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1.
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 ?109 kg (CO2) J1. At a CO2 concentration of 0?73 ? 103 kg m3 (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 ? 103 kg m3 (1200 vpm) they were only 5 percent greater. 相似文献
2.
The CO2 compensation point at 25 °C and 250 µEinsteinsm2 s1 wasmeasured for 27 bryo-phyte species, andwas found to be in the range of 45160 µl CO2 I1air. Under the same conditions Zea mays gave a value of 11 µlI1 and Horde um vulgare 76 µI1. The rate of loss of photosyntheticallyfixed 14CO2 in the light and dark in six bryophytes (three mosses,two leafy liverworts, one thalloid liverwort) was determinedin CO2-free air and 100% O2. The rate of 14CO2 evolution inthe light was less than that in the dark in CL2-free air, butin 100% O2 the rate in the light increased, so that in all butthe leafy liverworts it was greater than that in the dark. Raisingthe temperature tended to increase the rate of 14CO2 evolutioninto CO2-free air both in the light and dark, so that the light/dark(L/D) ratio did not greatly vary. The lower rate of loss of14CO2 in the light compared tothe dark could be due to partialinhibition of dark respiration reactions in thelight, a low rate of glycolate synthesis and oxidation, or partialreassimilation of the 14CO2 produced, or a combination of someor all of these factors. 相似文献
3.
The rates of CO2 assimilation by potted spray carnation plants(cv. Cerise Royalette) were determined over a wide range oflight intensities (45450 W m2 PAR), CO2 concentrations(2003100 vpm), and leaf temperatures (535 °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 m2PAR but it increased progressively with increasing light intensityand CO2 concentration up to 27 °C at 450 W m2 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 m2.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
4.
Tomato plants were grown in solution culture in a controlledenvironment at 20 ?C with a 12 h photoperiod of 400 µmolquanta m2 s1 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
5.
Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N2 fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO2, and temperature 23/18 °C day/night temperaturesat 680 µmol mol1 CO2, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol1 CO2 (C340)After 34 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO2 and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 1729%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO2 mol H2O1)was also significantly increased Plants acclimated to elevatedCO2, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves instantaneouslyexposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO2, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO2 at 23 °C increased graduallyfrom approx 10 % at 100 µmol m1 s1 to >27 % at 1170 µmol m2 s1 In parallel, wateruse efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 In parallel,water use efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 to approx100 % at the highest irradiance Elevated CO2, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO2 and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N2, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO2, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO2, elevated temperature, water use efficiency, N2 fixation 相似文献
6.
Measuring the Canopy Net Photosynthesis of Glasshouse Crops 总被引:3,自引:0,他引:3
HAND D. W.; CLARK G.; HANNAH M.A; THORNLEY J. H. M.; WILSON J. WARREN 《Journal of experimental botany》1992,43(3):375-381
A null balance method is described for measuring net photosynthesisof mature canopies of cucumber and other protected crops overperiods of 10 min in a single-span glasshouse (c. 9m x 18m inarea). Accuracy of control of the CO2 concentration in the greenhouseatmosphere is within ±10 vpm of the normal ambient level(c. 350 vpm). The amounts of CO2 used in canopy net photosynthesisare measured with linear mass flowmeters accurate to within±0.80g. The total errors incurred in measuring canopynet photosynthesis at an ambient CO2 level are estimated tobe of the order of ± 1·2% in bright light (350W m2, PAR)and ±3·6% in dull light (100W m2, PAR). Measurements of the rates of net photosynthesis of a maturecanopy of a cucumber crop were made at near-ambient CO2 concentrationsover a range (0350 W m2) of natural light fluxdensities. A model of light absorption and photosynthesis applicableto row crops was used to obtain a net photosynthesis versuslight response curve for the cucumber crop. At a light fluxdensity of 350 W m2 the fitted value of canopy net photosynthesiswas 2.65 mg CO2 m2s1 (equivalent to over 95 kgCO2 ha1h1). The results are discussed in relationto the need for CO2 supplements to avoid depletion in both ventilatedand unventilated glasshouses during late spring and summer. Key words: Glasshouse crops, cucumber, measurement, canopy photosynthesis, light, CO2 相似文献
7.
The Carbon Economy of Rubus chamaemorus L. II. Respiration 总被引:1,自引:0,他引:1
Respiratory activity and seasonal changes in carbohydrate contentof the storage organs of Rubus chamaemorus L. have been investigated.Leaf dark respiration rate increases in a non-linear mannerfrom 0·7 mg CO2 evolved dm2 h1 at 0 °Cto 4·6 rng CO2 evolved dm2 hh1 at 30 °C.Root and rhizome respiration rates increase from 1 µ1O2 uptake g1 fresh weight h1 at 0.7 ° C to10 µ10, uptake g1 f. wt h1 at 20 °C.Rhizome carbohydrate reserves decline from a September peakof 33 per cent alcohol insoluble d. wt to 16 per cent in May. The circumpolar distribution of R. chamaemorus is discussedin relation to the evidence presented here and in the precedingpaper of the series. 相似文献
8.
Net photosynthetic rates per unit ground area for plant standsof Solanum melongena L. var. esculentum (aubergine) and Amaranthuscaudatus L. var. edulis (grain amaranth) were measured over10 min intervals in an airtight, glass, controlled-environmentcabinet for a range of light flux densities provided by thediurnal variation in daylight. Light response curves for photosynthesisof stands, grown at ambient CO2 concentration, were definedat 400, 800 and 1200 vpm CO2. Light compensation points for these stands were around 20-30J m-2 s-1 and decreased slightly at higher CO2 concentrations.For aubergine, a C3 species, the short-term effects of CO2 enrichmentwere to increase the initial slope as well as the asymptoteof the light response curve, reducing light saturation at moderateto high light flux densities; but for amaranthus, a C4 species,saturation was less apparent and CO2 enrichment scarcely increasedphotosynthesis except at light flux densities above 150 J m-2s-1. The canopies intercepted 93-98% of incident light. The efficiencyof utilization of intercepted light in photosynthesis (µgCO2 J-1) increased from zero at the light compensation pointto a maximum at an optimum light flux density of about 100 Jm-2 s-1 (the optimum rose a little with CO2 enrichment) anddecreased slightly with further increase in light. Maximum utilizationefficiencies at 400 vpm CO2 were 8-9 µg CO2 J-1. Enrichmentto 1200 vpm did not affect the peak utilization efficiency ofthe C4 amaranthus, but increased that aubergine to 12·2µg CO2 J-1 (equivalent to some 14% when using the heatof combustion of plant dry matter to convert to the dimensionlessform). This is among the highest recorded efficiencies of lightutilization for stands, and relates to the exceptionally favourableenvironment, with optimal control of CO2 concentration, humidity,temperature, water supply and mineral nutrition.Copyright 1993,1999 Academic Press Amaranthus caudatus L. var. edulis, Solanum melongena L. var. esculentum, canopy photosynthesis, CO2 enrichment, light interception, light utilization, photosynthetic efficiency 相似文献
9.
Temperature Effects on Rice at Elevated CO2 Concentration 总被引:1,自引:0,他引:1
The continuing increase in atmospheric carbon dioxide concentration([CO2]) and projections of possible future increases in globalairtemperatures have stimulated interest in the effects of theseclimate variables on agriculturally important food crops. Thisstudywas conducted to determine the effects of [CO2] and temperatureon rice (Oryza sativa L., cv. IR30). Rice plants weregrownseason-long in outdoor, naturally sunlit, controlled-environment,plant growth chambers in temperature regimes ranging from 25/18/21°Cto 37/30/34°C (daytime dry bulb air temperature/night-timedry bulb air temperature/paddy water temperature)and [CO2] of660 µmol CO2 mol1 air. An ambient chamber was maintainedat a [CO2] of 330 µmol mol1 and temperature regimesof 28/21/25°C. Carbon dioxide enrichment at 28/21/25°Cincreased both biomass accumulation and tillering and increasedgrain yield by 60%. In the 660 µmol mol1 [CO2]treatment, grain yield decreased from 10.4 to 1.0 Mg ha1with increasing temperature from 28/21/25°C to the 37/30/34°Ctemperature treatment. Across this temperature range, the numberof panicles plant1 nearly doubled while the number ofseeds panicle1 declined sharply. These results indicatethat while future increases in atmospheric [CO2] are likelyto be beneficial to rice growth and yield, potentially largenegative effects on rice yield are possible if air temperaturesalso rise. Key words: Oryza sativa, CO2, temperature, growth, yield 相似文献
10.
Long-term effects of atmospheric carbon dioxide concentration(ambient or 700 µmol mol1) and air temperature(simulation of field conditions or + 4 C) on leaf photosyntheticrate were examined in Lolium perenne L. cv. Vigor, exposed tonatural illumination during winter. Photosynthetic capacitywas compared over a range of air temperatures and photon fluxdensities of photosynthetically active radiation which wererepresentative of winter climate (515 C and 0500µmol m2s1), with CO2 level during measurementsimilar to that during the experimental period. Long-term exposureto increased air temperature reduced leaf CO2 fixation capacityby 23% (averaged over all measurement conditions), resultingfrom a decline in lightsaturated uptake rate, but not in incident-lightquantum efficiency. CO2- stimulation was largely absent in plantsgrown in ambient temperature, but pronounced in plants grownunder +4 C, where it compensated for two-thirds of the 23%drop. This enhancing effect of elevated CO2 level on leaf CO2uptake rate observed in the warmer treatment, was strongly dependenton measurement temperature, increasing from 5% at 5 C, to upto 32% at 15 C. Measurements of chlorophyll fluorescence anddry matter corresponded with the observed changes in assimilationcapacity, which could not be attributed to a deteriorated nitrogenstatus of the leaves as there was a similar N content on anarea basis. Several hypotheses are considered to explain theobserved CO2-temperature interactions. Key words: Acclimation, chlorophyll fluorescence, elevated CO2 level, global warming, low temperature 相似文献
11.
KUMARASINGHE K. S.; KEYS A. J.; WHITTINGHAM C. P. 《Journal of experimental botany》1977,28(5):1163-1168
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
12.
The respiratory losses of 14CO2 from whole plants of uniculmbarley and maize were measured following exposure of the wholeplant or a single leaf to air containing a uniform specificactivity of 14CO2 for 3060 min during normal photosynthesis.The total respiratory efflux of 14CO2 could be described interms of two main components: an intense efflux characterizedby a half-life of 48 h, which was identified with thebiosynthesis of new tissue in meristems; and a much less intenseefflux characterized by a half-life of 26120 h, whichwas primarily identified with the maintenance of metabolic activity.The (bio)synthetic efflux of 14CO2 totalled between 25 and 35per cent of the labelled assimilate (14C: 14C), and was generallyinsensitive to temperature and light intensity. The maintenanceefflux totalled between 12 and 27 per cent of the labelled assimilateor its derivatives: the total generally increased with hightemperature and low light intensity. The rate of the maintenanceefflux showed a normal temperature response (Q102). It is concludedthat the efficiency of conversion of assimilate into new growthis unlikely to exceed 65 per cent in the long term, and willgenerally be less. 相似文献
13.
A study has been made of photosynthetic 14CO2 fixation by isolatedmature internodes of Nitella translucens. Experimentalconditions were similar to those used in studies of the ionicrelations of these cells. Maximum rates of photosynthesis were3340µµmoles CO2, fixed per cm2 of surfacearea per second (equivalent to 1215 /xmoles fixed permg chlorophyll per hour). l4CO2 fixation was inhibited to thedark level by 3(3,4,dichlorophenyl)-1, 1-dimethylurea (at 0-6µM or 10µM) and by the uncoupler carbonyl cyanide-m-chlorophenylhydrazone(SµM). The presence of imidazole or ammonium sulphate(both of which uncouple ATP production in vitro) did not resultin an inhibition of 14CO2 fixation. These results are discussedin relation to published work on solute uptake by Nitella translucens.During photosynthesis there was rapid movement of 14C-labelledorganic compounds out of the chloroplasts. 14C-labelled sucrose,ammo-acids, and sugar phosphates were found in samples of vacuolarsap. 相似文献
14.
KENDALL A. C.; TURNER J. C.; THOMAS S. M.; KEYS A. J. 《Journal of experimental botany》1985,36(2):261-273
Spring wheat plants were grown in a cage with a glass roof untilthree days after anthesis and then subjected to treatments inconstant environment rooms with any one of all combinationsof four irradiances and two concentrations of carbon dioxide.The photoperiod was 16 h and day/night temperatures 19?C/14?C.Growth and yield of grain were saturated at the two brightestirradiances. Carbon dioxide enrichment from 350 to 1200 mm3dm3 increased shoot dry weight and grain yield at finalharvest at all irradiances, by averages of 10.5 (not significant)and 23.5 (significant) percent respectively. However, increasingthe irradiance from 150 to 613 µE m2 s1caused much larger yield increases (approximately 3-fold). Increasedgrain production by increased light was caused by both increasesin dry weight per grain and by increases in grain number perspikelet. The increase caused by CO2 enrichment was mainly becauseof increased dry weight per grain. Increase in ear dry weightcaused by CO2 enrichment took place between 30 and 60 d afteranthesis. The increase in shoot dry weight took place immediatelyafter exposure to increased CO2 from 3 to 15 d after anthesis.Net photosynthesis by flag leaves on the main shoots was almostdoubled 16 d after anthesis by the CO2 enrichment even thoughstomatal resistance was also doubled. However, this increasewas not reflected by a proportional increase in yield, probablybecause increased mutual shading by bigger stems and late tillersreduced total assimilation and because of increased respirationby the shoots. The increase in photosynthesis was not due toa decrease in photorespiration but to an increase in gross photosynthesis. Key words: CO2enrichment, Photosynthesis, Photorespiration 相似文献
15.
Effect of Elevated CO2 on the Photosynthesis, Respiration and Growth of Perennial Ryegrass 总被引:1,自引:0,他引:1
Single, seed-grown plants of ryegrass (Lolium perenne L. cv.Melle) were grown for 49 d from the early seedling stage ingrowth cabinets at a day/night temperature of 20/15 C, witha 12 h photoperiod, and a CO2 concentration of either 340 or680µI 11 CO2. Following complete acclimation tothe environmental regimes, leaf and whole plant CO2 effluxesand influxes were measured using infra-red gas analysis techniques.Elevated CO2 increased rates of photosynthesis of young, fullyexpanded leaves by 3546% and of whole plants by morethan 50%. For both leaves and whole plants acclimation to 680µI1 CO2 reduced rates of photosynthesis in bothCO2 regimes, compared with plants acclimated to 340µll1. There was no significant effect of CO2 regime onrespiration rates of either leaves or whole plants, althoughleaves developed in elevated CO2 exhibited generally lower ratesthan those developed in 340µI I1 CO2. Initially the seedling plants in elevated CO2 grew faster thantheir counterparts in 340µI I1 CO2, but this effectquickly petered out and final plant weights differed by onlyc. 10%. Since the total area of expanded and unexpanded laminaewas unaffected by CO2 regime, specific leaf area was persistently1340% lower in elevated CO2 while, similarly, root/shootratio was also reduced throughout the experiment. Elevated CO2reduced tissue nitrogen contents of expanded leaves, but hadno effect on the nitrogen contents of unexpanded leaves, sheathsor roots. The lack of a pronounced effect of elevated CO2 on plant growthwas primarily due to the fact that CO2 concentration did notinfluence tiller (branch) numbers. In the absence of an effecton tiller numbers, any possible weight increment was restrictedto the c. 2.5 leaves of each tiller. The reason for the lackof an effect on tillering is not known. Key words: Lolium perenne, ryegrass, elevated CO2, photosynthesis, respiration, growth, development 相似文献
16.
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 µEm2 s1. At quantum flux densities of 150 µEm2 s1 (400700 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
17.
Photosynthetic Carbon Sources of Stream Macrophytes 总被引:15,自引:0,他引:15
Rates of photosynthesis of four submerged stream macrophyteswere examined under varying pH and composition of inorganiccarbon species. Callitriche stagnatis and Sparganium simplexused only CO2 for photosynthesis. Potamogeton crispus and P.pectinatus used HCO3 in addition to CO2, but with much lowerefficiency. The photosynthetic rates at air equilibrium anda total inorganic carbon concentration of 5.0 mM were 23times lower than maximum rates at CO2 saturation for the HCO3users and 1014 times lower for the CO2 users. The CO2compensation point of entire plants of Callitriche (2.5 µM)and Sparganium (6.0µM) was well below the equilibriumconcentration (15 µM). and the low saturation points (250500µM) also pointed to efficient use of CO2. Callitricheand Sparganium compete successfully with HCO3 users inhardwater streams, which have a higher exchange and generationcapacity of CO2 than stagnant and more soft waters. Rates ofphotosynthesis of Potamogeton crispus and P. pectinatus decreasedat high pH. Depending on the two alternative hypotheses forHCO3use, this decline can be explained by CO3inhibition of HCO3 uptake or by increasing capacity tobuffer H+efflux from the plant. Habitats subject to high pH,e. g. small ponds with dense vegetation, may have a strong selectionfor efficient mechanisms of HCO3 use. Key words: Photosynthesis, Macrophytes, Carbon-source 相似文献
18.
The photosynthetic response to CO2 concentration, light intensityand temperature was investigated in water hyacinth plants (Eichhorniacrassipes (Mart.) Solms) grown in summer at ambient CO2 or at10000 µmol(CO2) mol1 and in winter at 6000 µmol(CO2)mol1 Plants grown and measured at ambient CO2 had highphotosynthetic rate (35 µmo1(CO2) m2 s1),high saturating photon flux density (15002000) µmolm2 s1 and low sensitivity to temperature in therange 2040 °C. Maximum photosynthetic rate (63 µmol(CO2)m2 s1) was reached at an internal CO2 concentrationof 800 µmol mol1. Plants grown at high CO2 in summerhad photosynthetic capacities at ambient CO2 which were 15%less than for plants grown at ambient CO2, but maximum photosyntheticrates were similar. Photosynthesis by plants grown at high CO2and high light intensity had typical response curves to internalCO2 concentration with saturation at high CO2, but for plantsgrown under high CO2 and low light and plants grown under lowCO2 and high light intensity photosynthetic rates decreasedsharply at internal CO2 concentrations above 1000 µmol1. Key words: Photosynthesis, CO2, enrichment, Eichhornia crassipes 相似文献
19.
Acclimation of single plants of Lolium temulentum to changing[CO2] was studied on plants grown in controlled environmentsat 20°C with an 8 h photoperiod. In the first experimentplants were grown at 135 µ;mol m2 s1 photosyntheticphoton flux density (PPFD) at 415µl l1 or 550µll1 [CO2] with some plants transferred from the lowerto the higher [CO2] at emergence of leaf 4. In the second experimentplants were grown at 135 and 500 µmol m2 s1PPFD at 345 and 575 µl l1 [CO2]. High [CO2] during growth had little effect on stomatal density,total soluble proteins, chlorophyll a content, amount of Rubiscoor cytochrome f. However, increasing [CO2] during measurementincreased photosynthetic rates, particularly in high light.Plants grown in the higher [CO2] had greater leaf extension,leaf and plant growth rates in low but not in high light. Theresults are discussed in relation to the limitation of growthby sink capacity and the modifications in the plant which allowthe storage of extra assimilates at high [CO2]. Key words: Lolium, carbon dioxide, photosynthesis, growth, stomatal density 相似文献
20.
The rate of net photosynthesis (P) of whole plant stands oftomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativusL.) and sweet pepper (Capsicum annuum L.) was measured in sixlong-term experiments in large greenhouses under normal operatingconditions and CO2-concentrations between 200 and 1200 µmolmol-1. The objective was to quantify the responses to lightand carbon dioxide and to obtain data sets for testing simulationmodels. The method of measuring canopy photosynthesis involvedan accurate estimation of the greenhouse CO2 balance, usingnitrous oxide (N2O) as tracer gas to determine, on-line, theexchange rate between greenhouse and outside air. The estimatedrelative error in the observed P was about ± 10%, exceptthat higher relative errors could occur under particular conditions. A regression equation relating P to the photosynthetically activeradiation, the CO2 concentration and the leaf area index explained83-91% of the variance. The main canopy photosynthesis characteristicscalculated with the fitted regression equations were: canopyPmax 5-9 g m-2 h-1 CO2 uptake; ratio Pmax/LAI 1·5-3 gm-2 h-1; light compensation point 32-86 µmol s-1 m-2;light use efficiency (quantum yield) at low light 0·06-0·10µmol µmol-1 and CO2 compensation point 18-54 µmolmol-1. The results were related to the prevailing conditions.Copyright1994, 1999 Academic Press Canopy photosynthesis, Capsicum annuum L., carbon dioxide, CO2, CO2 balance, CO2 use efficiency, cucumber, Cucumis sativus L., glasshouse, greenhouse, light use efficiency, Lycopersicon esculentum Mill., sweet pepper, tomato, tracer gas 相似文献