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1.
The euryhaline charophyte Lamprothamnium papulosum (Wallr.)J. Gr. was adapted to media with decreasing salinities rangingfrom 550 to 0 mosmol kg1. Vegetative plants grown inmedia with osmotic pressures (0) in the range of 550 to 130mosmol kg1 maintained a constant turgor pressure () at309 + 7 mosmol kg1. The ions K+, Na+ and Cl, werethe predominant solutes in the vacuole. Changes in their concentrationsaccount for the variation in internal osmotic pressure (1) with,0. The divalent ions Mg2+, Ca2+ and were also present in significant amounts, but their concentrationsdid not alter with changes in, 0. In cells subjected to hypo-osmotic shock the regulation of was incomplete. The turgor pressure increased from 302 to 383mosmol kg1. The first rapid response to the sudden decreasein 0 was a loss of K+ and Cl. In contrast to the decreasein ionic concentrations an accumulation of sucrose occurredwhich could account for the increase of . The increase in sucroseconcentration started 24 to 48 h after the downshock and reachedits highest value after 3 to 4 weeks. The sucrose concentrationin the vacuole was up to 320 mol m3. During this timethe ionic content continued to decrease but did not counterbalancethe sucrose concentration sufficiently to regain the original. High sucrose levels accompanied by an enhanced were also observedduring the period of fructification (sexual reproduction: formationof antheridia and oogonia) in Lamprothamnium kept under conditionsof constant salinity. It is concluded that high sucrose content and elevated arecharacteristic of sexual reproduction in this charophyte. Lamprothamniumis able to tolerate different during various developmentalstages (e.g. vegetative and reproductive phases). Key words: Lamprothamnium papulosum, sucrose, turgor pressure 相似文献
2.
In recent years alternative ways have been proposed to transformmeasurements of leaf water potential, , and relative water content,R*, in order to derive values of osmotic pressure at full turgidityin leaves and shoots, o(when 0). Two types of transformationsare usually considered: 1/ versus R* and versus 1/R*, and linearregression is used to fit the data in the region where turgoris thought to be zero. It appears that when o is estimated bylinear extrapolation of 1/Psi; versus R* then apoplastic watermight not influence the accuracy of o but when the versus \/R*transformation is used apoplastic water causes an underestimateof o. We examine the accuracy of the estimate of o obtainedfrom the two transformations when there are random errors in, systematic errors in , and when the osmotic solutions arenon-ideal. The 1/ versus R* transformation generally producesthe best estimate of 0 by linear extrapolation. 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.
Smith, J. R. 1987. Potassium transport across the membranesof Chara. II. 42K fluxes and the electrical current as a functionof membrane voltage.J. exp. Bot. 38: 752777. The current required to clamp the trans-membrane voltage ofinternodal cells of Chara australis at different levels wasmeasured simultaneously with either the 42K influx or efflux.Examination of the voltage-dependence of the ratio of the electricalcurrent to the unidirectional tracer fluxes yielded no evidenceof any amplification of the electrical driving force on theK+ ions. There was thus no evidence for the interaction of K+ions with themselves or any other species during their passageacross the membrane. These measurements allow the determinationof , the fraction of the electrical current carried by K+ ions.When the external [K+] = 10 mol m3, the average valueof was 0?85 for Vm > 125 mV and 07?5 for Vm <150 mV. When the external [K+] = 0?1 mol m3, was 0?6 for Vm < 80 mV and 0?1 for Vm > 250mV. It was also found that the conductance associated with K+transport was inhibited by hyperpolarization. Key words: Potassium, conductance, flux-ratio 相似文献
5.
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
6.
Nitrate Uptake and Assimilation following Nitrate Deprivation 总被引:2,自引:0,他引:2
Upon first exposure to , the uptake and reduction capacities of dark-grown corn (Zea maysL.) roots are initially low, but increase markedly within 6h. The development of the accelerated uptake rate appears to be substrate induced as is reductase (NR), the first enzyme in the assimilatory pathway. However, the inductionof uptake is independent of NR induction. The effect of deprivation was studied to determine the role of endogenous on subsequent uptake and reduction. Corn roots were induced for 24 h in 05 mol m3 nutrient solution and then exposed for 0 to 32 h to -free nutrient solution. Uptake and reduction of were determined periodically by exposing sets of roots to a1 h pulse of 0.5 mol m3 . Neither uptake (4.57 µmol root1 h1)nor the percentage of absorbed reduced (27%) was changed significantly (P 0.05) by exogenous deprivation. However, the estimated induced componentof uptake decreased significantly (50% after 32 h). Concurrently, the non-induced basal componentof uptake increased. Previously accumulated decreased from 23 to 4.5 µmol root1 after 32 h of exogenous deprivation. Nearly equivalent quantities of endogenous were used for translocation and reduction during deprivation. During each 1 h pulse, the amounts of translocation and net efflux of to the uptake solution were similar. Net efflux of was strongly correlated (r = 0.991) to the amount of endogenous . The remaining endogenous and its rate of utilization were apparently sufficient to minimize a rapid declineor complete loss in both the induced uptake state and the rate of in vivo assimilation. Key words: reduction, translocation, efflux, root, Zea mays L 相似文献
7.
Lucas, W. J. and Ogata, K. 1985. Hydroxyl and bicarbonateassociatedtransport processes in Chara corallintr. Studies on the lightdarkregulation mechanism.J. exp. Bot. 36: 19471958.Experiments were undertaken on the fresh water alga Chara corallinato investigate the nature of the coupling between the chloroplastsand the lightdependent OH and -associated plasmalemma transport systems. Electrophysiologicalexperiments, in which DCMU was employed, revealed that thischemical could elicit a hyperpolarization of the membrane potentialthat was identical to that normally obtained by turning offthe light. This DCMUinduced hyperpolarization was obtainedunder control () and phosphatedecoupled conditions (). Measurements of the extracellular electric potentialswhich are associated with the acidic () and alkaline (OH) regions, indicated that, in the presenceof control ()or phosphatedecoupled conditions, normal profiles were established under air, oxygenor nitrogen environments. These results indicate that the generationof the control signal(s) is related to events associated withchloroplast electron transport, rather than to changes in theflow or levels of carbon intermediates within the reductivepentose phosphate or photorespiratory cycles. Although the levelof oxygen was found to have no effect on the lightinducedactivation of the OH regions, we found that in pure oxygen thedarkinduced inactivation of the OH efflux systemwas delayed, and that partial transport function could be maintainedin the dark. The possible involvement of changes in either theratio of oxidized to reduced ferridoxin or NADP? to NADPH, aspart of this lightmediated control signal, is discussed. Key words: Chara corallina, Plasma membrance transport, OH and , regulation 相似文献
8.
TOLLEY-HENRY LESLIE; RAPER C. DAVID JR.; GRANATO TOM C. 《Journal of experimental botany》1988,39(5):613-622
Net uptake of by non-nodulated soybean plants [Glycine max (L.) Merr.cv. Ransom] growing in flowing hydroponiccultures containing 05, 1.0 and 10-0 mol m3 was measured daily during a 24-d period of vegetativedevelopment to determine if amplitude of maximum and minimumrates of net uptake are responsive to external concentrations of . Removal of from the replenished solutions during each 24-h period was determinedby ion chromatography. Neither dry matter accumulation nor theperiodicity of oscillations in net uptakerate was altered bythe external concentrations. The maxima of the oscillations in net uptake rate, however, increased nearly3-fold in response to external concentrations. The maxima and minima, respectively, changed from 4.0 and 06mmol per gram root dry weight per day at an external solution level of 05 mol m3 to 152and -27 mmol per gram root dry weight per day at an external solution level of 100mol m3 . The negative values for minimum net uptake rate from100 mol m3 solutions show that net efflux was occurring andindicate thatthe magnitude of the efflux component of net uptake was responsiveto external concentration of . Key words: Nitrate uptake rate, carbon-nitrogen partitioning, flowing solution culture 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.
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
11.
Expression of Characteristics of Ammonium Nutrition as Affected by pH of the Root Medium 总被引:6,自引:1,他引:5
CHAILLOU S.; VESSEY J. K.; MOROT-GAUDRY J. F.; RAPER C. D. JR; HENRY L. T.; BOUTIN J. P 《Journal of experimental botany》1991,42(2):189-196
To study the effect of root-zone pH on characteristic responsesof -fed plants, soybeans (Glycine max {L.}Merr. cv. Ransom) were grown in flowing solution culture for21 d on four sources of N (1.0 mol m3 , 0.67 mol m3 plus 0.33 mol m3, 0.33 mol m3 plus 0.67 mol m3 , and 1.0 mol m3) with nutrient solutions maintained at pH 6.0, 5.5, 5.0, and 4.5. Amino acid concentration increased inplants grown with as the sole source of N at all pH levels. Total amino acid concentration in the rootsof -fed plants was 8 to 10 times higher than in -fed plants, with asparagine accounting for more than 70% of the total in the roots of these plants.The concentration of soluble carbohydrates in the leaves of-fed plants was greater than that of -fed plants, but was lower in roots of -fed plants, regardless of pH. Starch concentration was only slightlyaffected by N source or root-zone pH. At all levels of pH tested,organic acid concentration in leaves was much lower when was the sole N source than when all or part of theN was supplied as . Plants grown with mixed plus N sources were generally intermediate between - and -fed plants. Thus, changes in tissue compositioncharacteristic of nutrition when root-zone pH was maintained at 4.5 and growth was reduced, still occurredwhen pH was maintained at 5.0 or above, where growth was notaffected. The changes were slightly greater at pH 4.5 than athigher pH levels. Key words: Ammonium, nitrogen nutrition, root-zone pH, soybean, tissue composition 相似文献
12.
Nitrate Transport Characteristics in Hordeum vulgare L. Seedlings using Three Different Tracer Techniques 总被引:2,自引:0,他引:2
Deane-Drummond, C. E. and Thayer, J.R. 1986. Nitrate transportcharacteristics in Hordeum vulgare L. seedlings using threedifferent tracer techniques.J. exp. Bot. 37: 429439. and have been used to investigate various properties of nitrate uptake and translocation intoHordeum vulgare L seedlings. Short term / influx into seed lings grown in CaSO4 was stimulated by after a lag of 2 h. The apparent kinetics of shortterm / influx over the concentration range 0?00?7mol m fitted Michaelis-Menten equations The apparent Vmax didnot change when seedlings were used that had been pretreatedin 10 or 100 mmol m3 and Vmax=3.77 and 3?56µmol g1 fr. wt. h1respectively. The apparent Michaelis constants were also similarand Km=0?47 and 0?45 mol m3 respectively. Longer term pulse chase experiments with the heavy isotope 15Nhave shown that feeding roots with resulted in the preferential appearance of 15N labelled aminoacids in the xylem sap. Pulse chase experiments with the radioisotope13N have shown that feeding shoots with resulted in a radial pattern of distnbution of labelin the leaf veins, which can be detected using autoradiography. The limitations and advantages of all three techniques are comparedby reference to other known experimental data. Key words: 36Chlorate, 13nitrate, 15nitrate, Hordeum vulgare 相似文献
13.
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
14.
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
15.
SKIERCZYNSKA J.; ZAREBSKI W.; SIELEWIESIUK J.; SPIEWLA E. 《Journal of experimental botany》1977,28(1):37-55
Measurements of tonoplast resistance for unit area, T were carriedout by four methods. The T values obtained by two of these methods,when taking into account a correction for leakage current, were0.024 and 0.010 k cm2. The other two methods, which made itpossible to neglect leakage current, gave the T values of 0.036and 0.021 k cm2. Thus, the mean value of tonoplast resistancein the investigated cells of Nitellopsis obtusa was 0.023 kcm2, while the measurements in which leakage current was nottaken into account gave the value 10.6 k cm2. The results obtainedin this study indicate the fact that leakage current significantlyaffects measurements of tonoplast resistance and that the truevalue of that resistance is smaller by two or three orders ofmagnitude than that usually reported. 相似文献
16.
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
17.
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
18.
Germination-rate dependency on temperature in the sub-optimalrange and its spread in a seed population of Geranium carolinianumL. were analysed through a detailed time course study. Withand without Arrhenius transformation the relationship betweenthe germination rate and temperature could be well approximatedby straight lines. The thermal time (), one of the parameterscharacterizing the simple linear relationship had a distributionwithin the seed population, which could be described by thefollowing distribution function: F()= l[Am+ (A/3) )3 + 1) ? where m is the median of the distribution and A is a shape parametercharacterizing the pattern of the distribution. Moist chillingtreatment for 37 d caused a change in the value for Ato make the spread of germination time much wider. Key words: Germination rate, Temperature, Geranium caroliniantun 相似文献
19.
The quantitatively major nonasaccharide (XG9) derived from xyloglucanby digestion with cellulase exhibits anti-auxin activity inthe pea stem segment straight-growth bioassay; the most effectiveconcentration of XG9 is c. 109 M. Previous work had shownthat XG9 owes its biological activity to the presence of a terminal-L-fucopyranose residue. In order to investigate to what extentthe remainder of the XG9 molecule is essential for activity,several fucose-containing compounds were tested for their abilityto mimic the anti-auxin effect of XG9. A fucose-containing pentasaccharideof xyloglucan (XG5; probable structure FucGalXylGlcGlc) was,at 108 M, about as effective an anti-auxin as 109M XG9; unlike XG9, XG5 did not diminish in effectiveness at107 M. The human milk trisaccharide, 2'-fucosyl-lactose[L-fucopyranosyl--(12)-D-galactopyranosyl-ß-(14)-D-glucose],whose FucGal unit is identical with that of XG9, inhibited auxin-inducedelongation over a wide range of concentrations centred on about108 M. 2'-Fucosyl-lactose at 108 M was about aseffective an anti-auxin as 109 M XG9. Free L-fucose andmethyl--L-fucopyranoside were unable to inhibit auxin-inducedgrowth at any concentration tested (1010 M to 106M) and neither compound interfered with the inhibition causedby 109 M XG9 when co-incubated at concentrations up to104 M. The results confirm the essential r?le of an -linkedterminal fucose residue in the anti-auxin activity of XG9 andshow that the sub-terminal galactose residue may also be required.Possible reasons why high concentrations of XG9 fail to antagonizeauxin-induced growth while high concentrations of XG5 and 2'-fucosyl-lactosecontinue to do so are discussed. Key words: Anti-auxin, oligosaccharin, fucose 相似文献
20.
The rate of exponential growth of Amphidinium carterae Hulburtwas the same (0.025 h1) with either or as sole N-source. Nevertheless, in short-term experiments, cells growing exponentially with as N-source took up added 56 times faster than . accumulated in the cells. Addition of inhibited, reversibly, disappearance of from the medium; prior N-deprivation of the cells did not affect this inhibition. N-repIetecells, grown with as N-source, took up for several hours both in light and darkness, butthe uptake by such cells soon ceased in darkness although it continued in light. When uptake ceased, the cells could still take up rapidly in darkness. Ammonium taken up was assimilated rapidly into organic-N includingglutamine, other amino acids and protein. Ammonium uptake in darkness was accompanied by the utilizationof cellular polysaccharide, mainly glucose polysaccharide. Mostof this carbon was unavailable for the dark assimilation of. Addition of the analogue, methylammonium, did not initiate polysacchande catabolism. Itis suggested that a control mechanism is in operation, througha product of assimilation, which operates on one or more of the enzymes concerned with polysaccharidebreakdown, for example, -amylase or phosphorylase. Uptake of was accompanied by a high rate of dark 14CO2 fixation and with both Amphidintum klebsii Kof.et Swezy and A. carterae N-deprivation led to a marked increasein this rate following addition of ; addition of had much less effect. The possible implications of these findings for the eco-physiology of marine dinoflagellatesare discussed. Key words: Ammonium, nitrate, CO2 fixation 相似文献