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1.
The rates of CO2 assimilation by potted spray carnation plants(cv. Cerise Royalette) were determined over a wide range oflight intensities (45–450 W m–2 PAR), CO2 concentrations(200–3100 vpm), and leaf temperatures (5–35 °C).Assimilation rates varied with these factors in a way similarto the response of single leaves of other temperate crops, althoughthe absolute values were lower. The optimal temperature forCO2 assimilation was between 5 and 10 °C at 45 W m–2PAR but it increased progressively with increasing light intensityand CO2 concentration up to 27 °C at 450 W m–2 PARand 3100 vpm CO2 as expressed by the equation TOpt = –6.47-h 2.336 In G + 0.031951 where C is CO2 concentration in vpmand I is photo-synthetically active radiation in W m–2.CO2 enrichment also increased stomatal resistance, especiallyat high light intensities. The influence of these results on optimalization of temperaturesand CO2 concentrations for carnation crops subjected to dailylight variation, and the discrepancy between optimal temperaturesfor growth and net photosynthesis, are discussed briefly  相似文献   

2.
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   

3.
It has been confirmed that shading leaves from day 5 onwardslowers the rate of CO2 fixation when they are placed in saturatingirradiances. The reduction due to shade treatment is about 46per cent and a similar reduction in maximum chlorophyll contentof the leaf follows shading. Maximum amounts of total solubleprotein and of Fraction I protein are less in shaded leavesthan in control leaves and prolonged treatment leads to a declinein leaf protein content. The relative amounts of different proteinare also affected by treatment; in control leaves Fraction Iprotein accounts for about 45 per cent of the total but in shadedleaves the value is about 30 per cent. Increases and decreasesin leaf protein amount, with concomitant changes in the ratioof Fraction I to total protein can be brought about by removingshades and re-applying them. Such changes can be induced evenin fully expanded leaves in which net protein synthesis is notusually found. Maximal amounts of leaf protein are found in irradiances of60 W m–2 or more, with lower values at lower light intensities.Where the first leaf is held in a stream of CO2-free air a lowerlevel of protein is found. This, and the ratio of Fraction Ito total protein, are similar to values for shaded leaves, andsuggest the involvement of photosynthetic carbon fixation indetermining leaf protein amount. A 1:1 linear correlation between amount of Fraction I proteinand RuDP carboxylase activity is shown but the rate of CO2 incorporationby leaf extracts is 2–3 times greater than that of theintact leaf. The significance of this and the effect of irradianceon leaf protein amount are discussed.  相似文献   

4.
The rates of net photosynthesis by closed canopies of tomatoplants were measured at three CO2 concentrations and three humiditiesover a range of natural light flux densities. The data havebeen analysed using a model of canopy photosynthesis which allowsfor variation in leaf area index and other leaf and canopy characteristics.The model also deals explicitly with the effects of CO2 concentration,leaf conductance, and photorespiration on the leaf photochemicalefficiency, . The leaves were found to have a photochemicalefficiency in the absence of photorespiration, m, of 12?6 ?10–9 kg (CO2) J–1. At a CO2 concentration of 0?73 ? 10–3 kg m–3 (400vpm) the leaf photochemical efficiency, , and canopy light utilizationefficiency, c, were 18 per cent greater at a vapour pressuredeficit of 0?5 kPa than at 1?0 kPa. At a CO2 concentration of2?2 ? 10–3 kg m–3 (1200 vpm) they were only 5 percent greater.  相似文献   

5.
Effects of CO2-Enrichment on the Growth of Young Tomato Plants in Low Light   总被引:3,自引:0,他引:3  
HURD  R. G. 《Annals of botany》1968,32(3):531-542
Carbon dioxide-enrichment of young tomato plants grown in controlled-environmentcabinets at low light intensity (14 cal cm–2 day–1,visible radiation) increased their net assimilation rates and,initially, relative growth-rates. Subsequently, the relativegrowth-rate fell to near the rate of non-enriched plants, owingto a fall in leaf-area ratio associated with an increase inleaf dry weight/area. Sowing non-enriched plants a few daysearlier to reach the same total dry weight would not have producedidentical plants. The effects of CO2-enrichment to 1000 vpm could be simulatedby increasing light intensity by approximately one third exceptthat the plants had shorter internodes than those in extra CO2.This was a morphogenetic effect of light since CO2-enrichmentitself produced slightly shorter plants than controls for anequivalent total dry weight. CO2-enrichment did not change the dry-weight distribution inthe plants and had little effect on rate of leaf produoctionor the number of flower primordia. There were no indicationsthat beneficial effects of CO2-enrichment operated other thanthrough increased photosynthesis.  相似文献   

6.
Tomato plants were grown in solution culture in a controlledenvironment at 20 ?C with a 12 h photoperiod of 400 µmolquanta m–2 s–1 PAR with either normal ambient CO2,approximately 340 vpm, or with 1000 vpm CO2. The short- andlong-term effects of CO2 enrichment on photosynthesis were determinedtogether with the levels of ribulose-1, 5-bisphosphate carboxylase(RuBPco) E.C. 4.1.1.39 [EC] protein and activity throughout leafdevelopment of the unshaded 5th leaf above the cotyledons. Thehigh CO2 concentration during growth did not appreciably affectthe rate of leaf expansion or final leaf area but did increasethe fresh weight per unit area of leaf. With short-term CO2enrichment, i.e. only during the photosynthesis measurements,the light-saturated photosynthetic rate (Pmax) of young leavesdid not increase while those reaching full expansion more thandoubled their net rate of CO2 fixation. However, with longerterm CO2 enrichment, i.e. growing the crop in high CO2, theplants did not maintain this photosynthetic gain. While theCO2 concentration during growth did not affect the peak in Pmaxmeasured in 300 vpm CO2 or Pmax in 1000 vpm CO2, RuBPco proteinor its activity, the subsequent ontogenetic decline in theseparameters was greatly accelerated by the high CO2 treatment.Compared with plants grown in normal ambient CO2 the high CO2grown leaves, when almost fully expanded, contained only approximatelyhalf as much RuBPco protein and Pmax in 300 vpm CO2 and Pmaxin1000 vpm CO2 were similarly reduced. The loss of RuBPco proteinmay be a major factor associated with the accelerated fall inPmax since it was close to that predicted from the amount andkinetics of RuBPco assuming RuBP saturation. In the oldest leavesexamined grown in high CO2 additional factors may be limitingphotosynthesis since RuBPco kinetics marginally overestimatedPmax in 300 vpm CO2 and the initial slope of photosynthesisin response to intercellular CO2 was also less than expectedfrom the extractable RuBPco. Key words: Lycopersicon esculentum (Mill.) cv. Findon Cross, CO2 enrichment, acclimation to high CO2, photosynthesis, RuBPco protein and activity  相似文献   

7.
Dark fixation of CO2 by leaf disks or whole leaves taken fromplants of variety ‘Feuer Blute’ was measured using14CO2. Results indicate that dark fixation by leaf disks isindependent of photoperiodic induction of the plant, but isquantitatively related to the amount of light, over a fairlywide range, to which the leaf is exposed in the single precedinglight period.  相似文献   

8.
Effects of C02 enrichment on the rates of net photosynthesis (carbon fixation) and translocation (carbon transport) of tomato leaves were examined on a single mature leaf (seventh basal leaf) of plants grown initially under a light flux density of 40 W m-2 with 350 (control) or 1000 vpm (enriched) CO2, and then exposed for 6 h to various light flux densities (7, 20, 40 and 130 W m-2) or CO2 concentrations (350, 500, 700 and 1000 vpm). When measurements were made in the conditions in which plants were grown, the rates of carbon fixation and carbon transport were 20 and 40% respectively higher in enriched plants than in the control ones. Under conditions different from the growing conditions, the rates of carbon transport in the enriched plants were generally higher than those of the controls with a similar rate of carbon fixation. Leaves grown under a C02 enriched environment have a greater constant supply of mobile leaf assimilate than those under atmospheric C02. The higher efficiency of carbon transport in enriched plants was apparently retained even when the leaf was temporarily exposed to lower levels of light or CO2.  相似文献   

9.
Bunce  James A. 《Annals of botany》1995,75(4):365-368
Previous work has shown that elevated carbon dioxide (CO2) concentrationsin the dark reversibly reduce the rate of CO2 efflux from soybeans.Experiments were performed exposing soybean plants continuallyto concentrations of 350 or 700 cm3 m-3 for 24 h d-1, or to350 during the day and 700 cm3 m-3 at night, in order to determinethe importance of the reduced rate of dark CO2 efflux for plantgrowth. High CO2 applied only at night conserved carbon andincreased dry mass during initial growth compared with the constant350 cm3 m-3 treatment. Long-term net assimilation rate was increasedby high CO2 in the dark, without any increase in daytime leafphotosynthesis. However, leaf area ratio was reduced by thedark CO2 treatment to values equal to those of plants continuallyexposed to the higher concentration. From days 14-21, leaf areawas less for the elevated night-time CO2 treatment than foreither the constant 350 or 700 cm3 m-3 treatments. For the days7-21-period, relative growth rate was significantly reducedby the high night CO2 treatment compared with the 350 cm3 m-3continuous treatment. The results indicate that some functionallysignificant component of respiration was reduced by the elevatedCO2 concentration in the dark.Copyright 1995, 1999 AcademicPress Glycine max L. (Merr.), carbon dioxide, plant growth, respiration  相似文献   

10.
Effects of Certain Inhibitors on Photorespiration by Wheat Leaf Segments   总被引:1,自引:0,他引:1  
The effect on the carbon metabolism of wheat leaf segments ofcertain inhibitors of photorespiration was studied. Sodium 2-hydroxy-3-butynoatesupplied for 40 min resulted in accumulation of 14C in glycolicacid with only a 7% inhibition of photosynthesis; when suppliedfor 90 min, photosynthesis was inhibited by 47%. When 14CO2was replaced by 1000 vpm 12CO2, radioactivity in glycine decreasedbut increased more rapidly in sucrose with less release of 14CO2.Isonicotinyl hydrazide (INH) inhibited photosynthesis from 14CO2by 50% and glycine replaced sucrose as the main product. When,after 15 min, 14CO2 was replaced by 150 vpm 12CO2, in the presenceof INH less 14CO2 was released, 14CO in glycine decreased moreslowly, and less [14CO]sucrose accumulated. Glycidate (potassium2,3-epoxypropionate) at 2 mM had no effect on photosyntheticrate and little effect on carbon metabolism; 20 mM glycidateinhibited photosynthesis by 64% and resulted in less radioactivityin glycine, more in phosphate esters, and less 14CO2 released.When photosynthesis was measured in 1000 vpm CO2 the inhibitorsgave smaller effects on metabolism than during photosynthesisfrom 150 vpm 14CO2 but 20 mM glycidate still resulted in a 42%inhibition of photosynthesis. When U- [14CO]glycerate was appliedto leaf segments in air with 320 vpm 14CO2 the total uptakeof glycerate was not changed by the inhibitors. INH and glycidateboth decreased the amount of glycerate metabolised. More 14COaccumulated in glycine in the presence of INH and in phosphateesters and serine in the presence of glycidate. Hydroxybutynoateincreased the production of glycolate from glycerate but didnot affect the total amount of glycerate metabolised. Although all three inhibitors affected photorespiratory metabolismnone stimulated photosynthesis. The results are consistent withthe main release of CO2 in photorespiration arising from theconversion of glycine to serine.  相似文献   

11.
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   

12.
HEUER  BRURIA; PLAUT  Z. 《Annals of botany》1981,48(3):261-268
The influence of salinity in the growing media on ribulose-1,5-bisphosphate (RuBP) carboxylase and on CO2 fixation by intactsugar beet (Beta vulgaris) leaves was investigated. RuBP carboxylase activity was mostly stimulated in young leavesafter exposure of plants for 1 week to 180 mM NaCl in the nutrientsolution. This stimulation was more effective at the higherNaHCO2 concentrations in the reaction medium. Salinity also enhanced CO2 fixation in intact leaves mostlyat rate-limiting light intensities. A 60 per cent stimulationin CO2 fixation rate was obtained by salinity under 450 µEm–2 s–1. At quantum flux densities of 150 µEm–2 s–1 (400–700 nm) this stimulation was280 per cent. Under high light intensities no stimulation bysalinity was found. In contrast, water stress achieved by directleaf desiccation or by polyethylene glycol inhibited enzymeactivity up to fourfold at –1.2 MPa. Beta vulgaris, sugar beet, ribulose-1, 5-bisphosphate carboxylase, salt stress, water stress, carbon dixoide fixation, salinity  相似文献   

13.
Mutant barley plants containing only 8%, 16% or 38% of the wildtype level of glutamine synthetase activity have been isolated.The level of glutamine synthetase activity in the roots of themutant containing only 8% leaf activity was not affected bythis mutation. The plants accumulated high levels of ammoniain leaves exposed to air and although they were able to carryout photosynthetic CO2fixation normally at low levels of atmosphericO2, they were unable to maintain wild type rates of CO2fixationin air. The extent of this inhibition and the extent to whichammonia accumulated in the leaves was dependent on the photonfluence rate intercepted by the plant. When leaves from themutant plant were fed glutamine under non-photorespiratory conditionsfor 40 min before they were transferred to air, the plants exhibitedwild type rates of CO2 fixation in air but the ammonia contentof the leaves increased to an even higher level. At least inthe short term, therefore, ammonia accumulation was not responsiblefor the dramatic decline in the fixation rate of these mutantsin air. The most probable explanation is that as the supplyof potential amino donors diminished on transfer to air, therewas a restriction on the return of glycerate to the Calvin cyclewithin the chloroplast. Key words: Ammonia toxicity, photorespiration, photosynthesis, GS-deficient barley  相似文献   

14.
Effects of atmospheric CO2 enrichment to a level above 600 parts10–6 on leaf and canopy gas exchange characteristics wereinvestigated in Trifolium repens, using an open system for gasexchange measurement. The cuvettes of the system served as growthchambers, allowing continuous measurement in a semi-controlledenvironment of ±350 and ±600 parts 10–6CO2, respectively. Carbon balance data were compared with cropyield and effects on the canopy level were compared with measuredleaf responses of photosynthesis and stomatal behaviour. Photosyntheticstimulation by high CO2 was stronger at the canopy level (103%on average) than for leaves (90% in full light), as a consequenceof accelerated foliage area development. The latter increasedabsolute water consumption by 16%, despite strong stomatal closure.The overall result was a 63% improvement in canopy water useefficiency (WUE), while leaf WVE increased almost 3-fold insaturating light. The stomatal response was such that, whilethe internal CO2 concentration in the leaf, ch increased withrising atmospherical CO2 concentration, ca, ci/ca was somewhatdecreased. Total canopy resistance, Rc, was generally lowerat high CO2 levels, despite higher leaf resistance. Higher canopyCO2 loss at night and faster light extinction in a larger-sizedhigh CO2 canopy were major drawbacks which prevented a furtherincrease in dry matter production (the harvest index was increasedby a factor 1.83). Key words: CO2 enrichment, canopy CO2 exchange, carbon balance, water use efficiency, leaf and canopy resistance  相似文献   

15.
JONES  H.; EAGLES  J. E. 《Annals of botany》1962,26(4):505-510
Plants of tobacco and a variegated variety of Pelargonium wereused to investigate some aspects of translocation of 14Carbonwithin and between leaves, following assimilation of 14CO2 byone of the leaves. Bi-directional transport in leaves is consideredto result from import into immature regions and exports frommature regions. In variegated leaves the chlorotic areas behavelike immature areas in the sense that they continue to importtranslocate from outside the leaf to a greater extent than adjacentgreen areas. However, some transport occurs from green to chloroticareas via the veins in the same leaf. Using masking techniqueson tobacco leaves it was shown that labelled carbon failed tomove across darkened mesophyll. This was taken to indicate thatthe mechanism resulting in translocation from leaves was locatedin the veins. Labelled carbon was shown to leave the veins ofimporting leaves along their entire length. A simplified technique for freeze-drying plant material priorto wax-embedding is described and some of the limitations ofheat-drying as a preliminary to gross autoradiography of leavesare discussed.  相似文献   

16.
Wheat plants were grown in a controlled environment with daytemperatures of 18 ?C and with 500 µ Einsteins m–28–1 of photosynthetically active radiation for 16 h. Beforeanthesis and 2 to 3 weeks after, rates of net photosynthesiswere measured for leaves in 2 or 21% O2 containing 350 vpm CO2at 13, 18, 23, and 28 ?C and with 500 µEinsteins m–2s–1 of photosynthetically active radiation. Also, underthe same conditions of light intensity and temperature, therates of efflux of CO2 into CO2-free air were measured and,for mature flag leaves 3 to 4 weeks after anthesis, gross andnet photosynthesis from air containing 320 vpm 14CO2 of specificactivity 39?7 nCi µmol–1. When the O2 concentration was decreased from 21 to 2% (v/v)the rate of net photosynthesis increased by 32 per cent at thelowest temperature and 54 per cent at the highest temperature.Efflux of CO2 into CO2-free air ranged from 38 per cent of netphotosynthesis at 13 ?C to 86 per cent at 28 ?C. Gross photosynthesis,measured by the 14C assimilated during 40 s, was greater thannet photosynthesis by some 10 per cent at 13 ?C and 17 per centat 28 ?C. These data indicate that photorespiration was relativelygreater at higher temperatures.  相似文献   

17.
Carbon Translocation in the Tomato: Carbon Import and Fruit Growth   总被引:8,自引:0,他引:8  
WALKER  A. J.; HO  L. C. 《Annals of botany》1977,41(4):813-823
The rates of carbon import by fruits were measured over 48 has the sum of the change in the total organic carbon contentof the fruit and the respiratory loss of carbon. Over a rangeof fruit sizes from 20–90 per cent of the maximum volumethe smaller fruits imported carbon at an absolute rate (mgCfruit–1 h–1) nearly twice that of the larger fruits.The imported leaf assimilates, identified as the 14C-compoundsalong the pathway between a 14CO2-fed leaf and a young fruit,comprised 90 per cent sucrose and 10 per cent glutamic acid,aspartic acid and malic acid. Within the fruit the imported14C-sucrose was hydrolysed into hexoses. The changes in thelevels of starch and insoluble residue in the fruit were positivelycorrelated with the carbon import rates. In the largest fruitswith the lowest import rates, there was breakdown of insolubleresidue and less accumulation of starch, but a significant increasein the level of sucrose. The sink strength of a tomato fruitis dependent more on sink activity than on sink size.  相似文献   

18.
Mayoral, M. L., Plaut, Z. and Reinhold, L. 1985. Effect of sink-sourcemanipulations on the photosynthetic rate and carbohydrate contentof cucumber cotyledons.-J. exp. Bot. 36 1551–1558. The photosynthetic rate of cucumber cotyledons (Cucumis sativuscv. Dahla) reached a maximum value of 12 mg dm–2 h–1,10 d after emergence. In 12-d-old seedlings removal of one cotyledondoubled the CO2 fixation rate of the other, as observed 3 dafter treatment. When the primary leaf was removed, the photosyntheticrate of the cotyledons was decreased by 33%. At this stage ofgrowth elimination of the roots as a sink for assimilates bygirdling the hypocotyl affected neither the photosynthetic ratenor the carbohydrate content of the cotyledons. By contrast,in 18-d-old seedlings removal of the first leaf brought abouta 42% increase in the photosynthetic rate of the cotyledons.The simultaneous removal of the first leaf and one cotyledondoubled the rate of CO2 fixation of the remaining cotyledon.Girdling the hypocotyl lowered the photosynthetic rate of thecotyledons by 73%. In both 12- and 18-d-old seedlings a decreaseor increase in the sink-source ratio was correlated with anincrease or a decrease respectively in the carbohydrate contentof the cotyledons. The stomatal resistance of the cotyledonswas not affected by any of the treatments. The effect of sink-sourcemanipulations on photosynthesis and on the level of carbohydratespresent in the cotyledons was more evident in those seedlingsgrowing under high light intensity (580 µE m–2 s–1),than in those exposed to 300 µE m–2 s–1 Key words: Sink-source relationship, cotyledons, photosynthesis  相似文献   

19.
To examine 14CO2 fixation, potential translocation, and carbonflow among leaf chemical fractions of young developing leaves,the shoot tip of 24-leaf cottonwood (Populus deltoides Bartr.ex. Marsh) plants were cut off under water, placed in artificialxylem sap, and treated with 14CO2 in continuous and pulse-chaseexperiments. Additional leaves on whole plants were spot treatedon the lamina tip to follow export from the tip only. The analysedleaves ranged in age from leaf plastochron index(LPI) –5to 3, the spot treated leaves from LPI 2 to 5. After 30 minfixation, the specific activity in the lamina tip increasedlinearly with leaf age from LPI –5 to 1 (0.5 to 4.5 kBqmg–1). Specific activity in the lower lamina increasedslowly with leaf age and did not reach 500 kBq mg–1 untilLPI –1. Total 14CO2 fixed in the lower lamina exceededthat fixed in the tip by LPI –2 because of the large amountof tissue present in the lower lamina. Although the lamina tipfixed high levels of 14CO2, pulse-chase studies coupled withautoradiography indicated no vein loading or translocation fromthe tip until about LPI 4 or 5. The 14C fixed in both tip andlower lamina was incorporated at the site of fixation and wasnot distributed to younger tissue or translocated from the lamina.Although the percentage distribution (14C in each chemical fractioncompared with the total in all fractions) of 14C among certainchemical fractions, e.g. sugars, amino acids and proteins, indicatedthat the mesophyll of the tip was more mature than the lowerlamina, physiologically both leaf sectors were immature basedon the expected 14C distribution in mature tissue. Informationfrom this and other studies indicates that the extreme tip ofa developing cottonwood leaf first begins to export photosynthateabout LPI 4 or 5 on a 24-leaf plant. The first photosynthatetranslocated may be incorporated into the vascular tissues andmesophyll directly below the tip. However, as the tip continuesto mature photosynthate is translocated past the immature lowerlamina into the petiole and out of the leaf. Populus deltoides Bartr. ex. Marsh, eastern cottonwood, translocation, leaf development, 14C fixation, carbon metabolism  相似文献   

20.
Using a cost-benefit model, the leaf nitrogen concentrationand root : shoot ratio that maximize whole-plant relative growthrate are determined as a function of the above-ground environment(integrated daily photon flux density and the concentrationof carbon dioxide at the site of fixation within the leaf).The major advantage of this approach is that it determines theadaptive significance of leaf physiology by considering thefunctional integration of leaves and roots. The predicted responseto increasing daily photon flux densities is an increase inoptimal leaf N concentration (Nopt) and a concomitant increasein root: shoot ratio. Increased carbon dioxide concentrations,on the other hand, reduce Nopt and only slightly change root:shoot ratio. The observed increase in leaf nitrogen concentrationfound in plants growing at high altitudes (low CO2 partial pressure)is also predicted. Since these responses to light and CO2 maximizethe whole-plant relative growth rate, the observed adjustmentsthat plants make to light and carbon dioxide concentration appearto be adaptive. We show that the relationship between photosynthesis and leafnitrogen concentration is complex and depends on the light andCO2 levels at which photosynthesis is measured. The shape ofthis function is important in determining Nopt and the oppositeresponse of leaf nitrogen to light and carbon dioxide is shownto be the result of the different effects of light and CO2 onthe photosynthesis-leaf nitrogen curve. Plant growth, photosynthesis, leaf nitrogen, biomass allocation, optimization, carbon dioxide light  相似文献   

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