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1.
MATTSSON M.; LUNDBORG T.; LARSSON M.; LARSSON C.-M. 《Journal of experimental botany》1992,43(1):25-30
Barley (Hordeum vulgare L., cvs Golf, Mette, and Laevigatum)was grown under nitrogen limitation in solution culture untilnear maturity. Three different nitrogen addition regimes wereused: in the HN culture the relative rate of nitrate-Naddition (RA) was 0·08 d1 until day 48 and thendecreased stepwise to, finally, 0·005 d1 duringgrain-filling; the LN culture received 45% ofthe nitrogen added in HN; the CN culture was maintainedat RA 0·0375 d1 throughout. Kinetics of net nitrateuptake were measured during ontogeny at 30 to 150 mmol m3external nitrate. Vmax (which is argued to reflect the maximuminflux rate in these plants) declined with age in both HN andLN cultures. A pronounced transient drop was observed just beforeanthesis, which correlated in time with a peak in root nitrateconcentration. Similar, but less pronounced, trends were observedin CN. The relative Vmax (unit nitrogen taken up per unit nitrogenin plants and day) in all three cultures declined from 1·32·3d1 during vegetative growth to 0·10·7d1 during generative growth. These values are in HN andLN cultures 15- to more than 100-fold in excess of the demandset by growth rates throughout ontogeny. Predicted balancingnitrate concentrations (defined as the nitrate concentrationrequired to support the observed rate of growth) were below6·0 mmol m3 in HN and LN cultures before anthesisand then decreased during ontogeny. In CN cultures the balancingnitrate concentration increased during grain-filling. Apartfrom the transient decline during anthesis, most of the effectof ageing on relative Vmax can be explained in terms of reducedcontribution of roots to total biomass (R:T). The loss in uptakeper unit root weight is largely compensated for by the declinewith time in average tissue nitrogen concentrations. The quantitativerelationships between relative Vmax and R:T in ageing plantsare similar to those observed for vegetative plants culturedat different RAs. The data support the contention that the capacity for nitrateacquisition in N-limited plants is under general growth control,rather than controlled by specific regulation of the biochemicalpathway of nitrate assimilation. Key words: Barley, nitrogen concentration, root: total plant biomass ratio, Vmax 相似文献
2.
Nitrogen Utilization in N-limited Barley During Vegetative and Generative Growth: IV. TRANSLOCATION AND REMOBILIZATION OF NITROGEN 总被引:1,自引:0,他引:1
Barley (Hordeum vulgare L., cvs Golf and Laevigatum) was grownunder nitrogen limitation in solution culture until near maturity.Three different nitrogen addition regimes were used: in theHN culture, the relative rate of nitrate-N additionwas 0·08 d1 until day 48 and then stepwise decreasedto, finally, 0·005 d1 during late grain-filling;the LN culture received 45% of the nitrogen addedin HN; the CN culture was maintained at RA 0·0375d1 throughout growth. At four different growth stages(vegetative,anthesis, and twice during grain-filling), 15N-nitrate was fedto the plants. In some cases (split root cultures),label was fed only to one-half of the root system. These wereharvested directly after labelling, whereas standardcultured plants were harvested at termination of theexperiment (day 148). Absorption of added nitrate was nearlycomplete in the HN and LN cultures, and translocation of nitrogenwithin the plants could thus be studied independently of differencesin nitrate absorption. Cycling of nitrogen absorbed by vegetativeplants accounted for up to 50% of the nitrogen recovered inthe roots. The sink strength of the roots for cycling nitrogen,however, declined during post-anthesis growth, and net lossof nitrogen from both roots and vegetative shoot tissue occurredconcomitantly with incorporation of labelled 15N-nitrogen. Thenitrogen of the vegetative shoot tissue was substantially lesslabelled than the nitrogen entering the ears, indicating thattranslocation of recently absorbed nitrogen to ears occurs withminor prior exchange with the bulk nitrogen of shoots. In caseswhere the sink strength of the ears was weak, as in LN-culturedLaevigatum (due to high frequency of sterile flowers) and inCN-cultured Golf, nitrogen translocated from roots appearedto be incorporated into the vegetative shoot tissue. There werealso indications that a fraction of the remobilized nitrogenwas actually lost from the plants in these cases. It is concludedthat the root remains efficient in translocation of nitrogento the aerial parts throughout ontogeny and that nitrogen takenup during grainfilling is preferentially directly translocatedto the developing grains. The further translocation of nitrogenreceived by vegetative shoot parts to ears appears mainly relatedto the potential of the ear to accumulate nitrogen. Nitrogenabsorbed/remobilized in excess of the sink strength of the earsis either invested in continued shoot growth, or is irreversiblylost from the plants. Key words: Barley, 15N-labelling, post-anthesis, remobilization, translocation 相似文献
3.
MATTSSON M; JOHANSSON E; LUNDBORG T.; LARSSON M.; LARSSON C.-M. 《Journal of experimental botany》1991,42(2):197-205
Growth and nitrate uptake kinetics in vegetatively growing barley(Hordeum vulgare L., cvs Laevigatum, Golf, and Mette) were investigatedin solution culture under long-term limitations of externalnitrogen availability. Nitrate was fed to the cultures at relativeaddition rates (RA) ranging from 0.02 to 0.2 d1. Therelative growth rate (RG, calculated for total plant dry weight)correlated well with RA in the range 0.02 to 0.07 d1.In the RA range from 0.07 to 0.2 d1 RG continued to increase,but an increasing fraction of nitrogen, added and absorbed,was apparently stored rather than used for structural growth.The RG of the roots was less affected by RA. Vmax, for net nitrateuptake increased with RA up to 0.11 d1, but decreasedat higher RA. The decline in Vmax coincided with a build-upof nitrate stores in both roots and shoots. Vmax, expressedper unit nitrogen in the plants (the relative Vmax, was higherthan required for maintenance of growth (up to 30-fold) at lowRA, whereas at higher RA the relative Vmax decreased. Kineticpredictions of steady-state external nitrate concentrationsduring N-limited growth ranged from 0.2 to 5.0 mmol m3over the RG range 0.02 to 0.11 d1. It is suggested thatthe nitrate uptake system is not under specific regulation atlow RA, but co-ordinated with root protein synthesis and growthin general. At RA higher than 0.11 d1, however, specificregulation of nitrate uptake, possibly via root nitrate pools,become important. The three cultivars showed very similar growthand nitrate uptake characteristics. Key words: Barley, growth, nitrogen limitation, nitrate uptake, kinetics 相似文献
4.
《Journal of experimental botany》1977,28(6):1247
Effects of coupled solute and water flow in plant roots withspecial reference to Brouwer's experiment. Edwin L. Fiscus. p. 71 Abstract: Line 3 delete interval insertinternal. p. 73 Materials and Methods: line 6: delete diversion insert division line 9 equation should read Jv=Lp PRT(C0C1). 74 Last line of figure legend: 101 should read 1011. 75 Line 11: delete seems insert seem. le 1 column heading106 should read 1011. 77 delete ...membrane in series of... insert membranein series or... Delete final paragraph. 相似文献
5.
Interaction between Nitrogen Deficit of a Plant and Nitrogen Content in the Old Leaves 总被引:10,自引:0,他引:10
We examined changes in nitrogen content of the first leavesin relation to growth and nitrogen status of sunflower (Helianthusannuus L.) plants that were raised hydroponically at two irradiancelevels (high and low light, HL and LL) and at two nitrogen concentrations(high and low nitrogen, HN and LN). Initial increases in totaldry mass and total nitrogen of the whole plant were faster inHL-plants than in LL-plants irrespective of nitrogen supply,but in LN-plants the increase in total nitrogen was soon blunted.When plants grown under the same irradiance were compared, nitrogencontent of the first leaves (leaf N) decreased faster in LN-plantsthan in HN-plants, while for the plants grown at the same nitrogenconcentrations, it decreased faster in HL-plants than in LL-plants.Since these changes in leaf N were not explained solely by thechanges in plant dry mass or plant nitrogen, we introduced anindex, nitrogen deficit (ND*), to quantify nitrogendeficit of the whole plant. ND* was expressed as ND*(t)=[NmaxN(t)]xDM(t),where Nmax and N(t) were nitrogen contents in the young, expandingleaves that had just unfolded to expand, at the initial stagewith sufficient nitrogen and at time t, respectively, and DM(t),plant dry mass at t. The decrease in leaf N was expressed asa liner function of ND* irrespective of the growth conditions,which indicates validity of this index. Limitation of the useof ND*, and mechanisms by which leaves sense nitrogen demandare also discussed. (Received June 17, 1996; Accepted August 30, 1996) 相似文献
6.
Ammonia emission from young barley plants: influence of N source, light/dark cycles and inhibition of glutamine synthetase 总被引:3,自引:1,他引:2
Barley (Hordeum vulgare L. cv. Golf) plants were grown at twodifferent relative addition rates; 0.1 and 0.2 d1 ofnitrate. Three to five days before measurements started theplants were transferred to a nutrient solution with 2 mM nitrateor ammonium. The ammonium-grown plants showed increased ammoniumlevels in both shoots and roots and also increased ammoniumconcentrations in xylem sap. Ammonia emission measured in cuvettes connected to an automaticNH3 monitor was close to zero for nitrate-grown plants but increasedto 0.59 and 0.88 nmol NH3 m2 S1 for plants transferredto ammonium after growing at RA=0.2 and 0.1 d1, respectively.In darkness, NH3 emission decreased together with photosynthesisand transpiration, but increased rapidly when the light wasturned on again. Addition of 0.5 mM methionine sulphoximine (MSO) to the plantscaused an almost complete inhibition of both root and shootglutamine synthetase (GS) activity after 24 h. Ammonia emissionincreased dramatically and photosynthesis and transpirationdecreased in both nitrate- and ammonium-grown plants as a resultof the GS inhibition. At the same time plant tissue and xylemsap ammonium concentrations increased, indicating the importanceof GS in controlling plant ammonium levels and thereby NH3 emissionfrom the leaves. Key words: Hordeum vulgare, ammonia emission, ammonium, glutamine synthetase, nitrogen nutrition, photosynthesis, transpiration 相似文献
7.
Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus 总被引:1,自引:0,他引:1
The levels of purine and pyrimidine nucleotides in suspensioncultures of Catharanthus roseus were determined 24 h after stationary-phasecells were transferred to fresh complete (+Pi)or phosphate-deficient (Pi) Murashige-Skoogmedium. The levels of ATP, GTP, UTP and CTP were from approx.3 to 5-fold greater in the cells grown in +Pimedium than in the cells grown in Pi medium.The levels of almost all other nucleotides were slightly higherin the cells in +Pi medium. The rates of de novoand salvage biosynthesis of purine and pyrimidine nucleotideswere estimated from the rates of incorporation of radioactivityfrom [14C]formate, [214C]glycine, NaH14CO3, [614C]orotate,[814C]adenine, [814C]adenosine, [214C]uraciland [214C]uridine. The results indicated that the activityof both the de novo and the salvage pathway was higher in thecells in +Pi medium than in the cells in Pimedium. The rate of degradation estimated from the rate of releaseof 14CO2 from labelled purines and pyrimidines indicated thatdegradation of uridine was significantly reduced in the cellsin +Pi medium, but no significant difference wasfound in the degradation of adenine, adenosine and uracil. Thepossible role of Pi in the control of the biosynthesis of nucleotidesand in the degradation of uridine is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, nucleotides, purines, pyrimidines, biosynthesis, degradation 相似文献
8.
The Sensitivity of Net Photosynthesis in Several Plant Species to Short-term Fumigation with Sulphur Dioxide 总被引:4,自引:0,他引:4
The effects of exposure of up to 2 h with sulphur dioxide ona range of plant species was observed by measuring changes inthe rate of net photosynthesis under closely controlled environmentalconditions. Ryegrass, Lolium perenne S23 was thespecies most sensitive to SO2; significant inhibition was detectedat 200 nl l1. Fumigations at 300 nl l1 also inhibitedphotosynthesis in field bean (Vicia faba cv. Three FoldWhite and Blaze) and in barley (Hordeumvulgare cv. Sonja). No effect was detected inwheat (Triticum aestivum cv. Virtue) at concentrationsup to 600 nl l1 SO2, or in oil-seed rape (Brassica napuscv. Rafal) except at 800 nl l1 SO2). Recoverycommenced immediately after the fumigation was terminated andwas complete within 2 h when inhibition had not exceeded 20%during the SO2 treatment. Key words: Sulphur dioxide, short-term fumigation, photosynthesis 相似文献
9.
Feeding behavior of the brittle star Ophiura ophiura includesorienting posture, orienting movements, arm walking,changing the direction of walking arm coilingand ingestion. All sequential behavior patterns were releasedor enhanced by single low-molecular-weight compounds. Stimuliwhich released walking behavior at high concentrations(104 M) in all the test animals are listed in decreasingorder of sensitivity: sarcosine, glycine, urea, L-valine, L-leucine,L-methionine, L-homocysteine, L-norvaline, L-norleucine, L-threonine,L-serine, S-methyl-L-cysteine, L-proline. Threshold values forsingle amino acids were as much as 100 times different in differentindividuals and ranged from 3 x 109 to 3 x 107M for the most effective stimulus, sarcosine, and from 106to 104 M for proline. Above 105 M, only L-prolineregularly released a second behavior pattern, the arm coilingresponse, which temporarily inhibited the walkingbehavior. Behavioral thresholds for the walkingbehavior for L(+)-lactate and L-alanine were higher than thosefor the orienting movements. Thyoglycolic acid and ß-alaninereleased tube feet walking, which is not part of the feedingbehavior. Structureactivity comparisons were studied at estimated105 M concentrations. Gycline, sarcosine, L-valine, L-norvaline,L-leucine, L-isoleucine, DL-norleucine and DL-homocysteine releasedarm walking behavior in more than 75% of all thetests. With the exceptions of S-methyl-and S-ethyl-cysteine,and glycine methylester, derivatives of amino acids were noteffective behavioral stimuli in Ophiura ophiura. L-Isomers ofvaline and leucine regularly stimulated the walkingbehavior while their D-isomers were effective in some testsand ineffective in others. Acetylcholine iodide, acetyl-ß-methylcholine chloride and choline phosphate chloride regularly releasedwalking behavior at concentrations above 105M. 相似文献
10.
Floral buds of the False Horn plantain clonesMusa (AAB) Harton Verde, Harton Negra,and Currare terminate in a large single floralstructure. The apices of these floral buds are here designatedas determinate since they have lost the ability to produce additionalfloral initials or buds. Terminal peduncle segments can be culturedin a modified Murashige and Skoog (1962) medium supplementedwith N6-benzyl-aminopurine (5 mg I1). Under these conditions,this apparent inability to yield buds can be overcome as vegetativeshoot clusters form in the axils of the bracts. Rooted plantletsare obtainable by treating shoots with naphthaleneacetic acid(1 mg I1) and activated charcoal (0.025%). The adventitiousorigin of the shoots has been established. Musa cultivars, plantains, floral bud, adventitious buds, tissue culture 相似文献
11.
Kutk Jaromr; Ntr Lubomr; Demmers-Derks H.H.; Lawlor David W. 《Journal of experimental botany》1995,46(12):1797-1802
Sugar beet (Beta vulgaris L., cultivar Celt) plants were grownunder simulated field conditions in pots and supplied with adequateor deficient nitrogen (HN and LN, respectively) combined withtwo CO2 concentrations, ambient (c. 350µmol mol1C02AC), or elevated CO2 (c. 600 µmol mol1CO2HC). Chloroplast structure in mesophyll palisade cellsof mature leaves (leaf number 19 in HN and 9 in LN), sampledat midday on 16 August 1993 was studied by transmission electronmicroscopy and quantified stereologically. The ultrastructureof palisade parenchyma chloroplasts was affected by the elevatedCO2 concentration and strikingly affected by nitrogen supply.Chloroplast diameter (cross-sectional length) was slightly,but not significantly, greater in HC than AC treatments withinan N treatment, but was smaller in LN than HN; chloroplast cross-sectionalarea also increased with HC in both N treatments, but only significantlyso in LN. Elevated CO2 reduced the proportion of total thylakoids(significant at 5% and 0.1% in HN and LN, respectively) dueto decreased granal thylakoids, but the proportion of inter-granal(stromal) thylakoid membranes was not affected compared to chloroplastsfrom plants grown with ambient CO2. Chloroplast stroma increasedas a proportion of chloroplast volume with elevated comparedto ambient CO2 with HN but not LN. Starch inclusions were notsignificantly different with elevated compared to ambient CO2at HN, but the proportion of starch increased considerably atelevated compared to ambient C02 at LN, indicating an over-productionof assimilates. Plastoglobuli in chloroplasts increased withdeficient N, but decreased with elevated CO2. Larger chloroplastswith a greater proportion of stroma, but a smaller proportionof granal thylakoids, suggest increased CO2 assimilating capacityand decreased light harvesting/PSII capacity with elevated CO2. Key words: Chloroplast, ultrastructure, elevated CO2 concentration, nitrogen deficiency, sugar beet, Beta vulgaris 相似文献
12.
A Cytochrome P450 Mediated Naringenin 3'-Hydroxylase from Sweet Orange Cell Cultures 总被引:1,自引:0,他引:1
Doostdar Hamed; Shapiro Jeffrey P.; Niedz Randall; Burke M.D.; McCollum T. Gregory; McDonald Roy E.; Mayer Richard T. 《Plant & cell physiology》1995,36(1):69-77
A microsomal flavonoid 3'-hydroxylase (F3'H) catalyzing themetabolism of naringenin to eriodictyol in Citrus sinensis (L.)Osbeck cv. Hamlin cell suspension cultures wasshown to be a cytochrome P450 enzyme. This reaction requiredO2 and NADPH and was inhibited by CO, with partial reversalof CO-inhibition by light at 450 nm. Cytochrome P450 contentranged from 1020 pmol (mg microsomal protein)1.The F3'H reaction was shown to be linear in regard to proteinconcentration between 2.5 and 25 µg of microsomal protein.The optimum pH for the reaction was 7.47.6 and the temperatureoptimum was between 30 and 37°C. The apparent Km and Vmaxfor naringenin were 24 µM±3.2 and 81.4±7.9pmol eriodictyol min1 (mg protein)1, respectively.The microsomal F3'H was also capable of forming dihydroquercetinfrom dihydrokaempferol (40 pmol min1 (mg protein)1)and of quercetin from kaempferol (3.25 pmol min1 (mgprotein1). Cytochrome c and ketoconazole were the bestinhibitors of WH activity followed by piperonyl butoxide anda-naphthoflavone. Light was shown to be an inducer of the F3'Halmost doubling the specific activity and increasing the microsomalcytochrome P450 content by 30% over that of dark grown cells.F3'H activity was also confirmed in microsomal preparationsof young (new flush) leaves from Hamlin treesand flavedo of Hamlin oranges, Marshgrapefruit, and Lisbon lemon. No activity wasobserved in older, hardened leaves and albedo of all the fruittested. Initiation of embryogenesis in the Hamlincell suspension cultures by switching from a sucrose mediumto a glycerol-based medium resulted in the down-regulation ofF3'H.
1Mention of a trademark, warranty, proprietary product, or vendordoes not constitute a guarantee by the U.S. Department of Agricultureand does not imply its approval to the exclusion of other productsor vendors that may also be suitable. 相似文献
13.
Subterranean clover (Trifolium subterraneum L.) cv. Woogenellup swards were grown at 10, 15, 20 and 25 Cwith a 12 h photoperiod of 500 or 1000 µmol m2s1 [low and high photosynthetic photon flux density (PPFD)].Nitrogen-fixing swards received nutrient solution lacking combinednitrogen while control swards received a complete nutrient solution.Growth was measured by infra-red analysis of carbon dioxideexchange and by accumulation of dry matter. Swards were harvestedat intervals between 95 and 570 g d. wt m2 for estimationof nitrogenase activity by acetylene reduction and hydrogenevolution assays. Nitrogen fixation was also measured by increasein organic nitrogen. The growth rate was highest at 10 C at low PPFD, and at 1015C at high PPFD. Nitrogen-fixing swards grew slower than thosereceiving combined nitrogen. Nitrogen fixation measured by increasein organic nitrogen responded similarly to the growth rate,as did acetylene reduction between 10 and 20 C. At 25 C therelationship between acetylene reduction and nitrogen fixationwas distrupted. The difference between the rates of acetylenereduction and hydrogen evolution, theoretically proportionalto nitrogen fixation, was not a reliable indicator of nitrogenfixation because hydrogen uptake developed. Trifolium subterraneum L, subterranean clover, growth, nitrogen fixation, temperature, acetylene reduction 相似文献
14.
This study was conducted with Lolium temulentum, Festuca pratensis,and the two hybrids L. multiflorum x F. pratensis Elmetand L. perenne x F. pratensis Prior. In a comparisonof various durations (742 d) of pretreatment at 4 or7 °C the highest yield of microspore-derived callus of L.temulentum was obtained after pretreatment of spikes at 7 °Cfor 28 d, conditions which also proved optimal for panicle pretreatmentwith F. pratensis. For Elmet, durations of 2142d were optimal, and for Prior the responses tendedto decline with increasing duration. In L. temulentum addition of charcoal (12 g l1)to medium containing 2, 4-D and KN wa 相似文献
15.
The development of taurine uptake into the unicellular greenalga Chlorella fusca 211-8b was characterized as a specificresponse to either nitrate or sulphate limitation. Taurine transportunder nitrogen starvation was stimulated by low pH and showeda biphasic kinetics with Km-values of 1.1 x 103 mol dm3and 1.0 x 102 mol dm3. Uptake was substantiallyinhibited by all - and ß-amino acids tested, whereassulphonate analogues failed to diminish taurine accumulation.Thus, uptake seemed to be mediated by a general aminoacid permease, unable to discriminate between carboxyland sulphonyl groups. However, Chlorella fusca could not catabolizethis unusual ß-amino acid and mobilize the amino-boundnitrogen for growth. Only a small group of -amino acids supportedthe growth of Chlorella fusca as an efficient nitrogen source. Key words: Taurine uptake, nitrogen starvation, amino acid uptake, Chlorella fusca. 相似文献
16.
SINGH N; SINGH S N; SRIVASTAVA K; YUNUS M; AHMAD K. J; SHARMA S C.; SHARGA A N 《Annals of botany》1990,65(1):41-44
Five Gladiolus cultivars, namely Aldebaran, BrightEye, Illusion, Manisha andManmohan, were exposed to 1 and 2 µg l1sulphur dioxide to test their relative-sensitivity toleranceto the pollutant Plants were fumigated experimentally for 2h daily Foliar injury symptoms were observed first in Manishafollowed by Aldebaran and Illusionat the higher dose Photosynthetic pigments and leaf extractpH were significantly decreased, particularly in Manishaand Illusion Overall disturbances in the plantmetabolism due to SO2 treatment led to retarded growth of plants,as evident from decreased shoot length and phytomass valuesThe order of sensitivity of the five Gladiolus cultivars toSO2 was as follows, with the greatest first Manisha, Illusion,Aldebaran, Bright Eye, Manmohan Cultivars, Gladiolus, sensitivity, sulphur dioxide, tolerance 相似文献
17.
Nitrate provision has been found to regulate the capacity forChara corallina cells to take up nitrate. When nitrate was suppliedto N sufficient cells maximum nitrate uptake was reached after8 h. Prolonged treatment of the cells in the absence of N alsoresulted in the apparent ability of these cells to take up nitrate.Chlorate was found to substitute partially for nitrate in theinduction step. The effects on nitrate reductionwere separated from those on nitrate uptake by experiments usingtungstate. Tungstate pretreatment had no effect on NO3uptake induced by N starvation, but inhibitedNO3 uptake associated with NO3 pretreatment. Chloridepretreatment similarly had no effect on NO3 uptake inducedby N deprivation, but inhibited NO3 uptake followingNO3 pretreatment. The data suggest that there are atleast two mechanisms responsible for the inductionof nitrate uptake by Chara cells, one associated with NO3reduction and induced by CIO3 or NO3and one associated with N deprivation. Key words: Nitrate, Chlorate, Chara corallina, Induction 相似文献
18.
Plants of two genotypes of Lolium perenne L. cv. S23 and a L.perenne ? L. multiflorum Lam. hybrid cv. Augusta were grownin flowing solution culture. N was suppled in one treatmentat 10 mmol m3 NO3 throughout (HN), and in another(LN) the N supply was terminated after 10 d for 11 d. When was re-supplied both LN and HN plants were leftentire or defoliated. The two genotypes showed similar responsesto all treatments. The concentration of N in shoot dry matterdeclined from 4.4% to 2.0% and in the root from 2.8% to 1.0%over the 11 d of N deprivation, with 95% of the initially present being assimilated during this period. LN plantsassimilated 10% more of their total uptake than did HN plants. The in vitro nitrate reductase activity(NRA) was 10- to 50-fold higher in the youngest fully-expandedleaves than in roots and declined in the leaves during N deprivation.Between 26 d after defoliation, there was a large increasein NRA in leaves of HN (but not LN) plants. After defoliationof HN plants, net uptake from 10 mmol m3 declined to negligible levels within 15 h, but in defoliatedLN plants it increased to levels similar to those of entireHN plants (1520 µmol h1 g1 fr. wt.root) within 8 h. When was re-supplied to entire LN plants, uptake of increased to levels similar to those of entire HN plants within 2.3 h, butdid not markedly exceed that of HN plants for at least 10 h.Net uptake of by LN plants during depletion of stirred static nutrient solutions containing 1.0 mol m3 lagged behind that by HN plants by 70100 min, but the maximum unit absorption rate was similar for LNand HN plants (57 µmol h1 g1 fr.wt. root). The nature of the short-term demand for uptake following recovery from the stresses of defoliation andN starvation is discussed. Key words: Lolium perenne, Lolium multiflorum, N-deficiency, defoliation, nitrate uptake, nitrate reductase, N-assimilation 相似文献
19.
The metabolic fate of [U-14C]sucrose in suspension culturesof Catharanthus roseus cells was monitored for 96 h after thecells were transferred to fresh complete (+Pi)or to phosphate-deficient Murashige and Skoog (Pi)medium. Sucrose was hydrolysed extracellularly to glucose andfructose. The rate of uptake of sugars by the cells was 1.53times higher in +Pi culture than in Piculture. Little difference in the rate of incorporation of radioactivityinto the ethanol-soluble fraction was found between the +Piand Pi cultures during the initial 24h of culture, but after 48 h the rate in +Picultures was higher than that in Pi cultures.Incorporation of radioactivity into ethanol-insoluble macromoleculeswas always significantly higher in the cells in +Picultures than in those in Pi cultures.The results suggest that Pi strongly affects the utilizationof sugars by cultured plant cells through the stimulation oftransport of sugars as well as through the activation of metabolism. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, sucrose, transport, metabolism 相似文献
20.
Putrescine, spermidine, and spermine content were analysed inzygotic embryos of barley (Hordeum vulgare L.). Changes in polyaminecontent were observed during zygotic embryo growth. In two cultivars,Bomi and Golden Promise, the totalpolyamine content in the embryos was 2.62.9 nmol mg1fresh weight 10 d after anthesis, the highest content observed.It dropped to 1.3 nmol mg1 fresh weight 14 d after anthesis.This drop was caused by decreases in all three polyamine concentrations.From 14 to 35 d after anthesis the putrescine content continuedto decrease while the spermidine and spermine content increased,thus the total polyamine content remained constant until 35d after anthesis. The mutant Ris? 1508 showeda constant polyamine content around 1.3 nmol mg1 freshweight from 14 to 35 d after anthesis. The polyamine patternwas conserved in all three lines throughout the period of investigationshowing a spermidine content higher than putrescine contentwhich was, in turn, higher or equal to the spermine content.The polyamine content measured as nmol µg1 proteindecreased from 14 to 21 d post anthesis in all three lines,because the protein content (µg mg1 fresh weight)increased during the period. In dedifferentiating zygotic embryoscultured in vitro the putrescine content (nmol mg1 freshweight) rose by a factor of nine and the spermidine contentdoubled within the first week of cultivation, whereas sperminecontent did not change. For embryoderived calli a repeated patternof change in polyamine content was observed throughout the subculturingperiod. Key words: Polyamines, Hordeum vulgare L., embryo development 相似文献