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1.
Hansen, A. P., Pate, J. S. and Atkins, C. A. 1987. Relationshipsbetween acetylene reduction activity, hydrogen evolution andnitrogen fixation in nodules of Acacia spp.: Experimental backgroundto assaying fixation by acetylene reduction under field conditions.J.exp. Bot. 38: 112 Glasshouse grown, symbiotically-dependent seedlings of Acaciaalata R.Br., .A. extensa Lindl., and A. pulchella R.Br. wereexamined for acetylene reduction in closed assay systems usingundisturbed potted plants, excavated whole plants, nodulatedroots or detached nodules. Nitrogenase activity declined sharplyover the first hour after exposure of detached nodules to acetylene(10% v/v in air), less steeply or not at all over a 3 h periodin assays involving attached nodules. Using detached nodules,rates of acetylene reduction, nitrogen (15N2) fixation, andhydrogen evolution in air (15N2) and acetylene-containing atmosphereswere measured in comparable 30 min assays. Total electron flowthrough nitrogenase in air was determined from rates of nitrogen(15N2) fixation ( ? 3) plus hydrogen evolution, that in thepresence of acetylene from rates of acetylene reduction andhydrogen evolution in air: acetylene. Values for the ratio ofelectron flow in air: acetylene to that in air ranged from 0?43to 0?83 in A. pulcheila, from 0?44 to 0?66 in A. alala and from0?37 to 0?70 in A. extensa, indicating substantial inhibitionof electron flow through nitrogenase of detached nodules byacetylene. Relative efficiencies of nitrogenase functioningbased on hydrogen evolution and acetylene reduction were from0?15 to 0?79, those based on nitrogen (15N2) fixation and hydrogenevolution from 0?53 to 0?87. Molar ratios of acetylene reducedto nitrogen (15N2) fixed were 2?82 ? 0?24, 201 ? 0?15, and 1?91? 0?11 (?s.e.; n = 7) for A. pulcheila,A. extensa and A. alata respectively A standard 510 min acetylene reduction assay, conductedon freshly detached unwashed nodules in daytime (12.0014.00h), was calibrated for field use by comparing total N accumulationof seedlings with estimated cumulative acetylene reduction overa 7-week period of glasshouse culture. Molar ratios for acetylenereduced: nitrogen fixed using this arbitrary method were 3?58for A. alata, 4?82 for A. extensa and 1?60 for A. pulchella.The significance of the data is discussed. Key words: Acacia spp, nitrogenase functioning 相似文献
2.
Nitrogen Economy of Post-fire Stands of Shrub Legumes in Jarrah (Eucalyptus marginata Donn ex Sm.) Forest of S.W. Australia 总被引:1,自引:0,他引:1
HANSEN ALEXANDER P.; PATE JOHN S.; HANSEN ANNETTE; BELL DAVID T. 《Journal of experimental botany》1987,38(1):26-41
Hansen, A. P., Pate, J. S., Hansen, A. and Bell, D. T. 1987.Nitrogen economy of post-fire stands of shrub legumes in jarrah(Eucalyptus marginata Donn ex Sm.) forest of S.W. Australia.J.exp. Bot. 38: 2641. Growth, demography and N economy of 16-year-old standsof Acacia pulchella, A. alata, A. extensa and Bossiaea aquifoliumwere examined using population sampling to assess annual incrementsof N as living biomass, and returns of N as litter, seed anddead plants. Dependence on nitrogen fixation was assessed fromseasonal profiles of acetylene reduction, employing data fromprevious calibrations to convert C2H2 reduced to N2 fixed. After2 years of slow growth and minimal reproduction all speciesgrew rapidly to achieve maximum or near maximum size and seedproduction. Intense self-thinning of stands occurred in thesecond and third years, especially in the highly dense standsof the smallest species, A. alata. Annual turnover in standsranged from 0?3 to 127 kg N ha1 year1, dependingon species current age and density of a stand. Returns of Nas litter and shed seed comprised small proportions of the annualbudgets, but returns due to plant death equalled or exceededincrements of living biomass in years when stands were thinningrapidly. Proportional dependencies of the species on fixed N2were relatively high (1361%) in first year seedlings,and then declined markedly to 1?13?4percnt; in the second,0?31?6% in the third, and, with one exception, to wellbelow 1% in the fourth and sixth year stands. Mean annual ratesof N2 fixation over the 6-year post-fire period were 1?6 kgN ha1 year1 for A. alata, 049 for A. pulchella,0?19 for B. aquifolium and 0-10 for A. extensa Key words: Shrub legumes, post-fire N economy 相似文献
3.
HANSEN ALEXANDER P.; PEOPLES MARK B.; GRESSHOFF PETER M.; ATKINS CRAIG A.; PATE JOHN S.; CARROLL BERNARD J. 《Journal of experimental botany》1989,40(7):715-724
Growth and symbiotic performance of soybean (Glycine max (L.)Merrill) cv. Bragg and three of its induced nodulation mutants(nod49, non-nodulating; ntsl 116, intermediate supernodulator;nts1007, extreme supernodulator) were compared throughout developmentunder different nitrogen regimes (0, 2, 5 and 10 mol nitratem3). Nitrogen fixation was assessed using 15N-isotopedilution and xylem sap analysis for ureide content. Both techniquesconfirmed a complete lack of N2 fixation activity in nod49.Plant reliance on nitrogen fixation by the other genotypes wasdependent on the nitrate regime and the developmental stage.The ntsl007 and ntsl 116 mutants fixed more nitrogen than theparent cultivar in the presence of 10 mol m3 nitratein the nutrient solution, but higher input of symbioticallyderived nitrogen was still insufficient to offset the amountof nitrogen removed in the harvested seed. However, the mutantsutilized less nitrate for growth than Bragg. Comparison of estimatesof N2 fixation derived from the 15N-dilution technique withthose based on relative ureide content of xylem sap indicatedthat the latter offered a simple and reliable procedure forevaluating the symbiotic performance of supernodulating plants. Key words: 15N-isotope dilution, supernodulation, ureides 相似文献
4.
Nodulated 1-1.5-year-old plants of Acacia littorea grown inminus nitrogen culture were each partnered with a single seedlingof the root hemiparasite Olax phyllanthi. Partitioning of fixedN between plant organs of the host and parasite was studiedfor the period 48 months after introducing the parasite.N fluxes through nodules of Acacia and xylem-tapping haustoriaof Olax were compared using measured xylem flows of fixed Nand anatomical information for the two organs. N2 fixation duringthe study interval (635 µg N g FW nodules1 d1)corresponded to a xylem loading flux of 0.20 µg N mm2d1 across the secretory membranes of the pencycle parenchymaof the nodule vascular strands. A much higher flux of N (4891µg mm2 d1) exited through xylem at the junctionof nodule and root. The corresponding flux of N from host xylemacross absorptive membranes of the endophyte parenchyma of Olaxhaustorium was 1.15 µg N mm1 d1, six timesthe loading flux in nodules. The exit flux from haustorium toparasite rootlet was 20.0 pg N mm1 d1, 200-foldless than that passing through xylem elements of the nodule.Fluxes of individual amino compounds in xylem of nodule andhaustorium were assessed on a molar and N basis. N flux valuesare related to data for transpiration and partitioning of Cand N of the association recorded in a companion paper. Key words: Olax phyllanthi, host-parasite relationships, N flux, Acacia, N2 fixation 相似文献
5.
Phosphorus Deficiency Impairs Early Nodule Functioning and Enhances Proton Release in Roots of Medicago truncatula L. 总被引:10,自引:0,他引:10
The effect of phosphorus supply (115 µM) on protonrelease and the role of P in symbiotic nitrogen fixation inmedic (Medicago truncatula L. Jemalong) was investigated.As P concentration in the nutrient solution increased, shootand root growth increased by 19 and 15%, respectively by day35, with maximal growth at 4 µM P. A P concentration of15 µM appeared to be toxic to plants. Phosphorus supplyhad no influence on nodule formation by day 12 but increasednodule number by day 35. Nitrogenase activity was estimatedby in situ measurement of acetylene reduction activity (ARA)in an open-flow system. During the assay, a C2H2-induced declineof ARA was observed under all P concentrations except 4 µM.Specific ARA (per unit nodule weight) doubled when P supplywas increased from 1 to 8 µM. This effect of P was muchgreater than the effects of P on nodulation and host plant growth.Concentrations of excess cations in plants decreased with increasingP concentration in the nutrient solution. Phosphorus deficiencystimulated uptake of excess cations over anions by the plantsand hence enhanced proton release. The results suggest thatP plays a direct role in nodule functioning in medic and thatP deficiency increases acidification which may facilitate Pacquisition. Copyright 2001 Annals of Botany Company Medicago truncatula L. (medic), P deficiency, C2H2-ID, nitrogenase activity, proton release, cation-anion balance, open-flow system 相似文献
6.
From homogenates prepared from surface-sterilized nodules ofseedlings of Casuarina cunninghamiana grown aeroponically, astrain of Frankia designated HFPCc13 was isolated and has beengrown in pure filamentous culture in a defined synthetic nutrientmedium. Vesicle and sporangium formation can be induced by removalof combined nitrogen from the medium.Frankia strain HFPCc13nodulates young seedlings of C. cunninghamiana and C. equisetifoliawithin three weeks of inoculation with an optimum root mediumpH of 67 for nodulation and optimum temperature of 3035°C. The presence of combined nitrogen in the root mediuminhibits nodulation with NH4+ more inhibitory than NO3.Frankia HFPCc13 does not nodulate Allocasuarina species withinthe same family nor several other possible actinorhizal plantstested. Thus this strain is quite precise in its host specificity.The rate of acetylene reduction was greater in C. cunninghamianathan the closely related species C. equisetifolia. In neitherof these host species were vesicles observed to occur withinthe infected root nodules which had been demonstrated to beactively fixing dinitrogen. Root nodules were shown to be activein acetylene reduction over a range of O2 concentration in thegaseous environment with an optimum at about 20 per cent O2,the ambient PO2 of the air. The mechanism(s) for oxygen protectionof nitrogenase within the filamentous form of Frankia withinthese nodules remains to be explained. Casuarina, Frankia, nodulation, nitrogen fixation 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.
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
9.
The patterns of plant growth and N2 fixation capability in Pachyrhizusahipa (Wedd) Parodi inoculated with Bradyrhizobium PachyrhizusSpec 1 strains (Lipha Tech) were investigated in a zero-Nculture system under greenhouse conditions The P ahipa plantis day-neutral with respect to reproductive development Competitionoccurred between the two storage organs (legume and tuber) andprevented high tuber yield in P ahipa The symbiotic effectivenessof the association was high, as the profuse nodulation providedthe inoculated plants with adequate amounts of N Nodules werepresent throughout the cycle of P ahipa The change in rate ofN2 fixation (RNF) and relative growth rate (RGR) was almostparallel during ontogenesis The developmental pattern of N2fixation activity revealed that 65% of total N2 fixation occurredafter N began to accumulate in the reproductive (pod wall plusseed) tissue During pod filling allocation of N compounds tothe seeds exceeded N2 fixation, the pod walls being the primarysource of redistributed N, followed by the leaves. Pachyrhizus ahipa (Wedd) Parodi, ahipa, tuber crop, dinitrogen fixation, dry matter, N partitioning, reproductive growth 相似文献
10.
Cotyledons of faba bean (Vicia faba L. cv. Fiord) were removedto determine whether an apparent delay in nodulation of thiscultivar could be attributed to an inhibitor from these organs.Cotyledons were left intact or excised from seedling plants14 and 18 d after sowing and plants grown with or without 2·5mm NO3. Seedling growth was depressed when cotyledons were removed onday 14 but not when removed on day 18. Removal of the cotyledonsat day 14 reduced nodule number and nodule weight in the absenceof NO3, but in the presence of NO2, nodule numberwas unaffected and only nodule weight was reduced. Cotyledonremoval at day 18 increased both nodule number and nodule weightwith +NO3 but not with NO2. Acetylene reduction(AR) was markedly depressed by NO3. Cotyledon removalat day 14 decreased AR but removal at day 18 resulted in anincrease in AR. We suggest from these results that faba beancotyledons have an inhibitory effect on nodule activity andon nodulation and this interacts with NO3. This can beexplained through a feed-back regulation of N2fixation by soluble N in the seedling. Vicia faba, faba bean, nodule number, nodulation, nodule activity, acetylene reduction, N2 fixation, cotyledon removal, nitrate 相似文献
11.
When grown in a nutrient solution containing combined nitrogen(NH4NO3), Lotus pedunculatus and L. tenuis seedlings inoculatedwith a fast-growing strain of Rhizoblum (NZP2037) did neitherdevelop root nodules nor develop flavolans in their roots. Incontrast, the roots of nodulated seedlings growing in a nitrogen-freenutrient solution contained flavolans. Flavolan synthesis coincidedwith root nodule development on these plants. When added as a single dose, high concentrations of NH4NO3 (5and 10 mg N per plant) stimulated the growth of L. pedunculatusplants but suppressed nodulation and nitrogen fixation. In contrastthe continued supply of a low concentration of NH4NO3 (1?0 mgN d1 per plant) stimulated nitrogen fixation by up to500%. This large increase in nitrogen fixation was associatedwith a large increase in nodule fresh weight per plant, a doublingof nodule nitrogenase activity, and a lowering of the flavolancontent of the plant roots. The close relationship between nitrogendeficiency, nodule development, and flavolan synthesis in L.pedunculatus meant that it was not possible (by nitrogen pretreatmentof plants) to alter the ineffective nodule response of a Rhizobiumstrain (NZP2213) sensitive to the flavolan present in the rootsof this plant. 相似文献
12.
In studies of Trifolium repens nitrogen nutrition, the controlof nutrient solution pH using dipolar buffers, was evaluatedin tube culture under sterile conditions. Five buffers; MES,ADA, ACES, BES and MOPS with pK2s (20 °C) of 6.15, 6.60,6.90, 7.15 and 7.20 respectively, at a concentration of 2.0mol m3, were provided to inoculated Trifolium repensgrowing in nutrient solution containing 7.13 mol m3 nitrogenas (NH4)2SO4. Initial pH of each solution was adjusted to theappropriate buffer pK2 Two buffers, ADA and ACES completelyinhibited plant growth. The remaining buffers had little effectin limiting pH change, although plant dry matter was higherand nodule numbers lower in the presence of these buffers. MESand MOPS were supplied to nutrient solutions with and without7.13 mol m3 (NH4)2SO4, at concentrations ranging from012 mol m3. MES at 9 mol m3 and 12 molm3 reduced growth of plants reliant on the symbiosisfor providing nitrogen. The provision of MES to plants providedwith NH4+ significantly increased plant yield and reduced nodulenumber at all concentrations. MOPS did not affect plant yieldor nodule number. The use of dipolar buffers in legume nitrogennutrition studies is considered in terms of buffering capacity,and the side effects on plant growth and symbiotic development. Key words: Ammonium, Dipolar buffer, Nitrogen nutrition, pH control, Symbiosis, Trifolium repens 相似文献
13.
The specific respiration rates of nodulated root systems, ofnodules and of roots were determined during active nitrogenfixation in soya bean, navy bean, pea, lucerne, red clover andwhite clover, by measurements on whole plants before and afterthe removal of nodule populations. Similar measurements weremade on comparable populations of the six legumes, lacking nodulesbut receiving abundant nitrate-nitrogen, to determine the specificrespiration of their roots. All plants were grown in a controlled-environmentclimate which fostered rapid growth. The specific respiration rates of nodulated root systems ofthe three grain and three forage legumes during a 714-dayperiod of vegetative growth varied between 10 and 17 mg CO2g1 (dry weight) h1. This mean value consistedof two components: a specific root respiration rate of 69mg CO2 g1 h1 and a specific nodule respirationrate of 2246 mg CO2 g1 h1. Nodule respirationaccounted for 4270 per cent of nodulated root respiration;nodule weight accounted for 1240 per cent of nodulatedroot weight. The specific respiration rates of roots lackingnodules and utilizing nitrate nitrogen were generally 2030per cent greater than the equivalent rates of roots from nodulatedplants. The measured respiratory effluxes are discussed in thecontext of nitrogen nitrogen fixation, nitrate assimilation. Glycine max, Phaseolus vulgaris, Pisum sativum, Medicago sativa, Trifolium pratense, Trifolium repens, soya bean, navy bean, pea, lucerne, red clover, white clover, nodule respiration, root respiration, fixation, nitrate assimilation 相似文献
14.
Ryle, G. J. A., Powell, C. E. and Gordon, A. J. 1988. Responsesof N2 fixation-linked respiration to host-plant energy statusin white clover acclimated to a controlled environment.J.exp. Bot. 39: 879887. Single plants of white clover, acclimated to a controlled environmentand dependent for nitrogen on N2 fixation in their root nodules,were darkened, defoliated or exposed to enhanced CO2 levelsto establish the quantitative relationships between the photosynthesisof the host plant and the N2 fixation metabolism of root nodules. The nodule respiration associated with N2 fixation (FLR) declinedrapidly to 1015% of its normal rate following plant darkeningearly in the photoperiod. Darkening at progressively later intervalsduring the photoperiod demonstrated a positive, apparently linearrelationship between duration of illumination and total FLRduring the photoperiod and the following night period. Completeor partial defoliation reduced FLR according to the leaf arearemoved: again, there was a strong positive correlation betweencurrent rate of photosynthesis, whether of defoliated or undefoliatedplants and the FLR of root nodules. Doubling the current rateof photosynthesis, by enhancing CO2 levels around the shoots,promoted FLR within 12 h when plants were stressed bylack of light. However, enhanced CO2 levels increased FLR onlyslowly over a period of several hours in plants entrained tothe normal growing conditions. It is concluded that, in these plants acclimated to a uniformand favourable controlled environment, the supply and utilizationof photosynthetic assimilate in N2 fixation was finely balancedand quantitatively linked during a single diurnal period andthat nodule functioning was not depressed by lack of energysubstrate. Key words: White clover, N2 fixation, photosynthesis. 相似文献
15.
Hansen, A. P. and Pate, J. S. 1987. Evaluation of the 15N naturalabundance method and xylem sap analysis for assessing N2 fixationof understorey legumes in jarrah (Eucalyptus marginata Donnex Sm.) forest in S.W. Australia.J. exp. Bot 38: 14461458. Nodulated seedlings of Acacia pulchella, A. alata and A. extensawere grown in glasshouse sand culture under a range of levels(016 mol m3) of nitrate, supplied as 15NO3, or as unenrichedlaboratory grade nitrate (15N value 5·5%o). Nitrate at8·0 mol m 3 or above was highly inhibitory to growthof all species. Using 15N dilution analysis of the 15N enrichedcultures to measure symbiotic dependency, it was shown that15N values of the parallel unenriched cultures increased innear linear fashion from close to zero in fully symbiotic plantsto values close to that of the supplied NO3 in plants experiencingnitrate levels (4·0 mol m3 or above) inhibiting N2 fixationby over 90%. Xylem sap analyses (0·4 mol m3 NO3 treatments)showed asparagine as the major nitrogenous solute, relativelylittle spill-over of free nitrate, and no evidence of majorshifts in balance of amino compounds with increasing dependenceon nitrate. This essentially invalidated use of the techniqueas a field assay for N2 fixation by the species. 15N values for total N of soil sampled at 64 widely distributedsites in jarrah forest ranged from 2·15 to +5·4(mean +2·1). Comparable values for soil mineral N (NH+4and NO3) were +0·3 to + 14·2 (mean +5·1).15N values of the total plant N of the legumes and of non-N2-fixingreference species were also highly variable between sites, withlittle evidence of reference plant N accurately reflecting the15N abundance of soil nitrogen, or of visibly well nodulatedlegume components showing consistently lower 15N values thantheir companion reference plants. At one site it was possibleto compare 15N values of first season seedling legumes withpreviously published estimates of their progressive N2 fixationusing C2H2 reduction assays. It was concluded that heterogeneity in 15N discrimination ofsoil within the ecosystem precluded effective use of the 15Nnatural abundance technique for assessing legume N2 fixation. Key words: Acacia spp., 15N natural abundance,, xylem sap analysis,, nitrogen fixation. 相似文献
16.
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
17.
The effect of denitrification on N2 fixation was studied ina denitrifying photosynthetic bacterium, Rhodopseudomonas sphaeroidesforma sp. denitrificans. KNO3 inhibited diazotrophic growthin light, but NC3-dependent diazotrophic growth in darknesswas found. NO3 inhibited C2H2 reduction activity in lightin cells grown with NO3. NO3-dependent C2H2 reductionactivity in darkness also was present in cells grown with N2plus NO3, but not in cells grown on glutamate with NO3.NO3 repressed the synthesis of nitrogenase in light.This repression was not overcome by the addition of methioninesulfoximine. The inhibitory and repressive effect of NO3 was not mediatedby the NO2 produced from NC3 nor by the NH4+ excretedinto the medium. But, as N2 fixation is controlled by O2 (redoxcontrol) it seems to be mediated through the denitrificationprocesses. Much of the glutamine synthetase was adenylylatedin cells grown with NO3 and its adenylylation state closelyparallelled nitrogenase activity in the cells. (Received September 4, 1982; Accepted December 11, 1982) 相似文献
18.
Tennakoon Kushan U.; Pate John S.; Fineran Brian A. 《Journal of experimental botany》1997,48(5):1047-1060
Nodulated plants of Acacia littorea were pot cultured singlyin minus nitrogen sand culture in the presence or absence ofa transplanted seedling of the root hemiparasite Olax phyllanthiand harvests of cultures made 4 and 8 months after introducingthe parasite. Parasitism decreased host shoot growth while increasingroot growth to a similar extent. Final shoot:root dry weightratio was 2.2 for parasitized versus 4.3 for unparasitized Acacia.Partitioning of fixed N showed 4-fold larger N increments inshoots than roots of unparasitized plants, whereas parasitizedplants lost a small amount of shoot N, made a root gain of Ndouble that of unparasitized plants and lost over half of theirN to Olax. The increment of fixed N in the host:parasite associationwas similar to that of unparasitized Acacia. Data on dry mattergain per unit foliage area and mean CO2 assimilation rates pershoot of Olax and Acacia (parasitized or unparasitized) werediscussed in relation to an estimated heterotrophic gain ofxylem C from the host equivalent to 40% of the increment ofdry matter C made by the parasite. Growth of Olax was accompaniedby large increases in numbers of haustoria, 9% of which wereattached to root nodules as opposed to roots. Structural andnutritional features of direct parasitism of nodules are described.Models of flow and utilization of C and N in the Acacia:Olaxassociation and unparasitized Acacia are discussed in relationto published data for other host:parasite associations. Key words: Olax phyllanthi, host-parasite relationships, C and N partitioning, Acacia, N2 fixation 相似文献
19.
The influence of salinity in the growing media on ribulose-1,5-bisphosphate (RuBP) carboxylase and on CO2 fixation by intactsugar beet (Beta vulgaris) leaves was investigated. RuBP carboxylase activity was mostly stimulated in young leavesafter exposure of plants for 1 week to 180 mM NaCl in the nutrientsolution. This stimulation was more effective at the higherNaHCO2 concentrations in the reaction medium. Salinity also enhanced CO2 fixation in intact leaves mostlyat rate-limiting light intensities. A 60 per cent stimulationin CO2 fixation rate was obtained by salinity under 450 µEm2 s1. At quantum flux densities of 150 µEm2 s1 (400700 nm) this stimulation was280 per cent. Under high light intensities no stimulation bysalinity was found. In contrast, water stress achieved by directleaf desiccation or by polyethylene glycol inhibited enzymeactivity up to fourfold at 1.2 MPa. Beta vulgaris, sugar beet, ribulose-1, 5-bisphosphate carboxylase, salt stress, water stress, carbon dixoide fixation, salinity 相似文献
20.
Growth-chamber studies were conducted to evaluate nitrogen assimilationby three hypernodulated soybean [Glycine max (L.) Merr.] mutants(NOD13, NOD24, NOD37) and the Williamsparent. Seeds were inoculated at planting and transplanted atday 7 to nutrient solution with 1 mol m3 urea (optimizesnodule formation) or 5 mol m3 NO3 (inhibits noduleformation). At 25 d after planting, separate plants were exposedto 15NO2 or 15NO3 for 3 to 48 h to evaluate N2 fixationand NO3 assimilation. Plant growth was less for hypernodulatedmutants than for Williams with both NO3 and urea nutrition.The major portion of symbiotically fixed 15N was rapidly assimilated(30 min) into an ethanol-soluble fraction, but by 24 h aftertreatment the ethanolinsoluble fraction in each plant part wasmost strongly labelled. Distribution patterns of 15N among organswere very similar among lines for both N growth treatments aftera 24 h 15N2 fixation period; approximate distributions were40% in nodules, 12% in roots, 14% in stems, and 34% in leaves.With urea-grown plants the totalmg 15N fixed plant1 24h1 was 1·18 (Williams), 1·40 (N0D1-3),107 (NOD2-4), and 0·80 (NOD3-7). The 5 mol m-3 NO3- treatmentresulted in a 95 to 97% decrease in nodule mass and 15N2 fixationby Williams, while the three mutants retained 30 to 40% of thenodule mass and 17 to 19% of the 15N2 fixation of respectiveurea-grown controls. The hypernodulated mutants, which had restrictedroot growth, absorbed less 15NO3- than Williams, irrespectiveof prior N growthcondition. The 15N from 15NO3- was primarilyretained in the soluble fraction of all plant parts through24 h. The 15N incorporation studies confirmed that nodule developmentis less sensitive to external NO3- in mutant lines than in theWilliams parent, and provide evidence that subsequent metabolismand distribution within the plant was not different among lines.These results further confirm that the hypernodulated mutantsof Williams are similar in many respects to the hyper- or supernodulatedmutants in the Bragg background, and suggest that a common mutationalevent affectingautoregulatory control of nodulation has beentargeted. Key words: Glycine max (L.) Merr., soybean, N2fixation, nitrate assimilation, nodulation mutants, 15N isotope 相似文献