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1.
Comparison of the Disruption of Mitosis and Cell Plate Formation in Oat Roots by DCPA, Colchicine and Propham 总被引:1,自引:0,他引:1
Holmsen, J. D. and Hess, F. D. 1985. Comparison of the disruptionof mitosis and cell plate formation in oat roots by DCPA, colchicineand propham.J. exp. Bot. 36: 15041513. Concentrationsof DCPA, propham and colchicine were selected to cause from0% to greater than 60% inhibition of oat (Avena sativa L. Victory)root growth after 24 h exposure. Root growth progressively declinedas concentrations were raised from 1·0 to 5·6mmol m3 DCPA, 1·05·0 mmol m3propham, and 50500 mmol m3 colchicine. In additionto inhibiting root growth each mitotic disrupter caused theroot tips to swell to an extent dependent upon concentration.All three compounds effectively disrupted mitosis at concentrationsthat caused less than maximal root growth inhibition. Mitoticdisruption was manifest as a reduction in the number of normalmitotic figures and an increase in the number of condensed prophase,multipolar and anaphase bridge division figures. The frequencyof each type of division figure was different for each of thethree compounds. DCPA disrupted mitosis more effectively whencompared with propham and colchicine at concentrations whichcaused the same amount of root growth inhibition. Each mitoticdisrupter also induced the formation of aberrant cell walls.DCPA was the most effective at disrupting cell plate formation,whereas colchicine was least effective. These data suggest thatthe mechanism of action of DCPA is distinct from the mechanismof colchicine or propham Key words: Avena sativa L., mitotic disruption, DCPA, colchicine, propham 相似文献
2.
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
3.
FLEURAT-LESSARD P.; ROBLIN G.; BONMORT J.; BESSE C. 《Journal of experimental botany》1988,39(2):209-221
Fleurat-Lessard, P., Roblin, G., Bonmort, J. and Besse, C. 1988.Effects of colchicine, vinblastine, cytochalasin B and phalloidinon the seismonastic movement of Mimosa pudica leaf and on motorcell ultrastructure.J. exp. Bot. 39: 209221. Colchicine at 1 x 103 mol dm3 does not affectthe seismonastic movement of Mimosa pudica leaves but disruptsmicrotubules in motor cells. Vinblastine at 5 x 103 moldm3 does not affect this movement and partly disruptsmicrotubules. Vinblastine at 1 x 104 mol dm3 alwaysdisrupts microtubules, even after a 12 h reversibility whenthe movement is restored. These drugs, applied at the same respectiveconcentrations, do not alter cytoplasmic and vacuolar fibrils.Cytochalasin B and phalloidin alter the seismonastic movementof Mimosa leaves when applied at concentrations of 1.25 x 103and 2.4 x 104 mol dm3 respectively. These drugs,used at the same respective concentrations, also affect themotor cell structure and, in particular, modify the arrangementand the structure of the fibrils but they do not destroy themicrotubules. These data suggest that microtubules are not directly involvedin the seismonastic reaction whereas fibrils, formed by thin(3.0 nm wide) filaments, may be implicated in this reaction. Key words: Colchicine, cytochalasin B, phalloidin, Mimosa pudica, motor cells, vinblastine 相似文献
4.
Distinct roles of PMCA isoforms in Ca2+ homeostasis of bladder smooth muscle: evidence from PMCA gene-ablated mice 总被引:2,自引:0,他引:2
Liu L Ishida Y Okunade G Pyne-Geithman GJ Shull GE Paul RJ 《American journal of physiology. Cell physiology》2007,292(1):C423-C431
We previously showed that plasma membrane Ca2+-ATPase (PMCA) activity accounted for 2530% of relaxation in bladder smooth muscle (8). Among the four PMCA isoforms only PMCA1 and PMCA4 are expressed in smooth muscle. To address the role of these isoforms, we measured cytosolic Ca2+ ([Ca2+]i) using fura-PE3 and simultaneously measured contractility in bladder smooth muscle from wild-type (WT), Pmca1+/, Pmca4+/, Pmca4/, and Pmca1+/Pmca4/ mice. There were no differences in basal [Ca2+]i values between bladder preparations. KCl (80 mM) elicited both larger forces (150190%) and increases in [Ca2+]i (130180%) in smooth muscle from Pmca1+/ and Pmca1+/Pmca4/ bladders than those in WT or Pmca4/. The responses to carbachol (CCh: 10 µM) were also greater in Pmca1+/ (120150%) than in WT bladders. In contrast, the responses in Pmca4/ and Pmca1+/Pmca4/ bladders to CCh were significantly smaller (4050%) than WT. The rise in half-times of force and [Ca2+]i increases in response to KCl and CCh, and the concomitant half-times of their decrease upon washout of agonist were prolonged in Pmca4/ (130190%) and Pmca1+/Pmca4/ (120250%) bladders, but not in Pmca1+/ bladders with respect to WT. Our evidence indicates distinct isoform functions with the PMCA1 isoform involved in overall Ca2+ clearance, while PMCA4 is essential for the [Ca2+]i increase and contractile response to the CCh receptor-mediated signal transduction pathway. PMCA; bladder smooth muscle; gene-altered mice 相似文献
5.
Benzoic acid and its o-, m- and p-hydroxy derivatives appliedon excised leaves of Cassia fasciculata modified the dark-induced(scotonasty) and light-induced (photonasty) leaflet movements.Benzoic acid inhibited the scotonastic closure in a dose-dependentmanner from 104M to 103M and promoted the photonasticopening at optimum concentration of 5.104M. These effectswere dependent upon the position of hydroxyl group on the benzoicring, the o-derivative inducing a stronger effect than the m-and p-derivatives. Experiments showed that treatment with o-hydroxybenzoicacid had not to exceed 3060 min and that the maximumeffect was obtained at pH 5.5. (Received September 16, 1986; Accepted June 22, 1987) 相似文献
6.
Protoplasts were successfully isolated from internodal callustissues of both Oxalis glaucifolia and O. rhombeo-ovata whenthey were digested in a solution containing 0.1% (w/v) MacerozymeR-10, 0.5% (w/v) cellulase Onozuka R-10 and 0.3 mmol m3sucrose. Protoplasts proliferated to give cell colonies on Gamborget al.'s B5 medium supplemented with 0.3 mmol m3 mannitol,0.5 mg dm32, 4-D, and 2.0 mg dm3 kinetin. Calluswas produced upon transfer of cell colonies to Murashige andSkoog medium containing 2.0 mg dm3 l-naphthaleneaceticacid (NAA) and 0.1 mg dm3 kinetin for O. glaucifolia,or with 5.0 mg dm3 NAA and 0.5 mg dm3 6-benzylaminopurine,for O. rhombeo-ovata. Plants were regenerated from O. glaucifoliaprotoplasts on a medium containing 0.1 mg dm3 NAA, 1.0mg dm3 kinetin and 1.0 mg dm3 gibberellic acid,but only vascular nodules were differentiated by O. rhombeo-ovataprotoplast-derived calli. Key words: Tissue culture, protoplasts, plant regeneration, Oxalis spp 相似文献
7.
Nitrate Inhibition of Chloride Influx in Barley: Implications for a Proposed Chloride Homeostat 总被引:6,自引:0,他引:6
Net accumulation of Cl by intact barley plants was virtuallyeliminated in roots and reduced by 40% in shoots when externalmedia (0.5 mol m3 CaSO4 plus 05 mol m3KCI) 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 36 h. Kinetic analyses revealed that the inhibitionof 36C1 influx by external NO3- was complex. At 0.25mol m3 NO3- the Vmax for Cl influx was reducedby greater than 50%, with insignificant effects upon Km. At0.5 mol m3 NO3- there was no further effect upon Vmaxbut Km for influx increased from 38±5 mmol m3to 116±26 mmol m3. 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
8.
Zinc-induced Vacuolation in Root Meristematic Cells of Cereals 总被引:1,自引:0,他引:1
In the absence of Zn, vacuolar volume fractions of root meristematiccells of Secale cereale L. cv. K2, Triticum aestivum L. cv.Chinese Spring and Oryza sativa L. cv. IR34 were 5.64 x 102,2.17 x 102 and 1.63 x 102 µm3 vacuole µm3tissue, respectively. A 4-d exposure to a subtoxic concentrationof zine (0.2 µg Zn cm3) induced a 2.93-fold anda 6.78-fold increase in the total vacuolar volume fraction inOryza and Triticum, respectively, whereas no significant increasewas observed for Secale. It is proposed that this Zn-inducedvacuolation represents a compartmentalization mechanism. Theinitial total vacuolar volume fraction in Secale was greaterthan that for Oryza and Triticum and this may enable compartmentalizationof the metal soon after the onset of treatment so reducing itscytotoxic effects. These findings are similar to those observedin contrasting cultivars of Festuca rubra L. Triticum aestivum L, Secale cereale L, Oryza sativa L, zinc, root meristem, vacuolation 相似文献
9.
Modification in Cell Shape Unrelated to Cellulose Microfibril Orientation in Growing Thallus Cells of Chaetomorpha moniligera 总被引:1,自引:0,他引:1
Cellulose microfibril orientation patterns in thallus cellsof Chaetomorpha moniligera were studied, and the relationshipbetween the microfibril and the peripheral microtubule arrangementsduring cell-shape modification by colchicine was examined. Inthe cuttings from growing thalli, linearly arranged cylindricalcells developed into cask-shaped cells during 46 daysof culture at 27?C. In the cylindrical cells, microfibrils formingthe innermost portion of the wall were arranged alternatelyin longitudinal and transverse directions, but peripheral microtubuleswere always arranged only in a longitudinal direction. Thesefeatures were also noted in the cask-shaped cells. Colchicineat 103M and 3?103M accelerated both cell expansionand wall thickening with matrix deposition, but the directionsin which both microfibrils and microtubules were arranged werethe same as those of the cylindrical cells. These results indicatethat (1) the microfibril and microtubule arrangements of Chaetomorphaare not necessarily correlated, (2) changes in cell shape ofChaetomorpha are not necessarily accompanied by changes in thearrangement of cell-wall microfibrils, and (3) colchicine playsa role in the loosening and thickening of cell walls by enhancingmatrix deposition. (Received June 2, 1986; Accepted February 13, 1987) 相似文献
10.
Stem from three- and four-week-old Soyabean [Glycine max (L.)Merr. cv. Tracy] plants reduced from 0.3 to 0.7 µmol nitratehl gl f. wt. Leaf activity was 4.77.6 µmolnitrate hl gl f. wt. Outer stem was two to fourtimes more active at reducing nitrate than was inner stem. Plantnitrate nutrition had a strong effect upon the ratio of activitypresent in stem and leaf. More nitrate increased the proportionpresent in leaves. Glycine max L., soyabean, nitrate assimilation, nitrogen metabolism, Rhizobium japonicum 相似文献
11.
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 ? 104 mho cm1,LpE = 9 ? 106 cm3 s1 cm2 volt1 cm,and LPP = 0.16 cm3 s1 cm2 (J cm3)1cm. In uncut phloem strands LEE is about 1 ? 103 mhocm1. In xylem in 2 x 103 N KCI, Lpp = 50 to 225,LPE = 2 ? 104, and LEE = 4 ? 103. 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 cm1endogenous in the phloem. 相似文献
12.
Biochemical Limitations to Carbon Assimilation in C3 Plants--A Retrospective Analysis of the A/Ci Curves from 109 Species 总被引:9,自引:0,他引:9
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 m2 s1 for the coniferousspecies Picea abies to 194µmol m2 s1 forthe agricultural species Beta vulgaris, and averaged 64µmolm2 s1 across all species. The maximum rate ofelectron transport, Jmax, ranged from 17µmol m2s1 again for Picea abies to 372µmol m2 s1for the desert annual Malvastrum rotundifolium, and averaged134µmol m2 s1 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 µmolm2 s1 for the tropical perennial Tabebuia roseato 20·1 µmol m2 s1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm2 s1 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 m2 s1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm2 s1, 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
13.
Loliun perenne L. (cv.S. 23) was grown on vermiculite in winterin a heated greenhouse for 8 weeks under factorial combinationsof two potassium regimes (nominally 6 parts/106 and 156 parts/106in Hewitt's solution) and three densities of artificially supplementedvisible radiation flux (36.1, 7.3, and 2.2 W m2). Growthand potassium uptake were studied through the calculation ofvarious growth functions from fitted curves. There was little effect of potassium treatment but the experimentalmaterial responded markedly to light. Leaf-area ratio in thethree treatments showed extreme plasticity in increasing from23 x 102 through 6 x 102 to 89 x102 m2 g1 as light intensity decreased. Correspondingdecreases in unit leaf rate, however, caused over-all reductionsin relative growth rate. Specific absorption rates for potassium (AK, dry-weight basis)were strongly reduced at the lower light intensities but alsodisplayed complex ontogenetic drifts. Values of the allometricconstant, k (the ratio of root and shoot relative growth rates),decreased from c. 0.7 at 36.1 W m2 through c. 0.3 at7.3 W m2 to a value not significantly different fromzero (P < 0.05) at 2.2 W m2. In material grown under the two higher light intensities a constantinverse relationship was found between the mass ratio of rootand shoot and the corresponding activity ratio. The resultsconform to this model: Mass ratio = 0.001+45.0 (1/activityratio) where activity ratio is expressed as specific absorptionrate for potassium (in µg g root1 h1)/unitshoot rate (rate of increase of whole-plant dry weight per unitshoot dry weight, in mg g shoot1 h1). The implicationsof this relationship are discussed. 相似文献
14.
Salinity-induced Malate Accumulation in Chara 总被引:3,自引:0,他引:3
Ion absorption by Chara corallina from solutions containingpredominantly KC1 or RbCl at up to 100 mol m3 resultedin accumulation of salts and turgor regulation. Turgor regulationdid not occur in solutions containing Na+ or Li+salts. Duringion absorption from various salts of K+ and Rb+ vacuolar cationconcentration exceeded Cl concentration. This differencewas shown to be balanced by the synthesis and accumulation ofmalate. Vacuolar malate concentration reached 48 mol m3,with accumulation occurring at rates of up to 0.45 mol m3h1. Malate accumulation was inhibited by low externalpH and was dependent upon external HCO3 concentration.The synthesis of malic acid and its subsequent dissociationimposed a severe acid load on the cell. Biophysical regulationof cellular pH was achieved by a H+efflux at a rate of about40 nmol m2 s1from the cell. The results presentedargue against cytoplasmic Cl, HCO3 or pH regulatingmalate accumulation in Chara and it is suggested that malatetransport across the tonoplast may regulate malate accumulation. Key words: Malate, Chara corallina, pH regulation, salinity 相似文献
15.
(1) The penetrations of 14C-D-glucose and 3-O-methyl-14C-D-glucoseinto the isolated head of the fleshfly, Boettcherisca peregrina,from the tip of the longest chemosensory hair on the labrumwere investigated. (2) Both 14C-D-glucose and 3-O-methyl-14C-D-glucosepenetrated into the hair almost linearly with time and movedrapidly into the labrum. The isotopic activity was finally detectedin the head. (3) The isotopic activity of the hair dipped into14C-D-glucose solution increased in the preparation which hadbeen pretreated with 7.5 x 102M colchicine for 30 min,whereas in the case of 3-O-methyl-14C-D-glucose no effect by7.5 x 102M colchicine was found. (4) Both 14C-D-glucoseand 3-O-methyl-l4C-D-glucose which penetrated from the poreof the hair tip were detected in the dendritefree lumen andin the dendrite-containing lumen of the chemosensory hair. (5)These results suggest that D-glucose not only moves in the dendrite-freelumen and the dendrite-containing lumen but also in the dendrite(s).The suggestive results that 3-O-methyl-D-glucose moves in thedendrite(s) could not be obtained.
*Present address: Department of Physiology, Medical Collegeof Miyazaki, Miyazaki, Japan. 相似文献
16.
The effects of different applied NO3 concentrations onextension growth and final length and area of leaves 14of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO3 in the range 0.10.5.0mol m3 caused decreased duration of growth but increasedgrowth rate and final length of leaves 24 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale, x Triticosecaleand Triticum aestivum. For all cereals, increased NO3resulted in increased area of leaves 14. Pasture grasseswere supplied either 0.5 or 50 mol m3 NO3. Increasedapplied NO3 (0.55.0 mol m3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 14 of Bromus wiltdenowii, leaves 24ofFestuca 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 24 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
17.
Borate absorption in excised sugarcane leaves 总被引:1,自引:0,他引:1
Borate absorption in sugarcane consists of a rapid and reversibleinflux into the mesophyll cells of the leaf which is completedwithin 20 rains. (Phase I), followed by a slower and irreversibleaccumulatory phase (II). Phase II uptake represents the summationof 3 absorption mechanisms, each dependent upon the externalconcentration. Highly specific mechanisms 1 and 2 transportborate across the initial barrier into the cells, reaction 3carries the borate across the vacuolar membrane. Calcium isshown to be essential for maximum rates of borate absorption.All 3 reactions are inhibited by OH through a combinationof competitive inhibition and irreversible disruption of cellularfunction or structure. Temperature changes over the range of1040 profoundly affect Vmaz and Km1, but have no effecton Km2 and Km3. Reactions 1 and 2 are unaffected by 50 mtl Cl,SO or H2PO4, whereas each of these anionscompetes with H2BO3 for site 3. Specific metabolic inhibitorswere used to delineate a linkage of mechanisms 1 and 2 to respiratoryelectron transport. Mechanism 3 is coupled to oxidative phosphorylation.
1Published with the approval of the Director of the Hawaii AgriculturalExperiment Station as Technical Paper No. 954. 相似文献
18.
This paper elucidates the effects of chloroflurenol (morphactin,IT 3456) treatment on the kinetics of 14C-IAA transport throughZea mays L. (cv. Orla-266) coleoptile segments. Maximum inhibitionof transport was achieved when chloroflurenol remained in contactwith the tissue segments for at least 20 min or more. The treatment,without materially affecting the 14C-IAA-transport polarity,or uptake, significantly reduced the velocity from 20.5 mm h1to 8.79 mm h1 and also the intensity from 919 (ct/min)h1 to 413 (ct/min) h1. 相似文献
19.
A combined electrophysiological, behavioral, and biochemicalstudy was initiated to determine the effects of the sulfhydryl-specificreagent fluorescein mercuric acetate (FMA) on olfaction in thetobacco budworm moth Heliothis virescens. The electroantennogram(EAG) response to the standard odorant n-pentyl acetate showedboth a time and concentration dependent inhibition by FMA. Treatmentof insect antennae with 2.52 x 105 M FMA for 2 min reducedthe EAG by 50%, while treatment for 17 min reduced the EAG by80%. Incubation of antennae for 7 min with 2.52 x 106M FMA resulted in 30% inhibition, while incubation with 2.52x 106 M FMA for 7 min resulted in 65% inhibition. Antennalgrooming behavior was inhibited by FMA in a similar time andconcentration dependent manner as the EAG. Regeneration of previouslyinhibited behavioral and EAG responses has been observed withina 24-hr period. The interaction of protein, obtained by sonicatingintact antennae in phosphate buffer, with FMA was monitoredfluorometrically. Successive additions of antennal sonicateto FMA resulted in stepwise decreases in fluorescence. Partialrecovery of fluorescence was obtained by addition of cysteineto the FMA-antennal sonicate solution. The polarization of theFMA-antennal sonicate fluorescence decreased upon addition ofcysteine. These data indicate that FMA is reacting with a relativelylarge antennal protein (s) by mercaptide linkage and blockingthe olfactory transduction process. 相似文献
20.
The relationships between photosynthesis and photosyntheticphoton flux densities (PPFD, P-l) were studied during a red-tideof Dinophysis norvegica (July-August 1990) in Bedford Basin.Dinophysis norvegica, together with other dinoflagellates suchas Gonyaulax digitate, Ceratium tripos, contributed {small tilde}50%of the phytoplankton biomass that attained a maximum of 16.7µg Chla 1 and 11.93 106 total cells I1.The atomic ratios of carbon to nitrogen for D.norvegica rangedfrom 8.7 to 10.0. The photosynthetic characteristics of fractionatedphytoplankton (>30 µm) dominated by D.norvegica weresimilar to natural bloom assemblages: o (the initial slope ofthe P-l curves) ranged between 0.013 and 0.047 µg C [µgChla]1 h1 [µmol m s1]1the maximum photosynthetic rate, pBm, between 0.66 and 1.85µg C [µghla]1 h1; lk (the photoadaptationindex) from 14 to 69 µ,mol m2 s1. Carbonuptake rates of the isolated cells of D.norvegica (at 780 µmolm2 s1) ranged from 16 to 25 pg C cell1h and were lower than those for C.tripos, G.digitaleand some other dinoflagellates. The variation in carbon uptakerates of isolated cells of D.norvegica corresponded with PBmof the red-tide phytoplankton assemblages in the P-l experiments.Our study showed that D.norvegica, a toxigenic dinoflagellate,was the main contributor to the primary production in the bloom. 相似文献