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1.
Using the compartmental analysis the unidirectional Na+ fluxesin cortical cells of barley roots, the cytoplasmic and vacuolarNa+ contents Qc and Qv, and the trans-root Na+ transport R'have been studied as a function of the external Na+ concentration.Using the re-elution technique the effect of low K+ concentrationson the plasmalemma efflux co of Na+ (K+-Na+ exchange) and onR' was investigated at different Na+ concentrations and correspondinglydifferent values of the cytoplasmic sodium content Qc. The relationof the K+-dependent Na+ efflux coK+-dep to Qc or to the cytoplasmicNa+ concentration obeyed Michaelis-Menten kinetics. This isconsistent with a linkage of co, K+-dep to K+ influx by a K+-Na+exchange system. The apparent Km corresponded to a cytoplasmicNa+ concentration of 28 mM at 0·2 mM K+ and about 0·2mM Na+ in the external solution. 0·2 mM K+ stimulatedthe plasma-lemma efflux of Na+ and inhibited Na+ transport selectivelyeven in the presence of 10 mM Na+ in the external medium showingthe high efficiency of the K+-Na+ exchange system. However,co, K+-dep was inhibited at 10 mM Na1 compared to lower Na1concentrations suggesting some competition of Na1 with K1 atthe external site of the exchange system. The effect of theNa+ concentration on Na1 influx oc is discussed with respectto kinetic models of uuptake.  相似文献   

2.
The application of D-glucose to solutions bathing excised maize,wheat, pea and bean roots causes a rapid depolarization of theelectrical potentials between the cut tops of the roots andthe bathing solutions. Similar effects are observed for theplasma membrane potentials of maize lateral roots. A flow cell apparatus was used to demonstrate qualitative andquantitative relations between glucose induced H+ influx andthe transient decrease in current through the root. The currentchanges appear to be due entirely to H+ fluxes. Current andH+ fluxes are strongly influenced by external pH, the optimumpH for glucose induced current change being about 4.0. A similarpH optimum was found for 3-O-methyl-D-glucopyranoside but 1-O-methyl--D-glucopyranosidedid not significantly affect the trans-root potential at anypH, suggesting a significant role for the anomeric hydroxylgroup of glucose. Compounds which depolarize the trans-root potential also inhibitthe glucose induced depolarization. Surface -SH groups are probablynot involved in the glucose/H+ cotransport. Eadie-Hofstee plots relating the depolarization of trans-rootpotential to the concentrations of D-glucose or 3-O-methyl-D-glucopyranosidehave shown that Km values increase with increasing monosaccharideconcentration and are very similar to reported values of 3-O-methyl-D-glucopyranosideuptake in maize root segments. Km values for a similar rangeof D-glucose concentrations do not vary significantly with pHor with membrane depolarization due to a 10-fold increase ofKCl concentration. However, Vmax is lowered by an increase inexternal pH or a decrease in trans-root potential. It appearsthat both proton and electrical gradients can affect glucoseinduced H+ influx. The auxin herbicide, 2, 4-dichlorophenoxyethanoic acid (0.01mM) stimulates the glucose induced depolarizations in a mannerconsistent with an increase in cytoplasmic pH. This is discussedin relation to the reported action of indole-3-acetic acid andfusicoccin on maize root tissue.  相似文献   

3.
Smith, J. R. 1987. Potassium transport across the membranesof Chara. II. 42K fluxes and the electrical current as a functionof membrane voltage.—J. exp. Bot. 38: 752–777. The current required to clamp the trans-membrane voltage ofinternodal cells of Chara australis at different levels wasmeasured simultaneously with either the 42K influx or efflux.Examination of the voltage-dependence of the ratio of the electricalcurrent to the unidirectional tracer fluxes yielded no evidenceof any amplification of the electrical driving force on theK+ ions. There was thus no evidence for the interaction of K+ions with themselves or any other species during their passageacross the membrane. These measurements allow the determinationof , the fraction of the electrical current carried by K+ ions.When the external [K+] = 10 mol m–3, the average valueof was 0?85 for Vm > –125 mV and 07?5 for Vm <–150 mV. When the external [K+] = 0?1 mol m–3, was 0?6 for Vm < –80 mV and 0?1 for Vm > –250mV. It was also found that the conductance associated with K+transport was inhibited by hyperpolarization. Key words: Potassium, conductance, flux-ratio  相似文献   

4.
Macduff, J. H., Hopper, M. J., Wild, A. and Trim, F. E. 1987.Comparison of the effects of root temperature on nitrate andammonium nutrition of oilseed rape (Brassica napusL.) in flowingsolution culture. II. Cation-anion balance.—J. exp. Bot.38: 1589-1602. The effects of root temperature and form of N nutrition (NH4or NOJ) on the mineral composition of the plant, the balanceof inorganic cation-anion uptake and on the apparent net effluxof H +/OHions from the roots were studied with 49-d-oldoilseed rape (Brassica napusL. cv. Bien venu) in flowing solutionculture. Plants were pre-treated for 14 d at a root temperatureof 5 °C prior to constant root temperatures of 3, 7, 11or 17°C for 14 d, with a common shoot temperature of 20/15°Cday/night. Nitrogen was supplied as NH+44 or NO3 at 10mmol m3. Values of Q10 (7-17°C) for mean unit absorptionrates of all the major nutrient ions (K+ , Mg++ , NH+4, SO4,H2PO4, NO3), except Ca++, were > 2.0 over the first 5 d oftreatment but thereafter were < 1.5; the apparent effectof temperature on uptake rates diminished with time. Under NH+4nutrition, inorganic cation uptake (Mg+ + + K++Ca+ + +NH+4)exceeded inorganic anion uptake (SO44+ H2PO4) over 14d at all temperatures, with the proportion of cation uptakeas NH4 remaining constant (0.67-0-68) irrespective of root temperature.The net efflux of H + from the roots approximately balancedNH+4 uptake (1:1) over 14 d at each temperature and also balancedthe difference between the total uptake of inorganic cationsand inorganic anions. Under NO3 nutrition, the sum of the netefflux of OH and the change in the carboxylate contents of plantsover 14 d approximately balanced the sum of NO3 and SO4reduced in the plant. The majority of the negative charge associatedwith the reduction of NO3 and SO4 was apparently effluxedas OH, but this fraction was lower at low root temperatures.The results are discussed in terms of mechanisms that have beenproposed to regulate the internal pH of plants. Key words: Brassica napus, oilseed rape, root temperature, cation-anion balance, H+/OH efflux.  相似文献   

5.
Kennedy, C. D. and Gonsalves, F. A. N. 1988. H+ efflux and trans-rootpotential measured while increasing the temperature of solutionsbathing excised roots of Zea mays.—J. exp. Bot. 39: 37–49. Novel temperature-ramp procedures have been used to measureH+ efflux and trans-root potential of excised roots of Zea mays(var. Fronica). Two types of experiment were performed: (1),increasing temperature from 17°C, and (2), pre-cooling theroots to 1°C before starting the temperature ramp. The ratesof increase of temperature for H+ efflux and trans-root potentialexperiments were 0·5 and 2·1°C min–1respectively The H+ scans revealed strong sharp maxima at 30°C and 32°C,for non-pre-cooled and pre-cooled roots respectively, the latterbeing significantly smaller. The trans-root potential scansfor the pre-cooled roots showed a corresponding maximum at 30°C,which was inhibited by KCN (1-0 mmol dm–3) with or withoutSHAM (10 mmol dm–3), or Hg2+ (1, 10, 100 µmol dm–3)in the bathing solutions. Some of the evidence suggests thatthese maxima are associated with electrogenic H+ pumping, mediatedby a plasma membrane-bound ATPase. However, no correspondingmaximum was observed in the trans-root potential scans for non-pre-cooledroots, the potential remaining at about — 75 m V from20°C to 35°C. As there is a 7-fold increase in H+ effluxbetween 20°C and 30°C, the relationship between netH+ efflux and electrogenic proton pumping in these roots isby no means clear. Some possibilities are considered here. Pre-cooled and non-pre-cooled roots show clear maxima in thetrans-root potential scans at about 46°C, at which temperaturethere is a slight net H+ influx. This, and other less prominentfeatures observed, are briefly discussed. Key words: H+ efflux, trans-root potential, temperature-ramp procedure, Zea mays, roots  相似文献   

6.
Dunlop, J., Knighton, M. V. and White, D. W. R. 1988. Ion transportand the effects of acetic acid in white clover. II. Potassiumabsorption.—J. exp. Bot. 39: 89–96. Acetic acid stimulated K+ influx into cells of white cloverin suspension culture and net K+ influx by roots of intact whiteclover plants. At concentrations of acetic acid up to 2·0mol m–3 the stimulation continued unabated for at least2 h. However, at higher concentrations the rate of absorptiondeclined to near zero values after 2 h. When acetic acid wasremoved from the solution there was a net efflux of K+. Thestimulation was pH dependent with a maximum at pH 5·0.There was maximum stimulation at an acetic acid concentrationof 2·0 mol m–3 Net H+ efflux was reduced by 1·0 mol m–3 aceticacid. When Rb+ uptake and H+ efflux were measured at a rangeof RbCl concentrations Rb+ uptake increased with concentrationwhereas H+ efflux was maximum in the absence of Rb+ (and K+)and decreased as RbCl concentration was increased Acetic acid caused a hyperpolarization of the membrane electricalpotential difference (E) of about 25 mV. In 1·0 mol m–3acetic acid the hyperpolarization persisted for at least 2 hwhereas at 10 mol m–3 d E subsequently depolarized tovalues around –80 mV. With a slight lag, the time courseof the stimulation of the rate of K+ absorption followed thepolarization and depolarization of E. These results imply thatthe linkage between K+ and H+ movements is probably throughE. Key words: Proton efflux, membrane electrical potential difference, Trifolium repens  相似文献   

7.
This work aimed to study the impacts of acquisition and assimilationof various nitrogen sources, i.e. NO3, NH4+ or NH4NO3,in combination with gaseous NH3 on plant growth and acid-basebalance in higher plants. Plants of C3 Triticum aestivum L.and C4 Zea mays L. grown with shoots in ambient air in hydroponicculture solutions with 2 mol m–3 of nitrogen source asNO3, NH4+ or NH4NO3 for 21 d and 18 d, respectively,had their shoots exposed either to 320 µg m–3 NH3or to ambient air for 7 d. Variations in plant growth (leaves,stubble and roots), and OH and H+ extrusions as wellas the relative increases in nitrogen, carbon and carboxylatewere determined. These data were computed as H+/N, H+/C, (C-A)/N,and (C-A)/C to analyse influences of different nitrogen sourceson acid-base balance in C3 Triticum aestivum and C4 Zea maysplants. Root growth in dry weight gain was significantly reduced bytreatment with 320 µg m–3 NH3 in Triticum aestivumand Zea mays growing with different N-forms, whereas leaf growthwas not significantly affected by NH3. In comparison with C3Triticum aestivum, non-fumigated C4 Zea mays had low ratiosof OH/N in NO3–3-grown plants and of H+/N in NH4+- and NH 4NO3-grown plants. Utilization of NH3 from the atmospherereduced both the OHN ratios in NO3 -grown plantsand the H+/N ratio in NH4+ - and NH4NO3 -grown plants of bothspecies. Furthermore, Zea mays had higher ratios of (C-A)/Nin NH4+ - and NH4NO3-grown plants than Triticum aestivum. Thismeans that C4 Zea mays had synthesized more organic anion perunit increase in organic N than C3 Triticum aestivum plants.Within both species, different nitrogen sources altered theratios of (C-A)/N in the order: NH4NO3>NH4+>NO3.Fumigation with NH3 increased organic acid synthesis in NO3- and NH4+ - grown plants of Triticum aestivum, whereas it decreasedorganic acid synthesis in Zea mays plants under the same conditions.Furthermore, these differences in acid-base regulation betweenC3 Triticum aestivum and C4 Zea mays plants growing with differentnitrogen sources are discussed. Key words: Acid-base balance, ammonia, ammonium, nitrate, ammonium nitrate, C3 Triticum aestivum L., C4 Zea mays L.  相似文献   

8.
The vacuolar pH (pHv) and the cytoplasmic pH (pHc) of the marinegiant-celled green alga Chaetomorpha darwinii were measuredby pH microelectrode techniques on extracted vacuolar sap, andby the [I4C]DMO distribution method respectively. Equilibrationof DMO occurred with a half-time of about 2 h, with an apparentPDMO of 3.6 x 10–5 cm s–1, but the vacuolar concentrationof free, undissociated DMO was always less than the externalconcentration. The explanation offered for freshwater giant-celledalgae of net DMO leakage across the plasmalemma cannotapply to Chaetomorpha darwinii, since electrically-driven DMOexit from the cytoplasm should be similar across the plasmalemmaand the tonoplast in these cells with large, vacuole-positivepotential differences across the tonoplast. pHc was accordinglycomputed assuming either tonoplast or plasmalemma equilibrationof DMO, with correction for DMO metabolism within the cell.pHc was 8.0–8.3 in the light in artificial seawater (pHoabout 8.0), was some 0.5 units lower in the dark, and was slightlylower with an external pH of 7. Vacuolar pH was 6.5–6.9,without consistent effects of illumination or of external pHof 7 rather than 8. While µH+ at the tonoplast was similarto that in giant-celled freshwater algae (although with a greatercontribution from relative to pH), µH+ at the plasmalemmawas less than 8 kJ mol–1, i.e. less than one-third ofthe value in freshwater green algae. µNa+ was some 13kJ mol–1 at the plasmalemma. The possibility that theprimary active transport process at the plasmalemma of Chaetomorphadarwinii (and certain other marine algae) is Na+ efflux ratherthan H+ efflux is discussed.  相似文献   

9.
The translocation of various anions, cations, and acids acrossthe membrane system of turnip mitchondria has been investigatedby light scattering techniques. The results imply that the membranesof turnip mitochondria are not permeable to choline, K+, Na+,, , , and . It has been established that Cl,, and SCN– passively permeate the mitochondrial membrane. It is probable that permeates as NH3 and that and cross the membrane either as the corresponding acid or on ananion/ hydroxide antiporter. The alkali metals Na+ and K+ equilibrateacross the membrane via specific H+/Na+ and H+/K+ antiporters,having similar activity at neutral pH.  相似文献   

10.
In Trifolium repens L. there were immediate transient depolarizationsof the membrane electropotential (Evo) when KH2PO4 was addedto phosphate-free media, but these were of the same magnitudeas the controls (K2SO4 and KCI). Furthermore, the extents ofdepolarization were the same as the expected effect of the addedK+ calculated using the Goldman equation. There was no significantdepolarization on adding H3PO4 to buffered media. Consequently,there was no evidence for a depolarization caused by phosphate.This result provides evidence that the H+–H2PO4 symportin roots of T. repens operates with a stoichiometry of 1: 1. In a group of control plants ( + P plants) and a group whichwere stressed by reducing the supply of phosphate (– Pplants), the – P plants had lower values for Evo than+P plants (– 118 mV and – 130 mV, respectively).The absence of phosphate from the measurement media also reducedEvo (mean effect = 9 mV). A significant difference in Evo between– P and + P plants persisted when phosphate was addedto – P plants. The electropotential difference acrossthe tonoplast (Evo) in – P plants became more positivewith time. Key words: White clover, membrane transport, roots, tonoplast, symport  相似文献   

11.
Control of Passive Permeability in the Chara Plasmalemma   总被引:2,自引:0,他引:2  
Conductance to K+ alters as a function of membrane potential(m). Conductance to H+ (or OH) changes with externalpH (pHo) This conductance change can be modulated by alteringcytoplasmic pH or external K+ concentration, both of which alsoalter m. We suggest a role for H+ conductance in regulatingcytoplasmic pH above pHo 7.0.  相似文献   

12.
Thomas, H. 1987. Physiological responses to drought of Loliumperenne L.: Measurement of, and genetic variation in, waterpotential, solute potential, elasticity and cell hydration.—J.exp. Bot. 38: 115–125. Clonally-replicated genotypes of Loiium perenne L. were grownin a controlled environment. Leaf water potential (w) osmoticpotential (s), turgor potential (p = ws), elasticity(E), leaf hydration (g water per g dry matter, H) and numberof green leaves per tiller (NGL) were measured before and duringa 42 d drought treatment. A simplified method of estimating E (at w < 1?0 MPa) usingonly six measurements was developed to permit a measurementrate of 8 leaves per hour. Measurement errors in all characterswere 3% or less. During drought, w and s (at w = 0?5 MPa) decreased significantly,p and E increased significantly, and H decreased slightly. Plantsize during drought was negatively correlated with s, and Hand positively correlated with p, osmotic adjustment, E andNGL. Measurements made on the genotypes before draughting didnot give a reliable indication of their physiological conditionafter adaptation to drought. Genetically controlled variation (‘broad sense heritability’)of drought-adapted plants for E was 15%, w 23%, s, 34%, p, 35%,H 34% and NGL 64%. The possibilities for, and effectivenessof, divergent selection of genotypes with high and low expressionof the characters are discussed. Key words: Water relations, Lolium, genetic variation  相似文献   

13.
Changes in the concentrations of K+ and Cl occur in parallelduring turgor regulation, and account for the changes in osmoticpressure. Thus it is impossible to single out one ion whoseconcentration is directly controlled by a turgor regulatorymechanism. After an increase in external osmolality (o) of 400mosmol kg–1, turgor is restored to its normal value in4–5 d. The response to a decrease in o is much more rapid,with most of the change in 1 occurring in the first 2 h. Apparentcytoplasmic concentrations of sucrose are similar to vacuolarconcentrations, and increase slightly with increasing 1.  相似文献   

14.
Ion contents and concentrations (K+, Na+, Cl, Ca2+, Mg2+,SO2–4, NO3, HPOJ2–4, amino and organic acids)of P. purpurea have been studied in relation to salinity variation.Cells were shown to accumulate large amounts of K+ and Clagainst their respective gradients of electrochemical potentialin all dilute and concentrated seawater media. Active influxof SOJ2–4, NO3, and HPOJ2–4 is also suggested,while Na+ is actively excluded from cells under hyposaline andhypersaline conditions. The relative proportions of individualcomponents of the internal osmotic potential were found to changeaccording to the external salt concentration. KCL forms themajor fraction of j} in concentrated seawater media while K+-aminoacids form the major fraction in dilute seawaters. Other intracellularsolutes comprise less than 15% oftj, in all media. Unidirectional fluxes of K+ and Cl were studied by radioisotopicmeans. Fluxes of K+ and Cl are reduced in hyposalinemedia, as is absolute KCL content per cell. Intracelhilar KCLcontent was also found to be markedly dependent upon externalK+ concentration, rather than water potential. Changes in KC1levels induced by salinity variation occur over a 6 h period.  相似文献   

15.
The nephrotoxic metal Cd2+ causes mitochondrial damage and apoptosis of kidney proximal tubule cells. A K+ cycle involving a K+ uniporter and a K+/H+ exchanger in the inner mitochondrial membrane (IMM) is thought to contribute to the maintenance of the structural and functional integrity of mitochondria. In the present study, we have investigated the effect of Cd2+ on K+ cycling in rat kidney cortex mitochondria. Cd2+ (EC50 19 µM) induced swelling of nonenergized mitochondria suspended in isotonic salt solutions according to the sequence KCl = NaCl > LiCl >> choline chloride. Cd2+-induced swelling of energized mitochondria had a similar EC50 value and showed the same cation dependence but was followed by a spontaneous contraction. Mitochondrial Ca2+ uniporter (MCU) blockers, but not permeability transition pore inhibitors, abolished swelling, suggesting the need for Cd2+ influx through the MCU for swelling to occur. Complete loss of mitochondrial membrane potential (m) induced by K+ influx did not prevent contraction, but addition of the K+/H+ exchanger blocker, quinine (1 mM), or the electroneutral protonophore nigericin (0.4 µM), abolished contraction, suggesting the mitochondrial pH gradient (pHm) driving contraction. Accordingly, a quinine-sensitive partial dissipation of pHm was coincident with the swelling-contraction phase. The data indicate that Cd2+ enters the matrix through the MCU to activate a K+ cycle. Initial K+ load via a Cd2+-activated K+ uniporter in the IMM causes osmotic swelling and breakdown of m and triggers quinine-sensitive K+/H+ exchange and contraction. Thus Cd2+-induced activation of a K+ cycle contributes to the dissipation of the mitochondrial protonmotive force. bongkrekic acid; cyclosporin A; lanthanum; Ru360; ruthenium red  相似文献   

16.
Tomato cells (with the Cf-5 resistance gene) were treated withelicitor preparations containing the avr5 gene product fromtwo Cf-5 incompatible races of the fungal pathogen Cladosporiumfulvum (race 2.3 and race 4), or with elicitor preparationscontaining no avr5 gene product from two Cf-5 compatible races(race 5 and race 2.4.5.9 [EC] .11). Elicitor preparations from race2.3 or race 4 caused dephosphorylation of host plasma membraneH+ -ATPase in isolated plasma membranes, while the preparationsfrom race 5 or race 2.4.5.9 [EC] .11 did not. GTP()S, AlF4and cholera toxin (CTX) each induced similar dephosphorylationin the absence of active elicitors. The elicitor-induced dephosphorylationof the H+ -ATPase was blocked by preincubation of membraneswith an antibody raised against a stimulatory G protein -subunit(anti-Gs This antibody cross-reacted with a 42 kDa polypeptidefrom tomato plasma membranes. A 42 kDa polypeptide was alsoADP-ribosylated by CTX. When plasma membranes were treated withelicitor preparations from race 4 and separated on non-dissociatingPAGE, two proteins were detected on Western blots with the antibodyraised against the -subunit, suggesting the dissociation ofthe trimeric complex. No dissociation of the complex was detectedwith antibodies raised against either the - or ß-subunitswhen the plasma membranes were treated with elicitor preparationsfrom race 5. The results provide evidence for the activationof a stimulatory subtype of trimeric G proteins in the stimulationof elicitor-induced host defences to fungal pathogens. Key words: G protein, dephosphorylation, H+ -ATPase, fungal elicitor, tomato  相似文献   

17.
The effect of growth temperature on the short term influx of86Rb+/K+, 36Cl/Cl, , 45Ca2+/Ca2+and into barley plants (Hordeum vulgareL. cv. Betzes) has been examined. When barley plants were grownwith a differential root: shoot temperature (15 ?C/25 ?C) therewas a marked stimulation of influx of all ions except Ca2+.Q10 measurements were close to 2.0 for all ions except Ca2+,where Q10 1.0 was found. Kinetics of ion influx showed thatthere had been almost complete compensation for the lower growingtemperature over a range of concentrations. The regulation of uptake was affected by growth temperature. On exposure to 15?C efflux/influx fell initially but was restored after 5 d. Sensitivity of net uptake to was increased by growth at a lower temperature. The importance of these observations in relationto application to field experiments and the proposed mechanismfor uptake is discussed. Key words: Growth temperature, Nitrate, Ammonium  相似文献   

18.
The effects of -hydroxy-2-pyridinemethanesulphonic acid (-HPMS)upon net photosynthesis (Pn, the CO2 compensation point (),post-lower illumination burst of CO2 (PLIB) and post-lower temperatureburst of CO2 (PLTB) in detached rye (Secale cereale L.) leaveswere investigated. At low concentrations ( 0.5 mol m–3),-HPMS initially stimulated Pn and decreased the magnitude ofboth PLIB and PLTB. The decreased at all concentrations of-HPMS (0.05–5.0 mol m–3. The effects of -HPMS onPn and were time-dependent and, after a few minutes, the Pnwas inhibited while values increased considerably. At a higherconcentration (5.0 mol m –3), the transient effects of-HPMS were shorter () or not observed at all (Pn. Both PLIBand PLTB, when expressed in relation to Pn, increased at higherlevels of this compound. Similar data with respect to the effectsof -HPMS on PLIB and PLTB were found for leaves of dandelion(Taraxacum officinale L.). The results suggest that -HPMS may stimulate Pn by inhibitingphotorespiration, as originally suggested by Zelitch (1966),but only at low concentrations and over a short time span. Thedecrease of PLIB and PLTB values at low -HPMS levels is consistentwith these processes being a residual activity of the glycolatepathway. Key words: CO2 compensation point, -hydroxy-2-pyridinemethanesulphonic acid, photorespiration, photosynthesis  相似文献   

19.
An existing system of flowing solution culture, in which pHand the concentration of several nutrient ions are automaticallymonitored and controlled, has been extended to include at 10 mmol N m–3. A brief account is givenof the use of the equipment with a simulated sward of perennialryegrass (Lolium perenne L.). Uptake of measured over three successive days in June, varied with dailysolar radiation and exceeded 1000 mg N m–2 d–1.The uptake of showed a pattern of diurnal variation similar to the variation in solar radiation, but witha lag period for uptake of 5 h. Hourly uptake rates ranged from32 to 67 mg N m–2h–1 and solar radiation from 0to 2.8 MJ m–2 h–1. During a 24 h period, additionalmeasurements were made of K+ uptake and net H+ efflux, bothof which showed patterns of diurnal variation with lag periodsof 6 h hand 7 h, respectively. The stoichiometric ratio of thesum of and K+ to the net efflux of H+ was1.02: 1. Key words: Ion uptake, diurnal variation, Lolium perenne L.  相似文献   

20.
The diffusion symmetry developed by the alkaline and aeid bandsof Chara corallina was studied. The alkaline system developeda diffusion pattern which could not be fitted to the equationfor a continuous point-source efflux. However, good correlationwas obtained between experimental data and the diffusion equationfor a hollow sphere. The calculated OH- efflux values, obtainedusing the equation of a continuous spherical-surface source,were checked against the influx values of H14 obtained under the same experimental conditions. IndividualOH– band efflux values ranged from 0.07 to 5.95 pmol s–1and total cell fluxes of 25 pmol cm–2 s–1 for OH-and H were obtained (in the presence of 0.5 mM NaHCO3). The acid system developed a cylindrical diffusion pattern, butthis could not be fitted to a mathematical equation. Numericalanalysis will have to be employed to obtain values of H+ efflux.  相似文献   

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