to 0.13) g C m1 day1 The meansettling organic carbon flux measured by sediment trap at 20m was 0.19 (0.09-0.31) g C m1 day1 higher thanthe estimated value. It seemed that organic matter collectedby sediment trap may contain allochthonous matter and resuspendedepilimnetic sediment matter. 相似文献
10.
SIECIECHOWICZ KONRAD A.; JOY KENNETH W.; IRELAND ROBERT J. 《Journal of experimental botany》1988,39(6):695-706
During the growth of leaves of Pisum sativum L., levels of asparaginase(E.C. 3.5.1.1
[EC]
) showed a diurnal variation during a 3 d periodof leaf expansion, increasing in the light and decreasing inthe dark period; the greatest diurnal variation being foundin half-expanded leaves. Asparaginase activity in half-expandedleaves reached a maximum after 4 h exposure to light and thisactivity was maintained over the rest of the light period. Changesin asparaginase activity were not influenced by diurnal temperaturechanges. The increase in asparaginase activity during the lightperiod was directly proportional to the photon flux densityover the range 0285 µmol m-2 s-1 PAR. The increaseof asparaginase activity during illumination of detached leaveswas inhibited by the photosynthetic electron transport inhibitors3-(3', 4'-dichlorophenyl)-1, 1-dimethylurea (DCMU) and atrazine.These observations indicate that the increase in asparaginaseactivity in half-expanded leaves is dependent upon non-cyclicelectron transport. Key words: Pisum sativum, asparaginase, photosynthetic electron transport 相似文献
11.
Photosynthetic assimilation of exogenous 14CO2 and H14CO3by the aquatic angiosperm Potamogeton lucens L. is reported.Equivalent maximum rates of assimilation (1.5 µmol s1m2) were obtained in the presence of saturating levelsof 14CO2 (1.0 mol m3, pH 5.3) or H14CO3 (1.5 molm3, pH, 9.2). Under subsaturating 14CO2 levels, bothgaseous diffusion and H14CO3 transport were shown tooperate simultaneously, such that maximal photosynthetic rateswere established. An induction lag of approximately 3 min was observed when exogenous14CO2 was assimilated. A longer lag of approximately 12 minwas required, however, before linear assimilation rates wereestablished when H14CO3 acted as the carbon source. The light-activatedH14CO3 transport system was found to be quite labile.A brief (5 min) dark treatment returned the system to the inactivestate. Bicarbonate transport was shown to be competitively inhibitedby CO32ions. The possibility is discussed that this formof inhibition may be common to many HCO3 assimilators. Preliminary polar cation transport studies (from lower to upperleaf surface) indicated an almost exact one to one relationshipbetween the rates of Na+ influx and efflux and H14CO3assimilation. The possible relationship(s) between these transportprocesses and the requirement for electrical neutrality is brieflydiscussed. 相似文献
12.
Mistletoes usually have slower rates of photosynthesis thantheir hosts. This study examines CO2assimilation, chlorophyllfluorescence and the chlorophyll content of temperate hostparasitepairs (nine hosts parasitized by Ileostylus micranthus and Carpodetusserratus parasitized by Tupeia antarctica). The hosts of I.micranthus had higher mean annual CO2assimilation (3.59 ±0.41 µmol m-2 s-1) than I. micranthus(2.42 ± 0.20µmol m-2 s-1), and C. serratus(2.41 ± 0.43 µmolm-2 s-1) showed higher CO2assimilation than T. antarctica(0.67± 0.64 µmol m-2 s-1). Hosts saturated at significantlyhigher electron transport rates (ETR) and light levels thanmistletoes. The positive relationship between CO2assimilationand electron transport suggests that the lower CO2assimilationrates in mistletoes are a consequence of lower electron transportrates. When photosynthetic rates, ETR and chlorophyll a /b ratioswere adjusted for photosynthetically active radiation, hostsdid not have significantly higher CO2assimilation (3.21 ±0.37 µmol m-2 s-1) than mistletoes (2.54 ± 0.41µmol m-2 s-1), but still had significantly higher ETRand chlorophyll a / b ratios. The electron transport rates,saturating light and chlorophyll a / b ratios of sun leavesfrom mistletoes were similar to host shade leaves. These responsesindicate that in comparison with their hosts, mistletoe leaveshave the photosynthetic characteristics of the leaves of shadeplants. Copyright 2000 Annals of Botany Company CO2assimilation, photosynthetic active radiation (PAR), chlorophyll fluorescence, electron transport rate (ETR), photochemical quenching (qp), non-photochemical quenching (qn), sun and shade leaves, chlorophyll content, Ileostylus micranthus, Tupeia antarctica, New Zealand 相似文献
13.
Effects of 3-(3, 4-dichlorophenyl)-l, 1-dimethylurea (DCMU)on photosynthetic oxygen evolution, respiratory oxygen uptake,phototactic response and swimming rate in Cryptomonas sp. weredetermined and compared. Photosynthetic oxygen evolution wascompletely inhibited in the presence of 105 M DCMU. Thetreatment did not significantly affect the rates of respiratoryoxygen uptake, phototaxis, and swimming, indicating that directparticipation of photosynthesis in the phototaxis of this algacan be ruled out. Wavelength dependency of photosynthetic oxygen evolution wasalso determined in the range of 560 to 700 nm. The rate of photosyntheticoxygen evolution at 680 nm was as high as that at 560 nm, butno phototactic activity was seen at 680 nm although it was maximumat 560 nm. This is consistent with the above conclusion. (Received February 16, 1976; ) 相似文献
14.
Photosynthesis by Guard Cell Chloroplasts of Vicia faba L.: Effects of Factors Associated with Stomatal Movement 总被引:1,自引:0,他引:1
The properties of photosynthetic O2 evolution by mesophyll cellchloroplasts (MCC) and guard cell chloroplasts (GCC) isolatedfrom protoplasts of Vicia faba L. have been studied and effectson O2 evolution of factors known to regulate stomatal movementshave been compared. The O2 evolution of GCC was CO2-dependent.The saturating light intensity for O2 evolution was between150 and 200 µmol m2s1 for MCC and was between400 and 1,000µmol m2s1 for GCC. Light quality(red vs. blue) had no significant effect on O2 evolution byeither MCC or GCC. The O2 evolution rate of MCC was stronglydependent on external K+ concentration, but GCC did not respondsignificantly to variations in external K+ concentration between0 and 250 mM. The optimal external pH for O2 evolution by MCCwas approximately 7.5, and either higher or lower external pHsignificantly inhibited O2 evolution. However, O2 evolutionby GCC was only slightly enhanced when external pH was increasedfrom 6.0 to 8.0. Our observation of differential sensitivityof MCC and GCC to light intensity and to variations of cytoplasmicK+ and pH may indicate differential regulation of photosynthesisin MCC and GCC.
1Current address: Biology Department, Pennsylvania State University,208 Mueller Laboratory, University Park, PA 16802, U.S.A. 相似文献
15.
The Effect of Current Photosynthesis on the Origin of Translocates in Old Tomato Leaves 总被引:3,自引:0,他引:3
The rate of carbon transport from an old tomato leaf (54 days),grown at 80 W m2, was measured under light flux densitiesbetween 7 and 90 W m2. Under low light, the rate of carbontransport over a 6 h period was about 1 mg C dm2 h1,well in excess of the concurrent photosynthetic rate. The lossfrom these leaves of 14C-leaf assimilate which was fixed beforethe experimental period amounted to 62 per cent of the totalinitial uptake and was higher than that from leaves with higherconcurrent photosynthetic rates. The higher loss of 14C fromleaves with low photosynthetic rates was due to a greater contributionof 14C from the starch and residue fractions. The rate of transportappeared to be determined by the concentration of the labilesucrose, not the total sucrose concentration. In comparisonwith young fully-expanded tomato leaves (Ho, 1976) the sizeof the labile sucrose pool appeared to decrease with age. Thephotosynthesistranslocation coefficient was low (k1k2=021)for an old tomato leaf. Based on these results a scheme of carbonpartitioning in relation to translocation is proposed. Criteriafor assessing the efficiency of translocation in leaves arediscussed. 相似文献
16.
Effect of Sink-Source Manipulations on the Photosynthetic Rate and Carbohydrate Content of Cucumber Cotyledons 总被引:1,自引:0,他引:1
MAYORAL MARIA LUISA; PLAUT ZVI; REINHOLD LEONORA 《Journal of experimental botany》1985,36(10):1551-1558
Mayoral, M. L., Plaut, Z. and Reinhold, L. 1985. Effect of sink-sourcemanipulations on the photosynthetic rate and carbohydrate contentof cucumber cotyledons.-J. exp. Bot. 36 15511558. The photosynthetic rate of cucumber cotyledons (Cucumis sativuscv. Dahla) reached a maximum value of 12 mg dm2 h1,10 d after emergence. In 12-d-old seedlings removal of one cotyledondoubled the CO2 fixation rate of the other, as observed 3 dafter treatment. When the primary leaf was removed, the photosyntheticrate of the cotyledons was decreased by 33%. At this stage ofgrowth elimination of the roots as a sink for assimilates bygirdling the hypocotyl affected neither the photosynthetic ratenor the carbohydrate content of the cotyledons. By contrast,in 18-d-old seedlings removal of the first leaf brought abouta 42% increase in the photosynthetic rate of the cotyledons.The simultaneous removal of the first leaf and one cotyledondoubled the rate of CO2 fixation of the remaining cotyledon.Girdling the hypocotyl lowered the photosynthetic rate of thecotyledons by 73%. In both 12- and 18-d-old seedlings a decreaseor increase in the sink-source ratio was correlated with anincrease or a decrease respectively in the carbohydrate contentof the cotyledons. The stomatal resistance of the cotyledonswas not affected by any of the treatments. The effect of sink-sourcemanipulations on photosynthesis and on the level of carbohydratespresent in the cotyledons was more evident in those seedlingsgrowing under high light intensity (580 µE m2 s1),than in those exposed to 300 µE m2 s1 Key words: Sink-source relationship, cotyledons, photosynthesis 相似文献
17.
Eastmond Peter; Kolc Lucie; Rawsthorne Stephen 《Journal of experimental botany》1996,47(11):1763-1769
The aim of this study was to assess the photosynthetic potentialof developing seeds of oilseed rape (Brassica napus L.) andto compare photosynthetic properties of embryo plastids withthose of leaf chloroplasts from the same species. Measurementsof CO2-dependent O2 evolution show that developing seeds ofB. napus are photosynthetically active in vitro. Essentially,all of the photosynthetic activity of the developing seed isaccounted for by the embryo. The rate of photosynthesis by developingembryos increased until the onset of desiccation, after whichit declined, so that by maturity embryos were no longer photosyntheticallyactive. Photosynthetic activity was positively correlated withchlorophyll content throughout development. Comparison of thephotosynthetic characteristics of leaf and embryo chloroplastsrevealed that rates of uncoupled electron transport were 2.5-foldgreater in those from the embryo. Light-saturated rates of CO2-dependentO2 evolution, per unit chlorophyll, and CO2 saturation pointswere similar for chloroplasts from both tissues. However, light-saturationpoints and chlorophyll a/b ratios were lower for embryo thanfor leaf choroplasts. Embryos and embryo chloroplasts also containedconsiderably less ribulose 1,5-bisphosphate carboxylase/oxygenaseprotein per unit total protein, than leaves. Although excisedembryos were capable of high rates of CO2-dependent O2 evolution(90100 mol mg1 chlorophyll h1) under asaturating photosynthetic photon flux density (PPFD), low transmittanceof light through the silique wall (30%), together with the highPPFD required to achieve light compensation points in developingseeds (500 mol m2 s1), suggests that photosynthesisin vivo is unlikely to make a net contribution to carbon economyunder normal environmental conditions. Key words: Embryo, development, photosynthesis, chloroplast, Brassica napus L. 相似文献
18.
The effects of cyanide on the electron flow in NO3 andNO2 reductions and photosynthetic electron transfer wereinvestigated with intact cells of a photodenitrifier, Rhodobactersphaeroides f. s. denitrificans. In the presence of 30 µMKCN, electron transfer for NO3 reduction was inhibitedby about 70% and the concomitant H translocation was completelyinhibited. However, neither NO2 reduction nor photosyntheticcyclic electron transfer was affected at 30 µM. Theseresults suggested that the electron transfer pathway to NO3has, in addition to a b-type cytochrome and the nitratereductase,a component sensitive to a low concenration of cyanide whichis not involvedin the cytochrome bc1 complex. (Received April 13, 1987; Accepted July 23, 1987) 相似文献
19.
Photoinhibition and light-induced cyclic electron transport in ndhB(-) and psaE(-) mutants of Synechocystis sp. PCC 6803 总被引:2,自引:0,他引:2
The ndhB and psaE mutants of the cyanobacteriumSynechocystis sp. PCC 6803 are partly deficient in PSI-drivencyclic electron transport. We compared photoinhibition in thesemutants to the wild type to test the hypothesis that PSI cyclicelectron transport protects against photoinhibition. Photoinhibitorytreatment greatly accelerated PSI cyclic electron transportin the wild type and also in both the mutants. The psaEmutant showed rates of PSI cyclic electron transport similarto the wild type under all conditions tested. The ndhBmutant showed much lower rates of PSI cyclic electron transportthan the wild type following brief dark adaptation but exceededwild type rates after exposure to photoinhibitory light. Thewild type and both mutants showed similar rates of photoinhibitiondamage and photoinhibition repair at PSII. Photoinhibition atPSI was much slower than at PSII and was also similar betweenthe wild type and both mutants, despite the known instabilityof PSI in the psaE mutant. We conclude that photoinhibitorylight induces sufficient PSI-driven cyclic electron transportin both the ndhB and psaE mutants to fulfill anyrole that cyclic electron transport plays in protection againstphotoinhibition.
4 Corresponding author: E-mail, sherbert@uwyo.edu; Fax, +1-307-766-2851;Phone, +1-307-766-4353. 相似文献
20.
Photosynthetic Characteristics of Spinach Leaves Grown with Different Nitrogen Treatments 总被引:15,自引:0,他引:15
Spinach plants (Spinacia oleracea L.) were grown hydroponicallywith different concentrations of nitrate nitrogen, ranging from0.5 to 12 mM, in a glasshouse under full sunlight. Using anopen gas exchange system, the rate of CO2 assimilation, A, wasdetermined as a function of intercellular partial pressure ofCO2, Pi, with a constant amount of absorbed light per unit Chl.When expressed on a leaf area basis, A measured at high irradianceand at pi=500 µbar, was proportional to the in vitro rateof uncoupled whole-chain electron transport as well as to Chlcontent. There was a curvilinear relationship between the mesophyllconductance (the slope of the A : Pi curve near the CO2 compensationpoint) and the in vitro RuBP carboxylase activity. The curvaturedid not appear to be due to enzyme inactivation in vivo in leaveswith high nitrogen contents. The curvature suggested the presenceof a CO2 transfer resistance between the intercellular spacesand the site of carboxylation of 2.2 m2 s bar mol1 CO2,which is similar to that previously observed in wheat. Thisimplied that, while nitrogen deficiency increased the ratioof in vitro activity of electron transport to that of RuBP carboxylase,the two activities remained balanced in vivo. Irradiance response curves were determined by both net CO2 andO2 exchange. The two methods gave reasonable agreement at lightsaturation. The quantum yield measured by O2 evolution was 0.090?0.003mol O2 mol1 absorbed quanta, whereas after correctingfor pi = 500µbar, the quantum yield for CO2 assimilationwas only 82% of that measured by oxygen evolution.
2Present address: Plant Environmental Biology Group, ResearchSchool of Biological Sciences, The Australian National University,G.P.O. Box 475, Canberra, A.C.T. 2601, Australia. (Received July 29, 1987; Accepted November 2, 1987) 相似文献