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1.
The herbicide D5 (N-n-pentyl-N-methyl-N'-(3, 4-dichlorophenyl)-ureacan uncouple oxidative phosphorylation in isolated plant mitochondria.This paper confirms that D5 is an uncoupler that catalyzes thecollapse of the transmembrane potential gradient by inducinga movement of protons across the membrane. However, D5 is notitself capable of transporting protons. D5 gives complete uncouplingat 40 µM, a lower concentration than that required foruncoupling by the n-butyl homologue neburon. Analysisof the shape of the state 4 stimulation curve suggests thatD5 might act as a dimer in the membrane. Attempts to demonstrate binding of D5 to a membrane target gaveambiguous results, binding is not evident at 10 °C and 25°C but might occur at 15 °C and 20 °C. The calculatedherbicide concentration in the membrane (40 µM of which40 µM is as the dimer) is high and similar to thatof the major phospholipids. The calculated partition coefficientbetween medium and membrane (3.8 x 103) is in agreement withthe lipophilicity of the substituted urea herbicides. In the presence of a substrate, D3 blocks both influx and effluxcalcium movement through the mitochondrial membrane but in theabsence of substrate, D5 induces binding of calcium. Bindingrequires Mg++ but not K+ or phosphate and leads to a releaseof H+. Ruthenium Red causes a partial inhibition of bindingbut no other reagent or ionophore tested had any effect. Sincebinding does not occur in turnip mitochondria which are unableto transport Ca++ it is concluded that the effect is not directlylinked to the uncoupling action. The mechanism of action of D5 is discussed and it is concludedthat D5 probably acts as a dimer and perturbs membrane structure.The site of action is probably the lipid components of the membrane. Key words: Plant mitochondria, Herbicide, Substituted ureas, Calcium, Uncoupling 相似文献
2.
The Permeability of the Guard Cell Plasma Membrane and Tonoplast 总被引:4,自引:0,他引:4
Uptake experiments and efflux compartmental analysis of planthormones, osmotica and toxins using isolated guardcells of Valerianella locusta and guard cell protoplasts (GCP)of Vicia faba were performed in order to study the permeabilityproperties of guard cell plasma membrane and tonoplast. Theplasma membrane of guard cells exhibits a higher permeabilitythan plasma membranes of mesophyll cells for most solutes investigated.The permeability coefficients (Ps calculated for the guard cellplasma membranes are also significantly higher than the Ps valuesfor the guard cell tonoplast. This applies also for protonatedABA. We suppose that the high permeability for ABAH could bepart of the target cell properties. A Collander analysis demonstratesa linear correlation between Ps, values and the ratio Kr/Mr1,5for both plasma membrane (r = 0.87) and for the tonoplast (r=0.93). Because of deviations from the observed correlations,the permeation of some solutes (ABA, GA, IAA through the tonoplast;methylamine through the plasma membrane) seems to be facilitatedby an additional transport mechanism. The Collander analysisof the plasma membrane of GCP shows very similar results tothe analysis of the plasma membrane of isolatedguard cells, indicating that isolation of protoplasts does notalter the permeability of the guard cell plasma membrane. Key words: Permeability coefficient, guard cells, plasma membrane, tonoplast 相似文献
3.
The effect of sucrose, H2BO3, KNO3, Ca(NO2)2.4H2O and MgSO4.7H2O on pollen germination of Phytolacca dodecandra L. (endod)in a liquid medium was investigated. Sucrose and H3BO3 werecritical to pollen germination. A concentration of 10% sucroseand 161.8 µm H2BO3 gave over 70% germination. The germinationof pollen was not enhanced by Ca(NO3)2.4H2O, KNO3 and MgSO4.7H2O.Endod pollen was dehydrated over CaCl2 and stored in gelatincapsules in cryogenic vials at 175 °C, 1±1°C and 24±2 °C. The pollen moisture content atcollection was approx. 7.8% (f. wt basis) and dehydration overCaCl2 reduced it to about 1.4%. Pollen stored at 1±1°C and 175 °C maintained viability for over 6months. Pollen stored at room temperature lost viability within4 weeks of storage. Pollination with cryopreserved pollen resultedin normal fruit set. Phytolacca dodecandra, endod, pollen germination, pollen storage 相似文献
4.
Internodal cells of Nitellopsis were made tonoplast-free byperfusion with a medium containing EGTA. Cytoplasmic concentrationsof solutes were controlled by a second perfusion with mediaof known composition. The electrogenic pump current (Ip), whichwas calculated from electrical data obtained from cells withand without ATP, was compared with the current carried by H+(IH+) across the plasma membrane. A close correlation betweenIp and IH+ was found under various internal and external conditions.(1) Ip and IH+ depended on the internal ATP and showed Michaelis-Mententype saturation curves. For Ip, Km was 120 µM and themaximum current Vmax was 15.1 mA m2, while for IH+, Kmwas 160 µM and Vmax was 16.6 mA m2. (2) Ip andIH+ showed almost the same IH2+ dependence. The Mg2+-dependentIp was 19.5 mA m2, while the Mg2+-dependent IH2+ was17.7 mA m2. (3) IH2+ was maximal at an external pH of8 and decreased both in acidic and alkaline pH ranges. Ip wasnearly equal to IH+ in the pH range between 8 and 5. (4) IH+became maximal at an internal pH of 7.3, which is nearly thesame as the pH for maximal electrogenecity found by Mimura andTazawa (1984). All these facts support the idea proposed in our previous paper(Takeshige et al. 1985) that the electrogenic ion pump locatedin the plasma membrane of Nitellopsis is the H+ pump.
1 Dedicated to Professor Dr. Erwin Bünning on the occasionof his 80th birthday. (Received June 21, 1985; Accepted December 20, 1985) 相似文献
5.
Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd- (FG, Cucurbita ficifolia Bouché)seedlings in order to determine the effect of solution temperature(12, 22, and 32°C) on the mineral composition of xylem sapand the plasma membrane K+-Mg++-ATPase activities of the roots.Low solution temperature (12°C) lowered the concentrationof NO3 and H2PO4 in xylem sap of CG plants butnot of FG plants. Concentrations of K+, Ca++ and Mg++ in xylemsap were less affected than anions by solution temperature.The plasma membrane of FG plants grown in 12°C solutiontemperature showed the highest K+- Mg++-ATPase activity at allATP concentrations up to 3 mM and at low reaction temperatureup to 12°C, indicating resistance of figleaf gourd to lowroot temperature. (Received December 27, 1994; Accepted March 10, 1995) 相似文献
6.
Seeds of two lettuce cultivars (Lactuca sativa L., cv. Meikoninginand cv. Grand Rapids) were hermetically stored with constantmoisture contents ranging between 3.6 and 17.9 per cent (freshweight basis) at constant temperatures ranging between 5 and75 °C. The decline with time in percentage germination andpercentage normal seedlings was determined for each storagetreatment. The data were fitted to an equation which containsthe constants: K1, the probit of the initial percentage germinationor normal seedlings; KE, a species constant; CW, the constantof a logarithmic moisture term; CH, the constant of a lineartemperature term and CQ, the constant of a quadratic temperatureterm. Regression analysis of data from storage periods up to5.5 years at temperatures of 575 °C and seed moisturecontents of 3.613.6 per cent yielded the following values:KE= 8.218, CW=4.797±0.163, CH=0.0489±0.0050 andCQ=0.000365±0.000056. Although this equation consistentlyprovided a better fit, simplified equations, assuming eithera log-linear relationship between seed longevity and temperature,or a log-linear relationship between seed longevity and bothmoisture content and temperature, accounted for more than 94per cent of the variation at the restricted temperature rangeof 540 °C. Longevity of the same seed lots at sub-zero temperatures (5,10 and 20 °C) was studied in separate tests.Freezing damage, resulting in abnormal seedlings in the germinationtest, occurred at 20 °C when the moisture contentof the seeds exceeded 12 per cent. No decline in percentagenormal seedlings was observed after a storage period of 18 monthsor longer at 20 °C, provided the seed moisture contentdid not exceed 9.5 per cent. For seeds stored at 5 and10 °C with 9.612.5 per cent moisture content,the observed rate of decline of percentage normal seedlingswas adequately predicted by the viability equation, using theabove values for the constants. This suggests that for low moisturecontents the viability equation can be applied to estimate longevityat sub-zero temperatures. Lettuce, Lactuca sativa (L.), seed longevity, seed storage, viability constants, storage conditions 相似文献
7.
Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures 总被引:6,自引:1,他引:5
In previous work, we demonstrated that there was an optimummoisture level for seed storage at a given temperature (Vertucciand Roos, 1990), and suggested, using thermodynamic considerations,that the optimum moisture content increased as the storage temperaturedecreased (Vertucci and Roos, 1993b). In this paper, we presentdata from a two year study of aging rates in pea (Pisum sativum)seeds supporting the hypothesis that the optimum moisture contentfor storage varies with temperature. Seed viability and vigourwere monitored during storage under dark or lighted conditionsat relative humidities between 1 and 90%, and temperatures between-5 and 65°C. The optimum moisture content varied from 0·015g H2O g-1 d.wt at 65°C to 0·101 g H2O g-1 d.wt at15°C under dark conditions and from 0·057 at 35°Cto 0·092 g H2O g-1 d.wt at -5°C under lighted conditions.Our results suggest that optimum moisture contents cannot beconsidered independently of temperature. This conclusion hasimportant implications for 'ultra-dry' and cryopreservationtechnologies.Copyright 1994, 1999 Academic Press Seed storage, seed aging, seed longevity, water content, temperature, glass, desiccation damage, ultradry, Pisum sativum L., pea, cryopreservation 相似文献
8.
The influence of hydrogenase in Bradyrizobum-Phaseoleae symbioseswas studied ex-planta and in-planra in soybean (Glycine max)and cowpea (Vigna unguiculata). The hydrogenase was activatedby the addition of hydrogen in the incubation gas phase whichmodified the response of nitrogenase activity of Hup+ (hydrogenuptake positive) symbiosis to the external oxygen partial pressure.For bacteroids the hydrogenase expression increased nitrogenaseactivity at supraoptimal pO2, acting possibly as a respiratoryprotection of nitrogenase. However, at suboptimal pO2, nitrogenaseactivity of Hup+ bacteroids decreased with hydrogen, a phenomenonattributed to the lower efficiency of ATP synthesis from hydrogenthan from carbon substrates oxidation. For undisturbed nodules,the hydrogenase expression in soybean increased the optimalpO2 for ARA (COP), from 35.3 to 40.3 kPa O2, and the ARA atsupraoptimal pO2; at suboptimal PO2 there was a negative effectof hydrogenase on ARA, although this inhibition was less thanon bacteroids and was not detected if plants were grown at 15°C rather than 20 °C root temperature. No H2 effectwas detected on cowpea nodules. The results on soybean nodulesare consistent with the concept that symbiotic nitrogen fixationis oxygen-limited and that hydrogenase activity has no beneficialeffect on nitrogen fixation in O2 limitation. Key words: Glycine max, hydrogenase, nitrogenase, nitrogen fixation, nodules, Vigna unguiculata 相似文献
9.
Possible physiological mechanisms for production of hydrogen peroxide by the ichthyotoxic flagellate Heterosigma akashiwo 总被引:2,自引:0,他引:2
Blooms of the toxic red tide phytoplankton Heterosigma akashiwo(Raphidophyceae) are responsible for substantial losses withinthe aquaculture industry. The toxicological mechanisms of H.akashiwoblooms are complex and to date, heavily debated. One putativetype of ichthyotoxin includes the production of reactive oxygenspecies (ROS) that could alter gill structure and function,resulting in asphyxiation. In this study, we investigated thepotential of H.akashiwo to produce extracellular hydrogen peroxide,and have investigated which cellular processes are responsiblefor this production. Within all experiments, H.akashiwo producedsubstantial amounts of hydrogen peroxide (up to 7.6 pmol min1104 cells1), resulting in extracellular concentrationsof ~0.5 µmol l1 H2O2. Measured rates of hydrogenperoxide production were directly proportional to cell density,but at higher cell densities, accuracy of H2O2 detection wasreduced. Whereas light intensity did not alter H2O2 production,rates of production were stimulated when temperature was elevated.Hydrogen peroxide production was not only dependent on growthphase, but also was regulated by the availability of iron inthe medium. Reduction of total iron to 1 nmol l1 enhancedthe production of H2O2 relative to iron replete conditions (10µmol l1 iron). From this, we collectively concludethat production of extracellular H2O2 by H.akashiwo occurs througha metabolic pathway that is not directly linked to photosynthesis. 相似文献
10.
Light-induced H+ Efflux from Intact Cells of Cyanidium caldarium 总被引:1,自引:0,他引:1
Light-induced pH changes in suspensions of an acidophilic unicellularalga, Cyanidium caldarium Geitler, were studied as a functionof the pH of the medium. In the neutral pH region, alkalizationof the medium due to photosynthetic CO2 uptake was observed.In the acidic pH region, illumination caused a significant decreasein the pH of the medium, indicating the efflux of H+ from thecells. Both the rate and extent of the pH decrease increasedas the pH of the medium was lowered to 3.0. The H+ efflux wasnot affected by 3-(3',4'-dichlorophenyl)-l,l-dimethylurea, butwas inhibited by phenylmercuric acetate. The fastest H+ effluxoccurred at 45°C, whereas its extent was almost constantfrom 25 to 50°C. The activity decreased at temperaturesabove 50°C and was inactivated completely at 60°C. Itsaction spectrum corresponded the spectrum for chlorophyll aabsorption. Results indicate that the light-induced H+ effluxis driven by photosystem I and is important in the maintenanceof the intracellular pH at the functional neutral region againsta steep pH gradient across the cell membrane. (Received May 6, 1981; Accepted August 8, 1981) 相似文献
11.
In this report I discuss ventilatory and circulatory adjustmentsthat prov for increased O2transport associated with increasedbody temperature in the snake Coluber constrictor. Also includedis the effect of temperature upon acid-base status. Minute ventilationincreases with rising body temperature but does not keep pacewith the increment in resting O2 consumption. The decrease inair convection requirement (i.e., ventilation ÷ oxygenconsumption) causes lung pO2 and arterial oxygen contentto falland lung pCO2 to rise. With the rise in lung pCO2, systemicarterial pCO2 and H+; concentration increase while plasma bicarbonateconcentration does not change. The effect of temperature uponair convection requirement, arterial pCO2, and pH are most pronouncedat body temperatures above about 27°C whereColuber behavesapproximately as an alphastat pH regulator. Despite the inverserelationship between temperature and lung pO2, systemic arterialpO2 is about 80 torr lower at 15°C than at 35°C. Thisdecline in arterial pO2 as temperature falls is explained byleft shifting the oxygen dissociation curve in the presenceof aconstant right-to-left intracardiac shunt. 相似文献
12.
Pappas TC Motamedi M Christensen BN 《American journal of physiology. Cell physiology》2004,287(5):C1219-C1228
Rattlesnakes, copperheads, and other pit vipers have highly sensitive heat detectors known as pit organs, which are used to sense and strike at prey. However, it is not currently known how temperature change triggers cellular and molecular events that activate neurons supplying the pit organ. We dissociated and cultured neurons from the trigeminal ganglia (TG) innervating the pit organs of the Western Diamondback rattlesnake (Crotalus atrox) and the copperhead (Agkistrodon contortix) to investigate electrophysiological responses to thermal stimuli. Whole cell voltage-clamp recordings indicated that 75% of the TG neurons from C. atrox and 74% of the TG neurons from A. contortix showed a unique temperature-activated inward current (IT). We also found an IT-like current in 15% of TG neurons from the common garter snake, a species that does not have a specialized heat-sensing organ. A steep rise in the current-temperature relationship of IT started just below 18°C, and cooling temperature-responsive TG neurons from 20°C resulted in an outward current, suggesting that IT is on at relatively low temperatures. Ion substitution and Ca2+ imaging experiments indicated that IT is primarily a monovalent cation current. IT was not sensitive to capsaicin or amiloride, suggesting that the current did not show similar pharmacology to other mammalian heat-sensitive membrane proteins. Our findings indicate that a novel temperature-sensitive conductance with unique ion permeability and low-temperature threshold is expressed in TG neurons and may be involved in highly sensitive heat detection in snakes. snake; thermosensory; trigeminal; ion conductance 相似文献
13.
The hyperpolarizing response of the Chara internodal cell wasstudied by applying the voltage clamp and constant current techniques.By assuming the membrane as an electromotive force (emf) inseries with a resistance r (which is the sum of a series resistancers and the membrane resistance rm), it was shown that the hyperpolarizingresponse was brought about not only by the increase in membraneresistance but by the increase in membrane emf. The time dependentcurrent-voltage (IVm) curve obtained under the voltageclamp during the hyperpolarizing response showed a negativeresistance. The hyperpolarizing response is also an excitation,since it is a transition process of the membrane across a negativeresistance region. (Received July 22, 1974; ) 相似文献
14.
Fioretti B Pietrangelo T Catacuzzeno L Franciolini F 《American journal of physiology. Cell physiology》2005,289(1):C89-C96
We report here the expression in C2C12 myoblasts of the intermediate-conductance Ca2+-activated K+ (IKCa) channel. The IKCa current, recorded under perforated-patch configuration, had a transient time course when activated by ionomycin (0.5 µM; peak current density 26.2 ± 3.7 pA/pF; n = 10), but ionomycin (0.5 µM) + 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (100 µM) evoked a stable outward current (28.4 ± 8.2 pA/pF; n = 11). The current was fully inhibited by charybdotoxin (200 nM), clotrimazole (2 µM), and 5-nitro-2-(3-phenylpropylamino)benzoic acid (300 µM), but not by tetraethylammonium (1 mM) or D-tubocurarine (300 µM). Congruent with the IKCa channel, elevation of intracellular Ca2+ in inside-out patches resulted in the activation of a voltage-insensitive K+ channel with weak inward rectification, a unitary conductance of 38 ± 6 pS (at negative voltages), and an IC50 for Ca2+ of 530 nM. The IKCa channel was activated metabotropically by external application of ATP (100 µM), an intracellular Ca2+ mobilizer. Under current-clamp conditions, ATP application resulted in a membrane hyperpolarization of 35 mV. The IKCa current downregulated during myogenesis, ceasing to be detectable 4 days after the myoblasts were placed in differentiating medium. Downregulation was prevented by the myogenic suppressor agent basic FGF (bFGF). We also found that block of the IKCa channel by charybdotoxin did not inhibit bFGF-sustained myoblast proliferation. These observations show that in C2C12 myoblasts the IKCa channel expression correlates inversely with differentiation, yet it does not appear to have a role in myoblast proliferation. ATP; cell proliferation 相似文献
15.
The activity of plasma membrane H+-ATPase was measured withmembrane fragments of guard-cell protoplasts isolated from Viciafaba L. ATP hydrolytic activity was slightly inhibited by oligomycinand ammonium molybdate, and markedly inhibited by NO3and vanadate. In the presence of oligomycin, ammonium molybdateand NO3, the ATP-hydrolyzing activity was strongly inhibitedby vanadate. It was also inhibited by diethylstilbestrol (DES),p-chloromercuribenzoic acid (PCMB) and Ca2+, but slightly stimulatedby carbonyl cyanide m-chlorophenylhydrazone (CCCP). The acitivityhad higher specificity for ATP as a substrate than other phosphoricesters such as ADP, AMP, GTP and p-nitrophenylphosphate; theKm was 0.5 mM for ATP. The activity required Mg2+ but was notaffected by K+, and it was maximal around pH 6.8. When guard-cellprotoplasts were used instead of membrane fragments, the ATPaseactivity reached up to 800µmol Pi.(mg Chl)1.h1in the presence of lysolecithin. These results indicate thatthe guard cell has a high plasma membrane H+-ATPase activity. (Received December 23, 1986; Accepted April 28, 1987) 相似文献
16.
Kim Daekyung; Nakashima Takuji; Matsuyama Yukihiko; Niwano Yoshimi; Yamaguchi Kenichi; Oda Tatsuya 《Journal of plankton research》2007,29(3):241-247
Raphidophycean flagellates, Chattonella marina and C. ovata,are harmful red tide phytoplankters; blooms of these phytoplanktersoften cause severe damage to fish farming. Previous studieshave demonstrated that C. marina and C. ovata continuously producereactive oxygen species (ROS) such as superoxide anion (O2)hydrogen peroxide (H2O2) under normal growth conditions, andan ROS-mediated toxic mechanism against fish and other marineorganisms has been proposed. Although the exact mechanism ofROS generation in these phytoplankters still remains to be clarified,our previous study suggested that NADPH oxidase-like enzymelocated on the cell surface of C. marina may be involved inO2 generation. To investigate the localization of O2and H2O2 generation in C. marina and C. ovata, we employed 2-methyl-6(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin-3-oneand 5-(and-6)-carboxy-2',7'-dichlorodihydrodihydrofluoresceindictate, acetyl ester, which are specific fluorescent probefor detecting O2 and H2O2, respectively. Observationby fluorescence microscopy of live phytoplankters incubatedwith each probe revealed that O2 is mainly generatedon the cell surface, whereas H2O2 is generated in the intracellularcompartment in these phytoplankters. When the cells were rupturedby ultrasonic treatment, O2 levels of C. marina and C.ovata decreased significantly, whereas a few times higher levelsof H2O2 were detected in the ruptured cell suspensions whencompared with the levels of the live cell suspension. In immunoblottinganalysis, the protein recognized by anti-human gp91 phox wasdetected in both species. These results suggest that, in bothphytoplankters, the underlying mechanisms of O2 and H2O2generation may be distinct and such systems are independentlyoperating in the cells. 相似文献
17.
Photosynthetic Responses of Different Varieties of Wheat to High Temperature: II. EFFECT OF HEAT STRESS ON PHOTOSYNTHETIC ELECTRON TRANSPORT 总被引:3,自引:0,他引:3
The effect of heat stress on photosynthetic electron transportwas investigated in thylakoids isolated from the wheat (Triticumaestivum L.) varieties APU (Finland) and K65 (India) grown underboth cool (13 °C day, 10 °C night) and warm (30 °Cday, 25 °C night) regimes which gave rise to varietal differencesin photosynthetic temperature acclimation. The responses ofthe uncoupled activities of both whole-chain electron transportand photosystem II to heat stress were similar. Both activitiesexhibited higher rates in thylakoids isolated from warm-grownplants and were more resistant to high temperature pretreatmentthan in those isolated from cool-grown plants, but varietaldifferences were not observed. Uncoupled photosystem I activity driven by either reduced 2,6-dichlorophenol indophenol (DCPIPH2) or N,N,N',N'-tetramethyl-p-phenylenediamine (TMPDH2) showed a stimulation following high temperaturepretreatment which was more marked in thylakoids isolated fromwarm-grown plants, followed by inhibition at extreme high temperatures.This stimulation was due largely to an increase in Vmax butdid not occur when reduced diaminodurene, which is highly lipophilic,was used as the electron donor. It appears that stimulationof PS I activity may involve increased accessibility of someartificial electron donors to the native acceptor sites withinthe thylakoid membrane in a process which is influenced by growthtemperature. Key words: Photosynthetic electron transport, heat stress, Triticum aestivum 相似文献
18.
Effects of temperature (15°, 20° and 25°C), O2 partialpressure (PO2=0, 1, 2, 4, and 6 kPa), and individual size(1279 mm shell length; SL) on survivorship of specimensof the non-indigenous, marine, brown mussel, Perna perna, fromTexas were investigated to assess its potential distributionin North America. Its hypoxia tolerance was temperature-dependent,survivorship being significantly extended at lower temperaturesunder all tested lethal PO2. Incipient tolerated PO2 was 4 and6 kPa at 15 and 20°C, respectively, with >50% mortalityoccurring at 25°C at all tested levels of hypoxia. PO2 hadless of an effect on survival of hypoxia than temperature. At25°C, survivorship was not different over a PO2 range of02 kPa and increased only at 4 and 6 kPa. Survivorshipwas size-dependent. Median survival times increased with increasingSL in anoxia and PO2=1 kPa, but at 2, 4 and 6 kPa,smaller individuals survived longer than larger individuals.With tolerance levels similar to other estuarine bivalve species,P. perna should withstand hypoxia encountered in estuarine environments.Thus, its restriction to intertidal rocky shores may be dueto other parameters, particularly its relatively low temperaturetolerance. (Received 26 January 2004; accepted 31 March 2005) 相似文献
19.
Fluorescence spectra of the pigment system at 196°Cin membrane fragments of Anabaena variabilis and A. cylindricawere investigated. The fluorescence spectra of membrane fragments having four emissionbands at 645655, 685, 695 and 725 nm were basically similarto those reported for intact cells of blue-green algae, thoughthe emission from phycocyanin (645655 nm) was far strongerwith membrane fragments than with intact algal cells. Incubation of membrane fragments of A. variabilis in a dilutebuffer (102M, pH 7.5) caused an increase in the 645 nmfluorescence and slight decreases in the 685 and 695 nm fluorescences,but had no influence on the 725 nm fluorescence. The decreasein the 685 and 695 nm fluorescences of A. cylindrica was moremarked and had the same kinetics as the inactivation of photosystemII reaction measured by DPIP-photoreduction. When membrane fragments of A. cylindrica were incubated in thebuffer solution at room temperature or in the presence of MgCl2(103M) at 0°C; phycobilin aggregates, which emittedthe 655 and 685 nm fluorescence, were solubilized. This solubilizationwas not observed with membrane fragments of A. variabilis. (Received August 31, 1972; ) 相似文献
20.
Diurnal temperature fluctuations induced change in soya bean-pod[Glycine max (L.) Merr.] carbon exchange rate (CER, where positiveCER represents CO2 evolution). CER appeared to depend linearlyon temperature. Linear regressions of CER on temperature interceptedthe temperature axis at 5°C (i.e. zero CER at 5°C).Slopes of these regressions (i.e. temperature sensitivity) changedover the season. The CER-temperature sensitivity coefficient,K, (calculated from observed values of CER. pod temperatureand temperature intercept) rose from less than 0·02 mgCO2 h1 pod1 °C1 during early pod-flll,peaked at over 0·04 mg CO2 h1 pod1 °C1at mid pod-fill, and then declined during late pod-fill andmaturation. Glycine max (L.) Merr., Soya bean, carbon exchange rate, temperature 相似文献