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1.
Macduff, J. H., Hopper, M. J. and Wild, A. 1987. The effectof root temperature on growth and uptake of ammonium and nitrateby Brassica napus L. CV. Bien venu in flowing solution culture.II. Uptake from solutions containing NH4NO3.J. exp. Bot.38: 5366 The effects of root temperature on uptake and assimilation ofNH4+ and NO3 by oilseed rape (Brassica napus L. CV. Bienvenu) were examined. Plants were grown for 49 d in flowing nutrientsolution at pH 6?0 with root temperature decrementally reducedfrom 20?C to 5?C; and then exposed to different root temperatures(3, 5, 7, 9, 11, 13, 17 or 25?C) held constant for 14 d. Theair temperature was 20/15?C day/night and nitrogen was suppliedautomatically to maintain 10 mmol m3 NH4NO3 in solution.Total uptake of nitrogen over 14 d increased threefold between313?C but was constant above 13?C. Net uptake of NH4+exceeded that of NO3 at all temperatures except 17?C,and represented 4765% of the total uptake of nitrogen.Unit absorption rates of NH4+ and of 1?52?7 for NO3suggested that NO3 absorption was more sensitive thanNH4+ absorption to temperature. Rates of absorption were relativelystable at 3?C and 5?C compared with those at 17?C and 25?C whichincreased sharply after 10 d. Tissue concentration of N in theshoot, expressed on a fresh weight basis, was independent ofroot temperature throughout, but doubled between 325?Cwhen expressed on a dry weight basis. The apparent proportionof net uptake of NO3 that was assimilated was inverselyrelated to root temperature. The results are used to examinethe relation between unit absorption rate adn shoot:root ratioin the context of short and long term responses to change ofroot temperature Key words: Brassica napus, oilseed rape, root temperature, nitrogen uptake 相似文献
2.
KEYS A. J.; SAMPAIO E. V. S. B.; CORNELIUS M. J.; BIRD I. F. 《Journal of experimental botany》1977,28(3):525-533
Wheat plants were grown in a controlled environment with daytemperatures of 18 ?C and with 500 µ Einsteins m281 of photosynthetically active radiation for 16 h. Beforeanthesis and 2 to 3 weeks after, rates of net photosynthesiswere measured for leaves in 2 or 21% O2 containing 350 vpm CO2at 13, 18, 23, and 28 ?C and with 500 µEinsteins m2s1 of photosynthetically active radiation. Also, underthe same conditions of light intensity and temperature, therates of efflux of CO2 into CO2-free air were measured and,for mature flag leaves 3 to 4 weeks after anthesis, gross andnet photosynthesis from air containing 320 vpm 14CO2 of specificactivity 39?7 nCi µmol1. When the O2 concentration was decreased from 21 to 2% (v/v)the rate of net photosynthesis increased by 32 per cent at thelowest temperature and 54 per cent at the highest temperature.Efflux of CO2 into CO2-free air ranged from 38 per cent of netphotosynthesis at 13 ?C to 86 per cent at 28 ?C. Gross photosynthesis,measured by the 14C assimilated during 40 s, was greater thannet photosynthesis by some 10 per cent at 13 ?C and 17 per centat 28 ?C. These data indicate that photorespiration was relativelygreater at higher temperatures. 相似文献
3.
FARADAY CHRISTOPHER D.; QUINTON PAUL M.; THOMSON WILLIAM W. 《Journal of experimental botany》1986,37(4):482-494
Faraday, C. D., Quinton, P. M. and Thomson, W. W. 1986. Ionfluxes across the transfusion zone of secreting Limonium saltglands determined from secretion rates, transfusion zone areasand plasmodesmatal frequencies.J. exp. Bot. 37: 482494. The epidermal salt-secreting glands of Limonium (Plumbaginaceae)are enclosed in a cuticular envelope. Ions and metabolites enterthe glands from the mesophyll through gaps in the cuticularenvelope, the transfusion zones. Net influxes of ions acrossthe transfusion zone were calculated from measurements of secretionrates and transfusion zone areas. When leaves of L. pereziiF. T. Hubb. were treated with 300 mol m3 NaCl, transfusionzone influxes of Na+ K+, Ca++ and Cl as high as 7?0?105,1.7?105, 5?8?107 and 8.5?105 mol m2s1 respectively, were calculated. Assuming a transmembranepathway, these fluxes would be some of the highest reportedfor ions in plant cells. Key words: Salt glands, ion fluxes, ultrastructure 相似文献
4.
Cytoplasmic pH (pHc) in Chara corallina was measured (from [14C]stribution)as a function of external pH (pH0)and temperature. With pH0near 7, pHc at 25?C is 7.80; pHcincreases by 0.005 pH units?C1 temperature decrease, i.e. pHc at 5 ?C is 7.90. WithpH? near 5.5, the increase in pHc with decreasing temperatureis 0.015 units ?C1 between 25 and 15?C, but 0.005 units?C1 between 15 and 5?C. This implies a more precise regulationof pHc with variations in pHo at 5 or 15 ?C compared with 25?C. The observed dp Hc/dT is generally smaller than the 0.017units ?C1 needed to maintain a constant H+/OH1,or a constant fractional ionization of histidine in protein,with variation in temperature. It is closer to that needed tomaintain the fractional ionization of phosphorylated compoundsor of CO2HCO3 The value of dpHc/dT has importantimplications for several regulatory aspects of cell metabolism.These include (all as a function of temperature) the rates ofenzyme reactions, the H+ at the plasmalemma(and hence the energy available for cotransport processes),and the mechanism for pHc regulation by the control of bidirectionalH+ fluxes at the plasmalemma. 相似文献
5.
In azuki bean (Azukia angularis = Vignia angularis) epicotylsections, 5 ? 104 M coumarin inhibited the incorporationof radioactivity from [U14C]glucose into the cellulosefraction by 35% in the absence of indole-3-acetic acid (IAA)and by 40% in the presence of 1 ? 104 M IAA. There wasno inhibitory effect on the incorporation of radioactivity intothe other fractions. Coumarin at 5 ? 104 M reversed thepromoting effect of 1 ? 105 M gibberellin A3 (GA) andthe inhibitory effect of 1 ? 105 M kinetin on IAA-inducedelongation of sections with no significant effects on IAA-inducedelongation. Neither GA nor kinetin had any appreciable effectson cellulose synthesis. No inhibition of cellulose syntheiswas observed with 1 ? 103 M colchichine, which has beenreported to have effects similar to those of coumarin on GA-or kinetin-affected stem elongation. Coumarin at 5 ? 104M was ineffectual in breaking up wall microtubules, while adisrupting effect on wall microtubules was clearly demonstratedwith 3 ? 104M colchicine. From these results, the possible involvement of cellulose synthesisin cell expansion controlled by GA or kinetin was suggested. (Received August 3, 1973; ) 相似文献
6.
Barley plants (Hordewn vulgare L. cv. Atem) were grown fromseed for 28 d in flowing solution culture, during which timeroot temperature was lowered decrementally to 5?C. Plants werethen subjected to root temperatures of 3, 5, 7, 9, 11, 13, 17or 25 ?C, with common air temperature of 25/15 ?C (day/night).Changes in growth, plant total N, and NO3 levels, andnet uptake of NH4+ and NO3 from a maintained concentrationof 10 mmol m3 NH4NO3 were measured over 14 d. Dry matterproduction increased 6-fold with increasing root temperaturebetween 325 ?C. The growth response was biphasic followingan increase in root temperature. Phase I, lasting about 5 d,was characterized by high root specific growth rates relativeto those of the shoot, particularly on a fresh weight basis.During Phase I the shoot dry weight specific growth rates wereinversely related to root temperature between 313 ?C.Phase 2, from 514 d, was characterized by the approachtowards, and/or attainment of, balanced exponential growth betweenshoots and roots. Concentrations of total N in plant dry matterincreased with root temperature between 325 ?C, moreso in the shoots than roots and most acutely in the youngestfully expanded leaf (2?l6?9% N). When N contents wereexpressed on a tissue fresh weight basis the variation withtemperature lessened and the highest concentration in the shootwas at 11 ?C. Uptake of N increased with root temperature, andat all temperatures uptake of NH4+, exceeded that of NO3,irrespective of time. The proportions of total N uptake over14 d absorbed in the form of NH4+ were (%): 86, 91, 75, 77,76, 73, 77, and 80, respectively, at 3, 5, 7, 9, Il, 13, 17,and 25 ?C. At all temperatures the preference for NH4+ overNO3 uptake increased with time. An inverse relationshipbetween root temperature (311 ?C) and the uptake of NH4+as a proportion of total N uptake was apparent during PhaseI. The possible mechanisms by which root temperature limitsgrowth and influences N uptake are discussed. Key words: Hordeum vulgare, root temperature, ammonium, nitrate, ion uptake, growth rate 相似文献
7.
The Uptake of Gaseous Ammonia by the Leaves of Italian Ryegrass 总被引:5,自引:0,他引:5
Lockyer, D. R. and Whitehead, D. C. 1986. The uptake of gaseousammonia by the leaves of Italian ryegrass.J. exp. Bot.37: 919927. Plants of Italian ryegrass (Lolium multiflorum Lam.) grown insoil with two rates of added 15N-labelled nitrate were exposed,in chambers, for 40 d to NH3 in the air at concentrations of16, 118 and 520 µg m3. At the highest concentrationof NH3, this source provided 47?3% of the total nitrogen inplants grown with the lower rate of nitrate addition (100mgN kg1 dry soil) and 35?2% with the higher rate (200mgN kg1 dry soil) At the intermediate concentration ofNH3, the contributions to total plant N were 19?6% and 10?8%,respectively, at low and high nitrate while, at the lowest concentrationof NH3, they were 5?1% and 32%. Most of the N derived from theNH3 remained in the leaves, but some was transported to theroots. The amount of N derived from the NH3 that was presentin the leaves was not reduced by washing the leaves in waterat pH 5?0 before harvesting, indicating that the N was assimilatedby the plant and not adsorbed superficially. Rates of uptakeof NH3 per unit leaf area ranged from 1?7 µg dm2h1 at a concentration of 16 µg m3 to 29?0µg dm2 h1 at a concentration of 520 µgm3 and with the lower rate of nitrate addition. Increasingthe supply of nitrate to the roots slightly reduced the rateof uptake of NH3 per unit leaf area. Uptake of N from the higherrate of nitrate was reduced at the highest concentration ofNH3 in the air. Key words: Ammonia, nitrogen, leaf sorption, Lolium multiflorum 相似文献
8.
Root Hydraulic Conductivity of Two Cactus Species in Relation to Root Age, Temperature, and Soil Water Status 总被引:6,自引:1,他引:5
The effects of root age, temperature, and soil water statuson root hydraulic conductivity (LP) were investigated for twocactus species, Ferocactus acanthodes and Opuntia ficus-indica.The volumetric flux density of water was measured for excisedroot segments, either using negative hydrostatic pressures appliedto the proximal end or using reverse flow of water from theroot to the soil. For both species, LP at 20 ?C increased withroot age, average values reaching a maximum of 3.9 ? 107m s1 MPa1 for F. acanthodes and 5.2 ? 107m s1 MPa1 for O.ficus-indica at 11 to 17 weeksof age; LP subsequently declined with increasing root age forboth species. LP was maximal at a temperature of about 10 ?Cfor the youngest roots (13 weeks), this optimum shiftingto 40 ?C for 8-week-old roots of both species. For older roots(up to 1.5-years-old), LP increased with temperature from 0?C to 50 ?C, with a Q10 of 1.3 between 20 ?C and 30 ?C. At asoil water potential (soil) of 0.016 MPa, root LP wasindependent of the direction of water flow for both species.Depending on root age, LP declined 45- to 500-fold for F. acanthodesand 90- to 800-fold for O.ficus-indica as soil was reduced from0.016 to 1.06 MPa, consistent with a rectifier-likebehaviour with respect to water movement between soil and roots.Incorporation of such responses into water uptake models shouldlead to a better understanding of root function. Key words: Ferocactus acanthodes, Opuntia ficus-indica, water potential, tension, reverse flow 相似文献
9.
Measurements of K+, Na+, and Cl were made on a halotolerantstrain of Dunaliella growing at 500 mM NaCl, 25 ?C, and a relativelylow light intensity (6000 Lx). Much effort was spent in searchingfor a means of measuring the extracellular volume of fluid trappedbetween the cells of centrifuged pellets. All of the sugarstried as markers were rejected because they were found to bedigested in the cell suspension. The most suitable marker wasfound to be [14C]polyethylene glycol2 (mol. wt. 4000); althoughthis substance was apparently adsorbed to the cell exterior,it was found possible to correct for adsorption and then obtaina reasonable figure for the trapped fluid. The final concentrationsof cell K+ and Na+ were 128 ? 53 mM and 131 ? 117 mM respectively.Cl balanced the sum of K+ Na+. Influxes of 22Na+, 42K+,and 36C1 were measured in cells in which the ions werein the steady state. Averages of 610 and 6.6 nmol m2s1 were obtained for Na+ and K+ respectively. Clinflux was divided into 2 phases with values of 1540 and 178mmol m2 s1. The faster influx was considered tobe across the outer cell membrane. The membrane responsiblefor the slower influx has not been identified. By comparingvalues of the potential difference calculated from the Nernstand Goldman equations, it was concluded that Na+ and K+ areprobably controlled by active mechanisms, whereas cell Clis likely to be at thermodynamic equilibrium with the medium. 相似文献
10.
In disbudded epicotyl cuttings taken from light grown 5-dayold Azukia angularis Phaseolus angularis) seedlings, all adventitiousrootlets appeared on the second day of incubation. No root primordiawere observed within the first 24 hr and no increase in thenumber of roots occurred after 48 hr. Puromycin (5.5?105M), p-fluorophenylalanine (1?103M),2-thiouracil (2.3?104M) and 2,6-diaminopurine (2?105M)inhibited rooting when applied to cuttings on the second day,but showed no inhibition when applied on the first day. Unlike these inhibitors, pyrithiamine (7.2?105M) inhibitedrooting when it was applied to cuttings on the first day. A rooting promoting effect was observed with actinomycin D (2.4?106M),2,4-dinitrophenol (3?105M) and p-fluorophenylalanine(1?104M) applied to the cuttings on the first day, whereasindoleacetic acid (1.7?104M) showed its promoting effectmost effectively on the second day.
1Contribution No. 17 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo, Japan. (Received June 4, 1969; ) 相似文献
11.
The changes in morphology of the unicellular algae Cylindrocystisbrebissonii and two species of Micrasterias during freezingand thawing were observed on a light microscope fitted witha temperature controlled stage. At slow rates of cooling extensiveshrinkage of the protoplast was observed. The response of thecell wall varied with cell-type. In C. brebissonii plasmolysiswas not observed and the cell wall and protoplast shrank together.In Micrasterias the cell wall did not contract and a distinctplasmolysis was observed. Following freezing to and thawingfrom 25?C cells of C. brebissonii were non-viable butremained osmotically responsive. Cooling at faster rates inducedintracellular ice formation in all cell-types. The criticalrate of cooling varied with cell-type and was determined bycell volume and suface area. Intracellular gas bubbles wereobserved during thawing following both rapid and slow cooling. Following cooling in dimethylsulphoxide cells of C. brebissoniiwere protected against freezing injury. The recovery on thawingfrom 196?C being determined by the rate of cooling, anoptimum rate of 1?C min1 was observed. During slow ratesof cooling (<2?C min1) cells remained unshrunken,at faster rates (10?C min1) the loss of cell viabilitywas related to osmotic shrinkage during cooling rather thanto nucleation of intracellular ice. Intracellular ice formationwas observed only following significantly faster rates of cooling(>20?C min1). Key words: Cylindrocystis, Micrasterias, cryomicroscopy, freezing injury 相似文献
12.
Internal Factors Regulating Nitrate and Chloride Influx in Plant Cells 总被引:14,自引:0,他引:14
The primary factor determining the observed decrease in activeC1 influx during salt accumulation in carrot and barleyroot cells has been shown to be the concentration of C1+ NO3 in the vacuole. The relationship between C1 influx and the vacuolar concentrationsof various substances was examined after the tissues had accumulatedions from various salt solutions. After accumulating K+ malate,C1 influx was not reduced, but after accumulating C1or NO3 salts, C1 influx was reduced by up to 90per cent. Considering all treatments, C1 influx was notcorrelated with the vacuolar concentration of K+, Na+, (K++Na+),reducing sugars, malate, C1, or NO3, nor withthe cellular osmotic pressure. The correlation coefficient betweenCl influx and log (C1 + NO3 concentrationin the vacuole) was highly significant, and accounted for allthe variation in C1 influx in this experiment. Net NO3 influx is similarly reduced by a high C1concentration in the vacuole. External Cl and NO3have quantitatively different, apparently competitive, effectson C1 influx. These differ from the apparently negative-feedbackeffects of C1 and NO3 in the vacuole, which arequantitatively similar. Decreasing the internal hydrostatic pressure by raising theexternal osmotic pressure increased active K+ influx in Valoniaventricosa, but had no effect on C1 or K+ influx in carrotor maize root cells. Cl influx is not related to thereducing sugar concentration during ageing drifts in excisedcarrot root tissue. Acetazolamide did not inhibit C1 influx to carrot tissue. The implications of this type of negative feedback regulation,and the relationship between C1 and NO3 transportare discussed. 相似文献
13.
Induction and Growth of 'Microspore-Derived' Embryos of Brassica napus ssp. oleifera 总被引:2,自引:0,他引:2
DUNWELL J. M.; CORNISH M.; DE COURCEL A. G. L.; MIDDLEFELL-WILLIAMS J. E. 《Journal of experimental botany》1983,34(12):1768-1778
Three cultivars of spring rape (Brassica napus ssp. oleifera),Tower, Willi and Duplo, were used for a study of induction andgrowth of microspore-derived embryos, Buds, 2.0mm in length, containing uninucleate microspores were harvestedand stored for 14 d at 4 ?C in darkness. Anthers were then removedand cultured on a liquid medium based upon that of Murashigeand Skoog and containing 8% sucrose, 0.5 mg l1 naphthylaceticacid and 0.05 mg l1 benzylaminopurine. Cultures werepre-incubated at 35 ?C for 03 d and then incubated at30 ?C. After a total of 42 d incubation, cultures were scoredfor the presence of macroscopic embryos (12 mm in length)and for the presence of anthers containing abortive embryoidswhich had not developed further. The cultivars differed greatly in terms both of the frequencyof anthers showing induced embryoids and of the final yieldof embryos. Tower showed the highest frequency of induction(maximum 38% of cultured anthers with induced embryoids) whereasthe highest yield (equivalent to 1.1 embryo per cultured anther)was obtained from anthers of the cv. Duplo after a 3 d treatmentat 35 ?C. Yields from the other cultivars were much lower andwere relatively unaffected by the 35 ?C treatment. Key words: Brassica napus, Rape, Anther culture, Pollen, Haploid 相似文献
14.
Variable fluorescence (Fv) of intact leaves was measured whenthe temperature was lowered at a rate of 12?C per mn,from 20?C to 20?C. The quantum flux density of the excitinglight was 12 µE m2 sec1 in orderto sensitize F only at 20?C. The fluorescence yield decreasedrapidly at the freezing point of the leaf and upon further coolingthe fluorescence yield increased again. Fm was obtained a fewdegrees below the freezing point. Repeated freeze-thaw cycles caused successively increased damageto the thylakoid membranes on either the oxidizing or the reducingside of photosystem II. An eventual loss of Fv over Fo was typicalfor damage on the water splitting side of photosystem II, whereasdamage after the primary electron acceptor Q of photosystemII was characterized by an invariable fluorescence yield atFm over the temperature range examined. (Received January 18, 1982; Accepted June 12, 1982) 相似文献
15.
The effects of a number of growth-promoting and growth-inhibitingsubstances, including two fungal toxins, were studied on theextension of segments of etiolated tomato seedling hypocotyls.The bioassay was sensitive to small quantities of NaF, coumarinand 2, 4-DNP and inhibition was observed at all concentrations.2, 4-DNP or Iodoacetate stimulated growth at concentrationsbetween 1? 104 and 5 ? 106M. or 1 ? 106and 1 ? 107M. respectively. Inhibitor experiments inbuffered nutrient solution were approximately 10 per cent. moresensitive than those in deionized water. By means of paper partition chromatography small quantitiesof two fungal toxins, fusaric and alternaric acid were chromatographedand bioassayed. The effect of fussric acid (5, n-butyI picolinicacid) on hypocoty1 growth was detected at concentrations aslow as 1 ? 105M. Experiments with recongnized growth-promoting substances showedthat Kinetin inhibited growth at concentrations up to 1 ?108M.in both light and dark. IAA inhibited growth up to 1 ? 106M.At 1 ? 107 and 1 ? 108 only small increases occurredwith IAA and the effect of light was negligible. Gibberellicacid (GA2)stimulated growth at concentrations from 103to 107M. and significant increases up to 17 per cent.were recorded in the light. Since the light induced inhibitionwas only partly restored, the existence of some other naturallight sensitive growth substance is suggested. The value ofthe bioassay as a method for estimating natural growth-inhibitingand growth-promoting substances is discussed. 相似文献
16.
Effects of cooling and rewarming rates on the survival of carnationshoot apices frozen to the temperature of liquid nitrogen wereinvestigated. Ten percent dimethyl sulfoxide (DMSO), alone orin combination with 5% glucose, sucrose or sorbitol was mosteffective as a cryoprotectant for carnation shoot apices. Theshoot apices survived slow freezing at about 70?C inthe presence of 10% DMSO. About 80% of the shoot apices survivedfreezing at the temperature of liquid nitrogen after prefreezingat 50?C or below, regardless of the rewarming rates.Shoot apices in the presence of 10% DMSO were cooled at differentrates then rewarmed rapidly. The survival rate gradually decreasedto zero as the cooling rate increased from about 0.5?C/min to50?C/min. At cooling rates higher than 50?C/min, no survivalwas observed even at 5?104?C/min. However, in apices prefrozenat 15?C or below then cooled ultrarapidly at 104?C/min,all remained alive with subsequent rapid rewarming. These apicesdeveloped normal young plants. This ultrarapid cooling methodcombined with prefreezing seems to be useful for the cryopreservationof shoot apices from various plants.
1Contribution No. 2207 from the Institute of Low TemperatureScience, Hokkaido University. This work was supported in partby a Grant-in-Aid (No. 434035) for Scientific Research fromthe Ministry of Education, Science and Culture. (Received November 13, 1979; ) 相似文献
17.
Acclimation of NO3 transport fluxes (influx, efflux)in roots of oilseed rape (Brassica napus L. cv. Bien venu) andtheir sensitivity to growth at low root temperature was studiedin relation to external NO3 supply, defined by constantconcentrations ranging from sub- to supra-optimal with respectto plant growth rate. Plants were grown from seed in flowingnutrient solutions containing 250 mmol m3 NO3at 17°C for 20d, and solution temperature in half the cultureunits was then lowered decrementally over 3 d to 7°C. Threedays later plants were supplied with NO3 at 1, 10, 100or 1000 mmol m3 maintained for 18 d. Dry matter productionwas decreased more by low root zone temperature than low [NO3]e. Root specific growth rates were inversely related to [NO3]eand shoot:root ratios increased with time at [NO3]e between101000 mmol m3. Net uptake of NO3 at 17°Cwas twice that at 7°C, and at both temperatures it doubledwith increasing [NO3]e between 110 mmol m3with further small increases at higher [NO3]e. Mean unitabsorption rates of NO3 between 06 d and 614d were linearly related (r2 of 0.790.99) to log10[NO].Steady-state Q10 (717°C) for uptake between 06d were 0.91, 1.62, 1.27, and 1.10, respectively, at [NO3]eof 1, 10, 100, and 1000 mmol m3, compared with correspondingvalues of 0.98, 1.38, 1.68, and 1.89 between 614 d. Thedata indicated that net uptake rates at 7 and 17°C divergedover time at high [NO3]e. Short-term uptake rates from1 mol m3 NO3 measured at 17°C were higherin plants grown with roots at 7°C than at 17°C; for7°C plants there was a strong inverse linear relationship(r2=0.94) between uptake rate and treatment log10 [NO3]ewhilst rates in 17°C plants were independent of prior [NO3]e. Rates of NO3 influx and efflux under different steady-stateconditions of NO3 supply and root temperature were calculatedfrom dilution of 15N added to culture solutions. Efflux wassubstantial relative to net uptake in all treatments, and wasinversely related to [NO3]e at 17°C but not at 7°C.Ratios of influx: efflux ranged from 1.62.9 at 17°Cand 1.31.8 at 7°C, indicating the proportionatelygreater impact of efflux at low root temperature. Ratios ofefflux: net uptake were 0.531.56 at 17°C and 1.213.58at 7°C. The apparent sensitivities of influx and effluxto steady-state root temperature varied with [NO3]e.Both fluxes were higher at 17°C than 7°C in the presenceof 1001000 mmol m3 NO3 but the trend wasreversed at 110 mmol m3 NO. Concentrations oftotal N measured in xylem exudate were at least 2-fold higherat 7°C compared with 17°C, attributable mainly to higherconcentrations of NO3 glutamine and proline. The resultsare discussed in terms of acclimatory and other responses shownby the NO3 transport system under conditions of limitingNO3 supply and low root temperature. Key words: Brassica napus, nitrate supply, efflux, influx, root temperature, xylem exudate 相似文献
18.
In situ growth and development of Neocalanus flemingeri/plumchrusstage C1C4 copepodites were estimated by both the artificial-cohortand the single-stage incubation methods in March, April andMay of 20012005 at 56°C. Results from thesetwo methods were comparable and consistent. In the field, C1C4stage durations ranged from 7 to >100 days, dependent ontemperature and chlorophyll a (Chl a) concentration. Averagestage durations were 12.414.1 days, yielding an averageof 56 days to reach C5, but under optimal conditions stage durationswere closer to 10 days, shortening the time to reach C5 (fromC1) to 46 days. Generally, growth rates decreased with increasingstage, ranging from 0.28 day1 to close to zero but weretypically between 0.20 and 0.05 day1, averaging 0.110± 0.006 day1 (mean ± SE) for single-stageand 0.107 ± 0.005 day1 (mean ± SE) forartificial-cohort methods. Growth was well described by equationsof MichaelisMenten form, with maximum growth rates (Gmax)of 0.170.18 day1 and half saturation Chl a concentrations(Kchl) of 0.450.46 mg m3 for combined C13,while Gmax dropped to 0.080.09 day1 but Kchl remainedat 0.380.93 mg m3 for C4. In this study, in situgrowth of N. flemingeri/plumchrus was frequently food limitedto some degree, particularly during March. A comparison withglobal models of copepod growth rates suggests that these modelsstill require considerable refinement. We suggest that the artificial-cohortmethod is the most practical approach to generating the multispeciesdata required to address these deficiencies. 相似文献
19.
Photoadaptation in Antarctic phytopfankton: variations in growth rate, chemical composition and P versus I curves 总被引:1,自引:0,他引:1
The response of phytoplankton to variations in the light regimewas studied during the VULCAN and ACDA cruises in the Antarctic.Unenriched batch cultures of 1219 days' duration reachedchl concentrations of 1050 µg1 and exhibitedexponential growth rates, with the maximal rate being 0.41 doubl,day1. Ice edge algae exhibited maximum growth rates atphoton flux densities (PFD) of 30100 µE m2S1and the growth rate was reduced by about 30% at 5001000µE m2S1 The chl/C ratio ranged between 0.004and 0.018, with the lowest ratios at PFDs above 500 µEm2S1 chl/C ratios were also below maximum at PFDsbelow 4050 µE m2S1 The C:N:P ratioswere close to the Redfield ratios; the Si/C ratio averaged 0.16(atoms), and the ATP/C ratio averaged from 0.0024 to 0.0050in different culture senes. When thawed after having been frozenfor 10 days, shade-adapted cultures were in a much better conditionthan sun-adapted ones. P versus I data showed that the maximumassimilation number varied from 0.75 to 4.4 µg C (µgchl)1h1. It varied inversely with the chl/C ratio;therefore the maximum carbon turnover rate varied little betweensamples (0.024/0.035 h1). Low biomass communities exhibitedrelatively high values for (the initial slope of P versus Icurves), low values for 1sat (160330 µE m2S1),and they were susceptible to photoinhibition. In contrast, communitiesdominated by Odontella weissflogii exhibited low values for, a high value for Isat (560 µE m2S1 andthey tolerated high PFDs. The photo-adaptational status of thephytoplankton in natural water samples is discussed relativeto the profile of water column stability and mixing processes. 相似文献
20.
Tada Kuninao; Pithakpol Santiwat; Yano Rumiko; Montani Shigeru 《Journal of plankton research》2000,22(6):1203-1211
The carbon and nitrogen content of Noctiluca scintillans cellsfrom the Seto Inland Sea, Japan was investigated in order toestimate its biomass in natural samples. The carbon contentof N.scintillans ranged from 123 to 627 ng C cell1 witha mean value of 353 ng C cell1, or 1.12 to 2.67 fg Cµm3 with a mean value of 1.98 fg C µm3.The nitrogen content ranged from 36.0 to 232 ng N cell1with a mean value of 131 ng N cell1, or 0.499 to 0.910fg N µm3 with a mean value of 0.694 fg N µm3.Total cell carbon and nitrogen increased but the carbon andnitrogen per cell volume decreased with increasing cell volume.The C/N ratio of the cells ranged from 2.3 to 4.4, which wasrelatively low compared with the Redfield ratio. The carbonand nitrogen content was extremely low (91.2 ng C cell1,41.8 ng N cell1) for starved cells, whereas it was extremelyhigh (528 ng C cell1, 205 ng N cell1) for cellswhich had ingested the large diatom, Coscinodiscus wailesii.Our results suggest that the carbon and nitrogen content ofN.scintillans varies depending on its physiological conditionand the type of food that it has recently consumed. 相似文献