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1.
In hydroponically grown Lycopersicon esculentum (L.) Mill. cv.F144 the site of NO3 reduction and assimilation withinthe plant was shifted from the shoot to the root by salinity.Uptake of NO3 from the root solution was strongly inhibitedby salinization. Consequently, NO3 concentrations inthe leaf, stem and root tissues as well as the nitrate reductaseactivities of the leaves were lower in salinized than in controlplants. Lower NO3, but higher reduced-N, concentrationswere observed in the xylem sap as a result of the enhanced participationof the root in NO3 reduction in salinized plants. Lowerstem K+ concentrations and leaf malate concentrations were foundin salinized compared to control plants which indicates reducedfunctioning of the K+–shuttle in the salinized plants. Incorporation of inorganic carbon by the root was determinedby supplying a pulse of NaH14CO3 followed by extraction andseparation of the labelled products on ion exchange resins.The rate of H14CO3 incorporation was c. 2-fold higherin control than in salinized plants. In salinized plants theproducts of H14CO3 incorporation within the roots werediverted into amino acids, while the control plants divertedrelatively more 14C into organic acids. Products of inorganiccarbon incorporation in the roots of salinized plants providean anaplerotic source of carbon for assimilation of reducedNO3 into amino acids, while in control plants the productswere predominantly organic acids as part of mechanisms to maintainionic balance in the cells and in the xylem sap. Key words: Tomato, nitrate, PEPc, respiration, salinity  相似文献   

2.
Plant allocation to defensive compounds in response to growthin elevated atmospheric CO2 in combination with two levels ofnitrogen was examined. The aim was to discover if allocationpatterns of transgenic plants containing genes for defensivechemicals which had not evolved in the species would respondas predicted by the Carbon Nutrient Balance (CNB) hypothesis.Cotton plants (Gossypium hirsutum L.) were sown inside 12 environmentalchambers. Six of them were maintained at an elevated CO2 levelof 900 µmol mol-1 and the other six at the current levelof  相似文献   

3.
Quantitative and electrophoretic changes in o-diphenol oxidase(o-diphenol: O2 oxidoreductase, E.C. 1 10,3.1) were studiedduring the entire period of cotton (Gossypium arboreum L. cv.Sanjay) fibre development. A significant increase in o-diphenoloxidase activity was recorded during the fibre initiation phaseand it is suggested that a shift in redox balance towards oxidationmay play an important role in fibre initiation. Low o-diphenoloxidase activity during elongation and its high activity duringthe phase of secondary thickening, together with isoenzyme patterns,suggest an important role of this enzyme in cotton fibre development.The role of o-diphenol oxidase in relation to auxin turnoverand redox balance is discussed. Gossypium arboreum, cotton, fibre development, o-diphenol oxidase, redox balance, auxin turnover  相似文献   

4.
Translocation of Carbohydrate in Cotton: Movement to the Fruiting Bodies   总被引:1,自引:0,他引:1  
BROWN  K. J. 《Annals of botany》1968,32(4):703-713
The translocation of 14C-labelled assimilate was followed frommain stem leaves on the cotton plant (Gossypium hirsutum) tobolls on the lower sympodia. From the upper leaves the assimilatedescends the stem in well-defined strands in the phloem. Wheresympodia originate close to these strands some of the assimilateis distributed to the bolls on those sympodia. There is evidencethat the involucre, but not the green boll wall, contributesto boll nutrition by assimilation of external CO2.  相似文献   

5.
  1. In the presence of NADP+ and Mg++, the bundle sheath strandsisolated from corn (Zea mays) leaves by cellulase treatmentsdecarboxylated malate in the light at an initial rate (200 µmoles/mgchl.hr), which was sufficient to account for photosyntheticCO2 fixation in intact leaves. This rate gradually slowed downand then stopped. The final level of the malate decarboxylatedwas approximately equal to the amount of NADP+ added.
  2. Rapidand continued decarboxylation of malate was observed whenNADP+,3-phosphoglyceric acid and ATP (and Mg++) were addedtogether.The addition of ADP instead of ATP showed a similareffect.Light did not show any effect on the malate decarboxylationin the presence of ATP or ADP.
  3. When malate was added to thebundle sheath strands in the presenceof exogenous NADP+ NADP+was rapidly reduced. The reductionstopped after 2 min when,73% of the added NADP+ was reduced.The further addition of3-phosphoglyceric acid and ATP broughtabout a decrease in theNADPH-level, which rose again to attaina new steady level.
  4. The transfer of radioactivity from (1-14C-3-phosphoglycericacid to dihydroxyacetone phosphate in the bundle sheath strandsin the presence of ATP and NADP+ was greatly enhanced by theaddition of malate.
  5. In the presence of ribose 5-phosphateand ATP, the rate of 14C-transferfrom (4-14C)-malate to theintermediates of the reductive pentosephosphate cycle was equalto that of 14CO2 fixation in the light.
All these results support the current view that in the bundlesheath cells of C4 plants belonging to the NADP-malic enzyme-group,the decarboxylation of malate is coupled to the fixation ofthe released CO2 and the reduction of 3-phosphoglyceric acidformed as a result of CO2 fixation. 1 Part of this research was reported at the 40th Annual Meetingof the Botanical Society of Japan Osaka, December, 1975. 3 Present address: Laboratory of Chemistry, Faculty of Medicine,Teikyo University, 359 Otsuka, Hachioji-City, Tokyo 173, Japan. (Received April 30, 1977; )  相似文献   

6.
Plants of Lupinus albus L., cv. Ultra, were grown hydroponicallywith NO3-nutrition for 51 d under control (0.05 mol m–3Na+ and 10 mol m–3 Cl) and saline (40 mol m–3NaCI) conditions. Plants were harvested 41 and 51 d after germinationand analysed for content and net increment of C, N and the mineralcations K+, Na+, Mg2+, and Ca2+ and the anions Cl, NOJ,malate, phosphate, and SO42–. Roots, stem interaodes,petioles and leaflets were analysed separately. During the studyperiod net photosynthesis, respiratory losses of CO2 from shootand root and the composition of the spontaneously bleeding phloemsap and the root pressure xylem exudate were also determined.Using molar ratios of C over N in the transport fluids, incrementsof C and N, and photosynthetic gains as well as respiratorylosses of C, the net flows of C and N in the xylem and phloemwere then calculated as in earlier studies (Pate, Layzell andMcNeill, 1979a). Knowing the carbon flows, the ratios of ionto carbon in the phloem sap, and ion increments in individualorgans, net flows of K+, Na+, and Cl over the study periodwere also calculated. Salt stress led to a general decrease of all partial componentsof C and N partitioning indicating that inhibitions were notdue to specific effects of NaCI salinity on photosynthesis oron NO3 uptake. However, there were differences between variouslyaged organs, and net phloem export of nitrogenous compoundsfrom ageing leaves was substantially enhanced under saline conditions.In addition, NO3reduction in the roots was specificallyinhibited. Uptake and xylem transport of K+ was more severelyinhibited than photosynthetic carbon gain or NO3 uptakeby the root. K+ transport in the phloem was even more severelyrestricted under saline conditions. Na+ and Cl flowsand uptake, on the other hand, were substantially increasedin the presence of salt and, in particular, there were thenmassive flows of Na in the phloem. The results are discussedin relation to the causes of salt sensitivity of Lupinus albus.The data suggest that both a restriction of K+ supply and astrongly increased phloem translocation of Na+ contribute tothe adverse effects of salt in this species. Restriction ofK+ supply occurs by diminished K+ uptake and even more by reducedK+ cycling within the plant. Key words: Lupinus albus, salt stress, phloem transport, xylem transport, partitioning, carbon, nitrogen, K+, Na+, CI  相似文献   

7.
Mitochond$$$a isolated from Jerusalem artichoke tubers oxidizedendogenous NADH by both a piericidin A-sensitive and -resistantdehydrogenase if the level of oxaloacetate was kept low. Inwashed mitochondria the addition of NAD+ stimulated respirationin the presence of a variety of NAD+ -linked substrates. Inmitochondria purified through a sucrose density gradient exogenousNAD+ caused a substantial stimulation of respiration only inthe presence of malate. The apparent Km for malate was 20 mMin the absence of NAD+ and 2 mM in the presence of exogenousNAD+ The products of malate oxidation were altered by the additionof exogenous NAD+. Oxaloacetate and pyruvate were produced inequal amounts in the absence of added NAD+, but in the presenceof exogenous NAD+ more pyruvate was formed. The rapid oxidationof malate in the absence of added NAD+ required phosphate whilethe NAD+-stimulated component was not affected by the absenceof phosphate. Phenylsuccinate inhibited the reduction of exogenousNAD+ by malate; this compound was found to inhibit isolatedma!ate dehydrogenase and mahe enzyme. Several lines of evidencesuggest that electron flux through one of the NADH dehydrogenasesystems may directly affect the flow through the other dehydrogenases.  相似文献   

8.
The aim of this study was to investigate changes in cell wallchemical composition and polymer size in the root tip of intactcotton seedlings (Gossypium hirsutum L. cv. Acala SJ-2) grownin saline environments, in order to relate the interaction betweenhigh salinity and root growth to possible changes in cell wallmetabolism. Cotton seedlings were grown in modified Hoagland nutrient solutionwith various combinations of NaCl and CaCl2. Cell walls werefractionated into four fractions (pectin, hemicellulose 1 and2, cellulose), and analysed for their total sugar content, neutralsugar composition and size of polysaccharides. At 1 mol m–3Ca, 150 mol m–3 NaCl resulted in a significant increasein the cell wall uronic acid content, but a reduction in cellulosecontent on a per unit dry weight basis. Supplemental Ca overcamethe inhibitory effect of high Na on cellulose content. The neutralsugar composition of the cell wall fractions showed no majorchanges caused by varied Na/Ca ratios. Determinations of polysaccharidepolymer size showed that high Na at 1 mol m–3 Ca led toan increase in the amount of polysaccharides of intermediatemolecular size and a decrease in that of small size in the hemicellulose1 fraction, indicating a possible inhibition of polysaccharidedegradation by high Na. This change was not observed in the10 mol m–3 Ca treatments. The results reveal a relationshipbetween the effects of high salinity on root growth and cellwall metabolism, particularly in regard to cellulose biosynthesis Key words: Gossypium hirsutum, salinity, root, cell wall  相似文献   

9.
Potassium-Ammonium Uptake Interactions in Tobacco Seedlings   总被引:6,自引:0,他引:6  
Short-term (< 12 h) uptake experiments were conducted with6–7-week-old tobacco (Nicotiana tabacum L. cv. Ky 14)seedlings to determine absorption interactions between K+ andNH4+. At equal solution concentrations (0.5 mol m–3) netK+ uptake was inhibited 30–35% by NH4+ and NH4+ uptakewas decreased 9–24%. Removal of NH4+ resulted in completerecovery in K+ uptake rate, but NH4+ uptake rate did not recoverwhen K+ was removed. In both cases, inhibition of the uptakerate of one cation saturated as the concentration of the othercation was increased up to 0.5 mol m–3. The relative effectof K+-NH4+ interactions was not altered when Cl- was replacedwith SO42–, but the magnitudes of the uptake rates wereless in the absence of Cl-. The Vmax for NH4+ uptake was reducedfrom 128 to 105 µmol g–1 dry wt. h–1 in thepresence of 0.5 mol m–3 K+ and the Km for NH4+ doubledfrom 12 to 27 mmol m–3 in the presence of K+. The resultsof these K+-NH4+ experiments are interpreted as mixed-noncompetitiveinteractions. However, an enhanced efflux of K+ coupled to NH4+influx via an antiporter cannot be ruled out as contributingto the decrease in net K+ uptake. Key words: Nicotiana tabacum, K+, NH4+, Uptake interactions  相似文献   

10.
Siddiqi, M. Y. and Glass, A. D. M. 1987. Regulation of K+ influxin barley: Evidence for a direct control of influx by K+ concentrationof root cells.—J. exp. Bot. 38: 935–947. The kinetics of K+ (86Rb+) influx into intact roots of barley(Hordeum vulgare L. cv. Fergus) seedlings having different combinationsof root and shoot [K+], different growth rates and differentroot:shoot weight ratios were studied. K+ influx was stronglycorrelated with root [K+]; shoot [K+], growth rates, and root:shoot ratios appeared to have little effect on K+ influx. Adetailed study showed that both Vmax and Km for K+ influx wereaffected by root [K+] but not by shoot [K+]. We have suggestedthat factors such as growth rates and root: shoot ratio mayaffect K+ influx indirectly primarily via their influence onroot factors such as root [K+]. We have reiterated that othertypes of kinetic control, e.g. increased or decreased synthesisof ‘carrier systems’, may operate in addition todirect (allosteric?) control of K+ influx by root [K+]. Thenegative feedback signal from root [K+] appeared to be the primeeffector in the regulation of K+ influx. Key words: Barley, K+ influx  相似文献   

11.
Larsson, M., Larsson, C.-M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.I. Inorganic carbon-dependent O2 evolution, nitrate utilizationand nitrogen recycling.—J. exp Bot. 36: 1373–1386 Scenedesmus obtusiusculus Chod. was grown on an inorganic mediumflushed with either air or air supplemented with 3% CO2. Inair-grown cells, O2 evolution dependent on low, but not high,HCO3 concentrations was strongly inhibited by the carbonicanhydrase inhibitor acetazolamide. Cells grown with 3% CO2 exhibitedlow rates of O2 evolution at low external inorganic C; however,after 30 min in air O2 evolution rates at low inorganic C approachedthose of air-grown cells. These results are compatible withthe view that Scenedesmus develops a ‘CO2 concentratingmechanism’ in air, with carbonic anhydrase as an importantconstituent When 3% CO2-grown cells were subjected to air-level of CO2,just a transient decline in NO3 utilization was observed,but in the presence of acetazolamide the rate of the processdecreased drastically in response to the decrease in the CO2level. In CO2-free air NO3 was taken up at high ratesbut in a deregulated manner, leading to release of NH4+. A portionof the NO3 taken up in the absence of CO2 was apparentlyassimilated Cellular nitrate reductase (NR) activity initially decreasedbut subsequently recovered after a transition from 3% CO2 toair. In the presence of acetazolamide, a persistent decreasein NR activity was observed. Cellular glutamine synthetase (GS)activity increased after transition from 3% CO2 to air, theactivity increase being unaffected by acetazolamide. NH4+ releaseto the medium in the presence of L-methionine-D, L-sulphoximine(MSO) transiently increased in 3% CO2-grown cells in responseto a transfer to air. MSO-induced NH4+ release was in fact higherin air-grown cells than in 3% CO2-grown cells. Glycollate wasinitially released after transition from 3% CO2 to air, butthere was no difference in glycollate release between MSO-treatedand untreated cells. In air-adapted Scenedesmus, N recyclingseems to be of minor importance in comparison to primary N assimilation Key words: CO2-fixation, N recycling, nitrate uptake, Scenedesmus  相似文献   

12.
Marques, I. A., Oberholzer, M. J. and Erismann, K. H. 1985.Metabolism of glycollate by Lemna minor L. grown on nitrateor ammonium as nitrogen source.—J. exp. Bot. 36: 1685–1697. Duckweed, Lemna minor L., grown on inorganic nutrient solutionscontaining either NH4+ or NO3 as nitrogen source wasallowed to assimilate [1-14C]- or [2-14C]glycollate during a20 min period in darkness or in light. The incorporation ofradioactivity into water-soluble metabolites, the insolublefraction, and into the CO2 released was measured. In additionthe extractable activity of phosphoenolpyruvate carboxylasewas determined. During the metabolism of [2-14C]glycollate in darkness, as wellas in the light, NH4+ grown plants evolved more 14CO2 than NO3grown plants. Formate was labelled only from [2-14C]glycollateand in NH4+ grown plants it was significantly less labelledin light than in darkness. In NO3 grown plants formateshowed similar radioactivity after dark and light labelling.The radioactivity in glycine was little influenced by the nitrogensource. Amounts of radioactivity in serine implied that thefurther metabolism of serine was reduced in darkness comparedwith its metabolism in the light under both nitrogen regimes.In illuminated NH4+ plants, serine was labelled through a pathwaystarting from phosphoglycerate. After [1-14C]glycollate feedingNH4+ grown plants contained markedly more radioactive aspartateand malate than NO3 plants indicating a stimulated phosphoenolpyruvatecarboxylation in plants grown on NH4+. Key words: Photorespiration, glycollate, nitrogen, Lemna  相似文献   

13.
The influences of Ca2+-free solutions and increasing K+ concentrationson the H14CO3 influx capacity of Chara corallina wereinvestigated. It was found that contact with Ca2–freesolutions resulted in a gradual reduction in the H14CO3influx capacity of these cells. Recovery of this influx capacity,following the return of Ca2+ to the experimental solution, followeda ‘mirror-image’ of the time course of decay. Potassium concentrations above a certain critical value (2 mM)induced a rapid reduction in H14CO3 influx capacity.Normal activity was recovered within 60–90 min followingthe return to 0.2 mMK+ solutions. It was also shown that 10mM K+ can be used to determine the relative contribution of14C supplied by diffusion of 14CO2 and transport of H14CO3.The Ca2+ and K+ results are discussed in relation to the effectsof these treatments on the electrical properties of the plasmalemma.  相似文献   

14.
We studied the influence of internal ammonium and nitrate contenton the temperature response of ammonium and nitrate uptake inboth chilling sensitive and chilling resistant tomatoes. Threetaxa were examined: Lycopersicon esculentum Mill. cv. T-5, achilling sensitive cultivar, Lycopersicon hirsutum Humb. andBompl. LA 1264, a wild, chilling sensitive accession from thelowlands of Ecuador, and Lycopersicon hirsutum LA1778, a chillingresistant accession from the highlands of Peru. Short exposures(4 h) of L. esculentum cv. T-5 to chilling temperatures irreversiblyinhibited ammonium absorption for at least 6 h. Nitrate absorptionin this taxon and ammonium and nitrate absorption in the L.hirsutum accessions recovered fully and immediately from suchexposures. The chilling resistant accession, L. hirsutum LA1778,showed a lower Q10 for ammonium absorption (1?54?0?10, mean?s.e.)than its chilling sensitive relatives, L. hirsutum LA1264 (2?37?0?35)and L. esculentum cv. T-5 (1?92?0?11). The temperature responseof nitrate absorption depended on internal nitrate status; plantsgrown at high levels of ammonium and nitrate (200 mmol m–3)showed higher Q10's for nitrate uptake (2?29?0?10) than thosedepleted of internal (1?86?0?12). Key words: Lycopersicon, ammonium, nitrate, temperature response, chilling  相似文献   

15.
The circadian rhythm of CO2 output in leaves of Bryophyllumfedtschenkoi damps out after 3–4 d in continuous darknessand a CO2-free air stream at 15°C. The rhythm is reinitiatedafter a single exposure to white light of 2, 4, 6 or 8 h duration,damps out again after a further 3–4 d and can be reinitiatedfor a second time by a further exposure to light. During the exposure to light there is a burst of CO2 outputconsistent with the decarboxylation of malate, and the rhythmbegins afterwards with an initial high rate of CO2 fixation.Malate gradually accumulates in the leaves in continuous darknessto attain a maximum value (35 mol m–3) at the time whenthe circadian rhythm disappears, and decreases to a low value(19 mol m–3) after a 4 h exposure to light which reinitiatesrhythmicity. These results support the hypothesis that damping of the rhythmof CO2 output in continuous darkness is due to the accumulationof malate in the leaf cells, eventually reaching such a levelthat its removal from the cytoplasm into the vacuole cannottake place, with the result that PEPc activity, upon which therhythm of CO2 output depends, remains allosterically inhibited. Key words: CAM, circadian rhythm, Bryophyllum, CO2-fixation, malate metabolism  相似文献   

16.
A study was made of the incorporation of 14C by intact leavesof Coffea arabica (cultivars Mundo Novo, Catuai, 1130–13,and H 6586–2) and Coffea canephora (cultivar Guarini)supplied with gas mixtures containing 14CO2 under controlledconditions. Samples of the leaves were combusted and the 14Cin the CO2 produced measured using a liquid scintillation counter.The results were used to estimate photosynthetic rates. Theeffects of changing the partial pressures of O2 and CO2 on thephotosynthetic rate were studied and estimates made of the CO2compensation point and photorespiration. The data obtained show differences between the mean net photosyntheticrates of the C. arabica cultivars (6·14 mg CO2 dm–2h–1) and the mean rate for the C. canephora cultivar (3·96mg CO2 dm–2 h–1). The cultivar of the latter speciesphotorespired more rapidly than the cultivar Catuai of C. arabica.Rates of photosynthesis in coffee measured using the 14CO2 methodwere similar to rates obtained by others using an infrared gasanalyser. The 14CO2 method proved to be reliable for photosyntheticmeasurements and the apparatus is suitable for use in fieldconditions.  相似文献   

17.
Barley (Hordeum vulgare L.) varieties differed in their raponseto [K+]0, in terms of their utilization efficiencies (UE = freshweight. concentration of [K+]1–1). At low [K+]0, Compana,an efficient-non-responder demonstrated superior utilizationof absorbed K+. On the other hand, at high [K+]0, Fergus (anefficient responder) and BT 334 (an inefficient responder) hadhigher UE values for K+ than Compana which performed poorlyat this [K+]0. Kinetic parameters for K+ activation of the enzyme pyruvatekinase from 12 barley varieties, representing a range of UEvalues, were determined. Varieties showed substantial differencesin their Vmax values (P<0·01). Compana, an efficientvariety, had the highest Vmax (31 µmol g–1 freshwt. h–1) which was about 50% higher than that of Mingo,an inefficient variety. By contrast, Km values for the enzymeswere not significantly different among varieties The mean valuesfor all varieties (3·9±0·15 mol m–3K+) is far below the estimated cytoplasmic [K+] (100-200 molm–3). It is, therefore, unlikely that differences in theutilization of K+ by these varieties can be explained on thebasis of differential requirements for (K+) activation of theseenzymes. Alternative possibilities for differences in the utilizationof K+ are discussed. Key words: K+ utilization efficiency, Pyruvate kinase, Barley varieties  相似文献   

18.
Poly(A)+ mRNA was isolated from leaves of potato plants (Solatiumtuberosum L. cv. Desiree) according to standard protocols. Thispoly(A)+ mRNA was injected via glass microcapillaries into oocytesthat were surgically removed from the African clawed toad Xenopuslaevis. As a control, oocytes were either injected with H20or remained untreated. Three days after injection the oocyteswere analyzed by two electrode voltage clamping. Current voltageanalysis revealed that a K+ channel from potato was functionallyexpressed in injected oocytes. The identity of this K+ channelwas confirmed by its substrate specificity and a shift in thereversal potential. In particular, when the outside K+ concentrationwas increased the reversal potential of poly(A)+ injected oocytesshifted to more positive values. Furthermore, K+ outward currentsdeclined when the outside K+ concentration was raised from 0.1to 100 mM. Inward currents increased with an elevation of theK+ concentration. Several Pharmaceuticals were tested for theirpotential to block this K+ channel. As a result, the channelwas completely blocked by BaCl2. A three state reaction kineticmodel was used to simulate the currents through the K+ transportprotein as function of the extracellular K+ concentration. Inparticular, the simulation revealed current voltage relationsthat exactly matched the measured ones. Saturation of currentvoltage curves emerged from the simulation as a consequenceof high extracellular potassium concentration. (Received November 7, 1997; Accepted March 21, 1998)  相似文献   

19.
The patch-clamp technique was used to study effect of the Ca2+on K+ channels in the plasma membrane of protoplasts isolatedfrom tobacco (Nicotiana tabacum L., cv. Bright Yellow) culturedcells in suspension. The outward rectifying whole-cell K+ currentswere not affected by in-tracellular Ca2+, but they were reducedwith increasing extracellular Ca2+. Neither extracellular norintracellular Ca2+ affected the permeability ratios (pK+/PNa+)of the plasma membrane. These results suggest that the inhibitionof outward-rectifying K+ channels by extracellular Ca2+may partiallycontribute towards the mitigation of detrimental effects ofsalinity on growth by extracellular Ca2+. (Received January 19, 1998; Accepted July 30, 1998)  相似文献   

20.
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   

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