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1.
Carbon dioxide efflux from 5- to 20-day-old pea fruits was measuredfor plants grown in controlled environment at 15 °C and600 µmol s1 m2 photon flux density in a16 h photoperiod. The rate of CO2 output per fruit increasedquickly from 0.005 to 0.018 mg CO2 min1 during fruitelongation and subsequently more slowly to 0.030 mg CO2 min1as the fruits inflated. On a d. wt basis the rate was highest,0.175 mg CO2 g1 min1, in the youngest fruits anddeclined curvilinearly with increasing fruit weight to 0.02mg CO2 g1 min1. Separation of maintenance andgrowth components was achieved by starvation methods and bymultiple regression analysis. From the latter method estimatesof the maintenance coefficient declined hyperbolically from150±8.7 mg carbohydrate g1 d. wt day1 inthe very young fruits (0.05 g) to 10.4±0.36 mg carbohydrateg1 d. wt day1 in older fruits (2.0 g). On a nitrogenbasis maintenance costs decreased from 2240 to 310 mg carbohydrateg1 nitrogen day1 while nitrogen concentrationfell from 6.7 to 3 per cent d. wt. A simple linear relationshipbetween maintenance cost per unit d. wt and nitrogen concentrationwas not observed. A growth coefficient of 50±6.7 mg carbohydrate g1growth (equivalent to a conversion efficiency, YG, of 0.95)was estimated for all fruits examined. The overall efficiency, Y, increased from a mean of 0.70 to0.85 during fruit elongation and subsequently declined to 0.80.For a given fruit weight, efficiency increased asymptoticallywith relative growth rate; both asymptote and slope of the relationshipincreased as the fruits grew. Pisum sativum L., garden pea, legume fruit, carbon dioxide efflux, maintenance respiration, growth respiration 相似文献
2.
Fully light-intercepting simulated swards of S24 perennial ryegrasswere exposed to contrasting environmental conditions in a growthroom for 4 days. Half experienced 20 h days of 120 Wm2(400700. nm) and 5 °C, and came to have a WSC (watersoluble carbohydrate) content of 235 mg g1 and half 4h days of 20 Wm2 and 25 °C leading to a WSC of 25mg g1. Their rates of CO2 efflux were monitored at anumber of temperatures during an 8 h dark period; half experiencedincreasing (530 °C) and half decreasing (305°C) temperatures. The high WSC swards hadrespiration rates of 3.7 mg CO2 g1 (d. wt) h1at 15 °C, and the low swards 0.8 mg CO2 g1h1. The order in which the temperatures were experiencedwas immaterial. Even the low WSC swards showedno evidence of a respiratory decline during the dark periodthat could be attributed to substrate shortage. The relationshipbetween temperature and CO2 efflux was best represented by logisticcurves. Even so, a Q10 of 2 fitted the data reasonably well,at least up to 20 °C, and has practical advantages wheninterpolating estimated between measured values of respirationin the construction of a carbon balance sheet. Lohum perenne L., ryegrass, respiration, temperature, Q10, soluble carbohydrate content, simulated sward 相似文献
3.
Respiratory Efflux of Carbon Dioxide from Mature and Meristematic Tissue of Uniculm Barley During Eighty Hours of Continuous Darkness 总被引:1,自引:0,他引:1
Young plants of uniculm barley were grown singly in pots ina growth room at 23/21 °C, and an irradiance of 655 µEm2s1 during each 12 h photoperiod. At the fifth leaf stage,they were subjected to 80 h of continuous darkness during whichthe rates of CO2 efflux of vegetative shoot meristems, and maturefully expanded leaves, were separately monitored. Respiratoryefflux from the meristematic tissue was initially high, 1215mg CO2 g1 h1, equivalent to a daily loss in weightof 2025 per cent. It remained high, or even rose slightly,during what would have been the normal dark period, but thenfell sharply. Even so, it was still three times that of themature tissue at the end of the experimental period. The rateof CO2 efflux of the mature tissue began low, and fell evenfurther during the first 12 h of darkness. It then levelledoff at a rate of 2·02·5 mg CO2 g1h1, equivalent to a daily loss in weight of about 3 percent. It is suggested that the rate of mature tissuerespiration, established after 1224 h of darkness, mightbe a useful selection criterion to employ in attempts to increasethe total dry matter yield of the grass crop by breeding. Hordeum vulgare L., barley, respiration, synthetic respiration, maintenance respiration, meristem, mature tissue respiration, simulated sward 相似文献
4.
The specific respiration rates of nodulated root systems, ofnodules and of roots were determined during active nitrogenfixation in soya bean, navy bean, pea, lucerne, red clover andwhite clover, by measurements on whole plants before and afterthe removal of nodule populations. Similar measurements weremade on comparable populations of the six legumes, lacking nodulesbut receiving abundant nitrate-nitrogen, to determine the specificrespiration of their roots. All plants were grown in a controlled-environmentclimate which fostered rapid growth. The specific respiration rates of nodulated root systems ofthe three grain and three forage legumes during a 714-dayperiod of vegetative growth varied between 10 and 17 mg CO2g1 (dry weight) h1. This mean value consistedof two components: a specific root respiration rate of 69mg CO2 g1 h1 and a specific nodule respirationrate of 2246 mg CO2 g1 h1. Nodule respirationaccounted for 4270 per cent of nodulated root respiration;nodule weight accounted for 1240 per cent of nodulatedroot weight. The specific respiration rates of roots lackingnodules and utilizing nitrate nitrogen were generally 2030per cent greater than the equivalent rates of roots from nodulatedplants. The measured respiratory effluxes are discussed in thecontext of nitrogen nitrogen fixation, nitrate assimilation. Glycine max, Phaseolus vulgaris, Pisum sativum, Medicago sativa, Trifolium pratense, Trifolium repens, soya bean, navy bean, pea, lucerne, red clover, white clover, nodule respiration, root respiration, fixation, nitrate assimilation 相似文献
5.
Defoliation in White Clover: Nodule Metabolism, Nodule Growth and Maintenance, and Nitrogenase Functioning During Growth and Regrowth 总被引:1,自引:0,他引:1
In two experiments, the functioning and metabolism of nodulesof white clover, following a defoliation which removed abouthalf the shoot tissue, were compared with those of undefoliatedplants. In one experiment, the specific respiration rates of nodulesfrom undefoliated plants varied between 1160 and 1830 µmolCO2 g1h1, of which nodule growth and maintenanceaccounted for 22 ± 2 per cent, or 27 ± 3.6 percent, according to method of calculation. Defoliation reducedspecific nodule respiration and nodule growth and maintenancerespiration by 6070 per cent, and rate of N2 fixationby a similar proportion. The original rate of nodule metabolismwas re-established after about 5 d of regrowth; during regrowthnodule respiration was quantitatively related to rate of N2,fixation: 9.1 µmol CO2 µmol1N2. With the possible exception of nodules examined 24 h after defoliation,the efficiency of energy utilization in nitrogenase functioningin both experiments was the same in defoliated and undefoliatedplants: 2.0±0.1 µmol CO2 µmol1 C2H4;similarly, there was no change in the efficiency of nitrogenasefunctioning as rate of N2 fixation increased with plant growthfrom 1 to 22 µmol N2 per plant h1. Exposure of nodulated white clover root systems to a 10 percent acetylene gas mixture resulted in a sharp peak in rateof ethylene production after 1.52.5 min; subsequently,rate of ethylene production declined rapidly before stabilisingafter 0.51 h at a rate about 50 per cent of that initiallyobserved. Regression of peak rate of ethyleneproduction on rate of N2 fixation indicated a value of 2.9 µmolC2H4 µmol1 N2, for rates of N2 fixation between1 and 22 µmol N2 per plant h1. The relationshipsbetween nitrogenase respiration, acetylene reduction rates andN2 fixation rates are discussed. Trifolium repens, white clover, defoliation, nodule respiration, N2, fixation, nitrogenase 相似文献
6.
Growth and dark respiration were measured in dense, miniatureswards of kikuyu grass grown at constant temperatures of 15,20, 25 and 30 °C. Total respiration over the first 12 hof darkness was very high and CO2 efflux per unit surface areavaried from 2.4 to 3.9 g CO2 m2 h1 at 15 and 30°C respectively. Such rates were consistent with the correspondinglyhigh net growth rates of 24 and 63 g d. wt m2 d1and the heavy yields of herbage. When plants were kept in thedark, CO2 efflux subsequently declined rapidly to a lower, constantrate which was taken to be the maintenance respiration rate.The half-life of the declining phase of respiration averaged10.9 and 6.0 h at 15 and 30 °C respectively, and was curvilinearlyrelated to the specific maintenance respiration rate (m). Therapid decline in respiration was consistent with the low concentrationsof total soluble carbohydrate and starch in the herbage. Valuesof m for lamina and top growth increased with temperature witha Q10 of 2.6 and 1.42 respectively, but m of stems alone wasnot affected by temperature. Using results from this study forkikuyu and from McCree (1974) for sorghum and white clover,it was noted that all three species have similar m when grownat temperatures which are near their respective optimums forgrowth. Kikuyu, Pennisetum clandestinum, growth, respiration, temperature 相似文献
7.
The relationships between CO2 concentrating mechanisms, photosyntheticefficiency and inorganic carbon supply have been investigatedfor the aquatic macrophyte Littorella uniflora. Plants wereobtained from Esthwaite Water or a local reservoir, with thelatter plants transplanted into a range of sediment types toalter CO2 supply around the roots. Free CO2 in sediment-interstitial-waterranged from 101 mol m3 (Esthwaite), 0.79 mol m3(peat), 0.32 mol m3 (silt) and 017 mol m3(sand), with plants maintained under PAR of 40 µmol m2s1. A comparison of gross morphology of plants maintained underthese conditions showed that the peat-grown plants with highsediment CO2 had larger leaf fresh weight (069 g) andtotal surface area (223 cm2 g1 fr. wt. including lacunalsurface area) than the sand-grown plants (0.21 g and 196 cm2g1 fr. wt. respectively). Root fresh weights were similarfor all treatments. In contrast, leaf internal CO2 concentration[CO2], was highest in the sand-grown plants (269 molm3, corresponding to 6.5% CO2 in air) and lowest inthe Esthwaite plants (108 mol m3). Expressionof CAM in transplants was also greatest in the low CO2 regime,with H+ (measured as dawn-dusk titratable acidity) of 50µmolg fr. wt., similar to Esthwaite plants in natural sediment.Assuming typical CAM stoichiometry, decarboxylation of malatecould account largely for the measured [CO2]1 and would makea major contribution to daytime CO2 fixation in vivo. A range of leaf sections (02, 10, 50 and170 mm) was used to evaluate diffusion limitation andto select a suitable size for comparative studies of photosyntheticO2 evolution. The longer leaf sections (17.0 mm), which weresealed and included the leaf tip, were diffusion-limited witha linear response to incremental addition of CO2 and 10mol m3 exogenous CO2 was required to saturate photosynthesis.Shorter leaf sections were less diffusion-limited, with thegreatest photosynthetic capacity (36 µmol O2 g1 fr. wt. h1) obtainedfrom the 1.0 mm size and were not infiltrated by the incubatingmedium. Comparative studies with 1.0 mm sections from plants grown inthe different sediment types revealed that the photosyntheticcapacity of the sand-grown plants was greatest (45 µmolO2 g1 fr. wt. h1) with a K0.5 of 80 mmol m3.In terms of light response, saturation of photosynthesis intissue slices occurred at 8501000 µmol m2s1 although light compensation points (611 µmolm2s1) and chlorophyll a: b ratios (1.3) were low.While CO2 and PAR responses were obtained using varying numbersof sections with a constant fresh weight, the relationshipsbetween photosynthetic capacity and CO2 supply or PAR were maintainedwhen the data were expressed on a chlorophyll basis. It is concludedthat under low PAR, CO2 concentrating mechanisms interact inintact plants to maintain saturating CO2 levels within leaflacunae, although the responses of the various components ofCO2 supply to PAR require further investigation. Key words: Key words-Uttorella uniflora, internal CO2 concentration, crassulacean acid metabolism, root inorganic carbon supply, CO2 concentrating mechanism 相似文献
8.
Diurnal temperature fluctuations induced change in soya bean-pod[Glycine max (L.) Merr.] carbon exchange rate (CER, where positiveCER represents CO2 evolution). CER appeared to depend linearlyon temperature. Linear regressions of CER on temperature interceptedthe temperature axis at 5°C (i.e. zero CER at 5°C).Slopes of these regressions (i.e. temperature sensitivity) changedover the season. The CER-temperature sensitivity coefficient,K, (calculated from observed values of CER. pod temperatureand temperature intercept) rose from less than 0·02 mgCO2 h1 pod1 °C1 during early pod-flll,peaked at over 0·04 mg CO2 h1 pod1 °C1at mid pod-fill, and then declined during late pod-fill andmaturation. Glycine max (L.) Merr., Soya bean, carbon exchange rate, temperature 相似文献
9.
A study was made of the incorporation of 14C by intact leavesof Coffea arabica (cultivars Mundo Novo, Catuai, 113013,and H 65862) 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 dm2h1) and the mean rate for the C. canephora cultivar (3·96mg CO2 dm2 h1). 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
10.
Baxter R.; Bell S. A.; Sparks T.H.; Ashenden T.W.; Farrar J.F. 《Journal of experimental botany》1995,46(8):917-929
Agrostis capillaris L.5, Festuca vivipara L. and Poaalpina L.were grown in outdoor open-top chambers at either ambient (340 3µmol mol1) or elevated (6804µmol mol1)concentrations of atmospheric carbon dioxide (CO2) for periodsfrom 79189 d. Photosynthetic capacity of source leaves of plants grown atboth ambient and elevated CO2 concentrations was measured atsaturating light and 5% CO2. Dark respiration of leaves wasmeasured using a liquid phase oxygen electrode with the buffersolution in equilibrium with air (21% O2, 0.034% CO2). Photo-syntheticcapacity of P. alpina was reduced by growth at 680 µmolmol1 CO2 by 105 d, and that of F. vivipara was reducedat 65 d and 189 d after CO2 enrichment began, suggesting down-regulationor acclimation. Dark respiration of successive leaf blades ofall three species was unaltered by growth at 680 relative to340 µmol mol1 CO2. In F. vivipara, leaf respirationrate was markedly lower at 189 d than at either 0 d or 65 d,irrespective of growth CO2 concentration. There was a significantlylower total non-structural carbohydrate (TNC) concentrationin the leaf blades and leaf sheaths of A. capillaris grown at680µmol mol1 CO2. TNC of roots of A. capillariswas unaltered by CO2 treatment. TNC concentration was increasedin both leaves and sheaths of P. alpina and F. vivipara after105 d and 65 d growth, respectively. A 4-fold increase in thewater-soluble fraction (fructan) in P. alpina and in all carbohydratefractions in F. vivipara accounted for the increased TNC content. In F. vivipara the relationship between leaf photosyn-theticcapacity and leaf carbohydrate concentration was such that therewas a strong positive correlation between photosynthetic capacityand total leaf N concentration (expressed on a per unit structuraldry weight basis), and total nitrogen concentration of successivemature leaves reduced with time. Multiple regression of leafphotosynthetic capacity upon leaf nitrogen and carbohydrateconcentrations further confirmed that leaf photosynthetic capacitywas mainly determined by leaf N concentration. In P. alpina,leaf photosynthetic capacity was mainly determined by leaf CHOconcentration. Thus there is evidence for down-regulation ofphotosynthetic capacity in P. alpina resulting from increasedcarbohydrate accumulation in source leaves. Leaf dark respiration and total N concentration were positivelycorrelated in P. alpina and F. vivipara. Leaf dark respirationand soluble carbohydrate concentration of source leaves werepositively correlated in A. capillaris. Changes in source leafphotosynthetic capacity and carbohydrate concentration of plantsgrown at ambient or elevated CO2 are discussed in relation toplant growth, nutrient relations and availability of sinks forcarbon. Key words: Elevated CO2, Climate change, grasses, carbohydrate partitioning, photosynthesis, respiration 相似文献
11.
Seeds of apple cv. Golden Delicious were germinated and cultivatedin the greenhouse until the third leaf emerged. Respirationofgerminating seeds or photosynthesis of the first leaves wasmeasured by infra-red gas analysis and porometry, respectively.To study the role of phosphoenolpyruvate carboxylase (PEPC),the dominant carboxylase in the carbon economy, its CO2 refixationpotentialwas related to the amount of CO2 lost in respiration. With arange of 0.2 (dry seeds) to 18 (cotyledons) µmol CO2 h1g1 PEPC activity resembled or exceeded the amount ofC02 lost in respiration before the third leaf developed. Itis concludedthat PEPC largely contributes to economize the carbonmetabolism of apple seedlings before they become photosyntheticallycompetent. Key words: Apple (Malus pumila Mill.) seedling, carbon economy, phosphoenolpyruvate carboxylase, photosynthesis, respiration 相似文献
12.
The effect of the leafless mutation (in whichtendrils replace leaflets and the stipules are reduced to avestigial form) upon foliage area, photosynthetic net CO2 uptakepotential, dry matter production and seed yield in Pisum sativumwas studied by comparing two near-isogenic lines of genotypeafafstst and ++++. The mutation is of potential agronomic valuein that it offers improved lodging resistance, crop drying andharvester throughput. In the conventional phenotype the total foliage area of themain axis attained a plateau (456 cm2) at day 56 from seedlingemergence, whereas corresponding values for the leaflessmutant showed a total area of 208 cm2 at day 68 with no indicationof a plateau. The agronomic consequence of this is discussed.During the vegetative phase of the plant the maximum CO2 uptakepotential in the fully expanded conventional leaf was 8·5mg CO2 leaf1 h1 and in the leaflessmutant this value was 7·0 mg CO2 leaf1 h1.For most leaves of the latter phenotype this valuewas between 30 and 60 per cent less than for their conventionalcounterpart. There was a consistently higher photosyntheticpotential per unit area in tendrils of the leaflessmutant than in leaflets of the conventional phenotype. The respectivemean specific values for the two phenotypes were 53 and 37 mgCO2 dm2 h1. The problem of obtaining a meaningfulsurface area value for tendrils is discussed and the cylindricalnature of tendrils is taken into account. The leafless mutant consistently accumulated 50per cent less dry matter than did conventional plants in theperiod from seedling emergence to anthesis and yield of maturedry seed per plant showed a reduction of 50 per cent both inseed number and total seed weight. The implications for future breeding and selection programmesaimed at haulm reduction are discussed in relation to evaluatingthe ability of the background genotype to produce adequate tendrilsin the presence of afafstst. Triticum aestivum, wheat, callus culture, organogenesis 相似文献
13.
Barley (Hordeum vulgare L. cv. Digger) was grown for 22 d inenclosed chambers with a CO2 enrichment of 35, 155, 400 or 675µmol CO2 mol1. CO2 enrichment increased photosyntheticcapacity in the plants grown at either of the two highest levelsof pCO2. A CO2 enrichment of 675µmol CO2 caused a significantincrement of shoot dry weight, whereas no changes were observedin fresh weight, chlorophyll or protein levels. At a light intensityof 860µmol m2s1 CO2 enrichment caused photosyntheticcapacity to increase by 250%, whereas no effect was observedat 80 µmol m2 s1. Over time, photosynthesisdecreased by 70% independent of CO2. A time-dependent increasein the level of extractable fructose was observed whereas totalextractable carbohydrate only changed slightly. Key words: Carbohydrates, CO2 enrichment, Hordeum vulgare, photosynthesis, respiration 相似文献
14.
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
15.
Photosynthetic 14C fixation by Characean cells in solutionsof high pH containing NaH14CO3 gave a measure of the abilityof these cells to take up bicarbonate (H14CO3). Whereascells of Nitella translucens from plants collected and thenstored in the laboratory absorbed bicarbonate at 11.5µµmoles cm2 sec1, rates of 38µµmoles cm2 sec1 were obtained withN. translucens cells from plants grown in the laboratory. Influxesof 56 µµmoles cm2 sec1 wereobtained with Chara australis, 38 µµmolescm2 sec1 with Nitellopsis obtusa, and 15µµmoles cm2 sec1 with Tolypella intricata.It is considered that these influxes represent the activityof a bicarbonate pump, which may be an electrogenic process. In solutions of lower pH, H14CO3 uptake would be maskedby rapid diffusion of 14CO2 into the cells: the four Characeanspecies fixed 14CO2 at maximum rates of 3040 µµmolescm2 sec1 (at 21° C). 相似文献
16.
Lee, H. S. J. and Griffiths, H. 1987. Induction and repressionof CAM in Sedurn relephluni L. in response to photopcnod andwater stress.J. exp. Bot. 38: 834841. The introduction and repression of CAM in Sedurn telephiunmL, a temperate succulent, was investigated in watered, progressivelydrouglited and rewatered plants in growth chambers. Measurementswere made of water vapour and CO2 exchange, titratable acidity(TA) and xylem sap tension. Effects of photoperiod were alsostudied. CAM was induced by drought under long or short days,although when watered no CAM activity was expressed. C3-CAM intermediate plants were used for the investigation ofwater supply. Those which had received water and those drought-stressedboth displayed a similar nocturnal increase in TA, with a day-nightmaximum (H+) of 69 µmol g1 fr. wt. The wateredplants took up CO2 at a maximum rate of 2?2 µmol m2s1 only in the light period, while the droughted plantsshowed a maximum nocturnal CO2 uptake rate of 0?69 µmolm2 s1. Subsequently, as CAM was repressed, thewatered S. telephiwn displayed little variation in TA, withconstant levels at 42 µmol g1 fr. wt. (day 10).After 10 d of drought stress, the CAM characteristics of S.telephiurn were aLso affected, with reduced net CO2 uptake andH+. The transition between C3 and CAM in S. telephium can be describedas a progression in terms of the proportion of respiratory CO2which is recycled and refixed at night as malic acid, in comparisonwith net CO2 uptake. Recycling increased from 20% (day 1) to44% (day 10) as a result of the drought stress and was highin both the CAM-C3 stage (no net CO2 uptake at night) and alsoin the drought-stressed CAM stage (reduced net CO2 uptake atnight). The complete C3-CAM transition occurred in less than8 d, and the stages could be characterized by xylem sap tensionmeasurements: CAM = 0?50 MPa C3-CAM = 0?36 MPa C3 = 0?29 MPa. Key words: CAM, Sedum telephium L., recycling 相似文献
17.
RYLE G. J. A.; ARNOTT R. A.; POWELL C. E.; GORDON A. J. 《Journal of experimental botany》1984,35(8):1156-1165
The respiratory effluxes of nodules and of roots of FiskebyV soyabean (Glycine max (L.) Merr.), grown in a controlled environment,were measured at intervals in air and 3% O2 from shortly afterthe onset of N2 fixation until plant senescence. The respiratoryburdens linked with nitrogenase plus ammonia metabolism, andnodule growth and maintenance, were calculated from gas exchangedata and related to the concurrent rates of N2 fixation. The specific respiration rates of nodules increased to a maximumof 21 mg CO2 g1 h1 at the time pods began development:the equivalent maximum for roots was c. 4.5 mg CO2 g1h1. Maximum nodule and root respiration rates per plantwere attained about 25 d later at the time N2 fixation peakedat 15 mg N d1 plant1. The relationship between nodule respiration and N2 fixationindicated an average respiratory cost of 13.2 mg CO2 mg1N until the last few days of plant development Separation ofnodule respiration into the two components: nitrogenase (+ NH3metabolism) respiration and nodule growth and maintenance respiration,indicated that the latter efflux accounted for c. 20% of nodulerespiration while N2 fixation was increasing and new noduletissue was being formed. When nodule growth ceased and N2 fixationdeclined, this component of respiration also declined. The respiratorycost of nitrogenase activity plus the associated metabolismof NH3 varied between 11 mg CO2 mg1 N during vegetativeand early reproductive growth, to 12.5 mg CO2 mg1 N duringthe later stages of pod development. Key words: N2 fixation, Respiration, Nodules, Nitrogenase 相似文献
18.
Chloroplast preparations from the young primary leaves of Phaseolusvulgaris L. cv. Canadian Wonder carry out the DNA-dependentincorporation of UTP into RNA at rates between 8 and 14 pmolUTP µg1 chlorophyll h1. It is estimatedthat 90% of the activity was localized in the chloroplasts.The incorporation proceeded for between 20 and 30 min at 35°C. The maximum rates of RNA synthesis were attained atpH 8.3, in the presence of 15 mM MgCl2. Chloroplasts were alsoactive, to a lesser extent, with 1.5 mM MnCl2. The simultaneouspresence of MnCl2 and MgCl2 resulted in inhibition of activity.Nuclear material prepared from young P. vulgaris leaves incorporatedUTP at a rate of about 12 pmol UTP µg1 DNA h1.On a chloroplast (Tritonsoluble) DNA basis chloroplast activitywas over 40-fold that of nuclei. Methods of solubilizing chloroplastRNA polymerase were explored. Yields of over 75% were achieved,but methods suitable for one species were not always successfulwhen applied to another. The highest yields of the P. vulgarisenzyme were obtained using EDTA and KCl. All methods resultedin solubilization of DNA. RNA synthesis by the soluble P. vulgarisenzyme proceeded for more than 40 min at 35 °C. 相似文献
19.
Biochemical Limitations to Carbon Assimilation in C3 Plants--A Retrospective Analysis of the A/Ci Curves from 109 Species 总被引:9,自引:0,他引:9
Species-specific differences in the assimilation of atmosphericCO2 depends upon differences in the capacities for the biochemicalreactions that regulate the gas-exchange process. Quantifyingthese differences for more than a few species, however, hasproven difficult. Therefore, to understand better how speciesdiffer in their capacity for CO2 assimilation, a widely usedmodel, capable of partitioning limitations to the activity ofribulose-1,5-bisphosphate carboxylase-oxygenase, to the rateof ribulose 1,5-bisphosphate regeneration via electron transport,and to the rate of triose phosphate utilization was used toanalyse 164 previously published A/Ci, curves for 109 C3 plantspecies. Based on this analysis, the maximum rate of carboxylation,Vcmax, ranged from 6µmol m2 s1 for the coniferousspecies Picea abies to 194µmol m2 s1 forthe agricultural species Beta vulgaris, and averaged 64µmolm2 s1 across all species. The maximum rate ofelectron transport, Jmax, ranged from 17µmol m2s1 again for Picea abies to 372µmol m2 s1for the desert annual Malvastrum rotundifolium, and averaged134µmol m2 s1 across all species. A strongpositive correlation between Vcmax and Jmax indicated that theassimilation of CO2 was regulated in a co-ordinated manner bythese two component processes. Of the A/Ci curves analysed,23 showed either an insensitivity or reversed-sensitivity toincreasing CO2 concentration, indicating that CO2 assimilationwas limited by the utilization of triose phosphates. The rateof triose phosphate utilization ranged from 4·9 µmolm2 s1 for the tropical perennial Tabebuia roseato 20·1 µmol m2 s1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm2 s1 across all species. Despite what at first glance would appear to be a wide rangeof estimates for the biochemical capacities that regulate CO2assimilation, separating these species-specific results intothose of broad plant categories revealed that Vcmax and Jmaxwere in general higher for herbaceous annuals than they werefor woody perennials. For annuals, Vcmax and Jmax averaged 75and 154 µmol m2 s1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm2 s1, respectively. Although these differencesbetween groups may be coincidental, such an observation pointsto differences between annuals and perennials in either theavailability or allocation of resources to the gas-exchangeprocess. Key words: A/Ci curve, CO2 assimilation, internal CO2 partial pressure, photosynthesis 相似文献
20.
The carbon dioxide exchange of developing apple fruits was monitoredduring development. The results of measurements on detachedfruits in the laboratory were consistent with those made onattached fruit in the field. Respiration rate at 20 °C inthe dark declined from 120 ng CO2 g1 fr. wt. s1on 5 June (4 weeks after full bloom) to less than 3 ng g1fr. wt. s1 by late September. In the light, net CO2 evolutionwas much decreased, but on no occasion did photosynthesis exceedrespiration and no net CO2 uptake was detected. The Q10 fordark respiration over the interval from 15 to 25 °C changedfrom 2.8 in early June to 1.6 in early August 相似文献