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1.
The influence of hydrogenase in Bradyrizobum-Phaseoleae symbioseswas studied ex-planta and in-planra in soybean (Glycine max)and cowpea (Vigna unguiculata). The hydrogenase was activatedby the addition of hydrogen in the incubation gas phase whichmodified the response of nitrogenase activity of Hup+ (hydrogenuptake positive) symbiosis to the external oxygen partial pressure.For bacteroids the hydrogenase expression increased nitrogenaseactivity at supraoptimal pO2, acting possibly as a respiratoryprotection of nitrogenase. However, at suboptimal pO2, nitrogenaseactivity of Hup+ bacteroids decreased with hydrogen, a phenomenonattributed to the lower efficiency of ATP synthesis from hydrogenthan from carbon substrates oxidation. For undisturbed nodules,the hydrogenase expression in soybean increased the optimalpO2 for ARA (COP), from 35.3 to 40.3 kPa O2, and the ARA atsupraoptimal pO2; at suboptimal PO2 there was a negative effectof hydrogenase on ARA, although this inhibition was less thanon bacteroids and was not detected if plants were grown at 15°C rather than 20 °C root temperature. No H2 effectwas detected on cowpea nodules. The results on soybean nodulesare consistent with the concept that symbiotic nitrogen fixationis oxygen-limited and that hydrogenase activity has no beneficialeffect on nitrogen fixation in O2 limitation. Key words: Glycine max, hydrogenase, nitrogenase, nitrogen fixation, nodules, Vigna unguiculata  相似文献   

2.
Seventy-five per cent of the N2-fixing activity (measured asthe reduction of C2H2 to C2H4) and 50 per cent of the respiratoryactivity of detached soybean root nodules was lost when thewater potential () of the nodules was lowered from approximately–1 ? 105 Pa (turgid nodules) to –9 ? 105 Pa (moderatelystressed nodules). Severely stressed nodules ( = –1.8? 106 Pa) showed almost total loss of N2-fixing activity andup to 80 per cent loss of respiratory activity. Increasing theoxygen partial pressure (PO2) from 104 to 105 Pa completelyrestored both N2-fixation and respiration in moderately stressednodules, but only partial recovery was possible in severelystressed nodules. The activity of the stressed nodules was verylow at low PO2 (5 ? 103 and 104 Pa). The C2H2-reducing activityof nodule slices, nodule breis, and bacteroids from turgid andmoderately stressed nodules was almost identical but some activitywas lost in the breis and bacteroids from severely stressednodules. Calculations showed that at low PO2 (104 and 2 ? 104Pa), the rate of O2 diffusion into severely stressed noduleswas ten times lower than that for turgid nodules, but only fourtimes lower at a higher PO2 (4 ? 104 Pa). Carbon monoxide inhibitionof C2H2 reduction was slower in stressed nodules than in turgidnodules. The results are discussed in view of the possible developmentof a physical barrier to gaseous diffusion and/or the possiblealtered affinity of the nodule leghaemoglobin for O2 in thewater-stressed nodules.  相似文献   

3.
Cadaverine, a 5-carbon diamine, was identified as the cofactorof uricase activity previously found in soybean seedlings. Thesubstance purified from freeze dried hypocotyls was subjectedto liquid chromatography, mass spectrometry, 1H- and 13C-nuclearmagnetic resonance spectrometry for identification. The concentrationsof cadaverine in 3-day-old radicles and hypocotyls were 2.37mM and 5.09 mM, respectively. Other polyamine concentrationswere low. Biogenic polyamines (cadaverine, putrescine, spermidineand spermine) functioned as cofactors, whereas conjugated polyamines(tyramine and histamine) and amino acids had no effect. Theaddition of catalase to the assay system counteracted the effectof cadaverine. Peroxide at appropriate concentrations actedlike cadaverine with an identical Km value, suggesting thaturate degrading activity can be ascribed to the diamine oxidase-peroxidasesystem. (Received October 19, 1982; Accepted December 23, 1982)  相似文献   

4.
Blakeley, S. D., Robaglia, C, Brzezinski, R. and Thirion, J-P.1986. Induction oflow molecular weight cadmium-binding compoundin soybean roots.—J. exp. Bot. 37: 956–964. A Cd-binding compound has been identified in roots of Cd-treatedsoybean plants (Glycine max L.). Induction of synthesis of thiscompound after treatment with CdCl2 was monitored by labellingwith either 109Cd in vitro or with 35S-cysteine or 35S-methioninein vivo. The apparent molecular weight as determined by gelfiltration was about 14000 daltons. However, after carboxymethylationand electrophoresis under denaturing conditions its molecularweight was less than 3400 daltons. Simultaneous labelling with109 and 35S-cysteine demonstrated that the compound containscysteine residues. Gel electrophoresis of 35S-cysteine or 35S-methioninelabelled protein samples showed the compound to be rich in cysteinebut not in methionine, and that it was induced about 60-foldby 1?0 mol m–3 CdCl2 after 7 d. Key words: Soybean, cadmium, induction, root  相似文献   

5.
Bergersen  F. J. 《Annals of botany》1993,72(6):577-582
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   

6.
Kouchi, H., Yoneyama, T. and Akao, S. 1986. Compartmental analysisof the partitioning of photo-assimilated carbon in nodulatedsoybean plants during the light period.—J. exp. Bot. 37:994–1005. Dynamics of the partitioning of photo-assimilated carbon invegetative nodulated soybean (Glycine max L.) plants in thelight period was investigated by compartmental analysis basedon data from steady-state 13CO2 assimilation experiments. Themodel assumes a total of 18 compartments consisting of activeand temporary storage pools for soluble materials, starch andstructural materials in leaves, stems plus petioles, roots andnodules together with respired carbon from the roots and nodules.Carbon flow between compartments was described by 22 rate parameters.The rate parameters were evaluated by a non-linear least squaresearch method to optimize the fitness of the simulated resultswith the experimental tracer distribution. The compartment model was well applicable to interpret the carbonpartitioning in whole plants. The analysis showed that: (I)The largest carbon flux during the light period was to storagematerials (starch and temporary storage soluble pools) in theabove-ground parts. The total flux to storage pools was considerablylarger than the transporting flux to below-ground parts. (2)The main carbon flux to the nodules was via direct phloem pathwaysfrom the shoot and not via the compartment of root soluble materials.This flux was 72% of the total carbon flux from the shoot tothe nodulated root system. (3) A large amount of carbon wasreturned to the shoot from below-ground parts. The total returnof carbon flux to the shoot (85% from nodules) was equivalentto 54% of the total influx of carbon to below-ground parts.Direct carbon transfers between roots and nodules were relativelysmall. Key words: Compartmental analysis, carbon partitioning, root nodules, Glycine max L., 13CO2, assimilation  相似文献   

7.
Intracellular accumulation of inorganic carbon (Ci) and itsfixation in photosynthesis were investigated using siliconeoil layer filtering centrifugation technique with the cellsof Chlorella vulgaris 11h grown under ordinary air. Both CO2and HCO3 were transported into the cells from the reactionmedium and accumulated in the cells, but the rate of transportwas much faster for the former than the latter. 14C-fixationfrom the total transported Ci was much more efficient when CO2was added in the external medium than when HCO3 was added.This indicates that CO2 and HCO3 were not converted tothe common compound in the cells during the initial period ofphotosynthesis. Accumulation of Ci into the cells was much lesssusceptible to low temperature than its fixation. Accumulationof Ci was also observed in the dark. Ethoxyzolamide, an inhibitorof carbonic anhydrase (CA), inhibited the fixation of accumulatedCO2 in the cells, suggesting that CA enhanced the supply ofCO2 to the reaction site of ribulose bisphosphate carboxylasein the stroma. Mechanism for transport and fixation of Ci duringphotosynthesis in low-CO2 cells of C. vulgaris 1lh was proposedfrom these results. (Received March 19, 1986; Accepted June 26, 1986)  相似文献   

8.
Natural 15N abundances of various tissues from twelve speciesof leguminous plants and those of nodule fractions from threespecies grown in Japan were determined by mass spectrometry.The 15N concentrations of non-nodular tissues of nodulated plantswere close to the value of atmospheric N2. The nodules of soybean,mung bean, cowpea, kidney bean, adzuki bean, sword bean, whiteclover, Leucaena leucocephala, and horsegram showed highly elevated15N concentrations, and those of pea had a slightly enriched15N concentration compared to other tissue, while the nodulesof peanut and lucerne had 15N values similar to those of theirshoot tissues. The bacteroid fractions from horsegram, swordbean and peanut had higher 15N concentrations than the cytosolfractions. (Received March 17, 1984; Accepted August 21, 1984)  相似文献   

9.
Well-nodulated soya bean (Glycine max L.) plants were allowedto assimilate 13CO2 for 10 h in the light, under steady-stateconditions in which CO2 concentration and 13C abundance wereboth strictly controlled at constant levels. The respiratoryevolution of 13CO2 from roots and nodules and 13C incorporationinto various metabolic fractions were measured during the 13CO2feeding and subsequent 48 h chase period. CO2 respired from nodules was much more rapidly labelled with13C than that from roots. The level of labelling (percentageof carbon currently assimilated during the 13COM2 feeding period)of CO2 respired from nodules reached a maximum of about 87 percent after 4 h of steady-state l3CO2 assimilation and thereafterremained fairly constant. The absolute amount of labelled carbonevolved by the respiration of the nodules during the 10 h 13CO2feeding period was 1·5-fold that of root respiration.These results demonstrated that the currently assimilated (labelled)carbon was preferentially used to support nodule respiration,while root respiration relied considerably on earlier (non-labelled)carbon reserved in the roots. Sucrose pools were mostly composed of currently assimilatedcarbon in all tissues of the plants, since the levels of labellingaccounted for 86–91 per cent at the end of the 13CO2 feeding.In the nodules, the kinetics and levels of sucrose labellingwere in fairly good agreement with those of respired CO2, whilein the roots, the level of labelling of respired CO2 was significantlylower than that of sucrose. Succinate and malate were highly labelled in both roots andnodules but they were labelled much more slowly than sucroseand respired CO2. The kinetics and levels of labelling of theseKrebs cycle intermediates resembled those of major amino acidswhich are derived directly from Krebs cycle intermediates. Itis suggested that large fractions of organic acids in noduleswere physically separate from the respiration site. Glycine max L., Soya bean, 13CO2 assimilation, respiratory evolution of 13CO2, carbon metabolism in root nodules  相似文献   

10.
An extract from the roots of Lotus pedunculatus plants was foundto contain a compound toxic towards fast-growing Lotus rhizobia.This compound was identified as a flavolan, which has a prodeiphinidin:procyanidin ratio of 75:25. A fast-growing strain of Rhizobium(NZP2213) which forms ineffective root nodules on L. pedunculatuswas four times more sensitive to this flavolan (ED50 = 25 ?gml–1) than another strain (NZP2037, ED50 = 100 ?g ml–1)which forms effective root nodules on this species. The rootsof another Lotus species, L. tenuis, on which both strains ofRhizobium form effective root nodules, also contained a flavolan( 95% procyanidin) but both strains were relatively insensitiveto this flavolan (EDED50 = 350 to 500 ?g ml–1) L. pedunculatusplants bearing ineffective root nodules contained two to threetimes more flavolan in their roots (5–7 mg g–1 fr.wt.)than uninoculated control plants. Experiments with seven otherLotus species and with hybrid plants developed between L. pedunculatusand L. tenuis showed a relationship between the prodeiphinidin:procyanidin ratio of the flavolan in their roots and the effectivenessof root nodules formed on these plants by NZP2213. Quantitativebinding studies of the flavolan from L. pedunculatus to NZP2037and NZP2213 indicated that, while the affinity constants forbinding were similar for both strains, the surface of strainNZP2037 contained four times more binding sites than NZP2213,possibly correlating with this strain's ability to toleratehigher concentrations of this flavolan. It is suggested thatthe differential sensitivity of these two strains of Rhizobiumto flavolans is related to their ability to form effective rootnodules on Lotus species.  相似文献   

11.
KOUCHI  H.; YONEYAMA  T. 《Annals of botany》1984,53(6):883-896
Nodulated soya bean (Glycine max L.) plants at the early floweringstage were allowed to assimilate 13CO2 under steady-state conditions,with a constant 13C abundance, for 8 h in the light. The plantswere either harvested immediately or 2 d after the end of the13CO2 feeding, divided into young leaves (including flower buds),mature leaves, stems+petioles, roots and nodules; the 13C abundancein soluble carbohydrates, organic acids, amino acids, starchand poly-ß-hydroxybutyric acid was determined witha gas chromatography-mass spectrometry. The rapid turnover of 13C in the sucrose pools observed in allorgans of the plants showed that sucrose was the principal materialin the translocation stream of primary products of photosynthesis.At the end of the 13CO2 exposure, sucrose in the mature leavesas the major source organs and in the stems+petioles was labelledwith currently assimilated carbon to about 75 per cent, whereasa much higher labelling of sucrose was found in the roots andin the nodules. This suggests the existence of two or more compartmentedpools of sucrose in mature leaves and also in stems+petioles. The relative labelling patterns of individual organic acidsand amino acids were similar in various plant organs. However,the rapid turnover of succinate and glycine was characteristicof nodules. Treatment with a high concentration of nitrate inthe nutrient media increased the turnover rate of amino acidcarbon in shoot organs and roots, while it markedly decreasedthe labelling of amino acids in nodules. The cyclitols, exceptfor D-pinitol, were significantly labelled with assimilated13C in mature leaves, but in nodules, the labelling was verymuch less. In the nodules, which were actively fixing atmospheric nitrogen,a large proportion (80–90 per cent) of currently assimilatedcarbon was found as sucrose and starch at the end of the 13CO2feeding. This was also true of the roots. On the other hand,in young growing leaves, the distribution of currently assimilatedcarbon into sucrose, starch and other soluble compounds wasmuch less. This suggests that a large amount of carbon assimilatedby and translocated to young leaves was used to make up structuralmaterials, mainly protein and cell wall polymers synthesis,during the light period. Glycine max L., soya bean, 13CO2 assimilation, carbon metabolism in nodules  相似文献   

12.
A plant-determined pea mutant Sprint-2 Fix and the parentalline Sprint-2 were compared for selected physiological and biochemicalparameters. The Fix mutation prevented differentiationof Rhizobium leguminosarum bacteria into bacteroids and producedlarge, white, non-fixing nodules. These lacked nitrogenase-linkedrespiration, but had a background rate of CO2 evolution similarto the normal Fix+ nodules. The cortical structure of the ineffectivenodules suggests the existence of an oxygen diffusion barrierand this was supported by a low oxygen concentration in thecentral region (0.5–3.0%), measured using an O2 sensitivemicro-electrode. Sucrose and starch contents were similar innormal and ineffective nodules while ononitol content was about15 times lower in the Fix nodules. The distribution ofstarch was also different in the two nodule types. The activitiesof glutamine synthetase (GS), sucrose synthase (SS), phosphoenolpyruvatecarboxylase (PEPC) and alanine pyruvate aminotransferase (APAT)were markedly higher in Fix+ nodules while the activities ofpyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) andglutamate dehydrogenase (GDH) were higher in Fix nodules.The data from immunodetection of host nodule proteins confirmedthe reduced levels of sucrose synthase and the almost completeabsence of glutamine synthetase and leghaemoglobin in mutantnodules. There was no significant difference in the amount ofnitrogenase component 1 extracted from the microsymbiont ofnormal and ineffective nodules, but component 2 was hardly detectablein the Fix mutant. Key words: Pisum sativum, Fix mutant, nodules  相似文献   

13.
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 6–7 for nodulation and optimum temperature of 30–35°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   

14.
Photosynthetic rates of outdoor-grown soybean (Glycine max L.Merr. cv. Bragg) canopies increased with increasing CO2 concentrationduring growth, before and after canopy closure (complete lightinterception), when measured over a wide range of solar irradiancevalues. Total canopy leaf area was greater as the CO2 concentrationduring growth was increased from 160 to 990 mm3 dm–3.Photosynthetic rates of canopies grown at 330 and 660 mm3 CO2dm–3 were similar when measured at the same CO2 concentrationsand high irradiance. There was no difference in ribulose bisphosphatecarboxylase/oxygenase (rubisco) activity or ribulose 1,5-bisphosphate(RuBP) concentration between plants grown at the two CO2 concentrations.However, photosynthetic rates averaged 87% greater for the canopiesgrown and measured at 660 mm3 CO2 dm–3. A 10°C differencein air temperature during growth resulted in only a 4°Cleaf temperature difference, which was insufficient to changethe photosynthetic rate or rubisco activity in canopies grownand measured at either 330 or 660 mm3 CO2 dm–3. RuBP concentrationsdecreased as air temperature during growth was increased atboth CO2 concentrations. These data indicate that the increasedphotosynthetic rates of soybean canopies at elevated CO2 aredue to several factors, including: more rapid development ofthe leaf area index; a reduction in substrate CO2 limitation;and no downward acclimation in photosynthetic capacity, as occurin some other species. Key words: CO2 concentration, soybean, canopy photosynthesis  相似文献   

15.
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: 1–12 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 5–10 min acetylene reduction assay, conductedon freshly detached unwashed nodules in daytime (12.00–14.00h), 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   

16.
The lipid extract prepared from the pollen of the West African,oil palm, Elaeis guineensis, was found to contain p-methoxyallylbenzenein substantial amount. The pure substance after isolation bymeans of preparative gas-liquid chromatography and steam distillationwas characterized by using a combination of g.l.c.-mass spectrometry,infrared spectrometry, and chemical reactions. Mass spectrometrygave a spectrum with a parent ion at m/e 148 corresponding tothe molecular weight and fragmentation ions at m/e 133, 121,117, 105, 91, and 77. The structure was further confirmed bymeans of the infrared spectrum which showed major peaks at 1250,920, and 815 cm–1 corresponding to a CH3O group, a 1,4-substitutedaromatic ring, and a RCH=CH2 group respectively. Its chemicaland physical properties (hydrogenation, oxidation, etc.) werefound to be similar to those of its positional isomer, p-methoxy--phenylpropene.The physiological and economic importance of the compound arediscussed.  相似文献   

17.
Ward, D. A. and Drake, B. G. 1987. Photoinhibition under atmosphericO2, the activation state of RuBP carboxylase and the contentof photosynthetic intermediates in soybean and wheat.—J.exp. Bot. 38: 1937–1948. Associations between photosynthesis, the activation state ofRuBP carboxylase and the contents of photosynthetic intermediateswere compared in soybean and wheat leaves before and after exposureto photoinhibitory treatments in the presence of atmosphericO2. Exposing attached leaves to a supra-saturating irradiance(3 800 µmol quanta m– 2 s–1) for 2 h in CO2-freeair decreased carboxylation efficiency and the light-saturatedphotosynthetic rate in air by approximately 50%. Exposure tothe photoinhibitory treatment for periods in excess of 2 h didnot cause a further decrease of photosynthesis in soybean. Althoughphotosynthesis was reduced, the initial and total (fully-activated)activities of ribulose 1,5-bisphosphate carboxylase (RuBPCase)in leaf extracts were unaltered in each species by the photoinhibitorytreatment. This was true for leaves sampled under both air andat a rate-limiting intercellular CO2 partial pressure (Ci) of75 µPa Pa–1. The contents of ribulose l,5-bisphosphate(RuBP) and 3-phosphoglyceric acid (3-PGA) were reduced by thephotoinhibitory treatment in soybean leaves sampled in air andat a rate-limiting Ci, although the RuBP/3-PGA ratio was unaffected.The relative reduction of RuBP content in soybean leaves atrate-limiting C1 was similar to the corresponding reductionof carboxylation efficiency. For wheat,the relative reductionof RuBP content at rate-limiting Ci (–19%) caused by thephotoinhibitory treatment was considerably less than the correspondingdecrease of carboxylation efficiency (–49%).The RuBP/3-PGAratio of wheat was also increased significantly by the photoinhibitorytreatment The significance of these observations to the regulationof CO2-limited photosynthesis in leaves experiencing photoinhibitionunder atmospheric oxygen is discussed. Consideration is alsogiven to the previous contention that contemporary measurementsof initial activity in crude extracts may provide a spuriousindication of the amount of the enzyme-CO2-Mg2 + form of RuBPcarboxylase present in the leaf. Key words: Carboxylation efficiency, RuBP carboxylase, photoinhibition, RuBP, 3-PGA  相似文献   

18.
Inhibition of Nodule Development in Soybean by Nitrate or Reduced Nitrogen   总被引:5,自引:1,他引:4  
Imsande, J. 1986. Inhibition of nodule development in soybeanby nitrate or reduced nitrogen.—J. exp. Bot. 37: 348–355. Nodulation of hydroponically grown soybean plants [Glycine max(L.) Merr.] is inhibited by continuous growth in the presenceof 4· mol m–3 KNO3 The presence of 4·0 molm–3 ‘starter nitrate’ for 3-6 d during noduledevelopment, however, subsequently stimulates nodule dry weightaccumulation and nitrogenase activity. These stimulations occureven though 4· mol m–3 nitrate temporarily delaysnodule development, i.e. the late steps of nodule developmentare reversibly inhibited by a short-term exposure to 4·0mol m–3 nitrate. On the other hand, treatment with 4·0mol m–3 nitrate in excess of 14 d significantly reducesnodule dry weight Thus, extended growth in the presence of 4·0mol m–3 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 m–3 (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 m–3 (NH4)2SO4 butis partially inhibited by a prolonged exposure to (NH4)2SO4Because repression of nodulation by 4·0 mol m–3KNO3 is more severe than that by 2·0 mol m–3 (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   

19.
KOUCHI  H.; YONEYAMA  T. 《Annals of botany》1984,53(6):875-882
A long-term, steady-state 13CO2 assimilation system at a constantCO2 concentration with a constant 13C abundance was designedand applied to quantitative investigations on the allocationof photoassimilated carbon in nodulated soya bean (Glycine maxL.) plants. The CO2 concentration in the assimilation chamberand its 13C abundance were maintained constant with relativevariances of less than ±0.5 per cent during an 8-h assimilationperiod. At the termination of 8-h 13CO2 assimilation by plantsat early flowering stage, the currently assimilated carbon relativeto total tissue carbon (measured by the degree of isotopic saturation)were for young leaves (including flower buds), 13.9 per cent;mature leaves, 15.7 per cent; stems+petioles, 5.9 per cent;roots, 5.4 per cent and nodules, 6.9 per cent, 48 h after theend of the 13CO2 assimilation period, they were 12.3, 7.5, 7.4,6.8 and 6.1 per cent, respectively. The treatment with a highconcentration of nitrate in the nutrient media significantlydecreased the allocation of 13C into nodules. Experiments on13CO2 assimilation by plants at the pod-filling stage were alsoconducted. Labelling by 13C was weaker than at the early floweringstage, but an intense accumulation of 13C into reproductiveorgans was observed. Glycine max L., nodulated soya bean plants, 13CO2 assimilation, carbon dynamics  相似文献   

20.
Ruchti, M. and Widmer, F. 1986. Isocitrate lyase from germinatingsoybean cotyledons: purification and characterization.—J.exp. Bot. 37: 1685–1690. Isocitrate lyase (E.C. 4.1.3.1 [EC] ) was purified from the cotyledonsof 7-d-old soybean seedlings. Three molecular forms were detectedwith pi values of 6·46, 6·25 and 6·0. Themain form (pl = 6·46) had an approximate Mr of 130000,a pH optimum of 8·0, a Km (isocitrate) close to 2·0mol m–3 and a molecular activity of 615 min –1 at25 °C. The purified enzyme is not a glycoprotein and isheat labile. Key words: Isocitrate lyase, soybean  相似文献   

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