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1.
Panicum hians and Panicum milioides were found to have characteristicsintermediate to those of C3 and C4 species with respect to CO2compensation point, percentage inhibition of photosynthesisby O2 at various O2/CO2 solubility ratios, and water use efficiency.C4 species have a higher carboxylation efficiency than eitherthe intermediate or C3 species. During photosynthesis, evenunder 2.5% O2, C4 species have a higher affinity for intercellularCO2 (Km 1.6 µM) apparently due to the initial carboxylationthrough PEP carboxylase. Under low O2 the intermediate and C3species had a similar affinity for intercellular CO2 duringphotosynthesis (Km 57 µM) consistent with carboxylationof atmospheric CO2 through RuDP carboxylase. There were considerablevariation in photosynthesis/unit leaf area at saturating CO2levels in the species examined which in part is due to differencesin RuDP carboxylase /unit leaf area. The highest rates of photosynthesis/unitleaf area under CO2-saturating conditions were with the C3 specieswhich had a correspondingly high level of RuDP carboxylase/unitleaf area. Possibilities for the greater efficiency of P. hiansand P. milioides in comparison to C3 species in utilizing lowlevels of CO2 in the presence of atmospheric O2 are discussed.
1 This research was supported by the College of Agriculturaland Life Sciences, University of Wisconsin, Madison; and theUniversity of Wisconsin Research Committee with funds from theWisconsin Alumni Research Foundation. (Received June 25, 1977; ) 相似文献
2.
SCHMITT ANDREAS K.; LEE HELEN S. J.; LUTTGE ULRICH 《Journal of experimental botany》1988,39(11):1581-1590
Gas exchange measurements were undertaken on 2-year-old plantsof Clusia rosea. The plants were shown to have the ability toswitch from C3-photosynthesis to CAM and vice versa regardlessof leaf age and, under some conditions, CO2 was taken up continuously,throughout the day and night. The light response was saturatedby 120 µmol m2 s1 typical of a shade plant. Gas exchange patterns in response to light, water and VPD wereexamined. All combinations of daytime and night-time CO2 uptakewere observed, with rates of CO2 uptake ranging from 2 to 11µmol m2 s1 depending upon water status andlight. Categorization of this plant asC3, CAM or an intermediateis impossible. Differing VPD affected the magnitude of changesfrom CAM to C3-photosynthesis (0 to 0.5 and 0 to 6.0 µmolm2 s1 CO2, respectively) when plants were watered.Under well-watered conditions, but not under water stress, highPPFD elicited changes from CAM to C3 gas exchange. This is unusualnot only for a shade plant but also for a plant with CAM. Itis of ecological importance for C. rosea, which may spend theearly years of its life as an epiphyte or in the forest understorey,to be able to maximize photosynthesis with minimal water loss. Key words: Clusia rosea, CAM, C3, stress 相似文献
3.
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
4.
The capacity for C4 photosynthesis in Panicum milioides, a specieshaving reduced levels of photorespiration, was investigatedby examining the activity of certain key enzymes of the C4 pathwayand by pulse-chase experiments with 14CO2. The ATP$P1 dependentactivity of pyruvate,P1 dikinase in the species was extremelylow (0.140.18 µmol mg chlorophyll1 min1).Low activity of the enzyme was also found in Panicum decipiensand Panicum hians (related species with reduced photorespiration)and in Panicum laxum (a C3 species). The antibody to pyruvate,P1dikinase caused about 70% inhibition of the ATP$P1 dependentactivity of the enzyme in P. milioides. The activity of NAD-malicenzyme and NADP-malic enzyme in P. milioides was equally low(approximately 0.10.2 µmol mg chlorophyll1min1) and similar to the activity in P. decipiens, P.hians and P. laxum. Photosynthetic pulse-chase experiments underatmospheric conditions showed a typical C3-like pattern of carbonassimilation including the labelling of glycine and serine asexpected during photorespiration. During the pulse with 14CO2only about 1% of the labelled products appeared in malate and23% in aspartate. During a chase in atmospheric levelsof CO2 for up to 6 min there was a slight increase in labellingin the C4 acids. The amount of label in carbon 4 of aspartatedid not change during the chase, indicating little or no turnoverof the C4 acid via decarboxylation. The results indicate thatunder atmospheric conditions P. milioides assimilates carbondirectly through the C3 pathway. Photorespiration as indicatedby the CO2 compensation point may be repressed in the speciesby a more efficient recycling of photorespired CO2. (Received June 8, 1982; Accepted July 22, 1982) 相似文献
5.
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
6.
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
7.
Plants of Phaseolus vulgaris L were grown from seed in open-topgrowth chambers at present day (350 µmol mol1)and double the present day (700 µmol mol1) atmosphericCO2 concentration with either low (L, without additional nutrientsolution) or relatively high (H, with additional nutrient solution)nutrient supply Measurements of assimilation rate, stomatalconductance and water use efficiency were started 17 d aftersowing on each fully expanded, primary leaf of three plantsper treatment Measurements were made in external CO2 concentrations(C2) of 200, 350, 450, 550 and 700 µmol mol1 andrelated to both Ca and to C1, the mean intercellular space CO2concentration Fully adjusted, steady state measurements weremade after approx 2 h equilibration at each CO2 concentration The rate of CO2 assimilation by leaves increased and stomatalconductance decreased similarly over the range of Ca or C1 inall four CO2 and nutrient supply treatments but both assimilationrate and stomatal conductance were higher in the high nutrientsupply treatment than in the low nutrient treatment The relationbetween assimilation rate or stomatal conductance and C1 wasnot significantly different amongst plants grown in present-dayor elevated CO2 concentration in either nutrient supply treatment,i e there was no evidence of down regulation of photosynthesisor stomatal response Increase in CO2 concentration from 350to 700 µmol mol1 doubled water use efficiency ofindividual leaves in the high nutrient supply treatment andtripled water use efficiency in the low nutrient supply treatment The results support the hypothesis that acclimation phenomenaresult from unbalanced growth that occurs after the seed reservesare exhausted, when the supply of resources becomes growth limiting CO2 enrichment, Phaseolus vulgaris L., net CO2 assimilation rate, stomatal conductance, water use efficiency 相似文献
8.
Effects of nitrogen on Pinus palustris foliar respiratory responses to elevated atmospheric CO2 concentration 总被引:2,自引:0,他引:2
Mitchell R.J.; Runion G.B.; Prior S.A.; Rogers H.H.; Amthor J.S.; Henning F.P. 《Journal of experimental botany》1995,46(10):1561-1567
Indirect effects of atmospheric CO2 concentration [CO2], onlongleaf pine (Pinus palustris Mill.) foliage respiration werestudied by growing trees in a factorial arrangement of low andhigh [CO2] (369 and 729µmol CO2 mol1) and low andhigh N (40 and 400 kg ha1 yr1). Direct effectsof [CO2] on leaf respiration were tested by measuring respirationrates of foliage from all treatments at two CO2 levels (360and 720µmol CO2mol1) at the time of measurement.Elevated CO2 did not directly or indirectly affect leaf respirationwhen expressed on a leaf area or mass basis, but a significantincrease in respiration per unit leaf N was observed in treesgrown in elevated [CO2] (indirect response to elevated [CO2]).The lack of a [CO2] effect on respiration, when analysed onan area or mass basis, may have resulted from combined effectsof [CO2] on factors that increase respiration (e.g. greateravailability of non-structural carbohydrates stimulating growthand carbon export from leaves) and on factors that decreaserespiration (e.g. lower N concentration leading to lower constructioncosts and maintenance requirements). Thus, [CO2] affected factorsthat influence respiration, but in opposing ways. Key words: Pinus palustris, elevated CO2, nitrogen, foliar, respiration 相似文献
9.
Rintamäki, E. and Aro, E.-M. 1985. Photosynthetic and photorespiratoryenzymes in widely divergent plant species with special referenceto the moss Ceratodon purpureus: Properties of ribulose bisphosphatecarboxylase/oxygenase, phosphoenolpyruvate carboxylase and glycolateoxidase.J. exp. Bot. 36: 16771684. Km(CO2) values and maximal velocities of ribulose bisphosphatecarboxylase/oxygenase (E.C. 4.1.1.39
[EC]
) were determined for sixplant species growing in the wild, consisting of a moss, a fernand four angiosperms. The maximum velocities of the RuBP carboxylasesvaried from 0.13 to 0.;62 µmol CO2 fixed min1 mg1soluble protein and the Km(CO2) values from 15 to 22 mmol m3CO2. The highest Km(CO2) values found were for the moss, Ceratodonpurpureus, and the grass, Deschampsia flexuosa. These plantsalso had the highest ratios of the activities of RuBP carboxylaseto RuBP oxygenase. Glycolate oxidase (E.C. 1.1.3.1
[EC]
) activitieswere slightly lower in D.flexuosa, but not in C. purpureus,than for typical C3 species. Phosphoenolpyruvate carboxylase(E.C. 4.1.1.31
[EC]
) was not involved in the photosynthetic carboxylationby these two plants. However, another grass, Phragmites australis,was intermediate in PEP carboxylase activity between C3 andC4 plants The properties of RuBP carboxylase/oxygenase are discussedin relation to the activities of PEP carboxylase and glycolateoxidase and to the internal CO2 concentration. Key words: RuBP carboxylase, oxygenase, Km(CO2), moss 相似文献
10.
Effect of Elevated CO2 on Stomatal Density and Distribution in a C4 Grass and a C3 Forb under Field Conditions 总被引:1,自引:0,他引:1
Knapp Alan K.; Cocke Meagan; Hamerlynck Erik P.; Owensby Clenton E. 《Annals of botany》1994,74(6):595-599
Two common tallgrass prairie species, Andropogon gerardii, thedominant C4 grass in this North American grassland, and Salviapitcheri, a C3 forb, were exposed to ambient and elevated (twiceambient) CO2 within open-top chambers throughout the 1993 growingseason. After full canopy development, stomatal density on abaxialand adaxial surfaces, guard cell length and specific leaf mass(SLM; mg cm-2) were determined for plants in the chambers aswell as in adjacent unchambered plots. Record high rainfallamounts during the 1993 growing season minimized water stressin these plants (leaf xylem pressure potential was usually >-1·5 MPa in A. gerardii) and also minimized differencesin water status among treatments. In A. gerardii, stomatal densitywas significantly higher (190 ± 7 mm-2; mean ±s.e.) in plants grown outside of the chambers compared to plantsthat developed inside the ambient CO2 chambers (161 ±5 mm-2). Thus, there was a significant 'chamber effect' on stomataldensity. At elevated levels of CO2, stomatal density was evenlower (P < 0·05; 121 ± 5 mm-2). Most stomatawere on abaxial leaf surfaces in this grass, but the ratio ofadaxial to abaxial stomatal density was greater at elevatedlevels of CO2. In S. pitcheri, stomatal density was also significantlylower when plants were grown in the open-top chambers (235 ±10 mm-2 outside vs. 140 ± 6 mm-2 in the ambient CO2 chamber).However, stomatal density was greater at elevated CO2 (218 ±12 mm-2) compared to plants from the ambient CO2 chamber. Theratio of stomata on adaxial vs. abaxial surfaces did not varysignificantly in this herb. Guard cell lengths were not significantlyaffected by growth in the chambers or by elevated CO2 for eitherspecies. Growth within the chambers resulted in lower SLM inS. pitcheri, but CO2 concentration had no effect. In A. gerardii,SLM was lower at elevated CO2. These results indicate that stomataland leaf responses to elevated CO2 are species specific, andreinforce the need to assess chamber effects along with treatmenteffects (CO2) when using open-top chambers.Copyright 1994, 1999Academic Press Andropogon gerardii, elevated CO2, Salvia pitcheri, stomatal density, tallgrass prairie 相似文献
11.
Eastmond Peter; Kolc Lucie; Rawsthorne Stephen 《Journal of experimental botany》1996,47(11):1763-1769
The aim of this study was to assess the photosynthetic potentialof developing seeds of oilseed rape (Brassica napus L.) andto compare photosynthetic properties of embryo plastids withthose of leaf chloroplasts from the same species. Measurementsof CO2-dependent O2 evolution show that developing seeds ofB. napus are photosynthetically active in vitro. Essentially,all of the photosynthetic activity of the developing seed isaccounted for by the embryo. The rate of photosynthesis by developingembryos increased until the onset of desiccation, after whichit declined, so that by maturity embryos were no longer photosyntheticallyactive. Photosynthetic activity was positively correlated withchlorophyll content throughout development. Comparison of thephotosynthetic characteristics of leaf and embryo chloroplastsrevealed that rates of uncoupled electron transport were 2.5-foldgreater in those from the embryo. Light-saturated rates of CO2-dependentO2 evolution, per unit chlorophyll, and CO2 saturation pointswere similar for chloroplasts from both tissues. However, light-saturationpoints and chlorophyll a/b ratios were lower for embryo thanfor leaf choroplasts. Embryos and embryo chloroplasts also containedconsiderably less ribulose 1,5-bisphosphate carboxylase/oxygenaseprotein per unit total protein, than leaves. Although excisedembryos were capable of high rates of CO2-dependent O2 evolution(90100 mol mg1 chlorophyll h1) under asaturating photosynthetic photon flux density (PPFD), low transmittanceof light through the silique wall (30%), together with the highPPFD required to achieve light compensation points in developingseeds (500 mol m2 s1), suggests that photosynthesisin vivo is unlikely to make a net contribution to carbon economyunder normal environmental conditions. Key words: Embryo, development, photosynthesis, chloroplast, Brassica napus L. 相似文献
12.
Ward, D. A. and Drake, B. G. 1987. Photoinhibition under atmosphericO2, the activation state of RuBP carboxylase and the contentof photosynthetic intermediates in soybean and wheat.J.exp. Bot. 38: 19371948. Associations between photosynthesis, the activation state ofRuBP carboxylase and the contents of photosynthetic intermediateswere compared in soybean and wheat leaves before and after exposureto photoinhibitory treatments in the presence of atmosphericO2. Exposing attached leaves to a supra-saturating irradiance(3 800 µmol quanta m 2 s1) for 2 h in CO2-freeair decreased carboxylation efficiency and the light-saturatedphotosynthetic rate in air by approximately 50%. Exposure tothe photoinhibitory treatment for periods in excess of 2 h didnot cause a further decrease of photosynthesis in soybean. Althoughphotosynthesis was reduced, the initial and total (fully-activated)activities of ribulose 1,5-bisphosphate carboxylase (RuBPCase)in leaf extracts were unaltered in each species by the photoinhibitorytreatment. This was true for leaves sampled under both air andat a rate-limiting intercellular CO2 partial pressure (Ci) of75 µPa Pa1. The contents of ribulose l,5-bisphosphate(RuBP) and 3-phosphoglyceric acid (3-PGA) were reduced by thephotoinhibitory treatment in soybean leaves sampled in air andat a rate-limiting Ci, although the RuBP/3-PGA ratio was unaffected.The relative reduction of RuBP content in soybean leaves atrate-limiting C1 was similar to the corresponding reductionof carboxylation efficiency. For wheat,the relative reductionof RuBP content at rate-limiting Ci (19%) caused by thephotoinhibitory treatment was considerably less than the correspondingdecrease of carboxylation efficiency (49%).The RuBP/3-PGAratio of wheat was also increased significantly by the photoinhibitorytreatment The significance of these observations to the regulationof CO2-limited photosynthesis in leaves experiencing photoinhibitionunder atmospheric oxygen is discussed. Consideration is alsogiven to the previous contention that contemporary measurementsof initial activity in crude extracts may provide a spuriousindication of the amount of the enzyme-CO2-Mg2 + form of RuBPcarboxylase present in the leaf. Key words: Carboxylation efficiency, RuBP carboxylase, photoinhibition, RuBP, 3-PGA 相似文献
13.
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
14.
Flag Leaf Photosynthesis of Triticum aestivum and Related Diploid and Tetraploid Species 总被引:22,自引:0,他引:22
Rates of net photosynthesis of the flag leaves of 15 genotypesof wheat and related species were measured throughout theirlife, using intact leaves on plants grown in the field. At thestage when rates were maximal, they were in general highestfor the diploid species, intermediate for the tetraploidspeciesand lowest for Triticum aestivum (means of 38, 32 and 28 mgCO2 dm2 h1 respectively). Rates were stronglynegatively correlated with leaf area, leaf width and the meanplan area per mesophyll cell and positvely correlated with stomatalfrequency and number of veins per mm of leaf width. The differencesamong species in these attributes were mainly related to ploidylevel. It was not possible to determine the relative importanceof each anatomical feature, though the changes in stomatal frequencyhad only slight effects on stomatal conductance and the observeddifferences in rates of photosynthesis were much greater thanwould be expected from those in stomatal conductance alone. There was genetic variation in rates of light dependent oxygenevolution of isolated protoplasts and intact chloroplasts butno difference attributable to ploidy. The mean rate, 91 µmolO2 mg1 chlorophyll h1, equivalent to 3.9 mg CO2mg-1chlorophyll h-1 was considerably less than the rate of photosynthesisin comparable intact leaves, which was 7.2 mg CO2 mg1chlorophyll h1. The total above-ground dry matter yields were least for thewild diploids T. urartu and T. thauodar and the wild tetraploidT. dicoccoides, but the other wild diploids produced as muchdry matter as the hexaploids. The prospects of exploiting differences in photosynthetic ratein the breeding of higher yielding varieties are discussed. Triticum aestivum L., wheat, Aegilops spp, photosynthesis, stomatal conductance, stomatal frequency, polyploidy 相似文献
15.
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
16.
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
17.
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
18.
The kinetic properties of phosphoenolpyruvate (PEP) carboxylasehave been studied among several Flaveria species: the C3 speciesF. cronquistii, the C3C4 species F. pubescens and F.linearis, and the C4 species F. trinervia. At either pH 7 or8, the maximum activities (in µmol.mg Chl1.h1)for F. pubescens and linearis (187513) were intermediateto those of the C3 species (1219) and the C4 species(2,1822,627). The response curves of velocity versusPEP concentration were hyperbolic for the C3 and C3C4species at either pH 7 or 8 while they were sigmoidal for theC4 species at pH 7 and hyperbolic at pH 8. The Km values forPEP determined from reciprocal plots were lowest in the C3 species,and of intermediate value in the C3C4 species comparedto the K' values of the C4 species determined from Hill plotsat either pH 7 or 8. Glucose-6-phosphate (G6P) decreased theKm values for PEP at both pH 7 and 8 in the C3 and C3C4species. In the C4 species, G6P decreased the K' values at pH8 but increased the K' values at pH 7. In all cases, G6P hadits effect by influencing the activity at limiting PEP concentrationswith little or no effect on the maximum activity. At pH 8 andlimiting concentrations of PEP the degree of stimulation ofthe activity by G6P was greatest in the C4 species, intermediatein F. linearis, a C3C4 species, and lowest in the C3species. In several respects, the PEP carboxylases of the C3C4Flaveria species have properties intermediate to those of theC3 and C4 species. (Received April 30, 1983; Accepted August 22, 1983) 相似文献
19.
Effects of elevated carbon dioxide on three grass species from montane pasture II. Nutrient uptake, allocation and efficiency of use 总被引:5,自引:0,他引:5
Baxter R.; Gantley M.; Ashenden T.W.; Farrar J.F. 《Journal of experimental botany》1994,45(9):1267-1278
Agrostis capillaris L.4 Festuca vivipara L. and Poa alpinaL.were grown in outdoor open-top chambers at either ambient (340µmol mol1) or elevated (680 µmol1)CO2 for periods from 79 to 189 d. Under these conditions thereis increased growth of A. caplllarls and P. alpina, but reducedgrowth of F. vivipara. Nutrient use efficiency, nutrient productivity(total plant dry weight gain per unit of nutrient) and nutrientallocation of all three grass species were measured in an attemptto understand their individual growth responses further andto determine whether altered nutrient-use efficiencies and productivitiesenable plants exposed to an elevated atmospheric CO2 environmentto overcome potential limitations to growth imposed by soilfertility. Total uptake of nutrients was, in general, greater in plantsof A. capillaris and P. alpina (with the exception of N andK in the latter) when grown at 680 µmol mol1 CO2.In F. vivipara, however, uptake was considerably reduced inplants grown at the higher CO2 concentration. Overall, a doubling of atmospheric CO2 concentration had littleeffect on the nutrient use efficiency or productivity of A.capillaris. Reductions in tissue nutrient content resulted fromincreased plant growth and not altered nutrient use efficiency.In P. alpina, potassium, magnesium and calcium productivitieswere significantly reduced and photosynthetic nitrogen and phosphorususe efficiencies were doubled at elevated CO2 with respect toplants grown at ambient CO2 F. vivipara grown for 189 d showedthe most marked changes in nutrient use efficiency and nutrientproductivity (on an extracted dry weight basis) when grown atelevated CO2, F. vivipara grown at elevated CO2 however, showedlarge increases in the ratio of non-structural carbohydrateto nitrogen content of leaves and reproductive tissues, indicatinga substantial imbalance between the production and utilizationof assimilate. Key words: Nutrient, allocation, nutrient use efficiency, grasses, nutrient productivity, elevated CO2, cliniate change 相似文献
20.
CAMPBELL WILLIAM J.; ALLEN L. H. JR; BOWES GEORGE 《Journal of experimental botany》1990,41(4):427-433
Photosynthetic rates of outdoor-grown soybean (Glycine max L.Merr. cv. Bragg) canopies increased with increasing CO2 concentrationduring growth, before and after canopy closure (complete lightinterception), when measured over a wide range of solar irradiancevalues. Total canopy leaf area was greater as the CO2 concentrationduring growth was increased from 160 to 990 mm3 dm3.Photosynthetic rates of canopies grown at 330 and 660 mm3 CO2dm3 were similar when measured at the same CO2 concentrationsand high irradiance. There was no difference in ribulose bisphosphatecarboxylase/oxygenase (rubisco) activity or ribulose 1,5-bisphosphate(RuBP) concentration between plants grown at the two CO2 concentrations.However, photosynthetic rates averaged 87% greater for the canopiesgrown and measured at 660 mm3 CO2 dm3. A 10°C differencein air temperature during growth resulted in only a 4°Cleaf temperature difference, which was insufficient to changethe photosynthetic rate or rubisco activity in canopies grownand measured at either 330 or 660 mm3 CO2 dm3. RuBP concentrationsdecreased as air temperature during growth was increased atboth CO2 concentrations. These data indicate that the increasedphotosynthetic rates of soybean canopies at elevated CO2 aredue to several factors, including: more rapid development ofthe leaf area index; a reduction in substrate CO2 limitation;and no downward acclimation in photosynthetic capacity, as occurin some other species. Key words: CO2 concentration, soybean, canopy photosynthesis 相似文献