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1.
Domozych, D. S. 1987. An experimental analysis of the dictyosomein the green alga, Tetraselmis convolutae.J. exp. Bot.38: 13991411. Tetraselmis convolutae possesses two well-defined, polar-orienteddictyosomes. These endo-membrane components have various functionsthat change during the cell cycle phases. The dictyosomes arealso very sensitive to various subcellular poisons. Disruptionof the cellular ionic balance with monovalent ionophores yieldsmaturing face curling, swelling and the production of unusualmultivesicular elements. Divalent ionophore application alsoimpairs maturing face vesiculation and vesicle transport inthe anterior cytoplasm. Caffeine restricts maturing face vesicleproduction, subsequently leading to gross enlargement of cisternallength. Application of the microtubule-inhibitor, colchicine,and the MTOC-affecting agent, IPC, leads to polar axis disruptionof the dictyosome and the formation of multiple, cisternal stacks.A discussion of dictyosome-microtubule-MTOC associations ispresented. Key words: Tetraselmis, dictyosome, disruption 相似文献
2.
X-Ray Microanalysis and Ultrastructural Studies of Cell Compartments of Dunaliella parva 总被引:1,自引:0,他引:1
HAJIBAGHERI M. A.; GILMOUR D. J.; COLLINS J. C.; FLOWERS T. J. 《Journal of experimental botany》1986,37(11):1725-1732
Hajibagheri, M. A., Gilmour, D. J., Collins, J. C. and Flowers,T. J. 1986. X-ray microanalysis and ultrastructural studiesof cell compartments of Dunaliella parva. -J. exp. Bot. 37:17251732. Ultrastructural studies of the unicellular green alga Dunaliellaparva showed the presence of cytoplasmic vacuoles. X-ray microanalysiswas performed on sections of cells which had been freeze substitutedin acetone. It was found that the concentrations of both Naand Cl were much higher in the vacuoles than in the cytoplasm.When cells were grown in 0·4 kmol m3 NaCl theNa and Cl concentrations in the vacuoles were 349 and 283 molm 3 respectively, whilst cytoplasmic Na and Cl concentrationswere 37 and 26 mol m3. Corresponding values for cellsgrown in 1·5 kmol m3 NaCl were 392 mol m3Na and 325 mol m3 Cl in the vacuoles and 36 mol m3Na and 30 mol m3 Cl in the cytoplasm. Immediately afterexposure to an increase in external salinity Na and Q concentrationsincreased in both vacuoles and cytoplasm. The results are discussedwith reference to compartmental models for the ionic relationsof Dunaiiella. Key words: X-ray microanalysis, ultrastructural studies, Dunaliella parva 相似文献
3.
We report that growth of Dunaliella salina at either 13°C/150µmol m2s1 or 30°C/2,500 µmol m2s1 results in the accumulation of comparable levels ofcarotenoids and the zeaxanthin-binding protein, Cbr. We concludethat carotenoid and Cbr abundance in this green alga respondto changes in PSII excitation pressure ratherthan to high light per se. (Received September 19, 1996; Accepted November 20, 1996) 相似文献
4.
THALER M.; STEIGNER W.; F?RSTER B.; K?HLER K.; SIMONIS W.; URBACH W. 《Journal of experimental botany》1989,40(11):1195-1203
The role of cytoplasmic calcium activity in activation of K+-channelsin the unicellular green alga Eremosphaera viridis has beenstudied. As reported previously, after a light offsignal a voltage independent opening of K+-channels in the plasmalemmais observed. This effect is indicated by a transient polarization(TP) with a simultaneous increase of the membrane conductance.TPs can also be triggered by different treatments, which allowinvestigations within a short-circuited signalchain. (i) After incubation with EGTA a single extended TP canbe released by a sudden increase of the external calcium concentration.The Ca2+-channel inhibitors nifedipine (10 2 mol m3)and verapamil (5 ? 102 mol m3) suppress the releaseof this TP. (ii) In the presence of external calcium the additionof the ionophore A23187
[GenBank] (103 mol m3) causes anextremely prolonged TP. (iii) Low external concentrations ofbarium (102 mol m3) induce repetitive TPs in thepresence of external calcium. In this case the Ca2+-channelinhibitors are less effective. (iv) Strontium (0.11.0mol m3) is able to trigger repetitive TPs even withoutexternal calcium. Whereas barium may stimulate a calcium influx,strontium can serve as a substitute for calcium to induce anopening of K+-channels. These results indicate strongly a Ca2+-dependentand voltage-independent activation of K+-channels in the plasmalemmaof Eremosphaera. The participation of cytoplasmic calcium inthe signal transduction chain after a light offsignal is discussed. Key words: Ca2+-dependent K+-channels, Ca2+-channel effectors, A23187, transient membrane potential, Eremosphaera 相似文献
5.
Determination of Volume of Dunaliella Cells by Lithium Dilution Measurements and Derivation of Internal Solute Concentrations 总被引:1,自引:0,他引:1
A method has been developed to measure the cell volume of theunicellular green alga Dunaliella parva 19/9 using Li+ measurementsonly. Concentrations of internal solutes can also be calculatedif they are assayed in the same samples as Li+. We found thatD. parva cells grown in 0.4 kmol m3 NaCl have an averageaqueous cell volume of 65.1 ?2.9 µm3, a K+ concentrationof 126?6 mol m3, a Na+ concentration of 11?11 mol m3and a glycerol concentration of 615?27 mol m3 (n= 12).Algae grown in 1.5 kmol m3 NaCl have an average aqueouscell volume of 131 ?7.5 µm3, a K+ concentration of 109?4mol m3, a Na+ concentration of 10?39 mol m3 anda glycerol concentration of 1 425?59 mol m3 (n = 12).These results indicate that D. parva cells adapted to high salinitieshave larger cell volumes than those adapted to lower salinities.However, there is no evidence for a significant difference ininternal Na+ concentration, despite the almost 4-fold differencein the concentration of external NaCl. The intracellular glycerolconcentration alone accounts for 65% and 54%, respectively,of the osmotic balance in low and high salt grown cells. Key words: Dunaliella, cell volume, intracellular solutes 相似文献
6.
The effects of five inhibitors of protein synthesis, viz. streptomycin,aurin tricarboxylic acid, tetracycline, chloramphenicol, andcycloheximide, on the calcification of Gloeotaenium loitlesbergarianumHansgirg, a freshwater green alga were studied. Streptomycinhad no effect while aurin tricarboxylic acid at 50 µgml1 and tetracyline, chloramphenicol and cycloheximideat 20 µg ml1 completely inhibited calcificationin the alga. High concentrations of chloramphenicol and cycloheximidewere not completely inhibitory when added 26 h and 32 h respectivelyafter the material was incubated in the induction medium. Itis concluded that the effects by these substrates are the resultsof inhibition of protein synthesis, which is directly or indirectlylinked to calcification. calcification, Gloeotaenium loitlesbergarianum Hansgirg, green alga, chlorophyceae, protein synthesis inhibitors 相似文献
7.
The effects of 0, 50, 100, 200, 300, 400 and 500 mol m3NaCl on growth and ion accumulation in the succulent, coastalhalophyte Sarcocornia natalensis (Bunge ex Ung.-Sternb.) A.J. Scott were investigated. Increase in salinity from 0 to 300 mol m3 NaCl stimulatedproduction of fresh, dry, and organic dry mass, increased succulenceand shifted resource allocation from roots to shoots. Growthwas optimal at 300 mol m3 and decreased with furtherincrease in salinity. Water contributed to a large proportion of the increase in freshmass. Inorganic ions, especially Na+ and Cl contributedsubstantially to the dry mass. At 300 mol m3 NaCl inorganicions contributed to 37% of total dry mass and NaCl concentrationin the shoots was 482 mol m3. Expressed sap osmotic potentialsdecreased from 2.10 to 3.95 MPa as salinity increasedfrom 0 to 300 mol m3 NaCl. Massive accumulation of inorganicions, especially Na+ and Cl, accounted for 86% of theosmotic adjustment at 300 mol m3 NaCl. Salinity treatments decreased the concentrations of K+ in shoots.Plant Na+ :K+ ratios increased steadily with salinity and reacheda maximum of 16.6 at 400 mol m3 NaCl. It is suggested that the exceptional salt tolerance of S. natalensisis achieved by massive inorganic ion accumulation which providessufficient solutes for osmoregulation, increased water fluxand turgor-induced growth. Key words: Sarcocornia natalensis, salt tolerance, halophyte 相似文献
8.
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
9.
Measurement of the Apoplastic Activity of K+ and Cl- in the Leaf Epidermis of Commelina communis in Relation to Stomatal Activity 总被引:2,自引:0,他引:2
Bowling, D. J. F. 1987. Measurement of the apoplastic activityof K+ and Cl in the leaf epidermis of Commelina communisin relation to stomatal activity.J. exp. Bot. 38: 13511355. Ionic activity of K+ and Cl in the apoplast of the lowerepidermis of the leaf of Commelina communis was measured usingion selective micro-electrodes. Large gradients across the stomatalcomplex were observed which were related to stomatal aperture.On stomatal closure the activity of K+ and Cl in theapoplast of the guard cell rose from 3·0 mol m3to 100 mol m3 and 33 mol m3 respectively. It wasconcluded that the apoplast is an important pathway for iontransport between the cells. Key words: Stomata, ionic activity, leaves, apoplast 相似文献
10.
The Root Cap as a Test System for the Evaluation of Golgi Inhibitors: I. STRUCTURE AND DYNAMICS OF THE SECRETORY SYSTEM AND RESPONSE TO SOLVENTS 总被引:2,自引:0,他引:2
Maize (Zea mays) seedlings were grown under standard conditionsand the time for reformation of a slime droplet of standardsize was determined. The structure of the secretory cells wasexamined by light and electron microscopy. Osmium-zinc iodide(OZI) impregnation was used to provide contrast enhancementof the dictyosome forming-face cisternae and the endoplasmicreticulum (ER). The three-dimensional structure and relationshipsof these membrane systems were established from examinationof 300 nm thick sections. The presence of a marginal cisternalnetwork at the forming-face was confirmed, but no specific orientationof the ER to this face, or connection of ER to any part of thedictyosome could be demonstrated. Neither observation of reforming slime droplets, nor quantificationof secretory vesicle numbers gave any support to the suggestionthat slime formation is a phasic, or cyclic, process. Dilute solutions of solvents (1% ethanol, 1% and 0.1% DMSO)commonly used to solubilize potential inhibitors of Golgi activitywere found to delay significantly the time taken for reformationof a slime droplet of standard size. These solutions also hadslight effects on the numerical density of secretory vesicles. Cytochalasin D-induced accumulation of secretory vesicles wasused to determine rates of vesicle formation (0.39 dictyosome1min1) and hence turnover times for cisternal (6.5 min)and total dictyosome (2639 min) membranes and the plasmamembrane (9.7 min). The volume contribution of the secretory vesicles to the slimedroplet was shown to be exceedingly small (01%), throwingdoubt on the value of using droplet reformation rates as anindicator of secretory activity. Key words: Maize, Root cap secretion, Dictyosome activity 相似文献
11.
Young, A. J., Collins, J. C. and Russell, G. 1987. Ecotypicvariation in the osmotic responses of Enteromorpha intestinalis(L.) Link.J. exp. Bot. 38: 13091324. The physiological basis for salt tolerance has been studiedin the euryhaline marine alga Enteromorpha intestinalis. Adaptationto dilute and concentrated seawaters has been investigated inthree separate populations of this alga: marine, rock pool andestuarine. Internal K+, Na+ and Cl levels have been determined usingtracer efflux analyses. K+ has been shown to be the major osmoticsolute within this alga. Cellular levels of Cl and, inparticular, Na+ are low although levels in the cell wall arehigh. Levels of these ions varied considerably between the separateplants; K+ levels within marine plants of E. intestinalis aretwo to four times those found in the other populations. Thetertiary sulphonium compound ß-dimethylsulphonio-propionateis maintained at relatively high levels, although it remainsfairly insensitive to change in the external salinity. Changes in the tissue water content and cell volume are large,particularly within the estuarine plants. The thin cell wallsof these plants allow large changes in volume in the diluteconditions experienced in an estuary, while low turgor preventscell rupture. Thicker cell walls and small cells of the marineand rock pool plants assist in tolerating high and low externalosmotic potentialthe estuarine plants respond poorlyto concentrated seawater. Key words: Enteromorpha, osmoregulation, ecotypes 相似文献
12.
The purification and properties of a nitrate reductase fromthe green alga Dunaliella tertiolecta are described. The enzymeis soluble, with a molecular weight greater than 500,000 andhas Km values of 0.26, 0.18, 0.10 and 0.06 m for NO3,NADH, NADPH and FADH2 respectively. Even at the highest specificactivity obtained, (0.86 µmoles NO3 reduced min1mg protein1) the enzyme retains the capacity to acceptelectrons from both NADH and NADPH. Unlike other nitrate reductasesit does not appear to be able to use reduced viologens as electrondonors. Its other properties are consistent with its being amolybdoflavoprotein of high molecular weight, which is alsoable to function as a cytochrome C reductase.
1 Supported in part by the National Research Council of Canada. (Received June 18, 1972; ) 相似文献
13.
Spring phytoplankton communities in the water column of EllisFjord are characterized by diatoms originating from the bottomsea-ice strand community. Upon ice breakout in early summer,these are replaced by blooms of the phytoflagellates, Phaeocystispouchetii, Cryptomonas cryophila, Pyramimonas gelidicola, silicoflagellatcsand dinoflagellates. The narrow entrance of the fjord and thedevelopment of summer stratification is probably limiting theavailability of nutrients and containing the magnitude of thesmall bloom (maximum 2.8 106 cells l1). 相似文献
14.
The native pyrenoid core matrix of the green alga Bryopsis maximawas isolated by diethyl ether treatment and sucrose densitygradient centrifugation using 1.8 M phosphate buffer. The purityof the pyrenoids was examined by microscopy, polyacrylamidegel electrophoresis and marker materials. The purified pyrenoidscontained the large subunit and the small subunit of ribulose1,5-bisphosphate carboxylase (RuBPCase) and more than 10 minorpolypeptides. They also showed RuBPCase activity when solubilizedon being transferred to a low-concentration buffer. The specificactivity was 0.62 µmol CO2 fixed (mg protein)1min1. This isolation method is suitable for obtainingintact pyrenoids not covered by starch sheaths or membraneswithout the need for chloroplast fixation. (Received July 27, 1987; Accepted October 20, 1987) 相似文献
15.
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 m3 CaCl2 r, P, Y and were20.7±4.6 µm min1, 0.77±0.05 MPa,0.07±0.03 MPa and 26±1.9 µm min1MPa1 (expressed as increase in length), respectively.Following 24 h growth in 10 mol m3 KC1 these parametersbecame 12.3±3.5 µm min1, 0.72±0.04MPa, 0.13±0.01 MPa and 21±0.7 µm min1MPa1. After 24 h osmotic adjustment in 150 mol m3mannitol/0.5 mol m3 CaCl2 r= 19.6±4.2 µmmin1, P = 0.68±0.05 MPa and Y and were 0.07±0.04MPa and 30±0.2 µm min1 MPa01, respectively.After 24 h growth in 350 mol m3 mannitol/0.5 mol m3CaCl2 r= 13.3±4.1 µm min1, P= 0.58±0.07MPa, Y=0.12±0.01 MPa and ø 32±0.2 tim min1MPa1. During osmotic adjustment in 200 mol m3mannitol/0.5 mol m3 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 min1,P=0.78 MPa, r=<0.2 MPa and =15±0.1 µm min1MPa1. Therefore, Y and are influenced by 10 mol m3 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
16.
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 m3 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 mg1 chl h1,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 mg1 chl h1 as compared to valuesin the order of 50 µmol phosphate mg1 chl h1for the second phase (this magnitude is also representativefor non-limited batch cultures). Concomitantly the Michaelisconstant was altered from 4 mmol m3 to 0·7 mmolm3. 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 m3 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
17.
Increase in fluence rates of white light over the range of 5to 80 µmol m2 s1 brought about a correspondingincrease in amounts of anthocyanin production in shoots of Zeamays L. seedlings. Roots also exhibited a similar relationshipbetween increased fluence rate and increased anthocyanin productionover the range of 5 to 40 µmol m2 s1 whereasfluence rates above 40 µmol m2 s1 broughtabout decreases in anthocyanin production. Rates of productionand amounts of accumulation of anthocyanin in both shoots androots were found to vary with the age of the seedlings at thetime of exposure to light. Age, fluence rates, anthocyanin, seedlings, Zea mays 相似文献
18.
19.
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
20.
Cultures of nine potato genotypes (seven Solanum tuberosum oneS. sparsipilum and one S. oplocense genotypes) were examinedfor their response to growing on medium containing either 60mol m3, 40 mol m3 or 20 mol m3 nitrogen.Genotypes differed in their response to nitrogen. Reducing thenitrogen regime tended to produce taller plants with longerinternodes, shoots had larger leaves but contained less chlorophyll.No change in fresh weight or number of nodes was observed. Genotypex nitrogen interactions were significant for chlorophyll content,shoot length and internode length. Results suggest that thechanges observed were as a result of changes in the total nitrogenlevel rather than changes in the ammonium : nitrate ratio. Thisstudy suggests that for certain potato genotypes, nitrogen levelsin MS medium are too high for producing desirable microplantsin terms of leaf area and shoot length Key words: Solanum tuberosum, S. sparsipilum, S. oplocense, micropropagation, morphogenesis 相似文献