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1.
Equipment is described which delivers air with concentrationsof CO2 and water vapour closely controlled in the ranges 0 to2500 ppm and 5 to 15 mb respectively, at flow rates of up to10 1 min-1, to each four leaf chambers. The leaf temperatureis controlled to ±0.5 °C and, with a light intensityof 0.3 cal cm-2 min-1 visible radiation (0.4 to 0.7 µm)leaf temperature can be maintained at 17.5 °C.The apparatusused to measure the concentration differences between the watervapour and CO2 entering and leaving the leaf chamber (used tocalculate transpiration, photosynthetic, and respiration rates)is described in detail.Results of tests, which show the necessityfor mounting a fan within the leaf chamber, are reported.Typicallight- and CO2-response curves are given for kale leaves (Brassicaoleracca var. acephala) and an attempt is made to quantify theerrors in the measurement of photosynthesis and transpiration. 相似文献
2.
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
3.
Pascopyrum smithii (C3) andBouteloua gracilis (C4) are importantforage grasses native to the Colorado shortgrass steppe. Thisstudy investigated photosynthetic responses of these grassesto long-term CO2enrichment and temperature in relation to leafnonstructural carbohydrate (TNC) and [N]. Glasshouse-grown seedlingswere transferred to growth chambers and grown for 49 d at twoCO2concentrations (380 and 750 µmol mol-1) at 20 and 35°C, and two additional temperatures (25 and 30 °C) at750 µmol mol-1CO2. Leaf CO2exchange rate (CER) was measuredat a plant's respective growth temperature and at two CO2concentrationsof approx. 380 and 700 µmol mol-1. Long-term CO2enrichmentstimulated CER in both species, although the response was greaterin the C3,P. smithii . Doubling the [CO2] from 380 to 750 µmolmol-1stimulated CER ofP. smithii slightly more in plants grownand measured at 30 °C compared to plants grown at 20, 25or 35 °C. CO2-enriched plants sometimes exhibited lowerCER when compared to ambient-grown controls measured at thesame [CO2], indicating photosynthetic acclimation to CO2growthregime. InP. smithii , such reductions in CER were associatedwith increases in TNC and specific leaf mass, reductions inleaf [N] and, in one instance, a reduction in leaf conductancecompared to controls. InB. gracilis , photosynthetic acclimationwas observed more often, but significant changes in leaf metabolitelevels from growth at different [CO2] were generally less evident.Temperatures considered optimal for growth (C3: 20 °C; C4:35 °C) sometimes led to CO2-induced accumulations of TNCin both species, with starch accumulating in the leaves of bothspecies, and fructans accumulating only inP. smithii. Photosynthesisof both species is likely to be enhanced in future CO2-enrichedand warmer environments, although responses will sometimes beattenuated by acclimation. Acclimation; blue grama (Bouteloua gracilis (H.B.K.) Lag ex Steud.); leaf nitrogen concentration; nonstructural carbohydrates; photosynthesis; western wheatgrass (Pascopyrum smithii (Rydb.) Love) 相似文献
4.
Resolution of Net Dark Fixation of Carbon Dioxide into Its Respiration and Gross Fixation Components in Bryophyllum daigremontianum 总被引:3,自引:0,他引:3
Dark respiration rate increased with temperature between 10and 24°C (Q10 =2.32.7). The rate of gross dark CO2fixation (GDF) was affected by temperature, but irregularly.Cumulative GDF was not affected by temperature in this range.Cumulative respiration increased from 17 per cent of cumulativeGDF at 10°C, to 72 per cent at 24°C and was thus responsiblefor the 65 per cent drop in net dark fixation between thesetwo temperatures. and respiration rates were functions of the light intensityin the preceding light period. The function for cumulativeGDFwas of the saturation form, maximum accumulation being obtainedat 12 mW cm2. It is concluded that both GDF and respirationrates depend on levels of substrates formed during the lightperiod. However, the rate of GDF did not appear to be directlyrelated to the rate of respiration. 相似文献
5.
A long-term, steady-state 13CO2 assimilation system at a constantCO2 concentration with a constant 13C abundance was designedand applied to quantitative investigations on the allocationof photoassimilated carbon in nodulated soya bean (Glycine maxL.) plants. The CO2 concentration in the assimilation chamberand its 13C abundance were maintained constant with relativevariances of less than ±0.5 per cent during an 8-h assimilationperiod. At the termination of 8-h 13CO2 assimilation by plantsat early flowering stage, the currently assimilated carbon relativeto total tissue carbon (measured by the degree of isotopic saturation)were for young leaves (including flower buds), 13.9 per cent;mature leaves, 15.7 per cent; stems+petioles, 5.9 per cent;roots, 5.4 per cent and nodules, 6.9 per cent, 48 h after theend of the 13CO2 assimilation period, they were 12.3, 7.5, 7.4,6.8 and 6.1 per cent, respectively. The treatment with a highconcentration of nitrate in the nutrient media significantlydecreased the allocation of 13C into nodules. Experiments on13CO2 assimilation by plants at the pod-filling stage were alsoconducted. Labelling by 13C was weaker than at the early floweringstage, but an intense accumulation of 13C into reproductiveorgans was observed. Glycine max L., nodulated soya bean plants, 13CO2 assimilation, carbon dynamics 相似文献
6.
Relationship between Leaf Structure and Gas Exchange in Wheat Leaves at Different Insertion Levels 总被引:3,自引:0,他引:3
Net photosynthesis rate (Pn), stomatal conductance to CO2 andresidual conductance to CO2 were measured in the last six leaves(the sixth or flag leaf and the preceding five leaves) of Triticumaestivum L. cv. Kolibri plants grown in Mediterranean conditions.Recently fully expanded leaves of well-watered plants were alwaysused. Measurements were made at saturating photosynthetic photonflux density, and at ambient CO2 and O2 levels. The specificleaf area, total organic nitrogen content, some anatomical characteristics,and other parameters, were measured on the same leaves usedfor gas exchange experiments. A progressive xeromorphic adaptation in the leaf structure wasobserved with increasing leaf insertion levels. Furthermore,mesophyll cell volume per unit leaf area (Vmes/A) decreasedby 52·6% from the first leaf to the flag leaf. Mesophyllcell area per unit leaf area also decreased, but only by 24·5%.However, nitrogen content per unit mesophyll cell volume increasedby 50·6% from the first leaf to the flag leaf. This increasecould be associated to an observed higher number of chloroplastcross-sections per mm2 of mesophyll cell cross-sectional areain the flag leaf: values of 23000 in the first leaf and 48000in the flag leaf were obtained. Pn per unit leaf area remainedfairly constant at the different insertion levels: values of33·83±0·93 mg dm2 h1 and32·32±1·61 mg dm2 h1 wereobtained for the first leaf and the flag leaf, respectively.Residual conductance, however, decreased by 18·2% fromthe first leaf to the flag leaf. Stomatal conductance increasedby 41·7%. The steadiness in Pn per unit leaf area across the leaf insertionlevels could be mainly accounted for by an opposing effect betweena decrease in Vmes/A and a more closely packed arrangement ofphotosynthetic apparatus. Adaptative significance of structuralchanges with increasing leaf insertion levels and the steadinessin Pn per unit leaf area was studied. Key words: Photosynthesis, structure, wheat 相似文献
7.
ROMERO-ARANDA R.; BONDADA B. R.; SYVERTSEN J. P.; GROSSER J. W. 《Annals of botany》1997,79(2):153-160
The effect of tetraploidy on leaf characteristics and net gasexchange was studied in diploid (2x ) and autotetraploid (4x) Valencia sweet orange (Citrus sinensis (L.)Osb.) and Femminello lemon (Citrus limon (L.)Burm. f.) leaves. Comparisons between ploidy levels were madeunder high irradiance (I) in a growth chamber or low total Iin a glasshouse. Tetraploids of both species had thicker leaves,larger mesophyll cell volume and lower light transmittance thandiploids regardless of growth I. Mesophyll surface area perunit leaf area of 2x leaves was 515% greater than on4x leaves. Leaf thickness and mesophyll cell volume were greaterin high I leaves than low I leaves. In high I, average leafarea was similar for 2x and 4x leaves, whereas in low I it was30% greater in 4x than in 2x leaves. Nitrogen and chlorophyllconcentration per cell increased with ploidy level in both growthconditions. The ratio of chlorophyll a:b was 25% greater in2x than in 4x leaves. When net CO2assimilation rate (ACO2) wasbased on leaf area, 4x orange leaves had 2435% lowerACO2than their diploids. There were no significant differencesin ACO2between 2x and 4x orange or lemon leaves when expressedon a per cell basis. Overall, lower ACO2per unit leaf area oftetraploids was related to increase in leaf thickness, largermesophyll cell volume, the decrease in mesophyll area exposedto internal air spaces, and the lower ratio between cell surfaceto cell volume. Such changes probably increased the resistanceto CO2diffusion to the site of carboyxlation in the chloroplasts. Cell volume; chlorophyll; irradiance; leaf thickness; nitrogen; photosynthesis; ploidy; Citrus limon ; C. sinensis ; Valencia sweet orange; Femminello lemon 相似文献
8.
Increasing the concentration of CO2 in the air from the usual300 ppm to 1, 000 ppm in growth rooms with temperatures of 20°C during the 16-h light period and 15° C during the 8-hdark period increased the total dry weight of sugar-beet, barley,and kale by about 5o per cent. A further increase in CO, concentrationto 3, 300 ppm increased dry weight slightly more. These effectsoccurred with light intensities ranging from 3.7 to II.6 caldm2 min1 of visible radiation supplied by a mixtureof fluorescent and tungsten lamps, and were only slightly greaterwith the brighter light. Extra CO2 also increased leaf area,though relatively less than dry weight, and the number of barleyshoots but not of sugar-beet or kale leaves; it decreased leaf-arearatio, specific leaf area, and the ratio of tops to roots. Maizewas taller with extra CO2. Net assimilation rates in 1, 000 and 3, 300 ppm CO2 were about20 and 30 per cent respectively greater than in 300 ppm. Uptakeof CO2 in the light by complete tops and single leaves alsoincreased with increase in CO2 concentration. Photosynthesisof leaves of plants recently transferred to a new CO2 concentrationdepended only on that concentration and not on the originalone. Doubling the light intensity from 3.7 to 7.7 cal dm2min1 affected dry weight, leaf area, net assimilationrate, etc., similarly to a tenfold increase in CO2 concentration. 相似文献
9.
Growth Response of a Chrysanthemum Crop to the Environment. I. Experimental Techniques 总被引:1,自引:0,他引:1
The construction and mode of operation of six daylit assimilationchambers and the methods used to measure canopy photosynthesisand radiation interception are described. The chambers havea cuboid plant space, with sides 1.2 m long, in which temperaturecan be controlled from ambient to 30 °C with a temporalvariation of ±0.5 °C. Conductimetric controllersmaintain CO2 concentration in the chambers within ±5per cent of the desired values. The amount of CO2 injected andother variables needed to relate mean CO2 assimilation ratesto mean radiation flux density over successive 10 min intervalsthroughout the day are recorded on punched tape for subsequentcomputer processing. The chambers have limitations in the number,range and variability of the environmental factors controlledbut they cost approximately one tenth as much as commercialdaylit cabinets and provide adequate, reproducible data formodelling many aspects of crop growth. 相似文献
10.
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
11.
Effects of Nitrogen Fertilizer on the Distribution of Photosynthate during Grain Growth of Spring Wheat 总被引:1,自引:0,他引:1
The distribution of photosynthate labelled with 14C was studiedin spring wheat grown with different amounts of nitrogen fertilizerin the three years 19724, after exposing the flag leafor the leaf below the flag leaf to 14CO2 at 610 or 1926days after anthesis. The movement of 14C to ears was unaffectedby nitrogen fertilizer except after early exposure in 1973,when nitrogen increased the retention of 14C in stems at maturity The concentration of sugar in the top part of the shoot at theend of the day was unaffected by nitrogen in 1973, but at 22days after anthesis in 1974 the concentration of sucrose inthe glumes and rachis, and in the flag leaf lamina was increasedby nitrogen. Loss of sugar by translocation and respirationduring the night may explain why this increase in concentrationwas not reflected in the 14C distribution 24 h after supplying14C. The proportion of the total 14C content of the shoot that wasin the ear at maturity ranged from 68 to 95 per cent dependingon when and to which leaf the 14CO2 was supplied. Less than5 per cent remained in the leaf exposed to 14CO2. The proportionof the final ear weight contributed by the leaf below the flagleaf was about half that contributed by the flag leaf. In 1974 about 24 per cent of the 14C absorbed by the flag leaf,and 56 per cent of that absorbed by the second leaf, was lostby maturity, presumably by respiration. Most loss occurred inthe first 24 h. 相似文献
12.
KEYS A. J.; SAMPAIO E. V. S. B.; CORNELIUS M. J.; BIRD I. F. 《Journal of experimental botany》1977,28(3):525-533
Wheat plants were grown in a controlled environment with daytemperatures of 18 ?C and with 500 µ Einsteins m281 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 m2s1 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 µmol1. 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
13.
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
14.
Experiments conducted at light intensities equivalent to thosereaching the embryo through the intact pericarp showed that: (a) excised embryos from green berries would not germinate,but those from transitional and pink (mature) berries begangermination immediately; (b) the viscid layer neither stimulated nor inhibited germination; (c) there was 100% germination at 1025°C but maximumelongation at 2530 °C, with a minimum at 4 °Cand death at 40°C; (d) there was 100% germination at 15% CO2 in air, butmaximum elongation at 1%. with>90% germination in air minusCO2 and negligible at 20% CO2, 16% O2, 64% N2|| or higher concentrationsof CO2; (e) the average gas concentration in mature berries, as measuredby gas spectrometry, was 127% CO2, 12% O2, 61% N2||. Minor fluctuationsin CO2/O2 content indicated limited photosynthesis as well asrespiration in both green and mature berries. The high CO2 concentrationin the berry is sufficient in itself to explain the maintenanceof dormancy until the seed is excised by birds; (f) contrary to previous assumptions, most elongation of theembryo was due to growth of the cotyledons rather than of thehypocotyl or radicle. 相似文献
15.
The Effect of Subjecting Peas to Air Enriched with Carbon Dioxide: II. RESPIRATION AND THE METABOLISM OF THE MAJOR ACIDS 总被引:1,自引:0,他引:1
Whole peas at about 75 per cent of their maximum fresh weightwere subjected to 530 per cent CO2 in air for periodsof from 16 d, then returned to air for a further 1 d.Samples were withdrawn at intervals and organic acids, TCO2and ethanol estimated as well as the rate of respiration. Slicesof cotyledons suspended in water were also subjected to highconcentrations of CO2 in air for 3 h. The rate of respiration was inhibited progressively by increasein CO2 content of the tissue. The high internal CO2 contentof the intact pea causes an inhibition of its rate of respirationby about 25 per cent. Alcohol production commenced at between10 and 15 per cent CO2 in the ambient gas and slowly increasedin rate up to 37 per cent. The CO2-air mixtures reduced the content of malate, pyruvateand -oxoglutarate, increased that of succinate and left citrateunaffected. On return to air malate rose rapidly and succinatefell slowly to their original concentrations. During the sameperiod the concentration of PEP fell sharply and after about1 h rose again, whereas oxalacetate showed a reverse response.It is argued that the rapid re-synthesis of malate was by carboxylationof PEP to oxalacetate and that this reaction was stimulatedby a change in pH rather than by the direct effect of the changein concentration of CO2. In one experiment 14CO2 was supplied for 2 h before return toair and the movement of 14C followed for 6 h. The results supportthe method of re-synthesis of malate proposed. 相似文献
16.
An understanding of volatilization of nitrogen (N) from leavesof crop and weed species may be important to the improvementof crop production. Foliar N loss (both reduced and oxidizedforms), net CO2 uptake, and transpiration rates were measuredconcomitantly at 30°C on soyabean (Glycine max (L.) Merr.)and sorghum (Sorghum bicolor (L.) Moench) leaves at low (1 percent), ambient (20 per cent), and high (40 per cent) levelsof oxygen. In soyabeans, maximum reduced and total N losseswere found at the highest O2 concentration, and the lowest Nlosses were measured at the lowest O2 level. Net CO2 assimilationwas significantly reduced with increasing O2 during two of threesamplings. Quantities of oxidized N lost were not altered. Sorghumshowed no significant effects from O2 on N loss or net CO2 assimilation.The increased ammonia released from soyabean foliage in thepresence of higher concentration of O2 probably affects metabolicpathways that contribute to the total reduced N volatilization. Glycine max, Sorghum bicolor, CO2 assimilation, nitrogen loss 相似文献
17.
Growth and Resource Use of Birch Seedlings Under Elevated Carbon Dioxide and Temperature 总被引:9,自引:2,他引:7
The effects of elevated CO2and temperature on the growth, resourceacquisition and resource allocation of small birch seedlings(Betula pendula Roth.) were examined under conditions of non-limitingsoil, water and nutrient supply. Seedlings were planted in potsand placed in controlled environment chambers either under normalambient conditions (CON), or in the presence of elevated CO2(approx.700 µmol mol-1; Elev. C), elevated temperature (approx.3 °C above the outside ambient temperature; Elev. T) ora combination of elevated CO2and elevated temperature (Elev.C + T). Both Elev. C and Elev. T significantly increased biomassaccumulation, but the extent of the increase depended greatlyon the stage of development of the seedlings. Furthermore, thetheoretically expected positive effect of the warmer temperatureon the CO2-induced stimulation of growth was not observed. Byanalysing resource acquisition (i.e. CO2 , nitrogen and wateruptake), seedling development, leaf area production and theallocation pattern, it was deduced that the CO2-stimulated increasein biomass resulted mainly from the initial fertilizationeffect of CO2while the temperature-induced increase in biomassstemmed from higher net carbon intake during the middle andlatter parts of the growing season achieved by virtue of theincreased leaf area and larger photosynthetic capacity. Thelack of positive stimulation by temperature under Elev. C +T may be related in part to (1) CO2-induced acceleration ofseedling development, which led to a small or no response toCO2enrichment and lower leaf area production during the latterpart of the growth season, and (2) a cumulative delay in theresponse of growth to the warmer temperature, which did notincrease net carbon intake when the seedlings were at a juvenilestage. Neither Elev. C nor Elev. T altered the root:shoot ratioduring early growth, but Elev. C increased it during the latterpart of the growth season while Elev. T decreased it, possiblyon account of a change in leaf area retention. Finally, thenitrogen and water use efficiencies of seedlings at differentstages of development are discussed. Copyright 2001 Annals ofBotany Company Photosynthesis, growth, resource acquisition and allocation, elevated CO2and temperature, Betula pendula Roth 相似文献
18.
Plants of ryegrass (Lolium perenne L. cv. Melle) were grownfrom the early seedling stage in growth cabinets at a day/nighttemperature of 20/15 °C, with a 12-h photoperiod, and aCO2 concentration of either 340 or 680 ± 15 µl11 CO2. Young, fully-expanded, acclimated leaves fromprimary branches were sampled for length of stomata, and ofepidermal cells between stomata, numbers of stomata and epidermalcells per unit length of stomatal row, numbers of stomatal rowsacross the leaf and numbers of stomatal rows between adjacentvein ridges. Elevated CO2 had no significant effect on any ofthe measured parameters. Elevated CO2, Lolium perenne, ryegrass, stomatal distribution, stomatal size 相似文献
19.
This study investigated how CO2and temperature affect dry weight(d.wt) accumulation, total nonstructural carbohydrate (TNC)concentration, and partitioning of C and N among organs of twoimportant grasses of the shortgrass steppe,Pascopyrum smithiiRydb. (C3) andBouteloua gracilis(H.B.K.) Lag. ex Steud. (C4).Treatment combinations comprised two temperatures (20 and 35°C)at two concentrations of CO2(380 and 750 µmol mol-1),and two additional temperatures of 25 and 30°C at 750 µmolmol-1CO2. Plants were maintained under favourable nutrient andsoil moisture and harvested following 21, 35, and 49d of treatment.CO2-induced growth enhancements were greatest at temperaturesconsidered favourable for growth of these grasses. Comparedto growth at 380 µmol mol-1CO2, final d.wt of CO2-enrichedP.smithiiincreased 84% at 20°C, but only 4% at 35°C. Finald.wt ofB. graciliswas unaffected by CO2at 20°C, but wasenhanced by 28% at 35°C. Root:shoot ratios remained relativelyconstant across CO2levels, but increased inP. smithiiwith reductionin temperature. These partitioning results were adequately explainedby the theory of balanced root and shoot activity. Favourablegrowth temperatures led to CO2-induced accumulations of TNCin leaves of both species, and in stems ofP. smithii, whichgenerally reflected responses of above-ground d.wt partitioningto CO2. However, CO2-induced decreases in plant tissue N concentrationswere more evident forP. smithii. Roots of CO2-enrichedP. smithiihadgreater total N content at 20°C, an allocation of N below-groundthat may be an especially important adaptation for C3plants.Tissue N contents ofB. graciliswere unaffected by CO2. Resultssuggest CO2enrichment may lead to reduced N requirements forgrowth in C3plants and lower shoot N concentration, especiallyat favourable growth temperatures. Acclimation to CO2; blue grama; Bouteloua gracilis ; carbohydrate; climate change; global change; grass; growth; growth temperature optima; nitrogen; N uptake; Pascopyrum smithii; western wheatgrass 相似文献
20.
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 CO2 exchange(CER) were measured at 27 °C and saturating light usinginfrared gas analysis. Stomatal (rs) and mesophyll resistances,CO2 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 CO2 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 chloroplastCO2 concentration (rm, o), but not when calculated assuminga chloroplast CO2 concentration equal to the CO2 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