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1.
We have examined the long-term effects of NO3 concentrationson NO3 (15NO3) fluxes and cellular pool sizesin roots of intact 30-d-old wheat (Triticum aestivum cv. Courtot)grown hydroponically. Compartmental analysis was performed understeady-state conditions at five different levels of NO3concentration (from 0.1 up to 5 mol m3 taking into accountmetabolism and secretion into the xylem (Devienne et al., 1994).Nitrate and reduced nitrogen levels in the tissues were largelyindependent of external NO3 concentration although below1.5 mol m3 NO3; concentration limited plant growth.In the chamber, marked diurnal variations in net uptake occurredand, in the light, higher NO3 concentrations yieldedhigher NO3 uptake rates. After transfer of the plantsto the laboratory, the increase in net uptake linked to elevationof NO3; concentrations was even larger (from 0.1 to 8.8µmolh1 g1 FW) as a result of a marked increase (x1011) in the unidirectional influx at the plasmalemmawhile NO3 efflux was less enhanced (x 45). Underthese conditions, influx into the vacuole was also higher (x24) while efflux from the vacuole was little affected(x 13). NO3 concentrations within the cell compartmentswere estimated under the clas sical assumptions. The vacuolarconcentration was a little modified by NO3 availabilitywhereas that in the cytosol increased from about 10 mol m3to about 20 mol m3 indicating that (1) the absolute valuefor the cytosol was high and (2) it displayed only a small increasedespite very large changes in NO3 fluxes. NO3distribution within the cells did not seem to involve an activeaccumulation of NO3 in the vacuole. Key words: Wheat, ion transport, nitrate, 15N, compartmentation 相似文献
2.
Light Dependency of Carboxylation Efficiency and Ribulose-1, 5-Bisphosphate Carboxylase Activation in Trifolium subterraneum L. Leaves 总被引:1,自引:0,他引:1
The effect of photosynthetic photon flux density (PPFD) on carboxylationefficiency, estimated as the initial slope (IS) of net CO2 assimilationrate versus intercellular CO2 partial pressure response curve,as well as on ribulose-1, 5-bisphosphate carboxylase (Rubisco)activation was measured in Trifolium subterraneum L. leavesunder field conditions. The relationship between IS and PPFDfits a logarithmic curve. Rubisco activation accounts for theIS increase only up to a PPFD of 550 µmol photons m-2s-1. Further IS increase, between 550 and 1000 µmol photonsm-2 s-1, could be related to a higher ribulose fcwphosphate(RuBP) availability. The slow, but sustained IS increase above1000 µmol photons m-2 s-1 could be explained by the mesophyllCO2 diffusion barriers associated with the high chlorophylland protein content in field developed leaves. Key words: Photosynthesis, initial slope, ribulose-1, 5-bissphosphate carboxylase activation, light response, Trifolium subterraneum L 相似文献
3.
A revised method has been described for assaying auxin by thegrowth of Triticum coleoptile sections. With additions of Ca(NO3)2104 and MgSO4 105 mol liter1 the sensitivityand accuracy have been increased. This is mainly due to Ca.The coleoptiles obviously suffer from Ca-deficiency. The importanceof a strict time schedule for manipulations is emphasiced. Theduration of the tests is limited to 6 hr.Indole-3-acetic acidcan be determined in concentrations down to 109mol liter1;from 1010 to 109mol liter1 the log-logrelation between concentration and growth is linear. Above 107mol liter1 elongation takes place under an abnormal increasein elastic extension, indicating that growth is limited by someunknown wallstabilizing factor. The interrelation between auxin,an anti-auxin and Ca are discussed. (Received May 8, 1973; ) 相似文献
4.
Fragments of maize leaves were incubated at controlled temperatureand irradiance either on distilled water or on one of threeconcentrations of cytokinin (101, 102 and 103mol m3). The effects of zeatin or kinetin on stomatalaperture were determined by stripping abaxial epidermis fromthe fragments after incubation and immediately measuring stomatalapertures under the microscope. At each cytokinin concentrationleaf pieces were incubated at 5 or 350 µmol mol1CO2 with or without ABA (101 mol m3). At 5.0 µmolmol1 CO2 increasing the concentrations of zeatin hada negligible effect upon stomatal aperture. When air containing350 umol mol1 CO2 was bubbled through the incubationsolutions, apertures of stomata incubated on water were morethan halved. Increasing cytokinin concentrations reduced theeffect of CO2 on stomata and incubation on 101 mol m3zeatin completely removed any CO2 response. The addition ofABA restored the effect of CO2, even at the highest cytokininconcentration. Key words: Maize, CO2 response, ABA, Cytokinins 相似文献
5.
Differentiating Day from Night Effects of High Ambient [CO2] on the Gas Exchange and Growth of Xanthium strumarium L. Exposed to Salinity Stress 总被引:2,自引:0,他引:2
Sodium chloride, at a concentration of 88 mol m-3in half strengthHoagland nutrient solution, increased dry weight per unit areaofXanthium strumarium L. leaves by 19%, and chlorophyll by 45%compared to plants grown without added NaCl at ambient (350µmol mol-1) CO2concentration. Photosynthesis, per unitleaf area, was almost unaffected. Even so, over a 4-week period,growth (dry weight increment) was reduced in the salt treatmentby 50%. This could be ascribed to a large reduction in leafarea (>60%) and to an approx. 20% increase in the rate ofdark respiration (Rd). Raising ambient [CO2] from zero to 2000 µmol mol-1decreasedRd in both control and salinized plants (by 20% at 1000, andby 50% at 2000 µmol mol-1CO2concentration) compared toRd in the absence of ambient CO2. High night-time [CO2] hadno significant effect on growth of non-salinized plants, irrespectiveof day-time ambient [CO2]. Growth reduction caused by salt wasreduced from 51% in plants grown in 350 µmol mol-1throughoutthe day, to 31% in those grown continuously in 900 µmolmol-1[CO2]. The effect of [CO2] at night on salinized plants depended onthe daytime CO2concentration. Under 350 µmol mol-1day-time[CO2], 900 µmol mol-1at night reduced growth over a 4-weekperiod by 9% (P <0.05) and 1700 µmol mol-1reduced itby 14% (P <0.01). However, under 900 µmol mol-1day-time[CO2], 900vs . 350 µmol mol-1[CO2] at night increasedgrowth by 17% (P <0.01). It is concluded that there is both a functional and an otiose(functionless) component to Rd, which is increased by salt.Under conditions of low photosynthesis (such as here, in thelow day-time [CO2] regime) the otiose component is small andhigh night-time [CO2] partly suppresses functional Rd, therebyreducing salt tolerance. In plants growing under conditionswhich stimulate photosynthesis (e.g. with increased daytime[CO2]), elevated [CO2] at night suppresses mainly the otiosecomponent of respiration, thus increasing growth. Consequently,in regions of adequate water and sunlight, the predicted furtherelevation of the world atmospheric [CO2] may increase plantsalinity tolerance. Xanthium strumarium ; respiration; photosynthesis; salt stress; sodium chloride; carbon dioxide; atmosphere 相似文献
6.
Barley, ryegrass, and fodder radish were grown in flowing nutrientsolutions at four potassium concentrations, [Ke+], from 0.05to 4 mg I1. During the first 2 weeks after germinationthe response to [Ke+] (fodder radish > barley > ryegrass)depended on the potential relative growth rate, the ratio ofroot surface area to plant weight, and on the K+ flux into theroots. Subsequently, there was no effect of [Ke+] on growthrate within the range tested. The K+ flux decreased from 423? 1012 mol cm2 s1 in the first 2 weeksafter germination, when it was concentration-dependent, to 25? 1012 mol cm2 s1 after 45 weeks,when it became independent of [Ke+] down to 0.05 mg 11.The results explain the importance of high [Ke+] and rapid rootgrowth during the first 2 weeks after seed germination. 相似文献
7.
L-Leucine Transport in Isolated Protoplasts of Vinca Suspension Culture: Characterization of Uptake 总被引:1,自引:0,他引:1
The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H+ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The Km values of thethree affinity sites were 1.4 x 103 M, 1.3 x 104M, 4.3 x 105 M; the maximum velocity values were 3.3x 108, 4.5 x 109, 1.8 x 109 mol/10 min/4x 106 cells. (Received April 18, 1981; Accepted August 25, 1981) 相似文献
8.
Control of Wheat Root Elongation Growth: I. EFFECTS OF IONS ON GROWTH RATE, WALL RHEOLOGY AND CELL WATER RELATIONS 总被引:2,自引:0,他引:2
Pritchard, J., Tomos, A. D. and Wyn Jones, R. G. 1987. Controlof wheat root elongation growth. I. Effects of ions on growthrate, wall rheology and cell water relations.J. exp.Bot. 38: 948959. The nature of the ions in the bathing medium of hydroponicallygrown wheat seedlings strongly influenced root growth rate.In 0·5 mol m3 CaSO4 the growth rate was 32 mm24 h1 (used as 100% control rate). K+ and SO ions(10 mol m3) each inhibited extension growth (to about40% and 70% of the control value respectively). In the absenceof K+, Cl greatly reduced the inhibition due to SO42.Measurement of tissue plasticity and elasticity in the expandingzone with an Instron-type tensiometer indicated that both werea function of growth rate although relationship of plasticityto growth rate was the steeper and the more pronounced. Turgor pressure at the proximal end of the expanding zone wasnot correlated to growth, being approximately 0·65 MPain all treatments. In mature tissue turgor pressure varied withtreatment, but was also not related to growth rate. Cell membranehydraulic conductivity (5 x 107 ± 1·3 (10)m s1 MPa2) was not influenced by the presenceof K+. We propose that K+ and SO42 influence root growthrates by modulating the rheological properties of the wallsof the expanding cell. The physiological significance of these properties is discussed. Key words: Growth, wall extensibility, turgor pressure, wheat roots 相似文献
9.
The Osmotic Pressure of Concentrated Solutions of Polyethylene Glycol 6000, and its Variation with Temperature 总被引:1,自引:0,他引:1
The vapour pressures of aqueous solutions of polyethylene glycol6000 have been measured (by equilibration with sucrose solutions)up to the saturation point at 25 °C (1.45 g g1 water).The reduced-osmotic-pressure (/c), when plotted versus concentration(c), rapidly and linearly increased up to a concentration ofabout 0.8 g g1 (crossing the similar plot for sucrose).Above this concentration, the reduced-osmotic-pressure rosemore slowly, but still more rapidly than sucrose. The maximumosmotic pressure achieved at saturation was nearly 18 MPa. Usingthe virial equation: /c= RT/M + RTA2c, the calculated secondvirial coefficient (A2) for the linear part is 4.5 x 103mol g1, a value slightly greater than most literaturevalues at 25 °C. Data are cited showing that A2 varies linearlyfrom 56 x 10x3 at 0 °C, to zero at 8090 °C 相似文献
10.
Longitudinal Water Movement in the Primary Root of Zea mays 总被引:1,自引:0,他引:1
The rates of transfer of tritiated water (THO) along lengthsof excised primary roots of Zea mays have been measured undera variety of conditions. The following values of apparentdiffusion coefficients for THO in the root tissue havebeen evaluated: 1.5±0.1x10-5 cm2 sec-1 in roots boiledfor 3 min before use,0.5±0.03x10-5 cm2 sec-1 in rootspoisoned with 10-2 M NaF,0.9±0.07x10-5 cm2 sec-1 in rootspoisoned with 10-2 M NaN3,and 2.1±0.2x10-5 cm2 sec-1in normal roots. The bathing medium in all cases was 1.0 mMKCl/0.1 mM CaCl2 with the addition of the inhibitors where appropriate.Thefourfold increase in the rate of THO transfer in normal rootscompared with poisoned ones is attributed to the existence ofa long-distance convective flow in the first case, which isterminated by the addition of inhibitors. Since experimentsshow that this convective flow must occur both acropetally andbasipetally with equal velocity, it is thought to occur in thephloem.By assuming the streaming transcellular strandsmodel for phloem transport, the rate of movement required togive the observed transfer has been computed as approximately4.5x10-2 cm sec-1 (160 cm h-1).The earlier report of the existenceof a highly impermeable barrier surrounding the xylem vesselshas been further substantiated by the experiments reported here. 相似文献
11.
Prostaglandin E2 activates outwardly rectifying Cl(-) channels via a cAMP-dependent pathway and reduces cell motility in rat osteoclasts 总被引:1,自引:0,他引:1
Okamoto F Kajiya H Fukushima H Jimi E Okabe K 《American journal of physiology. Cell physiology》2004,287(1):C114-C124
We examined changes in electrical and morphological properties of rat osteoclasts in response to prostaglandin (PG)E2. PGE2 (>10 nM) stimulated an outwardly rectifying Cl current in a concentration-dependent manner and caused a long-lasting depolarization of cell membrane. This PGE2-induced Cl current was reversibly inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), and tamoxifen. The anion permeability sequence of this current was I > Br Cl > gluconate. When outwardly rectifying Cl current was induced by hyposmotic extracellular solution, no further stimulatory effect of PGE2 was seen. Forskolin and dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) mimicked the effect of PGE2. The PGE2-induced Cl current was inhibited by pretreatment with guanosine 5'-O-2-(thiodiphosphate) (GDPS), Rp-adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS), N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide dihydrochloride (H-89), and protein kinase A inhibitors. Even in the absence of nonosteoclastic cells, PGE2 (1 µM) reduced cell surface area and suppressed motility of osteoclasts, and these effects were abolished by Rp-cAMPS or H-89. PGE2 is known to exert its effects through four subtypes of PGE receptors (EP1EP4). EP2 and EP4 agonists (ONO-AE1-259 and ONO-AE1-329, respectively), but not EP1 and EP3 agonists (ONO-DI-004 and ONO-AE-248, respectively), mimicked the electrical and morphological actions of PGE2 on osteoclasts. Our results show that PGE2 stimulates rat osteoclast Cl current by activation of a cAMP-dependent pathway through EP2 and, to a lesser degree, EP4 receptors and reduces osteoclast motility. This effect is likely to reduce bone resorption. prostanoid receptor agonists; electrophysiology; motile activity; bone resorption 相似文献
12.
Ribulose bisphosphate carboxylase (EC 4.1.1.39
[EC]
) activity wasvery low in tomato leaf extracts unless prepared in the presenceof Mg2+, and polyclar AT. With young leaves, but not with fully-expanded leaves, the RuBP carboxylase activityextracted was increased by prolonged illumination of the leaves(2 h). The main effect of the light treatment was to increasethe specific activity of the enzyme but there was also a smallincrease in RuBP carboxylase protein. Tomato leaf RuBP carboxylasein extracts had specific activities in the range 0.206µmol CO2 min1 mg-1 total protein extracted,or 0.51.2 µmol CO2 min1 mg1 RuBPcarboxylase, and an apparent Km (CO2) at 20 ?C of 9.3 ? 1.2µM (using a of 6.407). Key words: Tomato leaf, RuBP carboxylase, Properties 相似文献
13.
The diffusion of oxyleghaemoglobin, prepared from soybean rootnodules, was measured at 24°C in agar and agarose gels ofvarious strengths, or in 1% agarose containing 0-18% (w/v) bovineserum albumin, to simulate the protein content of the cytoplasmof root nodule cells. Values of Dp, the diffusion coefficient,were unaffected (Dp = 11·8 x 10-11 m2 s-1; s.e.m. 0·3x 10-11) until the protein concentration exceeded 6%, abovewhich Dp declined sharply. With 18% bovine serum albumin, theconcentration of total soluble protein calculated to be presentin the cytoplasm of infected cells, where most of the leghaemoglobinis located in vivo, Dp was 5·9 x 10-11 m2 s-1. Theseresults are discussed in relation to leghaemoglobin-facilitateddelivery of O2 to the respiring N2-fixing bacteroids in rootnodule cells.Copyright 1993, 1999 Academic Press Bacteroids, diffusion, Glycine max, N2 fixation, oxyleghaemoglobin, soybean, root nodules 相似文献
14.
The NADP$-specific isocitrate dehydrogenase was partially purifiedfrom photosynthetically-grown Rhodospirillum rubrum. The pHoptimum is between 7.5 and 9.0 in phosphate buffer. The apparentKm is 3.1x105 M for isocitrate, 5.1x105 M forNADP$, 1.7x105 M for manganese, 1.5x104 M formagnesium, and 3.5x103 M for inorganic orthophosphate.Arsenate exerts a slight inhibition. The Q10 between 17.5°Cand 40°C is 1.62, and the energy of activation at 25°Cis 9.74 Kcal/mole. Glyoxylate and oxalacetate cause concertedinhibition of the enzyme activity. Various nucleotides inhibitthe activity. The kinetics of inhibition by ATP was found tobe mixed type with respect to NADP$ and isocitrate, the Ki valuesbeing 1.17x103 M and 1.10x103 M respectively.The inhibition between ATP and orthophosphate is competitivewith a Ki of 104M. Thiol binding reagents are inhibitory;this inhibition is reversed by cysteine or reduced glutathione. (Received October 1, 1971; ) 相似文献
15.
Root growth of 7-d-old wheat (Triticum aestivum cv. Gamenya)seedlings was impaired at dissolved O2 concentrations of 0.01and 0.055 mol m3 O2, while growth at 0.115 mol m3O2 was the same as that in continuously aerated controls (0.26mol m3 O2). Oxygen uptake by apical (02 mm), expanding (24mm) and expanded (1012 mm) tissues of the roots decreasedbelow 0.16, 0.09 and 0.05 mol m3 O2, respectively. Thishierarchy is consistent with the metabolic rates of these tissues.There was a small (c. 9%) inhibition of O2 uptake and some netsynthesis of ethanol and alanine in root apices at 0.115 molm3 O2. Significant amounts of anaerobic end-productsaccumulated at 0.055 mol m3 O2 and even more so at 0.01mol m3 O2, indicating that oxidative phosphorylationwas strongly inhibited. Net alanine synthesis increased in fully expanded (1016mm) tissues exposed to <0.0030.01 mol m3 O2,and this increase was accompanied either by a proportionallysmaller increase in the concentration of other free amino acidsor by a net decrease in free amino acid levels excluding alanine.This suggests that alanine was synthesized as an end-productof anaerobic catabolism and did not accumulate simply becauseof decreased net protein synthesis. Comparing the carbon flow to CO2, ethanol, lactate and alaninein roots at 0.01 mol m3 O2 with carbon loss as CO2 inaerated roots suggests that carbon flow to products of metabolismwas not greatly enhanced due to O2 deficiency. This infers,but does not prove that, in wheat, generation of energy duringperiods of O2 deficiency is not enhanced due to a Pasteur effect. Key words: Anaerobic, fermentation, oxygen, wheat 相似文献
16.
Ritchie Raymond J.; Trautman Donelle A.; Larkum A.W.D. 《Plant & cell physiology》1997,38(11):1232-1241
Phosphate uptake rates in Synechococcus R-2 in BG-11 media (anitrate-based medium, not phosphate limited) were measured usingcells grown semi-continuously and in continuous culture. Netuptake of phosphate is proportional to external concentration.Growing cells at pHo 10 have a net uptake rate of about 600pmol m2 s1 phosphate, but the isotopic flux for32P phosphate was about 4 nmol m2 s1. There appearsto be a constitutive over-capacity for phosphate uptake. TheKm and Vmax, of the saturable component were not significantlydifferent at pHo 7.5 and 10, hence the transport system probablyrecognizes both H2PO4and HPO24. The intracellularinorganic phosphate concentration is about 3 to 10 mol m3,but there is an intracellular polyphosphate store of about 400mol m3. Intracellular inorganic phosphate is 25 to 50kJ mol1 from electrochemical equilibrium in both thelight and dark and at pHo 7.5 and 10. Phosphate uptake is veryslow in the dark ( 100 pmol m2 s1) and is light-activated(pHo 7.51.3 nmol m2 s1, pHo 10600 pmol m2s1). Uptake has an irreversible requirement for Mg2+in the medium. Uptake in the light is strongly Na+-dependent.Phosphate uptake was negatively electrogenic (net negative chargetaken up when transporting phosphate) at pHo 7.5, but positivelyelectrogenic at pHo 10. This seems to exclude a sodium motiveforce driven mechanism. An ATP-driven phosphate uptake mechanismneeds to have a stoichiometry of one phosphate taken up perATP (1 PO4 in/ATP) to be thermodynamically possible under allthe conditions tested in the present study. (Received June 16, 1997; Accepted September 4, 1997) 相似文献
17.
The effect of morphactin (methyl 2-chloro-9-hydroxyfluorene-9-carboxylate)on basipetal transport of auxin (Indol-3-ylacetic acid-2-14C)was studied in bean (Phaseolus vulgaris) hypocotyl with thedonor-receiver block method. Morphactin (5 x 106m) reduced IAA (5 x 106m) transportintensity by an average of 83 per cent and auxin transport capacityby 90 per cent, but transport velocity was not affected. Morphactin did not inhibit uptake of IAA into hypocotyl tissue,but it did prevent transfer of IAA from the tissue into receiverblocks. Chromatographic analysis of the tissue after 4 h IAA-2-14Ctransport showed that 54 per cent of the total activity wasin the form of IAA in the control and 42 per cent in the morphactintreated tissue. No difference was found in the rate of decarboxylationof IAA-1-14C between control and morphactin treated tissue sections.Nor could any difference between control and morphactin be shownin the radioactivity associated with a TCA ppt fraction. Ina study of the transportable auxin pool, morphactin decreasedthe size of the pool and increased the half-life of decay ofauxin transport from 122 h to 385 h. In a kineticanalysis of the reversal of morphactin (5 x 106m) inhibitionby increasing concentration of IAA-2-14C (5 x 106m to2 x 105m), it was shown that IAA transport resemblesMichaelis-Menten enzyme reaction kinetics, and that inhibitionby morphactin fitted a mixed type model. IAA hada dissociation constant of 85 x 106m and morphactinthat of 43 x 107m with a Km for the transport processof 85 x 106m. 相似文献
18.
The rate of net photosynthesis (P) of whole plant stands oftomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativusL.) and sweet pepper (Capsicum annuum L.) was measured in sixlong-term experiments in large greenhouses under normal operatingconditions and CO2-concentrations between 200 and 1200 µmolmol-1. The objective was to quantify the responses to lightand carbon dioxide and to obtain data sets for testing simulationmodels. The method of measuring canopy photosynthesis involvedan accurate estimation of the greenhouse CO2 balance, usingnitrous oxide (N2O) as tracer gas to determine, on-line, theexchange rate between greenhouse and outside air. The estimatedrelative error in the observed P was about ± 10%, exceptthat higher relative errors could occur under particular conditions. A regression equation relating P to the photosynthetically activeradiation, the CO2 concentration and the leaf area index explained83-91% of the variance. The main canopy photosynthesis characteristicscalculated with the fitted regression equations were: canopyPmax 5-9 g m-2 h-1 CO2 uptake; ratio Pmax/LAI 1·5-3 gm-2 h-1; light compensation point 32-86 µmol s-1 m-2;light use efficiency (quantum yield) at low light 0·06-0·10µmol µmol-1 and CO2 compensation point 18-54 µmolmol-1. The results were related to the prevailing conditions.Copyright1994, 1999 Academic Press Canopy photosynthesis, Capsicum annuum L., carbon dioxide, CO2, CO2 balance, CO2 use efficiency, cucumber, Cucumis sativus L., glasshouse, greenhouse, light use efficiency, Lycopersicon esculentum Mill., sweet pepper, tomato, tracer gas 相似文献
19.
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
20.
Plants were grown at either 350 or 1000 µl l-1CO2and inone of three photoperiod treatments: continuous short days (SD),continuous long days (LD), or short switched to long days atday 41 (SDLD). All plants received 9 h of light at 450µmol m-2s-1and LD plants received an additional 4 h oflight at 8 µmol m-2s-1. Growth of SD plants respondedmore positively to elevated CO2than did LD plants, due largelyto differences in the effect of CO2on unit leaf rate. High CO2increasedheight and decreased branching under SD conditions, but hadno effect under LD conditions. Elevated CO2also increased thenumber of buds and open flowers, the effect for flower numberbeing greater in short than in long days. The specific leafarea of plants grown at 1000 µl l-1CO2was reduced regardlessof daylength. High CO2also decreased leaf and increased reproductiveallocation, the magnitude of these effects being greater underSD conditions. Bud formation and flower opening was advancedunder high CO2conditions in SD plants but bud formation wasdelayed and there was no effect on flower opening under LD conditions.The effects of CO2on plants switched from SD to LD conditionswere largely intermediate between the two continuous treatments,but for some parameters, more closely resembled one or the other.The results illustrate that daylength is an important factorcontrolling response of plants to elevated CO2. Petunia hybridaHort. ex Vilm; carbon dioxide; photoperiod; functional growth analysis; daylength; global change; development; phenology 相似文献