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1.
Influence of Abscisic Acid on Nitrate Accumulation and Nitrate Reductase Activity in Potato Tuber Slices 总被引:1,自引:0,他引:1
Abscisic acid (ABA) at concentrations of 1 to 10 µg.ml1suppressed development of nitrate reductase activity in freshtuber slices of Solanum tuberosum L. incubated in KNO3. Suppressionof activity was evident after 3 hr and continued for 20 hr beforerecovery. This recovery may be due to inactivation of the hormone.Nitrate accumulation was enhanced by ABA. At exogenous NO3 levelsof 0.1 to 5 mM, the hormone enhanced both NO3 accumulation andnitrate reductase activity. When applied 24 hr after incubation in NO3, ABA promoted a markeddecline in enzyme activity in the absence of exogenous NO3,but was less effective in the presence of NO3. Slices incubatedin NO3 and ABA also exhibited increased loss of enzyme activityupon removal of NO3. Preincubating slices in the hormone for24 hr in a NO3- free medium resulted in stimulation of nitratereductase activity. Addition of NO3 resulted in a marked stimulationof enzyme activity over a period of 810 hr. The ABA response is not related to tissue levels of free aminoacids and is not affected by different NO3 sources. These resultssuggest the ABA effect on nitrate reductase activity is influencedby NO3 status of the cells. Where external NO3 levels are lowit stimulated NRA while it inhibited activity where NO3 contentis high. (Received May 12, 1981; Accepted October 12, 1981) 相似文献
2.
3.
Muzyamba MC Speake PF Gibson JS 《American journal of physiology. Cell physiology》2000,279(4):C981-C989
The effect of oxidants onK+-Cl cotransport (KCC) wasinvestigated in equine red blood cells. Carbon monoxidemimicked O2. The substituted benzaldehyde, 12C79 (5 mM),markedly increased O2 affinity. In N2, however,O2 saturation was low (<10%) but KCC remained active.Nitrite (NO2) oxidized heme to methemoglobin (metHb).High concentrations of NO2 (1 and 5 mM vs. 0.5 mM)increased KCC activity above control levels; it became O2independent but remained sensitive to other stimuli.1-Chloro-2,4-dinitrobenzene (1-3 mM) depleted reduced glutathione(GSH). Prolonged exposure (60-120 min, 1 mM) or high concentrations (3 mM) stimulated an O2-independent KCCactivity; short exposures and low concentrations (30 min, 0.5 or 1 mM)did not. The effect of these manipulations was correlated with changes in GSH and metHb concentrations. An oxy conformation of Hb was necessary for KCC activation. An increase in its activity over thelevel found in oxygenated control cells required both accumulation ofmetHb and depletion of GSH. Findings are relevant to understanding thephysiology and pathology of regulation of KCC. 相似文献
4.
Rideout James W.; Chaillou Sylvain; Raper C. David Jr; Morot-Gaudry Jean-Francois Jr 《Journal of experimental botany》1994,45(1):23-33
Soybean [Glycine max (L.) Merrill] plants that had been subjectedto 15 d of nitrogen deprivation were resupplied for 10 d with1.0 mol m3 nitrogen provided as NO3, NH4+, orNH4++NO3 in flowing hydroponic culture. Plants in a fourthhydroponic system received 1.0 mol m3 NO3 duringboth stress and resupply periods. Concentrations of solublecarbohydrates and organic acids in roots increased 210 and 370%,respectively, during stress. For the first day of resupply,however, specific uptake rates of nitrogen, determined by ionchromatography as depletion from solution, were lower for stressedthan for non-stressed plants by 43% for NO3- resupply, by 32%for NH4+ + NO3 resupply, and 86% for NH4+ resupply. Whenspecific uptake of nitrogen for stressed plants recovered torates for non-stressed plants at 6 to 8 d after nitrogen resupply,carbohydrates and organic acids in their roots had declinedto concentrations lower than those of non-stressed plants. Recoveryof nitrogen uptake capacity of roots thus does not appear tobe regulated simply by the content of soluble carbon compoundswithin roots. Solution concentrations of NH4+ and NO3 were monitoredat 62.5 min intervals during the first 3 d of resupply. Intermittenthourly intervals of net influx and net effluxoccurred. Rates of uptake during influx intervals were greaterfor the NH4+ -resupplied than for the NO3 -resuppliedplants. For NH4+ -resupplied plants, however, the hourly intervalsof efflux were more numerous than for NO3 -resuppliedplants. It thus is possible that, instead of repressing NH4+influx, increased accumulation of amino acids and NH4+ in NH4+-resupplled plants inhibited net uptake by stimulation of effluxof NH4+ absorbed in excess of availability of carbon skeletonsfor assimilation. Entry of NH4+ into root cytoplasm appearedto be less restricted than translocation of amino acids fromthe cytoplasm into the xylem. Key words: Ammonium, nitrate, nitrogen-nutrition, nitrogen-stress, soybean 相似文献
5.
Nitrate Inhibition of Chloride Influx in Barley: Implications for a Proposed Chloride Homeostat 总被引:6,自引:0,他引:6
Net accumulation of Cl by intact barley plants was virtuallyeliminated in roots and reduced by 40% in shoots when externalmedia (0.5 mol m3 CaSO4 plus 05 mol m3KCI) were supplemented with 0.25 mol m Ca(NO3)2. Plasmalemma36Cl influx (oc) was shown to be insensitive to externalNO3- in plants which had previously been grown in solutionslacking 3, but oc became sensitive to NO3-after a lagperiod of 36 h. Kinetic analyses revealed that the inhibitionof 36C1 influx by external NO3- was complex. At 0.25mol m3 NO3- the Vmax for Cl influx was reducedby greater than 50%, with insignificant effects upon Km. At0.5 mol m3 NO3- there was no further effect upon Vmaxbut Km for influx increased from 38±5 mmol m3to 116±26 mmol m3. By contrast, Cl effluxwas found to be insensitive to external NO3-. A model for theregulation of Cl influx is proposed which involves bothnegative feedback effects from vacuolar NO3- +Cl) concentrationand (external) NO3- inhibition of Cl influx at the plasmalemma.These combined effects serve to discriminate against Claccumulation, favouring NO3- accumulation, when the latter ionis available. Such observations are inconsistent with recentproposals for the existence of bona fide homeostats for chlorideaccumulation in higher plants. Key words: Nitrate inhibition, Chloride influx, Barley 相似文献
6.
A link between plant diversity, elevated CO2 and soil nitrate 总被引:1,自引:0,他引:1
Pascal A. Niklaus E. Kandeler P. W. Leadley B. Schmid D. Tscherko C. K?rner 《Oecologia》2001,127(4):540-548
Interactive effects of reductions in plant species diversity and increases in atmospheric CO2 were investigated in a long-term study in nutrient-poor calcareous grassland. Throughout the experiment, soil nitrate was persistently increased at low plant species diversity, and CO2 enrichment reduced soil [NO3-] at all levels of plant species diversity. In our study, soil [NO3-] was unrelated to root length density, microbial biomass N, community legume contents, and experimental plant communities differed only little in total N pools. However, potential nitrification revealed exactly the same treatment effects as soil [NO3-], providing circumstantial evidence that nitrification rates drove the observed changes in [NO3-]. One possible explanation for plant diversity effects on nitrification lies in spatial and temporal interspecific differences in plant N uptake, which would more often allow accumulation of NH4+ in part of the soil profile at low diversity than in more species-rich plant communities. Consequently, nitrification rates and soil [NO3-] would increase. Elevated CO2 increased soil water contents, which may have improved NO3- diffusion to the root surface thereby reducing soil [NO3-]. Higher soil moisture at elevated CO2 might also reduce nitrification rates due to less aerobic conditions. The accordance of the diversity effect on soil [NO3-] with previous experiments suggests that increased soil [NO3-] at low species diversity is a fairly general phenomenon, although the mechanisms causing high [NO3-] may vary. In contrast, experimental evidence for effects of CO2 enrichment on soil [NO3-] is ambiguous, and the antagonistic interaction of plant species reductions and elevated CO2 we have observed is thus probably less universal. 相似文献
7.
The relationship between thef-ratio [NO3 uptake/(NO3+ NH4+) uptake] and ambient nitrate concentration was evaluatedfor eight data sets from coastal waters. The f-ratio increasedasymptotically with increase in nitrate concentration in mostdata sets. However, the rate at which f-ratio increased at lownitrate concentration (slope = m) and the maximum attained f-ratio(fmax) varied among regions; the initial slope varied most withvalues ranging in excess of an order of magnitude. The datawere analyzed in relation to environmental factors and methodologicalconsiderations known to influence the f-ratio. Ambient ammoniumconcentration was important in accounting for regional differencesin the f versus NO3 relationship. A further analysisof the data, relating f-ratio to the ratio of NO3/(NO3+ NH4+) concentrations yielded a much more regionally consistentand approximately linear relationship; slopes varied by lessthan a factor of two in the extreme cases. Inclusion of knownalternative (aside from NH4+) sources of reduced-N (e.g. urea)and correction for methodological/computational errors (isotopedilution) systematically reduce f-ratio estimates. Other factors,e.g. reduced-N uptake by microheterotrophs, may systematicallyincrease the f-ratio. 相似文献
8.
Nitrate reductase and nitrate accumulation in relation to nitrate toxicity in Boronia megastigma 总被引:3,自引:0,他引:3
Moderate levels of N were toxic to the native Australian plant boronia (Boronia megastigma Nees). As NO-3 is the major N form available for plants under cultivated conditions, NO-3 reduction and accumulation patterns in boronia were examined following the supply of various levels of NO-3 to understand the physiological basis of this toxicity. At a low level of supplied NO-3 [15 mmol (plant)-1], NO-3 was reduced without any detectable accumulation and without nitrate reductase activity (NRA) reaching its maximum capacity. When higher NO-3 levels [≥25 mmol (plant)-1] were supplied, both NRA and NO-3 accumulation increased further. However, NRA increased to a maximum of ca 500 nmol NO-3 (g fresh weight)-1 h-1, both in the roots and leaves, irrespective of a 4-fold difference in the levels of supplied NO-3, whereas NO-3 continued to accumulate in proportion to the level of supplied NO-3. Chlorotic toxicity symptoms appeared on the leaves at an accumulation of ca 32 μmol NO-3 (g fresh weight)-1. High endogenous NO-3 concentrations inhibited NRA. The low level of NRA in boronia was not limited by NO-3 or electron donor availability. It is concluded that the low NR enzyme activity is a genetic adaptation to the low NO-3 availability in the native soils of boronia. Thus, when NO-3 supply is high, the plat cannot reduce it at high rates, leading to large and toxic accumulations of the ion in the leaf tissues. 相似文献
9.
《中国科学:生命科学英文版》2005,48(Z1):902-908
As rice can use both nitrate (NO3-) and ammonium (NH4+), we have tested the hypothesis that the shift in the pattern of cultivars grown in Jiangsu Province reflects the ability of
the plants to exploit NO3- as a nitrogen (N) source. Four rice cultivars were grown in solution culture for comparison of their growth on NO3- and NH4+ nitrogen sources. All four types of rice, Xian You 63 (XY63), Yang Dao 6 (YD), Nong Keng 57 (NK) and Si You 917 (SY917), grew well and produced similar amounts of shoot biomass with 1 mmol/L NH4+ as the only N source. However, the roots of NK were significantly smaller in comparison with the other cultivars. When supplied with 1 mmol/L NO3-, YD produced the greatest biomass; while NK achieved the lowest growth among the four cultivars. Electrophysiological measurements on root rhizodermal cells
showed that the NO3--elicited changes in membrane potential (ΔEm) of these four rice cultivars were significantly different when exposed to low external NO3- (<1 mmol/L); while they were very similar at high external NO3- (10 mmol/L). The root cell membrane potentials of YD and XY63 were more responsive to low external NO3- than those of NK and SY917. The ΔEm values for YD and XY63 rhizodermal cells were almost the same at both 0.1 mmol/L and 1 mmol/L NO3-; while for the NK and SY917 the values became larger as the external NO3- increased. For YD cultivar, ΔEm was measured over a range of NO3- concentrations and a Michaelis-Menten fit to the data gave a Km value of 0.17 mmol/L. Net NO3- uptake depletion kinetics were also compared and for some cultivars (YD and XY63) a single-phase uptake system with first order kinetics best fitted the data; while other cultivars (ND and SY917) showed a better fit to two uptake systems. These uptake systems had two affinity ranges: one had a similar Km in all the cultivars (0.2 mmol/L); the other much higher affinity system (0.03 mmol/L) was only present in NK and SY917. The expression pattern of twelve different NO3- transporter genes was tested using specific primers, but only OsNRT1.1 and OsNRT2.1 expression could be detected showing significant differences between the four rice cultivars. The results from both the physiological and molecular experiments do provide some support for the hypothesis that the more popular rice cultivars grown in Jiangsu Province may be better at using NO3- as an N source. 相似文献
10.
Nitrogen-fixing activity in two nodulated African legumes, Bambaragroundnut (Vigna subterraneaL.) and Kersting's bean (MacrotylomageocarpumL.), was assessed in the presence of nitrate (NO3-)ions in the rooting medium. Nitrogenase activity was unimpairedby the supply of 5 mol m-3NO3to both species. Also, large concentrationsof ureides dominated the transpiration stream of NO3-fed plants.Compared to other symbiotic legumes cultured with similar NO3concentrations,nodule functioning in the tested landraces of Bambara groundnutand Kersting's bean is tolerant of NO3ions in the rhizosphere.The potential benefits of such naturally occurring NO3-tolerantsymbioses are substantial, as they would permit inorganic Nfertilizer application in intercropping systems without inhibitingN2fixation in the associated legumes.Copyright 1998 Annals ofBotany Company NO3tolerance, Bambara groundnut, Kersting's bean, nitrogenase activity, xylem ureides. 相似文献
11.
Z. Barhoumi 《Russian Journal of Plant Physiology》2017,64(6):839-844
Optimization of nitrogen (N) use by grasses is a central issue of the current work. The effects of different N concentrations (0, 0.25, 0.5, 1.0, 2.5, and 5.0 mM NH4NO3) on growth of Brachypodium distachyon were assessed on controlled hydroponic culture. Maximal growth (132% of control) was obtained at 0.5 mM NH4NO3, critical N level, and was maintained at higher N concentrations. The highest N level (5.0 mM) has a similar effect on growth as 0.5 mM NH4NO3. It has no significant effects on water status, and total and reduced N contents in shoots while, increased those in roots, compared to plants receiving 0.5 mM NH4NO3. The high N availability, however, increased nitrate contents in shoots and roots by 3- and 20-folds, respectively, compared to those of plant receiving 0.5 mM NH4NO3. In addition, high N availability reduced the nitrogen use efficiency (NUE) by 18% compared to that of plant receiving only 0.5 NH4NO3. In view of B. distachyon productivity and environmental concerns, it is concluded that the critical level of N application should be 0.5 mM NH4NO3 and the excess fertilization led to a high nitrate accumulation. 相似文献
12.
硝酸镧对碱胁迫下黑麦草幼苗生长和光合生理的影响 总被引:2,自引:0,他引:2
在150 mmol·L-1 NaHCO3胁迫下,研究了不同浓度硝酸镧对黑麦草幼苗生长的影响及其对叶片光合生理响应的调节作用。结果表明,叶面喷施低浓度硝酸镧(0.05 mmol·L-1)预处理显著减小了碱胁迫下黑麦草幼苗生物量、叶片叶绿素和类胡萝卜素含量、叶绿体希尔反应、光合电子传递、光合磷酸化、Mg2+ ATP酶、RuBP羧化酶活性和光合效率的下降幅度,却对光呼吸调节酶乙醇酸氧化酶活性无明显影响。而高浓度硝酸镧(0.5 mmol·L-1)预处理不仅对碱胁迫没有缓解作用,反而加重了碱胁迫伤害。因此,适宜浓度硝酸镧可以通过改善光合功能从而缓解碱胁迫对黑麦草幼苗生长的抑制作用。 相似文献
13.
Absorption and distribution of K+ by two ryegrass genotypesfrom steady-state supplies at low external concentrations werefollowed through periods of NO3 deprivation and afterdefoliation. Electron microprobe analysis was also used to examineK+ concentrations across the root cortex and the effects onvacuolar/cytoplasmic K+ concentrations in the cortex. In manyrespects, the two genotypes behaved in a similar way. Totalquantities of K+ absorbed were less than 50% of those previouslyrecorded for NO3, and NO3 deprivation slightlyreduced cumulative K+ uptake. Unit absorption rates (K) declinedwith time in the control plants, and removal of NO3 resultedin a progressive decline in K, with an initial rapid responsewhich was independent of any effects of growth. In one genotypeabsorption rates did not recover but gradually did so in theother. Defoliation reduced K only slightly for 6 d, thereafterK, increased almost linearly so that values for plants withsustained NO3 supply were 2 ? those of entire plants.There was no evidence of an oscillatory cycle of K+ unit absorptionrates of the kind previously shown for NO3 during therecovery periods. Concentrations of K+ on both a dry matterand tissue water basis remained within a narrow range irrespectiveof treatment or time. The immediate decline in K+ unit absorption rate after NO3withdrawal indicated that at least a proportion of their uptakeswere coupled. Calculated values for the length of the diffusivepathway indicated that the primary site of absorption into thesymplasm was either the epidermis or the outermost corticalcell. This was supported by evidence from the electron microprobeanalysis which indicated a strong gradient of K+ concentrationswhich declined from outer to inner cortex and was much steeperin plants with a sustained NO3 supply. Concentrationsin the cytoplasm of most cortical cells were generally greaterthan in the vacuoles: this difference was greater in low N plants.The changes in K+ in the cortex were related to the role ofK+ in the transport of NO3 in the xylem and effects onrecycling to the roots in the phloem. Key words: Cytoplasm, defoliation, diffusion, electron probe X-ray microanalysis, Lolium, nitrate, potassium, S.E.M.,, unit absorption, vacuole 相似文献
14.
Nitrogen utilization by plant species from acid heathland soils: I. Comparison between nitrate and ammonium nutrition at constant low pH 总被引:4,自引:2,他引:2
Seven heathland species, four herbaceous plants and three dwarfshrubs, were tested for their capacity to utilize NH4+ or NO3. When cultured in solution at pH 4.0 with 2mol m3 N,all species showed similar growth responses with respect toN source. Nitrate was assimilated almost equally well as ammonium,with relative growth rate generally averaging 58% lowerfor NO3 grown plants, albeit not always significantly.However, N source was significantly and consistently correlatedwith biomass partitioning, as NH4+-fed plants allocated moredry matter to shoots and less to roots when compared to NO3-fed plants. The strong difference in biomass partitioning mayrelate to the relative surplus of carbon per unit plant N (or,alternatively, the relatively suboptimal rate of N assimilationper unit plantC) in NO3-fed plants Inherently slow-growing dwarf shrubs accumulated virtually nofree nitrate in their tissues and reduction of nitrate was strictlyroot-based. Faster-growing herbaceous plants, however, partitionedthe assimilation of nitrate over both shoots and roots, therebyaccumulating relatively high tissue NO3 levels. Ion uptakerates depended clearly on the relative shoot demand.At similar shoot demands, especially in the herbaceous species,specific uptake rates for N and total inorganic (non-N) anionswere higher in NH4+ -fed plants, whereas the uptake rate fortotal (non-N) cations was higher in NO3-fed plants. Rateof P uptake was enhanced with increasing plant demand, but wasindependent of the N source. Net H+ extrusions ranged from 1.00to 1.34 H+ per NH4+, and from 0.48 to 0.77 H+per NO3 taken up. Key words: Ammonium, biomass partitioning, heathland plants, low pH, nitrate, nitrate reductase activity, relative shoot demand, specific absorption rate 相似文献
15.
LARSSON CARL-MAGNUS; LARSSON MARIE; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1387-1395
Larsson, C.-M., Larsson, M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.II. Effect of ammonium and methionine sulphoximine on nitrateutilization.J. exp. Bot. 36: 13871395 In 3% CO2-grown Scenedesmus obtusiusculus Chod. utilizing NO3J as the N source, NH4+ addition caused a prompt inhibitionof NO3 utilization. Nitrate reductase (NR) activity declinedrapidly in response to the presence of NO4+, but the cessationof NO3 utilization was too rapid to be accounted forby the loss in NR activity. The first site of NO4+ inhibitionin these cells seems to be the entrance of NO3 into thecells. Upon exhaustion of NO4+ from the medium, NO3 utilizationwas rapidly restored and NR activity increased. Air-grown cellswere much less sensitive to the effect of NO4+, more than 30min being required for added NO4+ to cause complete inhibitionof NO3 utilization. In these cells, NO3 uptakeand NR activity decreased in parallel in response to NO4+ addition.In 3% CO2-grown cells simultaneously subjected to NO4+ and air-levelof CO2, NO4+ initially inhibited NO3 utilization completely,but a slight recovery took place after approximately 20 min The glutamine synthetase (GS) inhibitor L-methionine D, L-sulphoximine(MSO) behaved as a potent inhibitor of NO3 uptake in3% CO2-grown cells, but had considerably less effect in air-growncells, although the time-course of the MSO-induced inhibitionof GS was the same in both cases Key words: Ammonium, nitrate utilization, Scenedesmus 相似文献
16.
Effects of chilling (5 °C) period, light and applied nitrogen(N) on germination (%), rate of germination (d to 50% of totalgermination; T50%) and seed imbibition were examined inClematisvitalba L. In the absence of chilling, light and N, germinationwas minimal (3%). When applied alone, both chilling and N increasedgermination. Chilling for 12 weeks increased germination to64%, and 2.5 mM NO-3or NH+4increased germination to 1012%.Light did not increase germination when applied alone, but didwhen applied in combination with chilling and/or N. Half theseed germinated when light was combined with 2.5 mM NO-3or NH+4.The influence of chilling, light and/or N on germination wasgreater when combined, than when either factor was applied alone.Both oxidized (NO-3) and reduced (NH+4) forms of N increasedgermination, but non-N-containing compounds did not, suggestingthe response was due to N and not ionic or osmotic effects. Without additional N, T50%decreased from 1620 d at zerochilling, to around 5 d at 8 and 12 weeks chilling. AlthoughT50%was not influenced by an increase in NO-3or NH+4from 0.5to 5.0 mM , it did increase with additional applied N thereafter.However, the magnitude of the N effect was small compared tothat of chilling. Like germination, seed imbibition increasedwith a longer chilling period, but in contrast imbibition decreasedslightly with increased applied NO-3or NH+4. It is argued thatincreased imbibition is not directly related to an increasein total germination, but that it may be related to the rateof germination. Possible mechanisms involved in the reductionin dormancy ofC. vitalba seed are discussed. Clematis vitalba L.; germination; dormancy; imbibition; rate of germination; chilling; light; nitrate; ammonium; nitrogen; phytochrome 相似文献
17.
The Partitioning of Nitrate Assimilation Between Root and Shoot of a Range of Temperate Cereals and Pasture Grasses 总被引:2,自引:1,他引:1
Nitrate reductase activity (NRA, in vivo assay) and nitrate(NO-3) content of root and shoot and NO-3 and reduced nitrogencontent of xylem sap were measured in five temperate cerealssupplied with a range of NO-3 concentrations (0·120mol m3) and three temperate pasture grasses suppliedwith 0·5 or 5 0 mol m3 NO-3 For one cereal (Hordeumvulgare L ), in vitro NRA was also determined The effect ofexternal NO-3 concentration on the partitioning of NO-3 assimilationbetween root and shoot was assessed All measurements indicatedthat the root was the major site of NO3 assimilation in Avenasatwa L, Hordeum vulgare L, Secale cereale L, Tnticum aestivumL and x Triticosecale Wittm supplied with 0·1 to 1·0mol m3 NO-3 and that for all cereals, shoot assimilationincreased in importance as applied NO-3 concentration increasedfrom 1.0 to 20 mol m3 At 5.020 mol m3 NO3,the data indicated that the shoot played an important if notmajor role in NO-3 assimilation in all cereals studied Measurementson Lolium multiflorum Lam and L perenne L indicated that theroot was the main site of NO-3 assimilation at 0.5 mol m3NO-3 but shoot assimilation was predominant at 5.0 mol m3NO-3 Both NRA distribution data and xylem sap analysis indicatedthat shoot assimilation was predominant in Dactylis glomerataL supplied with 0.5 or 5.0 mol m3 NO-3 Avena sativa L., oats, Hordeum vulgare L., barley, Secale cereale L., rye, x Triticosecale Wittm., triticale, Triticum aestivum L., wheat, Dactylis glomerata L., cocksfoot, Lolium multiflorum Lam., Italian ryegrass, Lolium perenne L., perennial ryegrass, nitrate, nitrate assimilation, nitrate reductase activity, xylem sap 相似文献
18.
Significant differences in NO3 accumulation and nitrate reductaseactivity (NRA) were noted in the successive segments of developingyoung primary and nodal roots. This variation was also foundto be a function of root age. Nitrite reductase activity (NiRA)on the other hand had little variation among various segmentsof primary and nodal roots and also as a function of root age.These data suggest root NO3 accumulation and root NRA are twoprocesses which are not directly linked.
1 Present address: Division of Plant Physiology, Indian AgriculturalResearch Institute, New Delhi-110012, India. (Received December 3, 1983; Accepted June 18, 1983) 相似文献
19.
This study examined whether ‘Risnod2’ and ‘Risnod27’ non-nodulating mutants of pea (Pisum sativum L.) provided with increasing concentrations of nitrate could achieve a growth and nitrogen accumulation comparable to their
parental N2-fixing cv. Finale. In the cv. Finale, nodule number, nodule dry mass accumulation, total C2H2-reducing activity of nodulated roots (TAR) and estimated N2 fixation were considerably inhibited at 5.0 and 10.0 mM root medium NO3
− concentrations. In contrast a 0.63 mM level stimulated both the nodule dry mass and TAR. The cv. Finale N2-fixing plants grown on 0 to 2.5 mM NO3
− levels had higher shoot N concentrations than the Nod− mutants, but within the 5.0 to 10.0 mM levels the Nod− mutants approached or even overtopped the N concentration of the cv. Finale plants. Compared with a high positive correlation
found in the Nod− mutants, shoot N concentration in the cv. Finale was negatively correlated with the root medium NO3
− concentration. The pattern of nitrogen content in shoot dry mass was very similar to that seen in the shoot dry mass accumulation.
The Nod− mutants grown on the 5.0 and/or 10.0 mM NO3
− level had plant dry mass, shoot nitrogen concentration, shoot nitrogen content, and root/shoot dry mass ratio comparable
with those of the nodulating cv. Finale grown on the same nitrate levels. 相似文献
20.
Pb2+胁迫对两种小麦幼苗生理特性影响的研究 总被引:2,自引:1,他引:1
以两种小麦西旱2号和宁春4号幼苗为供试材料,研究了不同浓度Pb(NO3)2处理对其叶绿素含量、抗氧化酶活性及渗透性调节物等生理特性的影响。结果发现,两种小麦在低浓度铅处理下幼苗叶片叶绿素含量及超氧化物歧化酶(SOD)活性均无显著变化,而高浓度铅胁迫使其叶绿素a(Chla)、叶绿素b(Chlb)及叶绿素总量明显减少,但SOD活性显著升高,且相同浓度铅胁迫对小麦宁春4号幼苗叶片叶绿素的破坏作用明显强于对西旱2号的作用;不同浓度硝酸铅处理诱导两种小麦幼苗过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性升高,但不影响丙二醛(MDA)含量;此外,Pb2+处理使小麦幼苗叶片脯氨酸含量升高,此效应具有浓度依赖性,但铅处理不影响可溶性糖相对含量。结果表明,铅胁迫对两种小麦幼苗叶片叶绿素造成了破坏,却不同程度诱导抗氧化酶活性及脯氨酸含量升高,即表现出较强的抗氧化能力和渗透调节能力,增强了小麦对铅的耐受性,因而胁迫诱导两种小麦叶片MDA含量变化与对照比无显著性差异。 相似文献