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1.
The effect of changes in ambient oxygen concentration on the bioelectric properties of middle ear mucosa 总被引:2,自引:0,他引:2
Mandell DL Devor DC Madia JV Lo CY Hake H Hebda PA 《American journal of physiology. Cell physiology》2003,285(3):C618-C622
The purpose of the present study was to compare the effect of 24 h of exposure to 7% O2 (normal middle ear physiological conditions) vs. 21% O2 (found in the middle ear after ventilation tube placement) on transepithelial Na+ absorption and Cl secretion in cultured gerbil middle ear epithelial cell monolayers. Although no difference in apical Na+ absorption was identified, the UTP-induced stimulation of apical Cl secretion in the presence of apical Na+ channel blockade with amiloride was significantly enhanced after exposure to 21% O2 compared with 7% O2 exposure. In the presence of a calcium-activated Cl channel inhibitor, DIDS, UTP-induced stimulation of Cl secretion after 21% O2 exposure was decreased, suggesting a role for calcium-activated Cl channels in middle ear Cl secretion in response to relative hyperoxia. ion channels; sodium; chloride; hypoxia 相似文献
2.
Gibberellins GA1, GA4, GA8, GA9, GA19, GA20, GA29, GA44, GA81,indole-3-acetic acid (IAA) and abscisic acid (ABA) were identifiedin cambial region tissues of Eucalyptus globulus by comparingmass spectra and Kovats retention indices with those of authenticstandards. Using stable isotope labelled internal standardsGA19, GA20 and GA44 were quantified at levels of 27 ng(g fr wt)-1, other GAs were present at levels < 1 ng (g frwt)-1. Levels of IAA and ABA ranged from 4171, 140 ng(g fr wt)-1 and 86305 ng (g fr wt)-1 respectively. Thepresence of brassinosteroid-like substances was also indicatedbased on activity in the rice seedling leaf inclination assay. (Received April 28, 1995; Accepted June 20, 1995) 相似文献
3.
The role of Cl in the reactivation of O2 evolution inphotosystem II (PS II) particles derived from spinach chloroplastswas studied in the presence of various salts. Multivalent ion(especially anion) salts were found to strongly suppress thereactivation of O2 evolution by Cl in the Cl-depletedPS II particles in a competitive manner. The effectiveness ofanions in the suppression of Cl-supported O2 evolutionwas in the order of trivalent>divalent>monovalent ones.Multivalent anions similarly suppressed O2 evolution in theuntreated PS II particles under low and moderate Cl concentrations.pH dependence of the Cl-affinity (Km) value for Cl)was also studied. Within the pH range 5.5 to 8 the Km valuebecame higher as the pH of the medium increased. These resultssuggest that the membrane surface in the vicinity of the Claction site is net positively charged and attracts Clelectrostatically, and that the site is almost freely accessibleto various anions. The origin and role of the local net positivedomain and the role of peripheral proteins are discussed. (Received May 27, 1985; Accepted October 8, 1985) 相似文献
4.
The Uptake of Gaseous Ammonia by the Leaves of Italian Ryegrass 总被引:5,自引:0,他引:5
Lockyer, D. R. and Whitehead, D. C. 1986. The uptake of gaseousammonia by the leaves of Italian ryegrass.J. exp. Bot.37: 919927. Plants of Italian ryegrass (Lolium multiflorum Lam.) grown insoil with two rates of added 15N-labelled nitrate were exposed,in chambers, for 40 d to NH3 in the air at concentrations of16, 118 and 520 µg m3. At the highest concentrationof NH3, this source provided 47?3% of the total nitrogen inplants grown with the lower rate of nitrate addition (100mgN kg1 dry soil) and 35?2% with the higher rate (200mgN kg1 dry soil) At the intermediate concentration ofNH3, the contributions to total plant N were 19?6% and 10?8%,respectively, at low and high nitrate while, at the lowest concentrationof NH3, they were 5?1% and 32%. Most of the N derived from theNH3 remained in the leaves, but some was transported to theroots. The amount of N derived from the NH3 that was presentin the leaves was not reduced by washing the leaves in waterat pH 5?0 before harvesting, indicating that the N was assimilatedby the plant and not adsorbed superficially. Rates of uptakeof NH3 per unit leaf area ranged from 1?7 µg dm2h1 at a concentration of 16 µg m3 to 29?0µg dm2 h1 at a concentration of 520 µgm3 and with the lower rate of nitrate addition. Increasingthe supply of nitrate to the roots slightly reduced the rateof uptake of NH3 per unit leaf area. Uptake of N from the higherrate of nitrate was reduced at the highest concentration ofNH3 in the air. Key words: Ammonia, nitrogen, leaf sorption, Lolium multiflorum 相似文献
5.
The effects of phthalate esters on chlorophyll a2 fluorescencein radish plants (Raphanus sativus L. cv. Cherry Belle) wereexamined Fluorescence yield was increased in those plants exposedto an aerial concentration of 120 ng dm3 dibutyl phthaiatc(DBP) at a rate of 3.0 dm3 min1 for 13 d. Comparisonof fluorescence enhancement ratios and Fred/Fox, suggests thatDBP inhibits photosynthesis in radish plants at a site afterQA. Both DBP and diisobutyl phthalate (DIBP) strongly inhibiteduncoupled (PS2+PS1) electron transport rates in thylakoids isolatedfrom spinach. At a chlorophyll concentration of 10 µgcm3 the concentrations of DBP and DIBP exhibiting 50%inhibition were 44 mmol m3 and 42 mmol m3 respectively.Basal electron transport rates were also inhibited, with 87mmol m3 of DBP or DIBP producing 50% inhibition. Measurementof photosystcm 1 activity suggested that the main site of actionof these phthalates was localized at a site near the reducingside of photosystem 2. Key words: Phthalate, plasticiser, chlorophyll, fluorescence, photosynthesis, inhibition 相似文献
6.
Role of NBC1 in apical and basolateral HCO3- permeabilities and transendothelial HCO3- fluxes in bovine corneal endothelium 总被引:1,自引:0,他引:1
Corneal transparency and hydration control are dependent on HCO3 transport properties of the corneal endothelium. Recent work (13) suggested the presence of an apical 1Na+-3HCO3 cotransporter (NBC1) in addition to a basolateral 1Na+-2HCO3 cotransporter. We examined whether the NBC1 cotransporter contributes significantly to basolateral or apical HCO3 permeability and whether the cotransporter participates in transendothelial net HCO3 flux in cultured bovine corneal endothelium. NBC1 protein expression was reduced using small interfering RNA (siRNA). Immunoblot analysis showed that 515 nM siRNA decreased NBC1 expression by 8095%, 4 days posttransfection. Apical and basolateral HCO3 permeabilities were determined by measuring the rate of pHi change when HCO3 was removed from the bath under constant pH or constant CO2 conditions. Using either protocol, we found that cultures treated with NBC1 siRNA had sixfold lower basolateral HCO3 permeability than untreated or siCONTROL siRNA-treated cells. Apical HCO3 permeability was unaffected by NBC1 siRNA treatment. Net non-steady-state HCO3 flux was 0.707 ± 0.009 mM·min1·cm2 in the basolateral-to-apical direction and increased to 1.74 ± 0.15 when cells were stimulated with 2 µM forskolin. Treatment with 5 nM siRNA decreased basolateral-to-apical flux by 67%, whereas apical-to-basolateral flux was unaffected, significantly decreasing net HCO3 flux to 0.236 ± 0.002. NBC1 siRNA treatment or 100 µM ouabain also eliminated steady-state HCO3 flux, as measured by apical compartment alkalinization. Collectively, reduced basolateral HCO3 permeability, basolateral-to-apical fluxes, and net HCO3 flux as a result of reduced expression of NBC1 indicate that NBC1 plays a key role in transendothelial HCO3 flux and is functional only at the basolateral membrane. corneal endothelium; sodium bicarbonate cotransporter; small interfering RNA; bicarbonate transport 相似文献
7.
Guard cell protoplasts were isolated enzymatically from theepidermis of Vicia faba L. and their photosynthetic activitieswere investigated. Time courses of light-induced changes inthe chlorophyll a fluorescence intensity of these protoplastsshowed essentially the same induction kinetics as found formesophyll protoplasts of Vicia. The transient change in thefluorescence intensity was affected by DCMU, an inhibitor ofphotosystem II; by phenylmercuric acetate, an inhibitor of ferredoxinand ferredoxin NADP reductase; and by methyl viologen, an acceptorof photosystem I. Low temperature (77 K) emission spectra ofthe protoplasts had peaks at 684 and 735 nm and a shoulder near695 nm. A high O2 uptake (175 µmol mg1 Chl hr1)was observed in guard cell protoplasts kept in darkness, whichwas inhibited by 2 mM KCN or NaN3 by about 60%. On illumination,this O2 uptake was partially or completely suppressed, but itssuppression was removed by DCMU, which indicates that oxygenwas evolved (150 µmol mg1 Chl hr1) photosynthetically.We concluded that both photosystems I and II function in guardcell chloroplasts and that these protoplasts have high respiratoryactivity. (Received January 30, 1982; Accepted May 15, 1982) 相似文献
8.
Induction of CN-insensitive respiration with low concentrationsof respiratory inhibitors was studied. If roots were treatedwith 103 M CN for 96 hr, the plants died, whilethose treated with 104 M CN showed healthy growth. O2 uptake in untreated rice and wheat roots showed a negativeresponse to 102 M CN to a considerable extent.On the other hand, pretreatment with 104 M CNfor more than 6 hr did not greatly affect respiratory rate,but made respiration insensitive to 102 M CN.A similar induction of CN-insensitivity was also broughtabout with 104 and 103 M H2S and 104 MNaN3. (Received July 6, 1971; ) 相似文献
9.
Competitive inhibition of the HCO3 transport site, atthe plasmalemma of Chara coraUina, by the CO23 ion isdemonstrated. This CO23 inhibition was used to demonstratethat HCO3 ions enter the cell by facilitated diffusionwhen the HCO3 transport system has been inactivated bytreatment with 10 mM K+. Use of CO23 as a HCO3analogue is limited, however, because of the necessity to employsolutions of high pH. Inhibition was not observed in the presenceof a range of organic and inorganic acid anions. These resultsdemonstrate the stereo-specific nature of the HCO3 bindingsite. A variety of amino compounds were found to inhibit H14CO3influx. Inhibition appeared to be competitive, being completelyrelieved at higher substrate (HCO3) concentrations. Asimple correlation was not found between the degree of inhibitionand the concentration of neutral base. A combination of thepresence of neutral base and experimental pH values of at least8·0 was required to produce the reactive species thatinhibited HCO3 transport. This species is consideredto be the amino carbamate. These results are discussed withrespect to further HCO3 analogue experiments. 相似文献
10.
MACDUFF J. H.; JARVIS S. C.; LARSSON C-M.; OSCARSON P. 《Journal of experimental botany》1993,44(9):1475-1484
Two approaches to quantifying relationships between nutrientsupply and plant growth were compared with respect to growth,partitioning, uptake and assimilation of NO3 by non-nodulatedpea (Pisum sativum L. cv. Marma). Plants grown in flowing solutionculture were supplied with NO3 at relative addition rates(RAR) of 0·03, 0·06, 0·12, and 0·18d1, or constant external concentrations ([NO3)of 3, 10, 20, and 100 mmol m3 over 19 d. Following acclimation,relative growth rates (RGR)approached the corresponding RARbetween 0·030.12 d-1, although growth was notlimited by N supply at RAR =0.18 d-1. Growth rates showed littlechange with [NO3] between 10100 mmol m3(RGR=0·15 0·16 d-1). The absence of growthlimitation over this range was suggested by high unit absorptionrates of NO3, accumulation of NO3 in tissues andprogressive increases in shoot: root ratio. Rates of net uptakeof NO3 from 1 mol m3 solutions were assessed relativeto the growth-related requirement for NO3, showing thatthe relative uptake capacity increased with RGR between 0·030·06d1 , but decreased thereafter to a theoretical minimumvalue at RGR 相似文献
11.
Three distinct mechanisms of HCO3- secretion in rat distal colon 总被引:1,自引:0,他引:1
Vidyasagar S Rajendran VM Binder HJ 《American journal of physiology. Cell physiology》2004,287(3):C612-C621
HCO3 secretion has long been recognized in the mammalian colon, but it has not been well characterized. Although most studies of colonic HCO3 secretion have revealed evidence of lumen Cl dependence, suggesting a role for apical membrane Cl/HCO3 exchange, direct examination of HCO3 secretion in isolated crypt from rat distal colon did not identify Cl-dependent HCO3 secretion but did reveal cAMP-induced, Cl-independent HCO3 secretion. Studies were therefore initiated to determine the characteristics of HCO3 secretion in isolated colonic mucosa to identify HCO3 secretion in both surface and crypt cells. HCO3 secretion was measured in rat distal colonic mucosa stripped of muscular and serosal layers by using a pH stat technique. Basal HCO3 secretion (5.6 ± 0.03 µeq·h1·cm2) was abolished by removal of either lumen Cl or bath HCO3; this Cl-dependent HCO3 secretion was also inhibited by 100 µM DIDS (0.5 ± 0.03 µeq·h1·cm2) but not by 5-nitro-3-(3-phenylpropyl-amino)benzoic acid (NPPB), a Cl channel blocker. 8-Bromo-cAMP induced Cl-independent HCO3 secretion (and also inhibited Cl-dependent HCO3 secretion), which was inhibited by NPPB and by glibenclamide, a CFTR blocker, but not by DIDS. Isobutyrate, a poorly metabolized short-chain fatty acid (SCFA), also induced a Cl-independent, DIDS-insensitive, saturable HCO3 secretion that was not inhibited by NPPB. Three distinct HCO3 secretory mechanisms were identified: 1) Cl-dependent secretion associated with apical membrane Cl/HCO3 exchange, 2) cAMP-induced secretion that was a result of an apical membrane anion channel, and 3) SCFA-dependent secretion associated with an apical membrane SCFA/HCO3 exchange. chloride/bicarbonate exchange; short-chain fatty acid/bicarbonate exchange; anion channel; pH stat 相似文献
12.
Imsande, J. 1986. Inhibition of nodule development in soybeanby nitrate or reduced nitrogen.J. exp. Bot. 37: 348355. Nodulation of hydroponically grown soybean plants [Glycine max(L.) Merr.] is inhibited by continuous growth in the presenceof 4· mol m3 KNO3 The presence of 4·0 molm3 starter nitrate for 3-6 d during noduledevelopment, however, subsequently stimulates nodule dry weightaccumulation and nitrogenase activity. These stimulations occureven though 4· mol m3 nitrate temporarily delaysnodule development, i.e. the late steps of nodule developmentare reversibly inhibited by a short-term exposure to 4·0mol m3 nitrate. On the other hand, treatment with 4·0mol m3 nitrate in excess of 14 d significantly reducesnodule dry weight Thus, extended growth in the presence of 4·0mol m3 KNO3 seems to block both early and late stepsof nodule development. Nodulation of hydroponically grown soybeansis also inhibited by continuous growth in the presence of 2·0mol m3 (NH4)2SO4 This inhibition is not caused by acidityof the growth medium. On the other hand, nodule development6 d after inoculation with Rhizoblum japonicum is not delayedby a 7-d exposure to 2·0 mol m3 (NH4)2SO4 butis partially inhibited by a prolonged exposure to (NH4)2SO4Because repression of nodulation by 4·0 mol m3KNO3 is more severe than that by 2·0 mol m3 (NH4)2SO4and because ammonium taken up by the soybean plant is not activelyoxidized to nitrate, it is suggested that there are at leasttwo mechanisms by which nitrate utilization represses noduleformation in soybean. Key words: Glycine max, nitrogen, nitrogen fixation, nodulation 相似文献
13.
A 4 x 4 factorial experiment was conducted to examine the effectsof air polluted with 0, 10, 25, and 50 parts 108 of NOand NO2 on the rate of photosynthesis in tomato. Both gasesreduced net photosynthesis to approximately the same extent,from a mean rate of 13·03 in the controls to 9·40in 50 parts 108 NO and 8·84 in 50 parts 108NO2 (all values in mg CO2 dm2 h1). There was noevidence of any interaction between the two pollutants, buttheir effects were nearly additive over parts of the concentrationrange tested. Tomato appears to be more sensitive to the presence of nitrogenoxides in the atmosphere than other species so far investigated.NO and NO2 are generated by hydrocarbon burners used to provideCO2 enrichment for glasshouses, and can accumulate in concentrationswithin the range employed in this experiment. 相似文献
14.
Influx and Efflux of Nitrate and Ammonium in Italian Ryegrass and White Clover Roots: Comparisons Between Effects of Darkness and Defoliation 总被引:9,自引:2,他引:7
Seedlings of Italian ryegrass (Lolium multiflorum Lam. cv. RVP)and clonal stolon cuttings of white clover (Trifolium repensL. cv. Blanca) were grown for 19 d in flowing solution culture,with N supplied as either 250 mmol m3 NO3 or NH3+.Rates of net uptake, influx and translocation of NO3and NH4+ were then determined using 15N and 13N labelling techniques:between 35 h into the photoperiod following 8 h darknessfor white clover (CL), and for ryegrass plants that were eitherentire (IL) or with shoots excised 90 min prior to 13N influx(IC); and 75 min into the photoperiod following 3739h darkness for ryegrass (ID). Rates of net uptake, influx andefflux of NH4+ exceeded those of NO3 in IL and IC ryegrassplants: the opposite occurred in white clover (CL). The decreasein net uptake following defoliation of ryegrass was greaterfor NH4+ (62%) than NO3 (40%). For NH4+ this was associatedwith a large decrease in influx from 110 to 6.0µmol h1g1 root fr. wt; but for NO3, influx only decreasedfrom 42 to 37 µmol h1 g1. Prolonged exposureto darkness (ID plants) also lowered net uptake of NO3and NH4+ by, respectively, 86% and 95% of IL levels. For NH4+this was characterized by a large decrease in influx and a smalldecrease in efflux; whilst for NO3 the effect of a largedecrease in influx was reinforced by a smaller increase in efflux. The data were used to estimate the translocatory fluxes of NO3(0320µmol h1 g1) and NH4+ (0030.4µmolh1 g1), assimilation in the roots of NO3(0226µmol h1 g1) and NH+4 (0589 µmolh1 g1), and the concentrations of NO3 (915mol m3) in the cytoplasmic compartment of the roots.The relevance of variable influx and efflux to models for theregulation of N uptake is discussed. Key words: Lolium multiflorum, Trifolium repens, influx, efflux, nitrate, ammonium, 13N 相似文献
15.
Ion Fluxes in 'Isolated' Guard Cells of Commelina communis L. 总被引:4,自引:0,他引:4
Ion fluxes have been measured in isolated guardcells of Commelina communis L. using 86RbCl and K82Br, in epidermalstrips in which all cells other than guard cells have been killedby treatment at low pH. To avoid problems of slow free spaceexchange most fluxes have been measured at pH 3.9, at whichstomata open well in K(Rb) Cl(Br) and are stable for many hours.At pH 3.9 the intracellular 86Rb exchanged as a single compartmentwith a half-time of 23 h, independent of external concentration(Co). The influx of 86Rb rose with concentration, to a Vmaxof about 23 pmol mm2 h1. The efflux curve of 82Brcould be well fitted by two exponential terms, with half-timesof 38 min (independent of Co), and 535 h (falling withincreasing Co). Bromide contents of cytoplasm and vacuole (Qcand Qv), and fluxes at plasmalemma and tonoplast, were calculatedfrom the efflux kinetics. Over Co 2060 mM, as the apertureincreased from 7 µm to 17 µm, the tonoplast flux(0.511.5 pmol mm2h1) was always much lessthan the plasmalemma flux (777 pmol mm2 h1).Qc and Qv both increased with aperture. The increase in Qc of10.3 pmol mm2 µm1 is adequate to accountfor the osmotic changes required to change the aperture, aspreviously estimated. However, the change in vacuolar contentof only 5.9 pmol mm2 µm1 is much too smallto account for the osmotic changes required, or to balance thecytoplasmic changes. It appears therefore that increasing KBroutside not only increases the cytoplasmic salt content, andthe Br flux at the tonoplast, but also stimulates the vacuolaraccumulation of some other solute. 相似文献
16.
Photosynthetic 14C fixation by Characean cells in solutionsof high pH containing NaH14CO3 gave a measure of the abilityof these cells to take up bicarbonate (H14CO3). Whereascells of Nitella translucens from plants collected and thenstored in the laboratory absorbed bicarbonate at 11.5µµmoles cm2 sec1, rates of 38µµmoles cm2 sec1 were obtained withN. translucens cells from plants grown in the laboratory. Influxesof 56 µµmoles cm2 sec1 wereobtained with Chara australis, 38 µµmolescm2 sec1 with Nitellopsis obtusa, and 15µµmoles cm2 sec1 with Tolypella intricata.It is considered that these influxes represent the activityof a bicarbonate pump, which may be an electrogenic process. In solutions of lower pH, H14CO3 uptake would be maskedby rapid diffusion of 14CO2 into the cells: the four Characeanspecies fixed 14CO2 at maximum rates of 3040 µµmolescm2 sec1 (at 21° C). 相似文献
17.
A sulfite-dependent ATPase [EC 3.6.1.3
[EC]
] of Thiobacillus thiooxidanswas activated and solubilized by treatment with trypsin [EC3.4.4.4
[EC]
], and purified 84-fold with a 32% recovery. It requiredboth Mg2+ and SO32 for full activity, and its optimumpH was found at 7.58.0. Mn2+, Co2+, and Ca2+ could partiallysubstitute for Mg2+, while SeO32 and CrO42 couldpartially substitute for SO32. The enzyme hydrolyzed ATP and deoxy-ATP most rapidly and otherphosphate esters were poorer substrates. The apparent Km valuefor ATP was 0.33 mM. The enzyme activity was strongly inhibitedby 0.2 mM NaN3 and 10 mM NaF. (Received July 27, 1977; ) 相似文献
18.
Ma YH Wei HW Su KH Ives HE Morris RC 《American journal of physiology. Cell physiology》2004,286(1):C112-C118
Cl is essential for the vasoconstrictive response to angiotensin II (ANG II). In vascular smooth muscle cells (VSMC), we determined whether ANG II-induced transient increase in intracellular Ca2+ concentration ([Ca2+]i) is Cl dependent. After incubating the cells at different extracellular Cl concentration ([Cl]e) for 40 min, the ANG II-induced Ca2+ transients at 120 meq/l Cl were more than twice those at either 80 or 20 meq/l Cl. Replacing Cl with bicarbonate or gluconate yielded similar results. In addition, after removal of extracellular Ca2+, ANG II-induced as well as platelet-derived growth factor-induced Ca2+ release exhibited Cl dependency. The difference of Ca2+ release with high vs. low [Cl]e was not affected by acutely altering [Cl]e 1 min before administration of ANG II when [Cl]i was yet to be equilibrated with [Cl]e. Pretreatment of a Cl channel inhibitor, 5-nitro-2-(3-phenylpropylamino)benzoic acid, increased ANG II-induced Ca2+ release and entry at 20 meq/l Cl but did not alter those at 120 meq/l Cl. However, after equilibration, a reduced [Cl]e did not affect thapsigargin-induced Ca2+ release, suggesting that Cl may not affect the size of intracellular Ca2+ stores. Nevertheless, at high [Cl], the peak increase of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] induced by ANG II was approximately sixfold that at low [Cl]. Thus the Cl-dependent effects of ANG II on Ca2+ transients may be mediated, at least in part, by a Cl-dependent Ins(1,4,5)P3 accumulation in VSMC. anion; inositol 1,4,5-trisphosphate; Ca2+ release 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.
The use of chlorate as an analogue for NO3 during nitrateuptake into Chara corallina cells has been investigated. NO3inhibits 36C1O3 influx into Chara over the concentrationrange 01000 mmol m3. Lineweaver-Burke plots ofthe data are characteristic of competitive inhibition by NO3in the low concentration range (0300 mmol m3 ClO3)and apparent KINO3 is 140 mmol m3 which is of a similarorder of magnitude as apparent KmCIO3- 180 mmol m3. Athigher substrate concentrations the inhibition by NO3was not characteristic of competitive or uncompetitive inhibition. 36C1O3/NO3 influx was dependent on K+ and Ca2+in the external medium and inhibited by FCCP. NO3 pretreatmentor N starvation increased subsequent 36C1O3/NO3influx into Chara. A comparison between rates of net NO3uptake and 36C1O3/NO3 influx supported the previoushypothesis that NO3 efflux is an important componentin the determination of overall uptake rates. Key words: Nitrate, Chara, 36CIO3 相似文献