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1.
Dark CO2 fixation by Anabaena cylindrica was stimulated aboutthree-fold by the addition of NH4Cl to the cells. The 14CO2incorporation experiments showed that 14C is most rapidly incorporatedinto aspartate and then glutamine by adding NH4CI. Glutamineaccumulated predominantly after the addition of NH4Cl showingthat NH4 is incorporated into glutamine by glutamine synthetase.The stimulating effect of NH4Cl on CO2 fixation and amino acidsynthesis was suppressed by methionine sulfoximine, an inhibitorof glutamine synthetase. It was suggested that dark CO2 fixationwas stimulated by the action of glutamine synthesis which isenhanced by ammonia. (Received February 10, 1981; Accepted April 2, 1981) 相似文献
2.
M{euro}LLER R.; STEIGNER W.; GIMMLER H.; KAISER W. M. 《Journal of experimental botany》1990,41(4):441-448
At constant external [CO2], rates of dark-CO2 fixation of theunicellular green alga Eremosphaera viridis were drasticallyincreased (up to 40-fold) by addition of ammonium (NH3+ NH4+)at external pH values (pH0) between 6.0 and 8.0. The cytosolicpH was monitored under identical conditions by micro-pH-electrodemeasurements, and cytosolic and vacuolar pH by the 31P-NMR technique.Addition of ammonium (5.0 mol m pH0 7.0) caused a rapidand transient acidification of the cytosol during the first4 min. Thereafter, the cytosolic pH remained constant at itsoriginal value. A rather constant cytosolic pH was also confirmedby 31P-NMR measurements, which, in addition, indicated a slowalkalization of the vacuole (about 0.5 units within 30 min afteraddition of ammonium). Since the dramatic stimulation of dark-CO2 fixation by ammoniumis not mediated by an alkalization of the cytosol, nor by directammonium effects on phosphoenolpyruvate carboxylase (PEPC, E.C.4.1.1.31
[EC]
), the role of vacuolar alkalization as a possible triggerfor the stimulation of PEP-carboxylase is discussed. Key words: Cytosolic pH, dark-CO2 fixation, pH-regulation, vacuolar pH 相似文献
3.
Ohmori Masayuki; Miyachi Shizuko; Okabe Kei-ichiro; Miyachi Shigetoh 《Plant & cell physiology》1984,25(5):749-756
The effects of NH4Cl on respiration, adenylate and free aminoacid levels as well as dark CO2 fixation were investigated usingnitrogen-starved Chlorella vulgaris 11h cells with or withoutaddition of methionine sulfoximine (MSX), an inhibitor of glutaminesynthetase. Upon addition of NH4Cl (1 mM) to the cells not treatedwith MSX, respiration was stimulated and the level of ATP droppedrapidly, while the levels of ADP and AMP increased. NH4Cl alsostimulated amino acid synthesis, especially of glutamine, andmarkedly enhanced dark CO2 fixation. Addition of NH4Cl to MSX-treatedcells stimulated respiration and lowered the level of ATP, butdid not enhance glutamine synthesis and only slightly stimulateddark CO2 fixation.
4On leave from Institute of Medical Science, Advance R &D Co. Minami-Hashimoto, Sagamihara, Kanagawa-ken 220, Japan (Received January 28, 1984; Accepted April 19, 1984) 相似文献
4.
Chlorella cells incubated in the dark longer than 12 hr showedpronounced blue light-induced 14CO2 fixation into aspartate,glutamate, malate and fumarate (blue light effect), whereasthose kept under continuous light showed only a slight bluelight effect, if any. 2) During dark incubation of Chlorellacells, phosphoenolpyruvate carboxylase activity and the capacityfor dark 14CO2 fixation decreased significantly, whereas ribulose-1,5-diphosphatecarboxylase activity and the capacity for photosynthetic 14CO2fixation (measured under illumination of white light at a highlight intensity) did not decrease. 3) In cells preincubatedin the dark, intracellular levels of phosphoenolpyruvate and3-phosphoglycerate determined during illumination with bluelight were practically equal to levels determined during illuminationwith red light. 4) The blue light effect was not observed incells incubated widi chloramphenicol, indicating that blue light-inducedprotein synthesis is involved in the mechanism of the effect. (Received April 9, 1971; ) 相似文献
5.
Etiolated Avena sativa L. coleoptile sections were used to determinethe influence of C2H4 on in vivo and in vitro rates of CO2 fixation,and to measure the influence of various permutations of C2H4,CO2, and malate on growth. Whereas 1 mM malate or 320 µI-1 CO2 stimulated growth by approximately 100 per cent, inhibitionof growth by 10-8 µ I-1 C2H4 was substantial only in thepresence of malate or CO2 The increase in growth rate in responseto these two agents was eliminated by the simultaneous applicationof C2H4. The in vivo rate of dark [14C]bicarbonate fixationand in vitro enzymic assays of fixation were not measurablyinhibited by C2H4. These results are discussed in the lightof evidence which indicates that CO2-stimulated growth is mediatedby dark fixation. The data do not support the view that C2H4inhibition of growth results from an inhibition of fixation,but suggests that C2H4 may inhibit some step in the processby which malate stimulates growth. 相似文献
6.
Cratoneuron filicinum, a drought-sensitive moss, and Tortularuralis, a drought-tolerant moss, fix CO2 non-autotrophicallyat a rate of about 1.2 and 2.2 µmol h1 g1dry wt. respectively. During drying, T. ruralis fixes CO2 atan undiminished rate until the tissue loses about 60% of theinitial fresh weight. Thereafter, CO2 fixation rapidly declinesto zero. Dark CO2 fixation by C.filicinum declines steadilyduring the dehydration period. On rehydration, dark CO2 fixationis resumed immediately in T. ruralis but not in C.filicinum.When dried T. ruralis is equilibrated with an atmosphere ofnearly 100% relative humidity, its weight increases to about40% of the original fresh weight and dark CO2 fixation resumesat a rate about 60% of the fresh moss. In C.filicinum thereis only a small increase in weight and little CO2 fixation inthe dark. The non-autotrophically fixed carbon, in both mossesstudied, is incorporated into amino acids (more than 60% ofthe total, mainly into aspartate, alanine and glutamate) andorganic acids (less than 40% of the total, mainly into malate).It is suggested that on rehydration immediate availability ofNADPH, known to be produced by transhydrogenation from NADHduring dark CO2 fixation, may be an important factor in therepair of drought-induced cellular damage by reductive biosynthesisof membrane components and other cellular constituents. Key words: Mosses, Dehydration, Rehydration, Dark CO2 fixation, Amino acids, Organic acids, NADPH, Drought tolerance. 相似文献
7.
Role of Carbonic Anhydrase in Photosynthesis of Blue-Green Alga (Cyanobacterium) Anabaena variabilis ATCC 29413 总被引:2,自引:0,他引:2
The affinity for NaHCO3 (CO2) in photosynthesis of Anabaenavariabilis ATCC 29413 was much higher in the cells grown underordinary air (low-CO2 cells) than in those grown in air enrichedwith 24% CO2 (high-CO2 cells) (pH 8.0, 25?C). Ethoxyzolamide(50 µM) increased the Km(NaHCO3 in low-CO2 cells aboutnine times (from 14.3 to 125), while the maximum rate of photosynthesisdecreased about 20%. When high-CO2 cells were transferred tolow-CO2 conditions, carbonic anhydrase (CA) activity increased,while Km(NaHCO3) in photosynthesis decreased from 140 to 30µM within about 5 h. The addition of CA to the suspensionof both high- and low-CO2 cells enhanced the rates of photosyntheticO2 evolution under CO2-limiting conditions. The rate of 14CO2fixation was much faster than that of H14CO3 fixation.The former reaction was greatly suppressed, while the latterwas enhanced by the addition of CA. These results indicate thatthe active species of inorganic carbon utilized for photosynthesiswas free CO2 irrespective of the CO2 concentration given duringgrowth. It is suggested that CA plays an active role in increasingthe affinity for CO2 in photosynthesis of low-CO2 cells of thisblue-green alga. (Received January 24, 1984; Accepted October 22, 1984) 相似文献
8.
Accumulation and Utilization of Dissolved Inorganic Carbon by a Marine Unicellular Coccolithophorid, Emiliania huxleyi 总被引:1,自引:0,他引:1
The mechanism for utilization of dissolved inorganic carbon(DIC) was investigated in the marine unicellular calcareousalga Emiliania huxleyi, grown with constant aeration. The apparentK0.5 (DIC), the concentration of DIC which attains one-halfof the maximum velocity of apparent photosynthesis, for photosyntheticevolution of O2, measured under saturating light, was 5.5 mM(55 µM for CO2) at pH 8.0 and 25°C. The value of K0.5was not affected by inhibitors of carbonic anhydrase (CA), andan electrometric assay of CA showed that the enzyme was notinvolved in photosynthesis in this alga. The rate of photosyntheticfixation of 14C-DIC into acid-stable products was about 20 timeshigher than that into CaCO3, irrespective of the external concentrationof DIC. In short-term experiments, 14C-DIC was usually incorporatedinto the internal pool of DIC (IIC) to concentrations up to13 to 16 times higher than that of the external DIC. CO2 addedexternally was utilized mainly for fixation of CO2 and accumulationof IIC. By contrast, HCO-3 was utilized mainly for productionof CaCO3 and accumulation of IIC. Incorporation of 14C intoIIC was partially suppressed by DCMU or in darkness but itstransfer to CaCO3 was unaffected. These results suggest thataccumulation of IIC in this alga, even under ordinary circumstances,is only partially responsible for increasing the efficiencyof utilization of DIC by photosynthetic fixation but may bemost useful for the production of CaCO3. (Hydroxyethylidene) bisphosphonic acid, an inhibitor of thegrowth of CaCO3 crystals, completely suppressed production ofCaCO3. The accumulation of IIC was also partially suppressed,but photosynthetic fixation of CO2 was enhanced. In a pulse-chaseexperiment with 14CDIC, 14C incorporated into IIC and CaCO3in darkness was transferred to acid-stable products of photosynthesisin the light. These results suggest that 14C-DIC in IIC andpre-formed CaCO3 may be useful sources of carbon for fixationof CO2. (Received July 2, 1993; Accepted January 10, 1994) 相似文献
9.
GEHL KATHARINA A.; COOK CATHERINE M.; COLMAN BRIAN 《Journal of experimental botany》1987,38(7):1203-1210
The carbon dioxide compensation point of the unicellular greenalga, Chloretla saccharophila, was determined in aqueous mediumby a gas chromatographic method. Compensation points decreasedmarkedly from 63 cm3 m3 at an external pH of 4.0 to 3.2cm3 m3 at pH 8.0 and were not affected by the O2 concentrationof the medium. The calculated CO2 concentration required tosupport the half-maximum photosynthetic rate of the algal cellsranged from 6.0 mmol m3 at an external pH of 60 to 1.5mmol m3 at pH 8.0 and these values were not affectedby O2 concentration. The Km(CO2) of nbulose-l,5-bisphosphatecarboxylase isolated from cells grown either at pH 4.0 or pH8.0 was determined to be 64 mmol m3. These results indicatethat loss of CO2 by photorespiration does not occur in C. saccharophilacells at acid pH and the disparity between the apparent affinityfor CO2 of the intact cells and that of the carboxylase indicatesthe operation of a CO2 concentrating mechanismin this alga at acid pH. Key words: Acidophilic alga, bicarbonate transport, Chlorella saccharophila, compensation point, CO2 affinity, PH, RuBP carboxylase 相似文献
10.
In Kalanchoë blossfeldiana von Poellnitz cv. Tom Thumband cv. Feuer Blute interaction of CO2 fixation with photoperiodicinduction and water stress was examined. It was found that TomThumb raised in dilute culture solution and kept in photoinductivecycles (8 h light and 16 h dark) flowered but failed to showa net dark CO2 fixation. A net dark fixation was observed whenthe concentration of the culture solution was increased or plantswere sprayed with 300 or 750 mg 11 CCC or 300 or 2000mg 11 B-9. In a non-inductive photoperiod no net darkfixation was observed with these treatments although there wasa tendency for dark fixation to increase. Feuer Blute did not flower in inductive photoperiods when keptin half strength solution. It is suggested that in Tom Thumbboth photoperiodic induction and water stress are required forinitiation of net CO2 dark fixation. In Feuer Blute where CAMis occurring normally photo-induction is sufficient to induceflowering. In half strength solution CO2 dark fixation is disturbedand floral induction also does not occur. 相似文献
11.
Rooted cuttings of Kalanchoë blossfeldiana cv. Feuer Bluteand K. crenatum failed to show a net dark CO2 fixation whenraised in dilute nutrient solution. Dark CO2 fixation (CAM)in these plants was initiated either by increasing the soluteconcentration or lowering the water potential of the nutrientsolution by addition of mannitol (0.11 M and 0.25 M) and carbowax4000 (0.16 M and 0.3 M). Initiation was also brought about byspraying the leaves with B-9 (N,dimethylamino-succinamicacid,300mg11) or by addition of CCC (2 chloroethyl trimethylammonium chloride, 300 or 750 mg11) to the nutrient medium.Failure of CAM in dilute solution was suggested to be due tolack of accumulation of photosynthates in the leaves. Waterstress and growth retardants brought about reduction of monilizationand/or translocation thereby leading to accumulation of assimilatesin the leaves and to initiation of dark CO2 fixation. 相似文献
12.
Two Polypeptides Inducible by Low Levels of CO2 in Soluble Protein Fractions from Chlorella regularis Grown at Low or High pH 总被引:1,自引:0,他引:1
Previous studies suggested that certain protein(s) other thancarbonic anhydrase might play an important role in the facilitatedtransport of dissolved inorganic carbon (DIC) from the mediumto the site of CO2 fixation by ribulose-1,5-bisphosphate carboxylase/oxygenasein the unicellular green alga Chlorella regularis adapted tolow-CO2 (ordinary air) conditions [Shiraiwa et al. (1991) Jpn.J. Phycol. 39: 355; Satoh and Shiraiwa (1992) Research in Photosynthesis,Vol. III, p. 779]. The proteins that might be involved in thisfacilitated transport of DIC were investigated by pulse-labelingof induced proteins with 35S-sulfate during adaptation of cellsgrown under high-CO2 conditions to low CO2. Analysis by SDS-PAGErevealed that synthesis of two polypeptides, with molecularmasses of 98 and 24 kDa, respectively, was induced under low-CO2conditions. The 24-kDa polypeptide was induced at pH 5.5 butnot at pH 8.0, whereas the 98-kDa polypeptide was induced atboth pH 5.5 and pH 8.0. The possible role of these polypeptidesin the facilitated transport of DIC in Chlorella regularis isdiscussed. (Received October 30, 1995; Accepted February 26, 1996) 相似文献
13.
Hammel Kenneth E.; Cornwell Karen L.; Bassham James A. 《Plant & cell physiology》1979,20(8):1523-1529
Addition of 2 mM ammonium ion to isolated mesophyll cells ofPapaver somniferum resulted in a 3-fold or greater increasein their rate of dark 14C fixation, while even 0.1 mM NH4+ nearlydoubled that rate. The most rapid increase in the labeling ofa metabolite occurred in aspartate, and was accompanied by adecrease in the steady-state level of labeled phosphoenolpyruvate.No change in labeled pyruvate level occurred, and alanine labelingdeclined. Ammonium ion addition had no effect on the respiratoryrate of these cells in the dark. We conclude that NH4+ stimulatesphosphoenolpyruvate carboxylation in this system, but has nodetectable effect on the pyruvate kinase reaction in the dark.Our results are compared with earlier findings and the possibleregulatory function of ammonia is discussed. (Received July 23, 1979; ) 相似文献
14.
Activities of photosynthetic and photorespiratory enzymes viz.,ribulose bisphosphate carboxylase, phosphoenol pyruvate carboxylaseand glycolate oxidase from jute (Corchorus olitorius L.; cv.JRO 632) leaves were compared with those from maize (C4) andsunflower (C3) leaves. The photosynthetic CO2 fixation products,the release of 14CO2 in light and dark following photosynthesisin 14CO2, chlorophyll a: b ratio, gross leaf photosyntheticrate and dry matter production rate were also studied. The resultsshow that jute is a C3 plant. Key words: Jute, Corchorus olitorius, C3 photosynthesis 相似文献
15.
When Chlorella oulgaris ll h cells grown in air containing 4%CO2 (high-CO2 cells) were given low concentrations of14CO2 (<150ppm), the initial rate of photosynthetic 14CO2 fixation wasvery low and linear 14CO2 fixation was observed after an inductionperiod which lasted for ca. 45 min. No such induction period was observed when high-CO2 cells weregiven high concentrations of 14CO2 (10,000 ppm) or when IOW-CO2cells were given either low or high concentrations of 14CO2,supporting the observations by Briggs and Whittingham (l). However,irrespective of CO2 concentrations during growth and of 14CO2concentrations during the experiments, most of the 14C was incorporatedinto phosphate esters during the initial periods of photosynthetic14CO2 fixation. These results are in sharp contrast to the reportby Graham and Whittingham (4).
1 Requests for reprints should be addressed to S. Miyachi, RadioisotopeCentre, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan. (Received June 30, 1979; ) 相似文献
16.
Biochemical studies of epidermal tissue may not reflect metabolismof the guard cells which represent less than 5% of the tissuevolume. Pure samples of guard cell protoplasts of Commelinacommunis were therefore used to investigate CO2 fixation ratesand 14C-labelling patterns of metabolites in the light and thedark. Qualitatively, results were similar in most respects tothose obtained in a previous study (Schnabl, 1980) for guardcell protoplasts of Vicia faba. CO2 fixation rates by guardcell protoplasts of C. communis were the same in the light andthe dark but about 50 times lower than the values Schnabl obtainedfor V.faba. The 14C-labelling pattern of metabolites in C. communiswas also similar in the light and the dark: over 60% of thetotal fixed was in malate with only 1% in sugar phosphates.Label was also detected in starch, aspartate, glutamate andcitrate but not in glycollate as previously recorded in V. fabaguard cell protoplasts. The results confirm the view that the reductive pentose phosphatepathway does not occur in guard cells of C. communis. Key words: CO2 fixation, Guard cell protoplasts, Stomata 相似文献
17.
Leaves of different ages from B. calycinum were exposed to 14CO2in light during day and night. The labelling pattern on thechromatogram differed with leaf age. Young leaves had similarpatterns to those of C3 plants during both day and night. Matureleaves showed high incorporation of 14C into C4 acids, especiallyat night. In contrast, no significant difference with leaf agewas observed in the pattern of dark 14CO2 fixation products.Study of the enzyme activity and the content of titratable acidat each leaf age suggested that high incorporation of 14C inC4 acids during the night was due to the simultaneous absorptionof CO2 by both enzymes RuDPcarboxylase and PEPcarboxylase. (Received November 24, 1977; ) 相似文献
18.
GRODZINSKI BERNARD; JAHNKE SIEGFRIED; THOMPSON ROBERT 《Journal of experimental botany》1984,35(5):678-690
Tracer amounts of atmospheric [13N]-Iabelled ammonia gas, wereabsorbed by leaves of Lupinus albus and Helianthus annuus inboth the light and the dark. Exogenous [13N]-ammonia was onlyabsorbed in the dark when the feeding occurred shortly aftera period of illumination and the tissue was not depleted ofits carbohydrate reserves (e.g. starch). Incorporation of the[13N]-ammonia appeared to occur via the leaf glutamine synthetase/glutamatesynthase (GS/GOGAT) cycle since 2.0 mol m3 MSX, an inhibitorof the GS reduced uptake in both the light and dark. Photosyntheticincorporation of 11CO2 was not affected by this treatment Therate of movement of [13N]-assimilates in the petiole of attachedleaves of Helianthus and Lupinus was similar to that of the11Cl-photo assimilates. Export of both [13N] and [11C]-Iabelledassimilates from the leaf and movement in the petiole in boththe light and the dark was inhibited by source leaf anoxia (i.e.nitrogen gas). Translocation was re-established at the samerate when the feed leaf was exposed to gas containing more than2% O2 which permitted dark respiration to proceed. After aninitial feeding of either 11CO2 or [13N]-ammonia at ambient(21%) O2 exposure of the source leaf to 2% O2, or 50% O2 didnot alter the rates of translocation, indicating that changesin photosynthetic activity in the source leaf due to photorespiratoryactivity need not markedly alter, at least during the shortperiod, the loading and translocation of either [11C ] or [13N]-labelledleaf products. Key words: Translocation, CO2, NH3, Leaves, Helianthus annuus, Lupinus albus 相似文献
19.
Mass spectrometry has been used to investigate the transportof CO2 in the freshwater diatom Navicula pelliculosa. The timecourseof CO2 formation in the dark after addition of 100 mmol m3dissolved inorganic carbon (DIC) to cell suspensions showedthat no external carbonic anhydrase (CA) was present in thesecells. Upon illumination, cells pre-incubated at pH 75 with100 mmol m3 DIC, removed almost all free CO2 from themedium at an initial rate of 285 µmol CO2 mg1Chl h1. Equilibrium between HCO3 and CO2 in themedium occurred rapidly upon addition of bovine CA, showingthat CO2 depletion resulted from a selective uptake of CO2 ratherthan an uptake of all inorganic carbon species. However, photosyntheticO2 evolution rate remained constant after CO2 had been depletedfrom the medium indicating that photosynthesis is sustainedprimarily by active HCO3 uptake. Treatment of cells with2-iodoacetamide (83 mol m3) completely inhibited CO2fixation but had little effect on CO2 transport since initialrates of CO2 depletion were about 81% that of untreated cells.Transfer of iodoacetamide-treated cells to the dark caused arapid increase in the CO2 concentration in the medium largelydue to the efflux of the unfixed intracellular DIC pool whichwas found to be about 194 times the concentration of that inthe external medium. These results indicate that Navicula pelliculosaactively takes up molecular CO2 against a concentration gradientby a process distinct from HCO3 transport. Key words: Dissolved inorganic carbon, carbonic anhydrase, bicarbonate transport, CO2 transport, mass spectrometry 相似文献
20.
The rate of photosynthesis by the freshwater alga Lemanea mamillosais proportional to CO2 concentration, virtually to the pointof saturation, and inversely proportional to the radius of thethallus. By contrast, the CO2 response curve of very thin slicesof the thallus is a rectangular hyperbola with a (lower) halfsaturation concentration of 10 mmol m3. For the intactplant, the kinetics of CO2 fixation are strongly masked by internalCO2 transport limitations, although the maximum rate of photosynthesisis probably determined by the rate of supply of ribulose bisphosphate(RuBP). The flow of water over the alga becomes turbulent atwater velocities greater than about 90 mm s1 and thethallus stretches significantly at higher water velocities.In its natural habitat, therefore, the external unstirred layerwill be thin (< 10 µm) and the thallus will be stretched,leading to rapid external and increased internal rates of CO2transport from the bulk solution. The estimated maximum rateof CO2 transport is commensurate with the maximum rate of photosynthesis(i.e. the rate of supply of RuBP). Key words: Transport limitations, Kinetics of CO2 fixation 相似文献