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1.
Seedlings of cotton (Gossypium hirsutum L. cv. Acala SJ-2) weregrown in modified Hoagland nutrient solution with various combinationsof NaCl and CaCl2. Marking experiments and numerical analysiswere conducted to characterize the spatial and temporal patternsof cotton root growth at varied Na/Ca ratios. At 1 mol m–3Ca, 150 mol m–3 NaCl reduced overall root elongation rateto 60% of the control, while increasing Ca to 10 mol m–3at the same NaCl concentration restored the elongation rateto 80% of the control. Analysis of the spatial distributionof elongation revealed that the presence of 150 mol m–3NaCl in the medium shortened the growth zone by about 2 mm fromthe approximate 10 mm in the control and also reduced the relativeelemental elongation rate (i.e. the longitudinal strain rate,defined as the derivatives of displacement velocity of a cellularparticle with respect to position on root axis). Supply of 10mol m–3 Ca at the high salt condition restored partiallythe relative elemental elongation rate, but not the length ofthe growth zone. Compared to the control, the growth trajectoriesshowed that at 1 mol m–3 CaCl2 it took more time for acellular particle to move through the growth zone at 150 molm–3 NaCl, while at 10 mol m–3 CaCl it took lesstime and there was no difference between the NaCl treatments Key words: Gossypium hirsutum, salinity stress, root growth kinematics  相似文献   

2.
The effects of different applied NO3 concentrations onextension growth and final length and area of leaves 1–4of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO3 in the range 0.1–0.5.0mol m–3 caused decreased duration of growth but increasedgrowth rate and final length of leaves 2–4 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale, x Triticosecaleand Triticum aestivum. For all cereals, increased NO3resulted in increased area of leaves 1–4. Pasture grasseswere supplied either 0.5 or 50 mol m–3 NO3. Increasedapplied NO3 (0.5–5.0 mol m–3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 1–4 of Bromus wiltdenowii, leaves 2–4ofFestuca arundinaceae and leaves 3 and 4 of Lolium muitiflorum.In addition, length of leaves 3 and 4 of B. witidenowii increasedwith increased NO3. Increased NO3 resulted inincreased area of leaves 2–4 of Dactylis gtomerata andLolium perenne and leaves 3 and 4 of Phalaris aquaiica but hadno effect on extension growth of all three species. Avena sativa L, oat, Hordeum vulgare L, barley, Secale cereale L, rye, x Triticosecale Wittm, triticale, Triticum aestivum L, wheat, Bromus willdenowii Kunth, prairie grass, Dactylis gtomerata L, cocksfoot, Festuca arundinaceae Shreb, tall fescue, Lolium multijlorum Lam, Italian ryegrass, Lolium perenne L, perennial ryegrass, Phalaris aquatica L, nitrate, leaf extension, leaf expansion  相似文献   

3.
Two approaches to quantifying relationships between nutrientsupply and plant growth were compared with respect to growth,partitioning, uptake and assimilation of NO3 by non-nodulatedpea (Pisum sativum L. cv. Marma). Plants grown in flowing solutionculture were supplied with NO3 at relative addition rates(RAR) of 0·03, 0·06, 0·12, and 0·18d–1, or constant external concentrations ([NO3)of 3, 10, 20, and 100 mmol m–3 over 19 d. Following acclimation,relative growth rates (RGR)approached the corresponding RARbetween 0·03–0.12 d-1, although growth was notlimited by N supply at RAR =0.18 d-1. Growth rates showed littlechange with [NO3–] between 10–100 mmol m–3(RGR=0·15 –0·16 d-1). The absence of growthlimitation over this range was suggested by high unit absorptionrates of NO3, accumulation of NO3 in tissues andprogressive increases in shoot: root ratio. Rates of net uptakeof NO3 from 1 mol m–3 solutions were assessed relativeto the growth-related requirement for NO3, showing thatthe relative uptake capacity increased with RGR between 0·03–0·06d–1 , but decreased thereafter to a theoretical minimumvalue at RGR  相似文献   

4.
The effects of different applied NO3 concentrations onextension growth and final length and area of leaves 1–4of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO3 in the range 0.1–50mol m–3; caused decreased duration of growth but increasedgrowth rate and final length of leaves 2–4 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale x Triticosecaleand Triticum aestivum. For all cereals, increased NO3resulted in increased area of leaves 1-4. Pasture grasses weresupplied either 0.5 or 50 mol m–3; NO3. Increasedapplied NO3 (0.5–50 mol m–3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 1–4 of Bromus willdenowii leaves 2–4of Festuca arundinaceae and leaves 3 and 4 of Lolium multiflorum.In addition, length of leaves 3 and 4 of B. willdenowii increasedwith increased NO3. Increased NO3 resulted in increased areaof leaves 2–4 of Daciylis glomerata and Lolium perenneand leaves 3 and 4 of Phalaris aquatica but had no effect onextension growth of all three species. Avena saliva L., oat, Hordeum vulgare L., barley, Secale cereaie L., rye, x Triticosecale Wittm, triticale, Triticum aestivum L., wheat, Bromus willdenowii Kunth, prairie grass, Dactylis glomerata L., cocksfoot, Festuca arundinaceae Shreb, tall fescue, Lolium multiflorum Lam, Italian ryegrass, Lolium perenne L, perennial ryegrass, Phalaris aquatica L, nitrate,, leaf extension, leaf expansion  相似文献   

5.
In studies of Trifolium repens nitrogen nutrition, the controlof nutrient solution pH using dipolar buffers, was evaluatedin tube culture under sterile conditions. Five buffers; MES,ADA, ACES, BES and MOPS with pK2s (20 °C) of 6.15, 6.60,6.90, 7.15 and 7.20 respectively, at a concentration of 2.0mol m–3, were provided to inoculated Trifolium repensgrowing in nutrient solution containing 7.13 mol m–3 nitrogenas (NH4)2SO4. Initial pH of each solution was adjusted to theappropriate buffer pK2 Two buffers, ADA and ACES completelyinhibited plant growth. The remaining buffers had little effectin limiting pH change, although plant dry matter was higherand nodule numbers lower in the presence of these buffers. MESand MOPS were supplied to nutrient solutions with and without7.13 mol m–3 (NH4)2SO4, at concentrations ranging from0–12 mol m–3. MES at 9 mol m–3 and 12 molm–3 reduced growth of plants reliant on the symbiosisfor providing nitrogen. The provision of MES to plants providedwith NH4+ significantly increased plant yield and reduced nodulenumber at all concentrations. MOPS did not affect plant yieldor nodule number. The use of dipolar buffers in legume nitrogennutrition studies is considered in terms of buffering capacity,and the side effects on plant growth and symbiotic development. Key words: Ammonium, Dipolar buffer, Nitrogen nutrition, pH control, Symbiosis, Trifolium repens  相似文献   

6.
Species-specific differences in the assimilation of atmosphericCO2 depends upon differences in the capacities for the biochemicalreactions that regulate the gas-exchange process. Quantifyingthese differences for more than a few species, however, hasproven difficult. Therefore, to understand better how speciesdiffer in their capacity for CO2 assimilation, a widely usedmodel, capable of partitioning limitations to the activity ofribulose-1,5-bisphosphate carboxylase-oxygenase, to the rateof ribulose 1,5-bisphosphate regeneration via electron transport,and to the rate of triose phosphate utilization was used toanalyse 164 previously published A/Ci, curves for 109 C3 plantspecies. Based on this analysis, the maximum rate of carboxylation,Vcmax, ranged from 6µmol m–2 s–1 for the coniferousspecies Picea abies to 194µmol m–2 s–1 forthe agricultural species Beta vulgaris, and averaged 64µmolm–2 s–1 across all species. The maximum rate ofelectron transport, Jmax, ranged from 17µmol m–2s–1 again for Picea abies to 372µmol m–2 s–1for the desert annual Malvastrum rotundifolium, and averaged134µmol m–2 s–1 across all species. A strongpositive correlation between Vcmax and Jmax indicated that theassimilation of CO2 was regulated in a co-ordinated manner bythese two component processes. Of the A/Ci curves analysed,23 showed either an insensitivity or reversed-sensitivity toincreasing CO2 concentration, indicating that CO2 assimilationwas limited by the utilization of triose phosphates. The rateof triose phosphate utilization ranged from 4·9 µmolm–2 s–1 for the tropical perennial Tabebuia roseato 20·1 µmol m–2 s–1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm–2 s–1 across all species. Despite what at first glance would appear to be a wide rangeof estimates for the biochemical capacities that regulate CO2assimilation, separating these species-specific results intothose of broad plant categories revealed that Vcmax and Jmaxwere in general higher for herbaceous annuals than they werefor woody perennials. For annuals, Vcmax and Jmax averaged 75and 154 µmol m–2 s–1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm2 s–1, respectively. Although these differencesbetween groups may be coincidental, such an observation pointsto differences between annuals and perennials in either theavailability or allocation of resources to the gas-exchangeprocess. Key words: A/Ci curve, CO2 assimilation, internal CO2 partial pressure, photosynthesis  相似文献   

7.
Inhibition of Nodule Development in Soybean by Nitrate or Reduced Nitrogen   总被引:5,自引:1,他引:4  
Imsande, J. 1986. Inhibition of nodule development in soybeanby nitrate or reduced nitrogen.—J. exp. Bot. 37: 348–355. Nodulation of hydroponically grown soybean plants [Glycine max(L.) Merr.] is inhibited by continuous growth in the presenceof 4· mol m–3 KNO3 The presence of 4·0 molm–3 ‘starter nitrate’ for 3-6 d during noduledevelopment, however, subsequently stimulates nodule dry weightaccumulation and nitrogenase activity. These stimulations occureven though 4· mol m–3 nitrate temporarily delaysnodule development, i.e. the late steps of nodule developmentare reversibly inhibited by a short-term exposure to 4·0mol m–3 nitrate. On the other hand, treatment with 4·0mol m–3 nitrate in excess of 14 d significantly reducesnodule dry weight Thus, extended growth in the presence of 4·0mol m–3 KNO3 seems to block both early and late stepsof nodule development. Nodulation of hydroponically grown soybeansis also inhibited by continuous growth in the presence of 2·0mol m–3 (NH4)2SO4 This inhibition is not caused by acidityof the growth medium. On the other hand, nodule development6 d after inoculation with Rhizoblum japonicum is not delayedby a 7-d exposure to 2·0 mol m–3 (NH4)2SO4 butis partially inhibited by a prolonged exposure to (NH4)2SO4Because repression of nodulation by 4·0 mol m–3KNO3 is more severe than that by 2·0 mol m–3 (NH4)2SO4and because ammonium taken up by the soybean plant is not activelyoxidized to nitrate, it is suggested that there are at leasttwo mechanisms by which nitrate utilization represses noduleformation in soybean. Key words: Glycine max, nitrogen, nitrogen fixation, nodulation  相似文献   

8.
The acidophilic alga Dunaliella acidophila exhibits optimalgrowth at pH 1. We have investigated the regulation of phosphateuptake by this alga using tracer techniques and by performingintracellular phosphate measurements under different growthconditions including phosphate limitation. In batch culturewith 2·2 mol m–3 phosphate in the medium the uptakeof phosphate at micromolar phosphate concentrations followeda linear time dependence in the range of minutes and rates werein the range of 1 µmol phosphate mg–1 chl h–1,only. However, under discontinuous phosphate-limited growthconditions, tracer influx revealed a biphasic pattern at micromolarphosphate concentrations: An initial burst phase resulted ina 104-fold internal phosphate accumulation and levelled offafter about 10 s. A double reciprocal plot of the initial influxrates obtained for phosphate-limited and unlimited algae exhibitedMichaelis-Menten kinetics. Phosphate limitation caused a significantactivation of the maximum velocity of uptake, yielding Vmaxup to 1 mmol mg–1 chl h–1 as compared to valuesin the order of 50 µmol phosphate mg–1 chl h–1for the second phase (this magnitude is also representativefor non-limited batch cultures). Concomitantly the Michaelisconstant was altered from 4 mmol m–3 to 0·7 mmolm–3. The rapid uptake of phosphate was inhibited by arsenateand FCCP and was not stimulated by Na+. The pH dependence oftracer accumulation and measurements of the intracellular phosphatepool under different growth conditions indicate that at lowpH and low external phosphate concentrations the high protongradient present under these conditions is utilized for a H3PO4uptake or a H+/H2PO4 cotransport. However, when the externalphosphate concentration was increased to levels sufficientlyhigh for transport to be driven by the positive membrane potential(10 mol m–3 phosphate), the pH dependence of phosphateuptake was more complex, but could be explained by the uptakeof H3PO4 or a H+/H2PO4-cotransport at low pH and a differenttype H2PO4-transport (with unknown type of ion coupling)at high pH-values. It is suggested that this flexible couplingof phosphate transport is of essential importance for the acidresistance of Dunaliella acidophila. Key words: Acid resistance, Dunaliella acidophila, phosphate cotransport, phosphate limitation, plasma membrane, sodium  相似文献   

9.
The effects of a range of applied nitrate (NO3) concentrations(0–20 mol m3) on germination and emergence percentageof Triticum aestivum L. cv. Otane were examined at 30, 60, 90and 120 mm sowing depths. Germination percentage was not affectedby either sowing depth or applied NO3 concentration whereasemergence percentage decreased with increased sowing depth regardlessof applied NO3 concentration. Nitrate did not affectemergence percentage at 30 mm sowing depth, but at 60 to 120mm depth, emergence percentage decreased sharply with an increasedapplied NO3 concentration of 0 to 1·0 mol m–3then decreased only slightly with further increases in appliedNO3 of about 5·0 mol m–3. Root and shoot growth, NO3 accumulation and nitrate reductaseactivity (NRA) of plants supplied with 0, 1·0 and 1·0mol m–3 NO3 at a sowing depth of 60 mm were measuredprior to emergence. The coleoptile of all seedlings opened withinthe substrate. Prior to emergence from the substrate, shootextension growth was unaffected by additional NO3 butshoot fr. wt. and dry wt. were both greater at 1·0 and1·0 mol m–3 NO3 than with zero NO3.Root dry wt. was unaffected by NO3. Nitrate concentrationand NRA in root and shoot were always low without NO3.At 1·0 and 10 mol m3 NO3, NO3 accumulatedin the root and shoot to concentrations substantially greaterthan that applied and caused the induction of NRA. Regardlessof the applied NO3 concentration, seedlings which failedto emerge still had substantial seed reserves one month afterplanting. Coleoptile length was substantially less for seedlingswhich did not emerge than for seedlings which emerged, but wasnot affected by NO3. It is proposed that (a) decreasedemergence percentage with increased sowing depth was due tothe emergence of leaf I from the coleoptile within the substrateand (b) decreased emergence percentage with additional NO3was due to the increased expansion of leaf 1 within the substrateresulting in greater folding and damage of the leaf. Key words: Triticum aestivwn L., nitrate, sowing depth, seedling growth, seedling emergence  相似文献   

10.
Yield stress threshold (Y) and volumetric extensibility () arethe rheological properties that appear to control root growth.In this study they were measured in wheat roots by means ofparallel measurement of the growth rate (r) of intact wheatroots and of the turgor pressures (P) of individual cells withinthe expansion zone. Growth and turgor pressure were manipulatedby immersion in graded osmoticum (mannitol) solutions. Turgorwas measured with a pressure probe and growth rate by visualobservation. The influence of various growth conditions on Yand was investigated; (a) At 27 °C.In 0.5 mol m–3 CaCl2 r, P, Y and were20.7±4.6 µm min–1, 0.77±0.05 MPa,0.07±0.03 MPa and 26±1.9 µm min–1MPa–1 (expressed as increase in length), respectively.Following 24 h growth in 10 mol m–3 KC1 these parametersbecame 12.3±3.5 µm min–1, 0.72±0.04MPa, 0.13±0.01 MPa and 21±0.7 µm min–1MPa–1. After 24 h osmotic adjustment in 150 mol m–3mannitol/0.5 mol m–3 CaCl2 r= 19.6±4.2 µmmin–1, P = 0.68±0.05 MPa and Y and were 0.07±0.04MPa and 30±0.2 µm min–1 MPa–01, respectively.After 24 h growth in 350 mol m–3 mannitol/0.5 mol m–3CaCl2 r= 13.3±4.1 µm min–1, P= 0.58±0.07MPa, Y=0.12±0.01 MPa and ø 32±0.2 tim min–1MPa–1. During osmotic adjustment in 200 mol m–3mannitol/0.5 mol m–3 CaCl2, with or without KCl, the recoveryof growth rate corresponded to turgor pressure recovery (t1/2approximately 3 h). (b) At 15 °C. Lowered temperature dramatically influencedthe growth parameters which became r= 8.3±2.8 um min–1,P=0.78 MPa, r=<0.2 MPa and =15±0.1 µm min–1MPa–1. Therefore, Y and are influenced by 10 mol m–3 K+ ionsand low temperature. In each case the effective pressure forgrowth (P-Y) was large indicating that small fluctuations ofsoil water potential will not stop root elongation. Key words: Yield threshold, cell wall extensibility, wheat root growth, temperature, turgor pressur  相似文献   

11.
We have examined the long-term effects of NO3 concentrationson NO3 (15NO3) fluxes and cellular pool sizesin roots of intact 30-d-old wheat (Triticum aestivum cv. Courtot)grown hydroponically. Compartmental analysis was performed understeady-state conditions at five different levels of NO3concentration (from 0.1 up to 5 mol m–3 taking into accountmetabolism and secretion into the xylem (Devienne et al., 1994).Nitrate and reduced nitrogen levels in the tissues were largelyindependent of external NO3 concentration although below1.5 mol m–3 NO3; concentration limited plant growth.In the chamber, marked diurnal variations in net uptake occurredand, in the light, higher NO3 concentrations yieldedhigher NO3 uptake rates. After transfer of the plantsto the laboratory, the increase in net uptake linked to elevationof NO3; concentrations was even larger (from 0.1 to 8.8µmolh–1 g–1 FW) as a result of a marked increase (x10–11) in the unidirectional influx at the plasmalemmawhile NO3 efflux was less enhanced (x 4–5). Underthese conditions, influx into the vacuole was also higher (x2–4) while efflux from the vacuole was little affected(x 1–3). NO3 concentrations within the cell compartmentswere estimated under the clas sical assumptions. The vacuolarconcentration was a little modified by NO3 availabilitywhereas that in the cytosol increased from about 10 mol m–3to about 20 mol m–3 indicating that (1) the absolute valuefor the cytosol was high and (2) it displayed only a small increasedespite very large changes in NO3 fluxes. NO3distribution within the cells did not seem to involve an activeaccumulation of NO3 in the vacuole. Key words: Wheat, ion transport, nitrate, 15N, compartmentation  相似文献   

12.
Potassium-Ammonium Uptake Interactions in Tobacco Seedlings   总被引:6,自引:0,他引:6  
Short-term (< 12 h) uptake experiments were conducted with6–7-week-old tobacco (Nicotiana tabacum L. cv. Ky 14)seedlings to determine absorption interactions between K+ andNH4+. At equal solution concentrations (0.5 mol m–3) netK+ uptake was inhibited 30–35% by NH4+ and NH4+ uptakewas decreased 9–24%. Removal of NH4+ resulted in completerecovery in K+ uptake rate, but NH4+ uptake rate did not recoverwhen K+ was removed. In both cases, inhibition of the uptakerate of one cation saturated as the concentration of the othercation was increased up to 0.5 mol m–3. The relative effectof K+-NH4+ interactions was not altered when Cl- was replacedwith SO42–, but the magnitudes of the uptake rates wereless in the absence of Cl-. The Vmax for NH4+ uptake was reducedfrom 128 to 105 µmol g–1 dry wt. h–1 in thepresence of 0.5 mol m–3 K+ and the Km for NH4+ doubledfrom 12 to 27 mmol m–3 in the presence of K+. The resultsof these K+-NH4+ experiments are interpreted as mixed-noncompetitiveinteractions. However, an enhanced efflux of K+ coupled to NH4+influx via an antiporter cannot be ruled out as contributingto the decrease in net K+ uptake. Key words: Nicotiana tabacum, K+, NH4+, Uptake interactions  相似文献   

13.
Phosphate Uptake in the Cyanobacterium Synechococcus R-2 PCC 7942   总被引:4,自引:0,他引:4  
Phosphate uptake rates in Synechococcus R-2 in BG-11 media (anitrate-based medium, not phosphate limited) were measured usingcells grown semi-continuously and in continuous culture. Netuptake of phosphate is proportional to external concentration.Growing cells at pHo 10 have a net uptake rate of about 600pmol m–2 s–1 phosphate, but the isotopic flux for32P phosphate was about 4 nmol m–2 s–1. There appearsto be a constitutive over-capacity for phosphate uptake. TheKm and Vmax, of the saturable component were not significantlydifferent at pHo 7.5 and 10, hence the transport system probablyrecognizes both H2PO4and HPO2–4. The intracellularinorganic phosphate concentration is about 3 to 10 mol m–3,but there is an intracellular polyphosphate store of about 400mol m–3. Intracellular inorganic phosphate is 25 to 50kJ mol–1 from electrochemical equilibrium in both thelight and dark and at pHo 7.5 and 10. Phosphate uptake is veryslow in the dark ( 100 pmol m–2 s–1) and is light-activated(pHo 7.51.3 nmol m–2 s–1, pHo 10600 pmol m–2s–1). Uptake has an irreversible requirement for Mg2+in the medium. Uptake in the light is strongly Na+-dependent.Phosphate uptake was negatively electrogenic (net negative chargetaken up when transporting phosphate) at pHo 7.5, but positivelyelectrogenic at pHo 10. This seems to exclude a sodium motiveforce driven mechanism. An ATP-driven phosphate uptake mechanismneeds to have a stoichiometry of one phosphate taken up perATP (1 PO4 in/ATP) to be thermodynamically possible under allthe conditions tested in the present study. (Received June 16, 1997; Accepted September 4, 1997)  相似文献   

14.
The theory and practice of applying the thermodynamics of irreversibleprocesses to mass-flow theories is presented. Onsager coefficientswere measured on cut and uncut phloem and cut xylem strandsof Heracleum muntegazzimum. In 0.3 N sucrose + 1 mN KC1 theyare as follows. In phloem, LEE = 5 ? 10–4 mho cm–1,LpE = 9 ? 10–6 cm3 s–1 cm–2 volt–1 cm,and LPP = 0.16 cm3 s–1 cm–2 (J cm–3)–1cm. In uncut phloem strands LEE is about 1 ? 10–3 mhocm–1. In xylem in 2 x 10–3 N KCI, Lpp = 50 to 225,LPE = 2 ? 10–4, and LEE = 4 ? 10–3. The measurementsare tentative since the blockage of the sieve plates is an interferingfactor, but if they are valid they lead to the conclusion thatneither a pressure-flow nor an electro-kinetic mechanism envisaginga ‘long distance’ current pathway can be the majormotive ‘force’ for transport in mature phloem. Measurementsof biopotentials along conducting but laterally detached phloembundles of Heracleum suggest, nevertheless, that there may bea small electro-osmotic component of at least 0.1 mV cm–1endogenous in the phloem.  相似文献   

15.
The aim of this study was to investigate changes in cell wallchemical composition and polymer size in the root tip of intactcotton seedlings (Gossypium hirsutum L. cv. Acala SJ-2) grownin saline environments, in order to relate the interaction betweenhigh salinity and root growth to possible changes in cell wallmetabolism. Cotton seedlings were grown in modified Hoagland nutrient solutionwith various combinations of NaCl and CaCl2. Cell walls werefractionated into four fractions (pectin, hemicellulose 1 and2, cellulose), and analysed for their total sugar content, neutralsugar composition and size of polysaccharides. At 1 mol m–3Ca, 150 mol m–3 NaCl resulted in a significant increasein the cell wall uronic acid content, but a reduction in cellulosecontent on a per unit dry weight basis. Supplemental Ca overcamethe inhibitory effect of high Na on cellulose content. The neutralsugar composition of the cell wall fractions showed no majorchanges caused by varied Na/Ca ratios. Determinations of polysaccharidepolymer size showed that high Na at 1 mol m–3 Ca led toan increase in the amount of polysaccharides of intermediatemolecular size and a decrease in that of small size in the hemicellulose1 fraction, indicating a possible inhibition of polysaccharidedegradation by high Na. This change was not observed in the10 mol m–3 Ca treatments. The results reveal a relationshipbetween the effects of high salinity on root growth and cellwall metabolism, particularly in regard to cellulose biosynthesis Key words: Gossypium hirsutum, salinity, root, cell wall  相似文献   

16.
The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H+ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The Km values of thethree affinity sites were 1.4 x 10–3 M, 1.3 x 10–4M, 4.3 x 10–5 M; the maximum velocity values were 3.3x 10–8, 4.5 x 10–9, 1.8 x 10–9 mol/10 min/4x 106 cells. (Received April 18, 1981; Accepted August 25, 1981)  相似文献   

17.
DNA polymerases were purified several hundred-fold from the10 000 x g soluble (polymerase I) and particulate (polymeraseIII) fractions prepared from virus PBCV-1 infected ChlorellaNC64A extracts. Both DNA polymerases exhibited optimal activitywith activated calf thymus DNA at pH 8.5. DNA polymerase I required3.0 mol m–3 MgSO4 and 150 to 250 mol m–3 KCl foroptimum activity whereas, DNA polymerase III required 2.0 molm–3 MgSO4 and 150 mol m–3 KCl. Both enzymes wereinhibited by pyrophosphate, actinomycin D, ethidium bromide,dideoxythymidine triphosphate, and N-ethylmaleimide but wererelatively insensitive to aphidicolin. DNA polymerase I differedfrom DNA polymerase III in its response to cations (particularlyNH4Cl), elution from a DEAE cellulose column, and molecularweight. Key words: Algal virus, DNA polymerase, Chlorella  相似文献   

18.
Net accumulation of Cl by intact barley plants was virtuallyeliminated in roots and reduced by 40% in shoots when externalmedia (0.5 mol m–3 CaSO4 plus 0–5 mol m–3KCI) were supplemented with 0.25 mol m Ca(NO3)2. Plasmalemma36Cl influx (oc) was shown to be insensitive to externalNO3- in plants which had previously been grown in solutionslacking –3, but oc became sensitive to NO3-after a lagperiod of 3–6 h. Kinetic analyses revealed that the inhibitionof 36C1 influx by external NO3- was complex. At 0.25mol m–3 NO3- the Vmax for Cl influx was reducedby greater than 50%, with insignificant effects upon Km. At0.5 mol m–3 NO3- there was no further effect upon Vmaxbut Km for influx increased from 38±5 mmol m–3to 116±26 mmol m–3. By contrast, Cl effluxwas found to be insensitive to external NO3-. A model for theregulation of Cl influx is proposed which involves bothnegative feedback effects from vacuolar NO3- +Cl) concentrationand (external) NO3- inhibition of Cl influx at the plasmalemma.These combined effects serve to discriminate against Claccumulation, favouring NO3- accumulation, when the latter ionis available. Such observations are inconsistent with recentproposals for the existence of bona fide homeostats for chlorideaccumulation in higher plants. Key words: Nitrate inhibition, Chloride influx, Barley  相似文献   

19.
In situ growth and development of Neocalanus flemingeri/plumchrusstage C1–C4 copepodites were estimated by both the artificial-cohortand the single-stage incubation methods in March, April andMay of 2001–2005 at 5–6°C. Results from thesetwo methods were comparable and consistent. In the field, C1–C4stage durations ranged from 7 to >100 days, dependent ontemperature and chlorophyll a (Chl a) concentration. Averagestage durations were 12.4–14.1 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 day–1 to close to zero but weretypically between 0.20 and 0.05 day–1, averaging 0.110± 0.006 day–1 (mean ± SE) for single-stageand 0.107 ± 0.005 day–1 (mean ± SE) forartificial-cohort methods. Growth was well described by equationsof Michaelis–Menten form, with maximum growth rates (Gmax)of 0.17–0.18 day–1 and half saturation Chl a concentrations(Kchl) of 0.45–0.46 mg m–3 for combined C1–3,while Gmax dropped to 0.08–0.09 day–1 but Kchl remainedat 0.38–0.93 mg m–3 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   

20.
The addition of Braun and Wood's inorganic supplements (845mg l–1 KCl, 1800 mgl–1 NaNO3, 300 mg l–1 NaH2PO4.2H2O,790 mg l–1 (NH4)2SO4) to White's medium caused markedincreases in the growth of normal tissues of Helianthus annuus,Nicotiana rustica, Daucus carota, and Vinca rosea and crown-galltumour tissues of H. annuus. However, no evidence was obtainedwhich suggested that the presence of these extra salts markedlyinfluenced the essential requirements of normal callus for auxinsand kinetin. In contrast their presence significantly influencedthe hormonal requirements of certain habituated cultures ofH. annuus and V. rosea. These habituated cultures had specificauxin requirements on White's medium while either an auxin orkinetin was sufficient on high-salts medium. These results arediscussed in relation to previous reports which suggested thatthe biosyntheses of auxins and other growth factors in normaland crown-gall cultures are specifically activated by certaininorganic ions.  相似文献   

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