共查询到20条相似文献,搜索用时 31 毫秒
1.
DUREJA INAM; GUHA-MUKHERJEE SIPRA; PRASAD RAJENDRA 《Journal of experimental botany》1984,35(7):1022-1031
The uptake of L-leucine and glycine into pea protoplasts wasstudied under various conditions. The uptake of both L-leucineand glycine was pH dependent with the optimal pH being 4.0 and5.0 for L-leucine and glycine, respectively. A kinetic studyof L-leucine uptake showed that uptake is multiphasic; Km valuesof different phases were 1.1 mol m3, 33.3 mol m3and 100 mol m3. A similar analysis for glycine at a concentrationrange of 0.110 mol m3 also showed a multiphasictransport system for it. The uptake of L-leucine at lower concentrations(between0.12.0 mol m3) was energy dependent, since arsenate,azide, dinitrophenol and iodoacetate inhibited the uptake. However,the uptake of L-leucine was not inhibited by ouabain at anyconcentration of L-leucine employed. The uptake of glycine wasnot inhibited by any of these inhibitors suggesting that glycineuptake was not mediated by an active process. Key words: Pea protoplast, L-Leucine, Glycine transport, Active transport, Mediated transport 相似文献
2.
The cotyledons of Euphorbia lathyris L. take up sucrose andamino acids from the endosperm. The interaction between theuptake of sucrose and that of amino acids by cotyledons of intactseedlings was investigated. Sucrose (100 mol m3) reducedvaline uptake to 75% of the control rate; the active uptakecomponent of valine uptake was reduced from 45 to 25 % of thetotal uptake rate. In a reverse experiment, 100 mol m3valine inhibited sucrose uptake by 25%. At 500 mol m3sucrose, valine uptake was completely restored to the controlrate, whereas high valine concentrations failed to restore sucroseuptake. The stimulation of valine uptake by sucrose is linkedto the role of sucrose as a primary respiratory substrate. Whenthe cotyledons were bathed in sucrose concentrations rangingfrom 0 to 100 mol m3 (these concentrations are non-saturatingwith respect to sucrose uptake), a constant 1.8% of the sucrosetaken up was respired. The Km of the concentration-dependentsucrose oxidation (44±6 mol m3) agreed reasonablywell with that for sucrose uptake (29±6 mol m3).When the external sucrose concentration was increased from 100to 600 mol m3, the sucrose uptake increased by 30% again,while sucrose oxidation was increased by 300%. This increasewas not due to an increased engagement of the alternative (cyanide-resistant)pathway for respiration. Alternative pathway, Euphorbia lathyris L., fermentation, seedling, sucrose uptake, valine uptake 相似文献
3.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown as simulated swards for 71 d in flowing nutrientsolutions with roots at 11 C and shoots at 20/15 C, day/night,under natural illumination. Root temperatures were then changedto 3, 5, 7, 11, 13, 17 or 25 C and the total N2, fixation over21 d was measured in the absence of a supply mineral N. Alltreatments were subsequently supplied with 10 mmol m2NO2 in the flowing solutions for 14 d, and the relativeuptake of N by N2, fixation and NO3 uptake was compared.Net uptake of K+ was measured on a daily basis. Root temperature had little effect on root d. wt over the 35-dexperimental period, but shoot d. wt increased by a factor of3.5 between 3 and 25 C, with the sharpest increase occurringat 711 C. Shoot: root d. wt ratios increased from 25to 68 with increasing temperature at 725 C. N2-fixationper plant (in the absence of NO2 ) increased with roottemperature at 313C, but showed little change above13 C. The ratios of N2 fixation: NO2 uptake over 14d (mol N: mol N) were 0.470.77 at 37 C, 092154at 1117 C, and 046 at 25 C, reflecting the dominanceof NO3 uptake over N2 fixation at extremes of high andlow root temperature. The total uptake of N varied only slightlyat 1125 C (095110 mmol N plant1),the decline in N2 fixation as root temperature increased above11 C was compensated for by the increase in NO 3 uptake.The % N in shoot dry matter declined with decreasing root temperature,from 32% at 13 C to 15% at 3 C. In contrast, concentrationsof N expressed on a shoot water content basis showed a modestdecrease with increasing temperature, from 345 mol m3at 3 C to 290 mol m3 at 25 C. Trifolium repens L, white clover, root temperature, N2 fixation, potassium uptake, nitrate uptake, flowing solution culture 相似文献
4.
Potassium-Ammonium Uptake Interactions in Tobacco Seedlings 总被引:6,自引:0,他引:6
SCHERER HEINRICH W.; MACKOWN CHARLES T.; LEGGETT J. EVERETT 《Journal of experimental botany》1984,35(7):1060-1070
Short-term (< 12 h) uptake experiments were conducted with67-week-old tobacco (Nicotiana tabacum L. cv. Ky 14)seedlings to determine absorption interactions between K+ andNH4+. At equal solution concentrations (0.5 mol m3) netK+ uptake was inhibited 3035% by NH4+ and NH4+ uptakewas decreased 924%. Removal of NH4+ resulted in completerecovery in K+ uptake rate, but NH4+ uptake rate did not recoverwhen K+ was removed. In both cases, inhibition of the uptakerate of one cation saturated as the concentration of the othercation was increased up to 0.5 mol m3. The relative effectof K+-NH4+ interactions was not altered when Cl- was replacedwith SO42, but the magnitudes of the uptake rates wereless in the absence of Cl-. The Vmax for NH4+ uptake was reducedfrom 128 to 105 µmol g1 dry wt. h1 in thepresence of 0.5 mol m3 K+ and the Km for NH4+ doubledfrom 12 to 27 mmol m3 in the presence of K+. The resultsof these K+-NH4+ experiments are interpreted as mixed-noncompetitiveinteractions. However, an enhanced efflux of K+ coupled to NH4+influx via an antiporter cannot be ruled out as contributingto the decrease in net K+ uptake. Key words: Nicotiana tabacum, K+, NH4+, Uptake interactions 相似文献
5.
In "air-grown" Chroomonas sp. cells, low concentrations of DCMU(less than 0.1 µM) could prevent the inhibition of 14CO2fixation by anaerobiosis under light-saturating conditions (morethan 40 W.m2), with phenazine methosulfate showing asimilar effect. Antimycin A, carbonyl cyanide m-chlorophenylhydrazone(CCCP), and N,N'-dicyclohexylcarbodiimide strongly inhibitedanaerobic photosynthesis at concentrations which did not significantlyinhibit the rate under 2% O2 at high light intensity (200 W.m2),although 0.2 µM CCCP stimulated the rate under 2% O2 tosome extent. On the other hand, KCN inhibited the rate muchmore strongly under 2% O2 than N2, although it inhibited therate very strongly at concentrations above 5 µM both underN2 and 2% O2. These results suggest that the inhibition of photosynthetic14CO2 fixation by anaerobiosis in this alga result from ATPdeficiency caused by over-reduction of electron carriers ofthe cyclic electron flow and that oxygen can prevent the over-reduction.Cyclic electron flow seems to be necessary to provide additionalATP for CO2 reduction under anaerobic conditions, although itseems to be less necessary under aerobic conditions. (Received July 21, 1983; Accepted January 23, 1984) 相似文献
6.
Kreuzwieser Jrgen; Herschbach Cornelia; Stulen Ineke; Wiersema Peter; Vaalburg Willem; Rennenberg Heinz 《Journal of experimental botany》1997,48(7):1431-1438
The processes of NO3 uptake and transport and the effectsof NH4+ or L-glutamate on these processes were investigatedwith excised non-mycorrhizal beech (Fagus sylvatica L.) roots.NO3 net uptake followed uniphasic Michaelis-Menten kineticsin a concentration range of 10µM to 1 mM with an apparentKm of 9.2 µM and a Vmax of 366 nmol g1 FW h1.NH4+, when present in excess to NO3, or 10 mM L-glutamateinhibited the net uptake of NO3 Apparently, part of NO3taken up was loaded into the xylem. Relative xylem loading ofNO3 ranged from 3.21.6 to 6.45.1% of NO3 netuptake. It was not affected by treatment with NH4+ or L-glutamate.16N/13N double labelling experiments showed that NO3efflux from roots increased with increasing influx of NO3and, therefore, declined if influx was reduced by NH4+ or L-glutamateexposure. From these results it is concluded that NO3net uptake by non-mycorrhizal beech roots is reduced by NH4+or L-glutamate at the level of influx and not at the level ofefflux. Key words: Nitrate transport, net uptake, influx, efflux, ammonium, Fagus, Fagaceae 相似文献
7.
Effect of Salinity on Growth, Nodulation and Nitrogen Yield of Chickpea (Cicer arietinum L.) 总被引:2,自引:0,他引:2
Chickpea cultivar ILC 482 was inoculated with salt-tolerantRhizobium strain Ch191 in solution culture with different saltconcentrations added either immediately with inoculation or5 d later. The inhibitory effect of salinity on nodulation ofchickpea occurred at 40 dS m1 (34.2 mol m3 NaCl)and nodulation was completely inhibited at 7 dS m1 (61.6mol m3 NaCl); the plants died at 8 dS m1 (71.8mol m3 NaCl). Chickpea cultivar ILC 482 inoculated with Rhizobium strain Ch191spcstrwas grown in two pot experiments and irrigated with saline water.Salinity (NaCl equivalent to 14 dS m1) significantlydecreased shoot and root dry weight, total nodule number perplant, nodule weight and average nodule weight. The resultsindicate that Rhizobium strain Ch191 forms an infective andeffective symbiosis with chickpea under saline and non-salineconditions; this legume was more salt-sensitive compared tothe rhizobia, the roots were more sensitive than the shoots,and N2 fixation was more sensitive to salinity than plant growth. Key words: Cicer arietinum, nodulation, N2 fixation, Rhizobium, salinity 相似文献
8.
The inhibitory effects of antimycin on various photosyntheticactivities were investigated with Chromatium vinosum chromatophores. Photophosphorylation and proton uptake under continuous illumination,the slow phase of the flash-induced proton uptake, and re-reductionof flash-oxidized cytochrome C555 and the reaction center bacteriochlorophylldimer were half inhibited at about 5 x 107 M antimycinand almost completely inhibited at about 2 x 105 M. N-Methylphenazoniummethosulfate (100 µM) restored the inhibited activitiesof photophosphorylation and proton uptake to the original levels.These results indicated that antimycin, as it inhibits the cyclicelectron transfer in non-sulfur purple bacteria, inhibits thecyclic electron flow involving cytochrome C555 and hence inhibitsthe photosynthetic activities coupled to the electron flow. On the other hand, antimycin had little inhibitory effect onthe proton release by whole cells of Chromatium under continuousillumination. The ineffectiveness was probably due to the lowpermeability of antimycin to the cell wall of the bacterium. The rapid phase of the proton uptake induced by a single-turnoverflash was not inhibited by antimycin, suggesting that the protonuptake is not closely associated with the electron transferinvolving the antimycin-sensitive site. (Received November 20, 1980; Accepted March 11, 1981) 相似文献
9.
A study has been made of photosynthetic 14CO2 fixation by isolatedmature internodes of Nitella translucens. Experimentalconditions were similar to those used in studies of the ionicrelations of these cells. Maximum rates of photosynthesis were3340µµmoles CO2, fixed per cm2 of surfacearea per second (equivalent to 1215 /xmoles fixed permg chlorophyll per hour). l4CO2 fixation was inhibited to thedark level by 3(3,4,dichlorophenyl)-1, 1-dimethylurea (at 0-6µM or 10µM) and by the uncoupler carbonyl cyanide-m-chlorophenylhydrazone(SµM). The presence of imidazole or ammonium sulphate(both of which uncouple ATP production in vitro) did not resultin an inhibition of 14CO2 fixation. These results are discussedin relation to published work on solute uptake by Nitella translucens.During photosynthesis there was rapid movement of 14C-labelledorganic compounds out of the chloroplasts. 14C-labelled sucrose,ammo-acids, and sugar phosphates were found in samples of vacuolarsap. 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.
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
12.
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
13.
Cutler Horace G.; Crumley Farrist G.; Cox Richard H.; Wells John M.; Cole Richard J. 《Plant & cell physiology》1984,25(2):257-263
Cyclopenin (C17H14O3N2) and cyclopenol (C17H14O4N2), isolatedfrom an abberent strain of Penicillium cyclopium (NRRL 6233),significantly inhibited the growth of etiolated wheat (Triticumaestivum) coleoptile segments. The former inhibited at 103and 104 M, the latter at 103 M. Cyclopenin producedmalformation of the first set of trifoliate leaves in bean (Phaseolusvulgaris) at 102 M and necrosis and stunting in corn(Zea mays) at 102 M. Cyclopenol induced no apparent effectsin bean or corn plants. Neither compound changed the growthor morphology of tobacco (Nicotiana tabacum) plants. Cyclopenininduced intoxication, prostration and ataxia in day-old chicksat 500 mg/kg, but they recovered within 18 hours. Cyclopenolwas inactive against chicks when dosed at levels up to 500 mg/kg. (Received October 11, 1983; Accepted December 15, 1983) 相似文献
14.
The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (1052 and 105 7 mol m2 d1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d1 to 1 h d1), Camelina saliva (1 min d1to 8 h d1), Eruca saliva (1 min d1 to 24 h d1),Lepidium sativum (I min d1 to 8 h d1) and Rorippapalustris (1 min d1 to 8 h d1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO03 mol m2 d1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 104 M GA2, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 102 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA2, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA2, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA2 Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy 相似文献
15.
LARSON KIRK D.; SCHAFFER BRUCE; DAVIES FREDERICK S. 《Journal of experimental botany》1993,44(3):665-671
A system was developed to test the effects of floodwater O2concentration on ethylene evolution and stem lenticel hypertrophy,and the effects of exogenous ethylene on stem lenticel hypertrophyin mango (Mangifera indica L.) trees. Dissolved O2 concentrationsof 17x109 m3 m3 generally resulted in hypertrophyof stem lenticels within about 6 d of flooding, whereas floodwaterO2 concentrations of 1315 x 109 m3 m3 delayedhypertrophy until about day 9. After 14d of flooding, therewere more than twice the number of hypertrophied lenticels pertree with floodwater O2 concentrations of 17 x 109m3 m3 than with floodwater O2 concentrations of 15 x109 m3 m3. Ethylene evolution from stem tissueimmediately above the floodline increased 4- to 8-fold in treesexposed to floodwater O2 concentrations of 12 x 109m3 m3, increased 2-fold for trees exposed to floodwaterO2 concentrations of 67 x 109 m3 m3, butremained constant with floodwater O2 concentrations of 1315x 109 m3 m3. Plants maintained in highly oxygenatedfloodwater (1315 x 109 m3 m3), and givenexogenous ethylene developed many hypertrophied lenticels, whereasplants in highly oxygenated water and not given ethylene developedfewer or nohypertrophied lenticels. These data suggest thatethylene plays a role in promotion of stem lenticel hypertrophyin flooded mango trees, and that floodwater dissolved oxygenconcentration can regulate stem lenticel hypertrophy and ethyleneevolution in this species. Key words: Flooding, hypoxia, hypertrophic cell swelling 相似文献
16.
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
17.
K+ efflux from tobacco (Nicotiana tabacum L, cv. Samsun NN)leaf discs into the external medium was increased and the membranepotential (Em) changed in the positive direction with a changein pH from 8.0 to 4.0. Em was affected by the external concentrationof KCl, greatly decreasing with a change in concentration from1 mM to 100 mM. The equilibrium potential of the membrane forK+ (Ek) was decreased in a Nernst fashion with increasing externalconcentrations of KCl. Ek is more positive than Em above ca.50 µM KCl. Most of the experiments were carried out underconditions in which the difference between the electrochemicalpotential for K+ on the inside to the outside of the cell (µkis positive. Thus, K+ may passively flow to the outside of thecells accompanied by the depolarization of the membrane. Abscisic acid (ABA) increased the K+ efflux under conditionsof passive transport. K+ efflux was accelerated with an increasingconcentration of ABA, being maximal at 104 M103M. This acceleration was due to the enhancement of the potassiummotive force (µk/F) which is the force causing the netpassive transport of K+. The membrane potential was decreasedfrom 205 mV to 170 mV by 2 x 104 M ABAwithin 10 min. The depolarization was not transient, being lostfor at least 3 hr. These results show that ABA accelerated passive K+ efflux, whichaccompanied depolarization of the membrane. (Received June 22, 1981; Accepted August 24, 1981) 相似文献
18.
Measuring the Canopy Net Photosynthesis of Glasshouse Crops 总被引:3,自引:0,他引:3
HAND D. W.; CLARK G.; HANNAH M.A; THORNLEY J. H. M.; WILSON J. WARREN 《Journal of experimental botany》1992,43(3):375-381
A null balance method is described for measuring net photosynthesisof mature canopies of cucumber and other protected crops overperiods of 10 min in a single-span glasshouse (c. 9m x 18m inarea). Accuracy of control of the CO2 concentration in the greenhouseatmosphere is within ±10 vpm of the normal ambient level(c. 350 vpm). The amounts of CO2 used in canopy net photosynthesisare measured with linear mass flowmeters accurate to within±0.80g. The total errors incurred in measuring canopynet photosynthesis at an ambient CO2 level are estimated tobe of the order of ± 1·2% in bright light (350W m2, PAR)and ±3·6% in dull light (100W m2, PAR). Measurements of the rates of net photosynthesis of a maturecanopy of a cucumber crop were made at near-ambient CO2 concentrationsover a range (0350 W m2) of natural light fluxdensities. A model of light absorption and photosynthesis applicableto row crops was used to obtain a net photosynthesis versuslight response curve for the cucumber crop. At a light fluxdensity of 350 W m2 the fitted value of canopy net photosynthesiswas 2.65 mg CO2 m2s1 (equivalent to over 95 kgCO2 ha1h1). The results are discussed in relationto the need for CO2 supplements to avoid depletion in both ventilatedand unventilated glasshouses during late spring and summer. Key words: Glasshouse crops, cucumber, measurement, canopy photosynthesis, light, CO2 相似文献
19.
Investigations on the effects of low levels of Al on P adsorption,uptake and translocation in seedlings of the indigenous grassAgrostis capillaris were undertaken. Apparent uptake and transportof H2 32PO4 from nutrient solutions containing 10 or 100mmolm3 phosphate were characterized as functions of timeand concentration. Experiments on 32P uptake and transport insolutions containing no Al (control) or Al ranging from 3.7to 185 mmol m3 at pH ranging from 4.3 to 4.6, showedthat in 10 mmol m3 P, effects of Al at 3.7 and 37 mmolm3 on the size of the initial uptake shoulder were small,but some increase in subsequent P uptake to the roots was observed,though transport to the shoots was suppressed. With 37 mmolm3 Al in nutrient solution containing 100 mmol m3P, the uptake shoulder was much increased above the control.Subsequent root uptake was stimulated but transport was unaffected.Lack of toxicity of the Al concentrations used was indicatedby a lack of significant effect on plant fresh weight. AbsorbedAl was almost totally retained in the root in all treatments.Speciation calculations showed that the major species in Alamended nutrient solution at pH 4.4 were H2PO4, AI3+and AIHPO4+, together with substantial amounts of AISO4+ andsoluble aluminium hydroxy complexes (AIOH2+, AI(OH)2+), dependingon the relative concentrations of P and Al. The effects of Al,with 10 mmol m3 P, on adsorption of complexed P werepartly accounted for in terms of preferential cell wall adsorptionof Al complexes not containing P. Conclusions were drawn aboutthe P-economy of A. capillaris plants growing on soils withlow levels of P and Al. Key words: Phosphorus, aluminium, speciation, Agrostis capillahs L 相似文献
20.
Selective inhibition of antimycin A-insensitive respiration in Ustilago maydis and Ceratocystis ulmi
Sporidia of Ustilago maydis and conidia of Ceratocystis ulmipossess an antimycin A and azide-tolerant electron transportpathway which apparently diverts electrons to O2 from some pointon the substrate side of the antimycin A block. The alternatepathway (induced by 0.5 µg/ml antimycin A or 5x104M sodium azide) supports a respiratory rate 1.52 timesthat of the normal system, but has a terminal oxidase with alower than normal affinity for O2. A similarly high respiratoryrate in U. maydis is supported by the normal pathway when uncoupledby 4 µg/ml of 4,5-dichloro-2-trifluoromethylbenzimidazole,but a high affinity for O2 in this case indicates that the normalterminal oxidase is utilized. Respiration by the normal pathway in both fungi is only slightlyor moderately inhibited by 1.5x103 M benzohydroxamicacid (BHAM) and 5x104 M 8-hydroxyquinoline. The alternatepathway in U. maydis, however, is inhibited as much as 84 and92% respectively by these two compounds, while alternate respirationin C. ulmi can be inhibited as much as 86 and 76% respectively.BHAM, 8-hydroxyquinoline, 2-pyridinethiol-1-oxide, a,a'-dipyridyl,carboxin, and diphenylamine inhibit alternate respiration ata site on the alternate pathway which is not part of the normalelectron transport system. Antimycin A and azide-insensitiverespiration found in U. maydis and C. ulmi closely resemblesinhibitor insensitivity noted in several fungi and some higherplants. Such an alternate respiratory pathway may be an earlystep in the evolution of oxidative phosphorylation. (Received June 27, 1972; ) 相似文献