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1.
This work aimed to study the impacts of acquisition and assimilationof various nitrogen sources, i.e. NO3, NH4+ or NH4NO3,in combination with gaseous NH3 on plant growth and acid-basebalance in higher plants. Plants of C3 Triticum aestivum L.and C4 Zea mays L. grown with shoots in ambient air in hydroponicculture solutions with 2 mol m3 of nitrogen source asNO3, NH4+ or NH4NO3 for 21 d and 18 d, respectively,had their shoots exposed either to 320 µg m3 NH3or to ambient air for 7 d. Variations in plant growth (leaves,stubble and roots), and OH and H+ extrusions as wellas the relative increases in nitrogen, carbon and carboxylatewere determined. These data were computed as H+/N, H+/C, (C-A)/N,and (C-A)/C to analyse influences of different nitrogen sourceson acid-base balance in C3 Triticum aestivum and C4 Zea maysplants. Root growth in dry weight gain was significantly reduced bytreatment with 320 µg m3 NH3 in Triticum aestivumand Zea mays growing with different N-forms, whereas leaf growthwas not significantly affected by NH3. In comparison with C3Triticum aestivum, non-fumigated C4 Zea mays had low ratiosof OH/N in NO33-grown plants and of H+/N in NH4+- and NH 4NO3-grown plants. Utilization of NH3 from the atmospherereduced both the OHN ratios in NO3 -grown plantsand the H+/N ratio in NH4+ - and NH4NO3 -grown plants of bothspecies. Furthermore, Zea mays had higher ratios of (C-A)/Nin NH4+ - and NH4NO3-grown plants than Triticum aestivum. Thismeans that C4 Zea mays had synthesized more organic anion perunit increase in organic N than C3 Triticum aestivum plants.Within both species, different nitrogen sources altered theratios of (C-A)/N in the order: NH4NO3>NH4+>NO3.Fumigation with NH3 increased organic acid synthesis in NO3- and NH4+ - grown plants of Triticum aestivum, whereas it decreasedorganic acid synthesis in Zea mays plants under the same conditions.Furthermore, these differences in acid-base regulation betweenC3 Triticum aestivum and C4 Zea mays plants growing with differentnitrogen sources are discussed. Key words: Acid-base balance, ammonia, ammonium, nitrate, ammonium nitrate, C3 Triticum aestivum L., C4 Zea mays L. 相似文献
2.
《Journal of experimental botany》1996,47(4):604
Light response curves for () gross 16O2 evolution, and() CO2 uptake in 210 mmol mol1 O2 with 9001000µbar CO2 or () in air by leaves of Hirschfeldia incana.The difference between () and () or () was quantitativelyequivalent to the measured 18O2 uptake. The areas under thecurves are labelled to identify regions of assimilatory andnon-assimilatory electron flow redrawn from data of Canvin etal. (1980). It should be noted that the data and the labelling of the figureaxes are correct as printed. 相似文献
3.
LOBODA T.; KLECZKOWSKI L. A.; TARLOWSKI J.; NALBORCZYK E. 《Journal of experimental botany》1988,39(12):1765-1770
The effects of -hydroxy-2-pyridinemethanesulphonic acid (-HPMS)upon net photosynthesis (Pn, the CO2 compensation point (),post-lower illumination burst of CO2 (PLIB) and post-lower temperatureburst of CO2 (PLTB) in detached rye (Secale cereale L.) leaveswere investigated. At low concentrations ( 0.5 mol m3),-HPMS initially stimulated Pn and decreased the magnitude ofboth PLIB and PLTB. The decreased at all concentrations of-HPMS (0.055.0 mol m3. The effects of -HPMS onPn and were time-dependent and, after a few minutes, the Pnwas inhibited while values increased considerably. At a higherconcentration (5.0 mol m 3), the transient effects of-HPMS were shorter () or not observed at all (Pn. Both PLIBand PLTB, when expressed in relation to Pn, increased at higherlevels of this compound. Similar data with respect to the effectsof -HPMS on PLIB and PLTB were found for leaves of dandelion(Taraxacum officinale L.). The results suggest that -HPMS may stimulate Pn by inhibitingphotorespiration, as originally suggested by Zelitch (1966),but only at low concentrations and over a short time span. Thedecrease of PLIB and PLTB values at low -HPMS levels is consistentwith these processes being a residual activity of the glycolatepathway. Key words: CO2 compensation point, -hydroxy-2-pyridinemethanesulphonic acid, photorespiration, photosynthesis 相似文献
4.
Thomas, H. 1987. Physiological responses to drought of Loliumperenne L.: Measurement of, and genetic variation in, waterpotential, solute potential, elasticity and cell hydration.J.exp. Bot. 38: 115125. Clonally-replicated genotypes of Loiium perenne L. were grownin a controlled environment. Leaf water potential (w) osmoticpotential (s), turgor potential (p = w s), elasticity(E), leaf hydration (g water per g dry matter, H) and numberof green leaves per tiller (NGL) were measured before and duringa 42 d drought treatment. A simplified method of estimating E (at w < 1?0 MPa) usingonly six measurements was developed to permit a measurementrate of 8 leaves per hour. Measurement errors in all characterswere 3% or less. During drought, w and s (at w = 0?5 MPa) decreased significantly,p and E increased significantly, and H decreased slightly. Plantsize during drought was negatively correlated with s, and Hand positively correlated with p, osmotic adjustment, E andNGL. Measurements made on the genotypes before draughting didnot give a reliable indication of their physiological conditionafter adaptation to drought. Genetically controlled variation (broad sense heritability)of drought-adapted plants for E was 15%, w 23%, s, 34%, p, 35%,H 34% and NGL 64%. The possibilities for, and effectivenessof, divergent selection of genotypes with high and low expressionof the characters are discussed. Key words: Water relations, Lolium, genetic variation 相似文献
5.
MACDUFF J. H.; HOPPER M. J.; WILD A.; TRIM F. E. 《Journal of experimental botany》1987,38(10):1589-1602
Macduff, J. H., Hopper, M. J., Wild, A. and Trim, F. E. 1987.Comparison of the effects of root temperature on nitrate andammonium nutrition of oilseed rape (Brassica napusL.) in flowingsolution culture. II. Cation-anion balance.J. exp. Bot.38: 1589-1602. The effects of root temperature and form of N nutrition (NH4or NOJ) on the mineral composition of the plant, the balanceof inorganic cation-anion uptake and on the apparent net effluxof H +/OHions from the roots were studied with 49-d-oldoilseed rape (Brassica napusL. cv. Bien venu) in flowing solutionculture. Plants were pre-treated for 14 d at a root temperatureof 5 °C prior to constant root temperatures of 3, 7, 11or 17°C for 14 d, with a common shoot temperature of 20/15°Cday/night. Nitrogen was supplied as NH+44 or NO3 at 10mmol m3. Values of Q10 (7-17°C) for mean unit absorptionrates of all the major nutrient ions (K+ , Mg++ , NH+4, SO4,H2PO4, NO3), except Ca++, were > 2.0 over the first 5 d oftreatment but thereafter were < 1.5; the apparent effectof temperature on uptake rates diminished with time. Under NH+4nutrition, inorganic cation uptake (Mg+ + + K++Ca+ + +NH+4)exceeded inorganic anion uptake (SO4 4+ H2PO4) over 14d at all temperatures, with the proportion of cation uptakeas NH4 remaining constant (0.67-0-68) irrespective of root temperature.The net efflux of H + from the roots approximately balancedNH+4 uptake (1:1) over 14 d at each temperature and also balancedthe difference between the total uptake of inorganic cationsand inorganic anions. Under NO3 nutrition, the sum of the netefflux of OH and the change in the carboxylate contents of plantsover 14 d approximately balanced the sum of NO3 and SO 4reduced in the plant. The majority of the negative charge associatedwith the reduction of NO3 and SO 4 was apparently effluxedas OH, but this fraction was lower at low root temperatures.The results are discussed in terms of mechanisms that have beenproposed to regulate the internal pH of plants. Key words: Brassica napus, oilseed rape, root temperature, cation-anion balance, H+/OH efflux. 相似文献
6.
Water Relations of Chromium VI Treated Bush Bean Plants (Phaseolus vulgaris L. cv. Contender) under both Normal and Water Stress Conditions 总被引:1,自引:0,他引:1
BARCEL? JUAN; POSCHENRIEDER CHARLOTTE; GUNS? BENET 《Journal of experimental botany》1986,37(2):178-187
The effect of Chromium VI on leaf water potential (w), solutepotential (a), turgor potential (p) and relative water content(RWC) of primary and first trifoliatc leaves of Phaseolus vulgarisL. was studied under normal growth conditions and during anartificially induced water stress period in order to establishthe possible influence of this heavy metal on the water stressresistance of plants. Plants were grown on perlite with nutrientsolution containing 0, 10, 25, 50 or 100µg cm3 Cr as Na2Cr2O7.2H2O. The effect of Cr onwater relations was highly concentration dependent, and primaryand first trifoliate leaves were affected differently. The growthreducing concentrations of Cr (25, 50 and 100µg cm3) generally decreased s and w and increasedp in primary leaves. The 10 µg cm3 Cr treatmentdid not affect growth, but altered water relations substantially:in primary leaves w and p were increased and s decreased, whilein trifoliate leaves the effect was the opposite. All Cr treatedplants resisted water stress for longer than control plants.The higher water stress resistance may be due to the lower sand to the increased cell wall elasticity observed in Cr VItreated plants. Key words: Phaseolus vulgaris, Chromium VI, water stress, Richter plot 相似文献
7.
Allen, S., Thomas, G. E. and Raven, J. A. 1986. Relative uptakerates of inorganic nutrients by and grown Ricinus communis and by two Plantago species.J. exp. Bot. 37: 419428. The relative rates of uptake and assimilation of C, N, P, S,Cl, K+ , Na+ Ca2+ and Mg2+ by and grown Ricinus conimunisand by NH4NO3- grown Plantago lanceolata and P. major were calculatedfrom data presented elsewhere. Results showed that for grown Ricinus the short term relativeuptake rates, for each nutrient X did not change significantly over the steady-state periodof exponential growth. The average gave , the mean relative uptake rate during exponential growth, for each nutrient. The amountof each nutrient taken up from a nutrient solution over a periodof time could, therefore, be calculated. For and -grown R. communis,the relative uptake rate of each nutrient was a constant fractionof the relative rate of carbon assimilation. It is suggestedthat this is typical of plants of cauline habit. For both Plantago spp., the relative rates of nitrogen uptakeand assimilation fell significantly during the exponential growthphase It is suggested that this could be a characteristic ofthe growth habit of the rosette plant. Key words: Relative uptake rates, Ricinus, Plantago, ammonium, nitrate, cauline, rosette 相似文献
8.
The 13C values for epidermal and mesophyll tissues of two C3plants, Commelina communis and Tulipa gesneriana, and a CAMplant, Kalancho daigremontiana, were measured. The values forthe tissues of both C3 plants were similar. In young leavesof Kalancho, the epidermis and the mesophyll showed S13C valueswhich were nearly identical, and similar to those found in C3plants. However, markedly more negative values for epidermalcompared to mesophyll tissue, were obtained in the mature Kalancholeaf. This is consistent with the facts that the epidermis ina CAM leaf is formed when leaves engage in C3 photosynthesisand that subsequent dark CO2 fixation in guard cells or mesophyllcells makes only a small contribution to total epidermal carbon. (Received January 27, 1981; Accepted May 14, 1981) 相似文献
9.
By analysing the relationship between inverse water potential(1), and relative water content (RWC) measured on leavesof roses (Rosa hybrida cv. Sonia), grown soilless, it was foundthat a non-linear (NL) model was better suited than a linearmodel to reproduce values observed in the non-turgid region.To explain this apparent curvature, it is assumed that a reductionof the non-osmotic water fraction (Ap) takes place when decreases.Osmotic potentials () measured on fresh and frozen leaf discstend to support this hypothesis. A method for exploiting PVcurves, which takes into account the variation of Ap, is described.It delivers values for the turgor pressure (p), the relativeosmotic water content, and the mean bulk volumetric elasticitycoefficient, lower than those given by the linear model. Onthe other hand, it gives higher estimates for Ap and for . Whenapplying the traditional model to obtain estimates for waterrelations characteristics of rose leaves, and comparing resultsfrom two distinct salinity treatments (electrical conductivitiesof 1·8 mS cm1 and 3·8 mS cm1, respectively),one deduces a significant reduction of at turgor-loss in thehigh salinity treatment. The NL method is, in addition, ablesimultaneously to reveal a reduction of and a significant increasein p at RWC=100% this proves that soillessgrown roseplants are able to osmoregulate when subjected to a constantand relatively high degree of salinity. Key words: Apoplastic water, non-linear regression, pressure-volume curves, tissue-water relations 相似文献
10.
Growth and 2, 4-Diaminobutyric Acid Composition of Flatpea (Lathyrus sylvestris L.) as Influenced by Mineral- and Symbiotically Fixed-Nitrogen 总被引:1,自引:0,他引:1
Flatpea (Lathyrus sylvestris L. cv. Lathco) plants,grown hydroponically, were inoculated with rhizobia (Rhizobiumleguminosarum strain 92F2), supplied with nitrate nitrogen (2meq 11), or provided with both rhizobia and . Nodulated plants supplied with had the highest biomass and the highest level of free amino acids in leavesand roots. Nitrogen fixation was depressed 80% in inoculatedplants supplemented with . Compared to plants whose nitrogen requirement was satisfied either partially orfully by , plants that were totally dependent upon biological nitrogen fixation had fewer lateral shoots andlower concentrations of nitrogen, soluble protein, and totalfree amino acids in the shoots, especially in the leaves. Thesymbiotic association between plants and rhizobia for nitrogenfixation was not essential to the production and accumulationof 2,4-diaminobutyric acid (A2bu) and other non-protein aminoacids in flatpea. Levels of A2bu, and most of the other freeamino acids quantified, were significantly lower in the nodulatedplants grown in the absence of than in the inoculated or noninoculated plants supplied with . Arginine and glutamic acid were exceptions in that levels ofthese two amino acids were higher in roots bearing effectivenodules. Plant responses to the different treatments are attributedto the amount of nitrogen available to the plant, rather thanthe method or form of nitrogen supplied. Key words: 2,4-Diaminobutyric acid, Lathyrus, nitrogen 相似文献
11.
Shelp, B. J. 1987. Plant characteristics and nutrient compositionand mobility of broccoli (Brassica oleracea var. italica) suppliedwith NH+4, NO3 or NH4NO3.J. exp. Bot. 38: 16031618. The effects of varying NH+4, NO3 or NH4NO3 concentration onthe final plant characteristics, element composition, and accumulationof NO3-N, NH+4-N and organic-N were evaluated in broccoli (Brassicaoleracea var. italicacv. Futura and Premium Crop) plants culturedin vermiculite under greenhouse conditions supplemented withlight. NH+4-grown plants were stunted and exhibited signs ofmarginal necrosis on the old leaves, accompanied by an accumulationof NH4. The tissue levels of N, P, Mn, Cu, Zn and B were generallyincreased by NH+4 versus NO3 nutrition whereas the reverse wastrue for Ca; Mg and K were only slightly affected, if at all.These results are attributed to: changes in element availabilityresulting from reduced rhizosphere pH due to NH+4uptake ratherthan NO 3uptake; competition of Ca uptake by NH+4; and dilutionof N by increased vegetative growth with NO3-nutrition. Theelement concentrations of N, P or K were similar in all tissueswhereas Ca, B and Mn were markedly less in the florets and youngleaves compared to mature leaves; this supports literature indicatingthat the former elements are phloem-mobile whereas the latterare not. Assuming that the nutrient supply for mature leavesis delivered principally via the xylem stream, the data suggestthat nutrients for developing leaves and florets are suppliedpredominantly in the phloem. If so, under our experimental conditions.Zn and Cu were also readily mobile in the phloem whereas Mgmovement was restricted. NH4+ versus NO4+ J nutrition alteredthe distribution of these elements. The two broccoli cultivarstested under the greenhouse environment differed in NH+4 toleranceand in the distribution of K and Cu suggesting there was a geneticbasis for cultivar variation in mineral acquisition and redistribution. Key words: Plant nutrition, phloem mobility, elemental composition. 相似文献
12.
Effects of light flux density (LFD) during growth and uptakeassay on induction of transport system and kinetics of transport were studied using the Azolla pinnata-Anabaena azollae association (Azolla). Theinduction and uptake kinetics of the transport system were determined using an automated system that measuredthe NO3 concentration in the growth medium as a function oftime, using an on-line high performance liquid chromatograph(HPLC) with a UV-VIS detector. Full induction of the transport system required about 1.5 to 2.0 h and occurred without any apparent lag phase,regardless of the LFD provided. The level of induction of transport of Azolla grown at 600 µmol m2s1 LFD was higher than for that grown at 100 µmolm2 s1. Similarly, 600 µmol m1 s1LFD during the assay resulted in a higher level of inductionthan did 100 umol m2 s1. An increase in the LFDeither during the growth or the assay period increased the uptake rate; however, an increase in LFD duringthe latter period had greater effect. Azolla grown and assayedat 600 umol m2 s1 had the highest uptake rate. The uptake rate at 50 cm3 m3ambient CO2 concentration was initially higher than at 305 cm3m3, but the uptake rate decreased rapidly with time andeventually dropped below that at 305 cm3 m3 CO2. Thesedata suggest that the energy required for transport in Azolla may bypass the photosynthetic CO2 fixationand carbon-cycling. Key words: carbon dioxide, concentration dependence, light flux density, uptake 相似文献
13.
LARQUE-SAAVEDRA A.; RODRIGUEZ M. T.; TREJO C.; NAVA T. 《Journal of experimental botany》1985,36(11):1787-1792
Larqué-Saavedra, A., Rodriguez, M. T., Trejo, C. andNava, T. 1985. Abscisic acid accumulation and water relationsof four cultivars of Phaseolus vulgaris L. under drought.J.exp. Bot 36: 17871792. Plants of four cultivars of Phaseolus vulgaris L. differingin drought resistance were grown in pots under greenhouse conditionsand prior to flowering water was withheld from the pots untilthe mid-day transpiration rate reached values below 1.0 µgH2O cm2 s1 (designated the droughtstage). At this point leaves were harvested on 3 or 4 occasionsover 24 h to determine the abscisic acid (ABA) concentration,total water potential (), solute potential (1) and turgor potential(p). Results showed that values of , 1, and p differed between cultivarswhen they reached the drought stage. The stomatalsensitivity to changes in and p, was as follows: Michoacán12A3 > Negro 150 Cacahuate 72 > Flor de Mayo. These datacorrelated well with the pattern of drought resistance reportedfor the cultivars. ABA accumulation at the drought stage differedbetween cultivars at each sampling time, but overall differencesin ABA level between cultivars were not significant. ABA levelsdid not, therefore, correlate with the drought resistance propertiesreported for the cultivars. Results are discussed in relationto and hour of the day when bean samples were taken for ABAanalysis. Key words: Phaseolus vulgaris L., drought resistance, abscisic acid 相似文献
14.
The effect of growth temperature on the short term influx of86Rb+/K+, 36Cl/Cl, , 45Ca2+/Ca2+and into barley plants (Hordeum vulgareL. cv. Betzes) has been examined. When barley plants were grownwith a differential root: shoot temperature (15 ?C/25 ?C) therewas a marked stimulation of influx of all ions except Ca2+.Q10 measurements were close to 2.0 for all ions except Ca2+,where Q10 1.0 was found. Kinetics of ion influx showed thatthere had been almost complete compensation for the lower growingtemperature over a range of concentrations. The regulation of uptake was affected by growth temperature. On exposure to 15?C efflux/influx fell initially but was restored after 5 d. Sensitivity of net uptake to was increased by growth at a lower temperature. The importance of these observations in relationto application to field experiments and the proposed mechanismfor uptake is discussed. Key words: Growth temperature, Nitrate, Ammonium 相似文献
15.
Fidgeon, C. and Wilson, G. 1988. Uptake and accumulation ofa-naphthalene acetic acid by cell suspensions of Galium mollugoL.J. exp. Bot. 39: 241-249. Galium mollugo cell suspensions require -NAA for continued growthand cell division. The kinetics of -NAA uptake from the medium(B5) by Galium cells was assessed using 1-14C -NAA in a standardratio of cells to medium (0.25 g: 2.5 cm3). It was found thatthe uptake of -NAA was rapid, over 90% being taken up within4 h. Cells which had accumulated -NAA for 4 h or more did notrelease it back into the medium. It was found that Galium cellsaccumulated -NAA against a significant concentration gradient;suggesting the participation of an active component in the uptakemechanism. The effect of free-space and surface adsorption onthe uptake of -NAA was determined by means of a repeated washtechnique. These two factors were found to be of importanceonly during the first hour of uptake. Neither dead cells norplasmolysed cells absorbed -NAA. It is clear that, in the normal growth cycle, Galium cells cantake up the available -NAA within 3 or 4 h of inoculation andthat this can stimulate a cell division response of 3-4 generationsover the subsequent 14 d. Key words: Galium, cell suspension, -naphthalene acetic acid 相似文献
16.
The effects of Cl and pretreatment on 36Clinflux and influx into Characorallina cells were examined. Both treatments reduced 36Clinflux into C. corallina cells in the acid pH range (4.57.0). pretreatment stimulated influx into C. corallina cells, but Cl pretreatment hadno effect. There was a direct inhibitory effect of CI on influx into C. corallina cells, but no apparenteffect on net NO uptake. The time course of 36Cl accumulation into cytoplasmic and vacuolarcompartments during incubation of the cells with showed that significant radioactivity appeared in the vacuolarsap after 30 min. There was a linear increase in the percentageof total 36CI which crossed the tonoplast (c-v). There was noeffect of Cl or pretreatment on accumulation of radioactivity in the vacuole. Thin layer chromatography ofthe vacuolar sap showed that after 2 h only one component waspresent which had an RF which was similar to 36CI. Therate of accumulation of 36C1 in the vacuole could beused to estimate rates of reduction. Key words: Chloride, Chlorate, Chara, Nitrate 相似文献
17.
Charge balance and intracellular pH regulation were studiedin Phaseolus vulgaris grown in water culture on or as N source, or nodulated and in N-free medium. Seedlings and 36-d-old plants were analysed for total P, C, organic N and S and ash alkalinity;xylem sap was analysed for mineral ion content and amino acids,amides and dicarboxylates. Both water uptake and H+ or baseexcreted during water culture were measured. It was shown that in -grown plants, H+ excretedwas related directly to the uptake and assimilation of ; there was no cation uptake associated with netH+ exchange. All shoot N was supplied as organic N, mainly glutamine,so that shoot pH perturbation would be limited to uronate productionin situ. This could be regulated by both shoot reduction and the transport of OH-generating carboxylatesin the xylem. In plants on , the great majority of reduction occurred in the root and most of the OHproduced was converted to -COO, transported up the xylemand stored, so that the leaves in particular had a high ashalkalinity (20-fold that in the roots). Some OH, however,was excreted. Nodulated plants had a low N content, compared with the others,indicating a low rate of N2-fixation for the earlier periodof water culture. At harvest, however, the xylem sap organicN content was comparable to that of plants. H+ excretion was in excess of that required for N assimilation.It was concluded that in these plants some net H+/cation exchangehad occurred which may have been a response to low nutrient(i.e. nitrogen) status. Key words: Phaseolus vulgaris, pH regulation, nitrate nutrition, ammonium nutrition, dinitrogen fixation, xylem sap composition. 相似文献
18.
The Relationship Between Transpiration Rate, Water Potential, and Resistances to Water Movement in Sunflower (Helianthus annuus L.) 总被引:3,自引:0,他引:3
The effects of transpiration rate on the vertical gradientsof leaf and stem xylem water potential ( and ) were examinedusing hydroponic sunflower plants. Transpiration was variedby stepwise alterations of environmental conditions. The gradientsof and were relatively small (2.3 and 0.8 x 105 Pa m1)when transpiration rates approached zero, but increased sharplyto 5.4 and 2.3 x 105 Pa m1 as transpiration increased.However, the gradients were independent of transpiration ratesabove 0.4 g dm2 h1 owing to variability of theplant resistance. The gradients of I were usually less thanhalf those of I. 1 in individual leaves remained constant over a wide range oftranspiration rates (0.42.4 g dm2 h1) andeach leaf possessed a characteristic plateau value related toits elevation. I responded similarly but was approximately 2.0x 105 Pa higher than I at the same elevation. Identical resultswere obtained regardless of the procedure employed to vary transpiration. The drop in water potential between stem and leaf implies thatthe leaf resistance is appreciable. This was confirmed usingrapidly transpiring excised leaves freely supplied with water.I increased by 2.02.5 x 105 Pa following removal of theroot resistance but remained 2 x 105 Pa lower than similar excisedleaves in darkness. Furthermore, I in excised leaves remainedconstant over a wide range of transporting rates, demonstratingthat the leaf resistance is also variable. The results are discussed in relation to previous reports. 相似文献
19.
Diurnal variation in the simultaneous uptake and 'sink' allocation of NH4+ and NO3- by Lolium perenne in flowing solution culture 总被引:2,自引:0,他引:2
Ourry Alain; Macduff James H.; Prudhomme Marie-Pascale; Boucaud Jean 《Journal of experimental botany》1996,47(12):1853-1863
Perennial ryegrass (Lolium perenne L.) was grown in flowingsolution culture under artificial illumination with a 10 h lightperiod. The diurnal fluctuations in the net uptake of and from a 20 mmol m3 NH4NO3 supply were measured (i) fromthe amounts of these ions supplied automatically to maintainconcentrations in solution, and (ii) by 15N pulse-labellingthroughout the diurnal cycle. Diurnal variation in leaf extension,translocation and allocation of assimilated C (14CO2 pulse-labelling)and N (15N pulse and steadystate labelling) were also followed.The apparent sinkstrength of different organsfor recently assimilated C and N was calculated from the concentrationof label recovered in the tissues. Ammonium and showed qualitatively similar diurnal patterns ofnet uptake, with minimum and maximum rates, respectively, atthe start and end of the photoperiod; but uptake showed a proportionately steeper declineduring the dark period. This trend was mirrored by the decreasein translocation of N from roots to shoots during the dark,concurrent with an increase in the relative allocation of -N to expanding leaves and young tillers,and in -N to older expanded leaves. Overall the apparent sink-strength ofexpanding leaves for N declined during the dark period. Pulse-chasesof 14CO2 fed to the youngest fully expanded leaf at the startand end of the photoperiod showed that translocation of 14Cto the roots continued throughout the dark period, but thatthe apparent rate was halved after 9 h of darkness. The resultswere interpreted as contrary to the carbohydrate supplylimitation hypothesis for the dark-related decline inN uptake, but compatible with regulation by sink-strengthfor N. Key words: Nitrate, ammonium, diurnal variation, perennial ryegrass, translocation 相似文献
20.
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