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1.
When leaf discs of Xanthium strumarium L. a C 3 plant, or Zeamays L. a C 4 plant, are incubated in 1-aminocyclopropane-l-carboxylicacid (ACC) in closed flasks, ethylene is released. The rateof ethylene release appears to be dependent on the levels oflight and CO 2 available for photosynthesis in the tissues. In Xanthium the rate of ethylene release is lower in the lightthan in the dark regardless of the presence or absence of addedbicarbonate as a source of CO 2. The inhibition of ethylene releaseis most apparent in the absence of added bicarbonate (i.e. atthe CO 2 compensation point), and at light intensities sufficientto saturate photosynthesis (had the CO 2 level in the test flaskbeen maintained). In contrast, light dramatically promotes therate of ethylene release from Zea leaf tissue when the CO 2 levelis maintained above the CO2 compensation point. The rate ofethylene release from either Xanthium or Zea, incubated withor without added bicarbonate, does not appear to be alteredby further increasing the light intensity above the minimallevels sufficient to saturate photosynthesis. In the closed system used in these studies and at a light intensitysufficient to saturate photosynthesis, Xanthium and Zea leaftissue both appear to release comparable amounts of ethylenefrom ACC when the data is expressed on a chlorophyll basis.However, in Xanthium the rate of ethylene release is similarin light and dark, while in Zea the rate in the light is muchgreater than in the dark when the data is expressed either ona leaf area or on a chlorophyll basis. It is suggested thatthe different responses of these tissues to light/dark transientsmay reflect differences in their ability to metabolize ACC and/ordifferences in their ability to retain and metabolize ethyleneitself. 相似文献
2.
The effects of long-term and transient exposure to elevatedCO 2 concentrations on photosynthetic gas exchange and ethylenerelease by tomato leaves were investigated. The net CO 2 assimilationrate was enhanced when leaf tissue grown at ambient (35 Pa CO 2)levels was assayed at 100 Pa CO 2. Leaf tissue grown at high(130 Pa) CO 2 exhibited a lower net CO 2 assimilation rate athigh CO 2 levels than leaf tissue grown at ambient (35 Pa) CO 2.This decrease in CO 2 exchange rate in response to growth athigh CO 2 is typical of C 3 species. Rates of endogenous and 1-aminocyclopropane-l-carboxylicacid (ACC)-stimulated ethylene release from leaf tissue wereenhanced by exposure to elevated CO 2 levels whether the leaftissue had been grown at ambient or enriched CO 2 levels. Thedata demonstrate that CO 2 enhanced C 2H 4 release from leaf tissuein response to both short-term perturbations in CO 2 concentrationand long-term growth and development under high CO 2. Prolongedgrowth at elevated CO 2 concentrations induced a higher endogenousrate of C 2H 4 release relative to that of leaf tissue grown atlower CO 2 levels. Leaf tissue from all leaf positions of plantsgrown at high CO 2 consistently evolved more C 2H 4 than correspondingtissue from ambient-grown plants when assayed under standardizedconditions. Endogenous (ACC) tissue contents and rates of ACC-stimulatedethylene release were also higher at all leaf positions in CO 2-enrichedtissue. Thus the higher rates appeared to be due to both higherendogenous precursor (ACC) levels in the tissue and greaterACC to C 2H 4 conversion capacity. Growth at elevated CO 2 levelsresulted in a persistent increase in the rate of endogenousC 2H 4 release in leaf tissue. The capacity for increased ethylenerelease in response to CO2 did not decline after prolonged growthat high CO 2. Key words: CO 2enrichment, ethylene, leaves, tomato 相似文献
3.
Dunlap, J. R. 1988. Regulation of ACC-dependent ethylene productionby excised leaves from normal and albino Zea mays L. seedlings.J.exp. Bot. 39: 10791089. Albino corn ( Zea mays L.) seedlings lacking natural leaf pigmentswere obtained by germinating seeds treated with fluridone, aninhibitor of carotenoid biosynthesis. Basal rates of ethyleneproduction were less than 2.0 nl g 1 fr. wt h 1in both treated (albino) and untreated (normal) leaves but increasedby 10- to 20-fold in the presence of added ACC. ACC-dependentethylene production (ADEP) was inhibited by cobalt or cyanideions and stimulated by NaHCO 3, CO 2 and light. ADEP in both tissueswas stimulated by glucose, fructose, galactose and sucrose.The accumulation of respiratory CO 2 did not account for thecarbohydrate response. The decline in the ADEP characteristicof albino leaf tissue was slowed by incubation in the presenceof sucrose. IAA and ABA stimulated ADEP in normal leaves butinhibited ADEP in albino leaves. Sucrose-stimulated ADEP wasinhibited in albino leaf tissue treated with IAA or ABA indicatinga possible role for the chloroplast in carbohydrate-facilitatedADEP. However, results from this study suggest that chloroplastsperform a function in the regulation of ethylene productionby leaf tissue that extends beyond merely influencing internallevels of CO 2. In the absence of detectable ACC, EFE was responsiblefor the entire series of responses expressed in regulation ofethylene biosynthesis by corn seedling leaf tissue. Key words: Corn, ethylene, sugars, phytohormones 相似文献
4.
The effect of light and CO 2 on both the endogenous and 1-aminocyclopropane-1-carboxylic acid (ACC)-dependent ethylene evolution from metabolically active detached leaves and leaf discs of Gomphrena globosa L. is reported. Treatment with varying concentrations of ACC did not appear to inhibit photosynthesis, respiration, or stomatal behavior. In all treatments, more ethylene was released into a closed flask from ACC-treated tissue, but the pattern of ethylene release with respect to light/dark/CO 2 treatments was the same. Leaf tissue in the light with a source of CO2 sufficient to maintain photosynthesis always generates 3 to 4 times more ethylene than tissue in the dark. Conversely, the lowest rate of ethylene release occurs when leaf tissue is illuminated and photosynthetic activity depletes the CO2 to the compensation point. Ethylene release in the dark is also stimulated by CO2 either added to the flask as bicarbonate or generated by dark respiration. Ethylene release increases dramatically and in parallel with photosynthesis at increasing light intensities in this C4 plant. Ethylene release appears dependent on CO2 both in the light and in the dark. Therefore, it is suggested that the important factor regulating the evolution of ethylene gas from leaves of Gomphrena may be CO2 metabolism rather than light per se. 相似文献
5.
Woodrow, L. and Grodzinski, B. 1987. Ethylene evolution trombracts and leaves ol Poinsettia, Euphorbia pulcherrima Willd.J.exp. Bot. 38: 20242032. Ethylene release from fully expanded, red and white bracts andleaves of poinsettia, Euphorbia pulcherrima Willd., was compared.On a laminar (area) basis leaves contained about 50 times morechlorophyll and demonstrated 10 times the photosynthetic rateof the bracts. Both tissues contained starch, however, solublecarbohydrate in the bracts consisted primarily of reducing hexoseswhile the leaves contained mainly sucrose for translocation.The total free alpha-amino nitrogen content of the bract tissuewas twice that of the leaf tissue. The leaves contained moreACC (1-aminocyclopropane-1-carboxylic acid) and produced proportionallymore endogenous C 2H 4 than either the red or white bracts. ACC-stimulated 2H 4 release was also greatest from the green tissue indicatingthat the EFE (ethylene forming enzyme) was most active in theleaves. The specific activity of the 14C 2H 4/ 12C 2H 4 releasedfrom [2,3- 14C]ACC confirmed ACC as the primary precursor ofC 2H 4 in this tissue. Ethylene release from the non-photosynthetic,bract tissue was not markedly affected by alterations in CO 2or light conditions. In green leaf tissue endogeneous ethylenerelease increased from 1·5 to 6·0 pmol C 2H 4 cm 2h 1 while ACC-stimulated ethylene release increased from10 to 35 pmol C 2H 4 cm 2 h 1 as the CO 2 partial pressureincreased from 100 to 1 200 µbar. Key words: Poinsettia, ethylene, bracts 相似文献
6.
The role of photosynthesis in inducing adventitious bud formationon leaf segments of Heloniopsis orientalis was investigated.The effect of white light reached a maximum at about l25 J?m 2?sec 1.White, red, blue and far-red light were effective in inducingbud formation, but green light was not. In darkness, bud formationwas induced if sugar was added to the nutrient medium. The photosyntheticinhibitors DCMU and AT blocked the effect of light. Bud formationwas inhibited in CO 2-free air. The requirement of sucrose forbud formation in darkness could be replaced by citrate. It wasconcluded from these results that light appears to induce budson leaf segments through some processes dependent upon photosynthesis. (Received January 11, 1978; ) 相似文献
7.
Chlorella pyrenoidosa can utilize sodium acetate as a carbonsource for growth in the light. Growth proceeds under aerobicconditions both in the presence and in the absence of carbondioxide, but under anaerobic conditions only in its presence.The assimilation of acetate does not result from oxidation tocarbon dioxide followed by photosynthetic fixation because theproducts of 14C-acetate assimilation are different from theproducts of 14CO 2 fixation in the presence of unlabelled acetate. In aerobic conditions 10- 6 M DCMU induces a pattern of acetateassimilation in the light similar to that in the dark. Thus,in the presence of DCMU in the light, less acetate carbon isincorporated into cells, particularly into lipids, polysaccharide,and protein, and more is released as carbon dioxide than inits absence. The effect of 4 x 10 -3 M MFA on acetate assimilationin the presence of 10 -6 M DCMU is the same in light and dark.Acetate assimilation is unaffected by desaspidine and sodiumbisulphite. The mean generation time of C. pyrenoidosa growing on acetatein the light under aerobic conditions is 20 hours. When 10 -5M DCMU is added the mean generation time is 60 hours, the sameas that for Chlorella growing on acetate in the dark. The activityof the enzymes of the glyoxylate cycle, isocitrate lyase (E.C.4.1.3.1.)and malate synthetase (E.C.4.1.3.2.) is repressed in the light,but activity of both enzymes increases markedly when DCMU isadded. 相似文献
8.
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 m 3 MSX, an inhibitorof the GS reduced uptake in both the light and dark. Photosyntheticincorporation of 11CO 2 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 the 11Cl-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% O 2 which permitted dark respiration to proceed. After aninitial feeding of either 11CO 2 or [ 13N]-ammonia at ambient(21%) O 2 exposure of the source leaf to 2% O2, or 50% O 2 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, CO 2, NH 3, Leaves, Helianthus annuus, Lupinus albus 相似文献
9.
Two Phaseolus vulgaris L. cultivars were grown at 20/15, 25/20,and 30/25 °C day/night temperatures in growth chambers witha 16 h thermoperiod corresponding to the photoperiod. When thefirst trifoliolate leaf was fully expanded rates of CO 2 exchange(CER) were measured at 27 °C and saturating light usinginfrared gas analysis. Stomatal (r s) and mesophyll resistances,CO 2 compensation points, activities of the enzymes ribulosebisphosphate carboxylase (RuBPCase), glycolate oxidase (GAO),malate dehydrogenase (MDH), and fructose-1, 6 diphosphate (FDP),chlorophyll content, Hill activities, and leaf anatomy at boththe light and electron microscope level were also investigatedin these leaves. Rates of CO 2 exchange in the light, transpiration rate, andchlorophyll content increased with increasing growth temperaturewhile leaf thickness, specific leaf weight, RuBPCase activity,compensation point, and stomatal resistance decreased. Mesophyllresistance also decreased when calculated assuming zero chloroplastCO 2 concentration ( rm, o), but not when calculated assuminga chloroplast CO 2 concentration equal to the CO 2 compensationconcentration ( rm, g). Average leaf size was maximal in 25/20°C plants while dark respiration, MDH activity, stomataldensity, and starch were minimal. The activities of GAO andFDP and Hill activity were not affected by temperature pretreatment. 相似文献
10.
The effects of peeling the epidermis off Bryophyllum daigremontianumleaves on CO 2 uptake in light and darkness were investigated.Light-induced CO 2 uptake in the daytime was markedly enhancedin the peeled leaves, but dark fixation of CO 2 carried out atmidnight was not. The difference in promotion of CO 2 uptakein light and darkness was due to stomatal closing in the dayand opening at night. Also, deacidification was strikingly inhibitedby CO 2 in peeled leaves. (Received February 3, 1977; ) 相似文献
11.
Predicting responses of plant and global carbon balance to theincreasing concentration of carbon dioxide in the atmosphererequires an understanding of the response of plant respirationto carbon dioxide concentration ([CO 2]). Direct effects of thecarbon dioxide concentration at which rates of respiration ofplant tissue are measured are quite variable and their effectsremain controversial. One possible source of variation in responsivenessis the energy status of the tissue, which could influence thecontrol coefficients of enzymes, such as cytochrome-c oxidase,whose activity is sensitive to [CO 2]. In this study we comparedresponses of respiration rate to [CO 2] over the range of 60to 1000 µmol mol -1in fully expanded leaves of four C 3andfour C 4herbaceous species. Responses were measured near themiddle of the normal 10 h dark period, and also after another24 h of darkness. On average, rates of respiration were reducedabout 70% by the prolonged dark period, and leaf dry mass perunit area decreased about 30%. In all species studied, the relativedecrease in respiration rate with increasing [CO 2] was largerafter prolonged darkness. In the C 3species, rates measured at1000 µmol mol -1CO 2averaged 0.89 of those measured at 60µmol mol -1in the middle of the normal dark period, and0.70-times when measured after prolonged darkness. In the C 4species,rates measured at 1000 µmol mol -1CO 2averaged 0.79 of thoseat 60 µmol mol -1CO 2in the middle of the normal dark period,and 0.51-times when measured after prolonged darkness. In threeof the C 3species and one of the C 4species, the decrease in theabsolute respiration rate between 60 and 1000 µmol mol -1CO 2wasessentially the same in the middle of the normal night periodand after prolonged darkness. In the other species, the decreasein the absolute rate of respiration with increase in [CO 2] wassubstantially less after prolonged darkness than in the middleof the normal night period. These results indicated that increasingthe [CO 2] at the time of measurement decreased respiration inall species examined, and that this effect was relatively largerin tissues in which the respiration rate was substrate-limited.The larger relative effect of [CO 2] on respiration in tissuesafter prolonged darkness is evidence against a controlling roleof cytochrome-c oxidase in the direct effects of [CO 2] on respiration. Copyright 2001 Annals of Botany Company Carbon dioxide, respiration, Abutilon theophrasti(L.), Amaranthus retroflexus(L.), Amaranthus hypochondriacus (L.), Datura stramonium(L.), Helianthus annuus(L.), Solanum melongena(L.), Sorghum bicolor(L. Moench), Zea mays 相似文献
12.
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 (C 4) andsunflower (C 3) leaves. The photosynthetic CO 2 fixation products,the release of 14CO 2 in light and dark following photosynthesisin 14CO 2, chlorophyll a: b ratio, gross leaf photosyntheticrate and dry matter production rate were also studied. The resultsshow that jute is a C 3 plant. Key words: Jute, Corchorus olitorius, C 3 photosynthesis 相似文献
13.
Esashi, Y., Hase, S. and Kojima, K. 1987. Light actions in thegermination of cocklebur seeds. V. Effects of ethylene, carbondioxide and oxygen on germination in relation to light.J.exp. Bot. 38: 702710. Effects of ethylene, CO 2 and O 2 on the germination of after-ripenedupper cocklebur ( Xanthium pennsylvanicum Wallr.) seeds wereexamined in relation to pre-irradiation by red (R) or far-red(FR) light In order to remove the pre-existing Pfr, seeds weresoaked in the dark for various periods prior to light irradiationand gas treatments. Regardless of light, 0.3 Pa C 2H 4 promotedgermination at 23 ?C, but it strongly inhibited germinationwhen applied at 33 ?C, the optimal temperature for the germinationof this seed. However, delayed application of C 2H 4 during 33?C incubation stimulated germination independently of lightin a similar manner to that seen at 23 ?C. It is, therefore,suggested that the germination-regulating action of C2H4 iscompletely independent of phytochrome. In contrast, the germination-promoting effect of 30 kPaCO 2 was pronounced only when the seeds were previously irradiatedby R, regardless of temperature, suggesting that CO 2 actionto promote germination depends upon Pfr. A synergism betweenCO 2 and C 2H 4 at 23 ?C was observed only in the germination ofseeds pre-irradiated by R, while at 33 ?C an antagonism occurredindependently of light. The stimulation of C 2H 4 production byCO 2 was most striking in the cotyledonary tissue pre-irradiatedby R. However, the R-dependent enhancement of CO 2-stimulatedC 2H 4 production was negated by the subsequent FR and it wasnot found in the presence of 1-aminocyclopropane-1-carboxylicacid (ACC). Moreover, the R dependency of the germination-promotingCO 2 effect disappeared in the presence of C 2H 4. The R-dependentC 2H 4 production enhanced by CO 2 may thus be involved, at leastpartially, in some step of conversion from methionine to ACC. The germination-promoting effect of C 2H 4, but not CO 2, was enhancedby O 2 enrichment regardless of light. However, the germination-promotingeffect of pure O 2 itself appeared to depend upon pre-irradiationwith R Key words: Carbon dioxide, cocklebur seed, ethylene, far-red light, germination, oxygen, red light, Xanthium pennsyloanicum 相似文献
14.
We investigated the effect of anaerobiosis on deacidificationof the leaf of a CAM plant, Bryophyllum calycinum. When leafsegments were placed in a stream of N 2 in the dark, deacidificationwas suppressed remarkably. A similar effect also was observedwhen segments were placed in the light, provided that thesesegments were infiltrated with DCMU before use. Conversion ofchlorophylls into phaeophytins, wilting of the leaf segment,and a loss of the photosynthetic CO 2-fixation activity wereobserved simultaneously during the incubation period. We confirmed that these phenomena are caused by damage to cellscaused by the enormous amount of acids stored in the vacuolethat are extruded into the cytoplasm. (Received June 13, 1979; ) 相似文献
15.
It has been established that Kalanchoe blossfeldiana and Xanthiumpensylvanicum require CO 2 during the light period of short daysfor successful photoperiodic induction of flowering, even ifall but the induced leaf are held in normal air. In X. pensylvanicumfloral induction in normal air was independent of the starchstatus of the leaves but when reserves were reduced, lack ofCO 2 in the light suppressed floral induction to an even greaterextent. Injection into the induced leaf ( Kalanchoe) or leaftip feeding ( Xanthium) of carbohydrates, organic and amino acidsor several other metabolites failed to substitute for the CO 2requirement for induction. A small response was produced by10 mg ml 1 sucrose in X. pensylvanicum while in normalair 25 parts 10 6 ATP reduced the time to flowering in K. blossfeldiana and 10 4 M proline was inhibitory. Anexperiment on the light requirement established a need for redlight ( max 660 nm) during photoperiods but red light alonedid not facilitate maximal induction. It is concluded that someearly, possibly labile, product of photosynthetic CO 2 fixationis essential to floral induction in these species. 相似文献
16.
The mechanism of light-inhibited ethylene production in excised rice ( Oryza sativa L.) and tobacco ( Nicotiana tabacum L.) leaves was examined. In segments of rice leaves light substantially inhibited the endogenous ethylene production, but when CO 2 was added into the incubation flask, the rate of endogenous ethylene production in the light increased markedly, to a level which was even higher than that produced in the dark. Carbon dioxide, however, had no appreciable effect of leaf segments incubated in the dark. The endogenous level of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, was not significantly affected by lightdark or CO 2 treatment, indicating that dark treatment or CO 2exerted its effect by promoting the conversion of ACC to ethylene. This conclusion was supported by the observations that the rate of conversion of exogenously applied ACC to ethylene was similarly inhibited by light, and this inhibition was relieved in the presence of CO 2. Similar results were obtained with tobacco leaf discs. The concentrations of CO 2 giving half-maximal activity was about 0.06%, which was only slightly above the ambient level of 0.03%. The modulation of ACC conversion to ethylene by CO 2 or light in detached leaves of both rice and tobacco was rapid and fully reversible, indicating that CO 2 regulates the activity, but not the synthesis, of the enzyme converting ACC to ethylene. Our results indicate that light inhibition of ethylene production in detached leaves is mediated through the internal level of CO 2, which directly modulates the activity of the enzyme converting ACC to ethylene.Abbreviation ACC
1-aminocyclopropane-1-carboxylic acid
Recipient of a Republic of China National Science Council Fellowship 相似文献
17.
For a deeper understanding of the germination of chickpea( Cicer arietinum) seeds, which is dependent upon ethylene synthesis,a crude extract containing authentic ACC oxidase (ACCO) activitywas isolated in soluble form from the embryonic axes of seedsgerminated for 24 h. Under our optimal assay conditions (200mM HEPES at pH 7.0, 4µM FeS0 4, 6 mM Naascorbate,1 mM ACC, 20% 0 2, 3% CO 2 , and 10%glycerol) this enzyme was5fold more active than under the conditions we used initiallyin the present work. The enzyme has the following K m: 28 µMfor ACC (approximately 4fold less than in vivo), 1.2%for O 2 (in the presence of an optimal CO 2 concentration of 3%),and 1% for CO 2 in the presence of O 2 (20%). The enzyme is inhibitedby phenanthroline (PNT) (specific chelating agent of ferrousion), and competitively inhibited (K 1, =0.5 mM) by 2aminoisobutyricacid (AIB), and the enzymatic activity was not detectable inthe absence of CO 2. Under optimal assay conditions, the enzymehas two optimum temperatures (28 C and 35 C) and is inhibitedby divalent metal cations (Zn 2+> CO 2+>Ni 2+>Cu 2+>Mn 2+>Mg 2+) and by salicylic acid, propylgallate, carbonyl cyanidemchlorophenyl hydrazone (CCCP), dinitrophenol (DNP),and Nabenzoate. The in vitro ACCO activity which we recoveredin soluble form is equivalent to approximately 8085%of the apparent activity evaluated in vivo. Key words: ACC oxidase, Cicer arietinum, ethylene, germination, seeds 相似文献
18.
Pretreatment by darkness increased chilling (4°C) injuryin whole cotton ( Gossypium hirsutum L.) seedlings and isolatedcotyledonary tissue. Addition of sucrose in the dark periodprevented the effect of darkness. Application of the photosyntheticinhibitor DCMU in light simulated the effect of darkness. ABA(10 5 M) decreased chilling injury when applied in lightas a pretreatment before the onset of chilling. The same pretreatmentin darkness was almost ineffective, unless sucrose was added.ABA applied in light together with DCMU was ineffective in decreasingchilling injury. Lower light intensity resulted in increasedchilling injury and a decreased effect of ABA in the preventionof chilling injury. The antimicrotubular drug colchicine increased the chillinginjury. Pretreatment with ABA in light decreased the chillingand colchicine injury while the same pretreatment in darknesswas ineffective. These results suggest that a deficiency of a photosyntheticproduct increases the chilling sensitivity of the tissue. ABAapparently increases chilling resistance through a metabolicprocess which depends on photosynthetic activity.
3 Incumbent of the Seagram Chair in Plant Sciences (Received November 20, 1980; Accepted January 31, 1981) 相似文献
19.
Conditions and maintenance of growth were chosen so that plantsof Clusia minor L. were obtained which showed the C 3- and CAM-modes of CO 2-exchange, respectively. C. minor is known to accumulateconsiderable amounts of citric acid in addition to malic acidduring the dark-phase of CAM. 14CO 2-pulse-chase experiments were performed with these plants.Patterns of labelling during the pulse and redistribution oflabel during the chase in the C 3-mode were as expected for C 3-photosynthesis.Pulse-labelling in the CAM-mode during the last hour of thelight period, during the first part of the dark period and duringthe last hour of the dark period always led to an almost exclusiveincorporation of label into malate. Redistribution of labelfrom malate after the pulse at the end of the dark period duringthe chase in the subsequent light period followed the patternexpected for light-dependent reassimilation of CO 2 remobilizedfrom malate in CAM during the light period. During the chasesin the dark period, label was transferred from l4C-malate tocitrate. This suggests that during accumulation of citric acidin the dark period of CAM in C. minor, citrate is synthesizedin the mitochondria from malate or oxaloacetate after formationof malate via phosphoenolpyruvate carboxylase. The experiment also showed that no labelled compounds are exportedfrom leaves in the CAM-mode during the dark period. In plantsof the C 3-mode the roots proved to be strong sinks. Key words: Clusia minor, labelling, pulse-chase, 14CO 2 相似文献
20.
Young, expanding Xanthium leaves had many soluble proteins;older leaves had progressively fewer. The leaves that grew themost rapidly incorporated the most 14CO 2 into their proteins.The relative intensity of 14CO 2 incorporation into the differentsoluble proteins changed with leaf development. (Received November 17, 1969; ) 相似文献
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