共查询到20条相似文献,搜索用时 31 毫秒
1.
The effect of four pyrimidine base analogues and their antidoteson S. oligorrhiza was studied. FUdR stopped cell division at concentrations of 4 107M and higher. This effect could be nullified by the additionof 4 106 M thymidine. Neither uridine nor uracil hadan antidotal effect on FUdR. FU (8 106 M or higher concentration) affected celldivision, frond elongation and differentiation, and could notbe counteracted by either thymidine or uracil. TU (8 104 M) rather specifically inhibited differentiationof frond tissues, while not preventing cell division or theinitiation of new generations. Uracil and uridine at about equimolarconcentrations completely counteracted the TU effect. AzU (103 M) suppressed cell division, frond elongationand frond differentiation. When thymidine (103 M) wasadded simultaneously with AzU only cell elongation and differentiationof fronds were inhibited, but cell division proceeded. 103M uracil (but not uridine) counteracted all effects of AzU.
1 Based on a portion of the senior author's Ph.D. Thesis. 相似文献
2.
Lycorine, an alkaloid isolated from bulbs of Amarillidaceae,was found to be a powerful inhibitor of cell division and elongation.Adding different concentrations of lycorine from 106M to 104 M in an appropriate growth-medium strongly inhibitedcell division in explants of lettuce pith parenchyma. The sameresult was obtained with liquid yeast cultures growing exponentially. Lycorine-treated meristematic cells of the primary roots ofVicia faba also showed rapid inhibition of the mitotic indexwhile interphase cells increased proportionately. Lycorine alsoinhibited endogenous and auxin-induced cell elongation in Avenacoleoptiles and pea segments. Since both cell division and cell elongation require proteinsynthesis and RNA synthesis, the assumption is that lycorineprobably inhibits one of the two syntheses.
1This study was supported by a contract between the NationalResearch Council of Italy and University of Bari, Instituteof Botany. (Received November 27, 1972; ) 相似文献
3.
Induction of Cell Division in Leaf Cells of Coconut Palm by Alteration of pH and its Correlation with Glyoxalase-I Activity 总被引:1,自引:0,他引:1
Cell division in suspension cultures obtained from leaf cellsof coconut was influenced by pH of the culture media. A 3-foldincrease in cell number was obtained at pH 7.0 compared to suspensionsgrowing at pH 5.0. The pH of both cells and media changed after48 h of growth. Internal cell pH showed a significant increasewhen cultures were grown at pH 7.0 and 8.0 and increased onlyslightly at pH 5.0 and 6.0. Glyoxalase-I activity of cells insuspension culture was found to be pH-depcndent, showing maximumactivity at pH 7.0. Glutathione, a co-enzyme for the substratemethylglyoxaJ for glyoxalase-I, produced a 2-fold increase incell number at a concentration of 5 x 103 mol dm 3.The polyamine, spermidine, promoted cell division maximallyat a concentration of 106 mol dm3. Methylglyoxal-bis(guanylhydrazone), an inhibitor of spermidine biosynthesis,strongly inhibited cell division giving maximum inhibition ata concentration of 3 x 106 mol dm 3. These resultsindicate a positive correlation between cell division and glyoxalase-Iactivity. Key words: Cocos nucifera, glyoxalase-I, pH, spermidine 相似文献
4.
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
5.
Growth and grazing rates of Protoperidinium hirobis Abe, a thecate heterotrophic dinoflagellate 总被引:1,自引:0,他引:1
Growth and feeding rates of a laboratory-reared small thecateheterotrophic dinoflagellate, Protoperidinium hirobis Abè,grown on the diatom Leptocylindrus danicus, were measured inbatch cultures. Ingestion rates were determined directly bythe enumeration of empty diatom frustules produced by dinoflagellatefeeding. Both growth and feeding rates saturated at diatom concentrationsof {small tilde} 104 cells ml1, and reached maximum valuesof 1.7 divisions day1 and 23 diatoms grazer1 day1,respectively. This rate of cell division is notably high comparedto photosynthetic dinoflagellates, which seldom grow fasterthan 1 division day1. A maximal clearance rate of 0.5µl h1 was measured. Mean cell size varied proportionallywith food abundance, with food-saturated cells having doublethe mean volume of food-depleted cells. Tuning of cell divisionand grazing rate patterns were also examined; while mitosisoccurred chiefly during the dark period, no diel variationsin feeding rate were detected. These rates represent the firstdirect growth and ingestion measurements to be made for a thecateheterotrophic dinoflagellate. They serve to underscore one functionthese dinoflagellates perform within the microzooplanktonicfood web: that of transforming large diatoms into particlesmore easily ingested by microzooplankters. 相似文献
6.
Ammonium release by zooplankton in suspensions of heat-killed algae and an evaluation of the flow-cell method 总被引:1,自引:0,他引:1
Vanderploeg Henry A.; Laird Gwenyth A.; Liebig James R.; Gardner Wayne S. 《Journal of plankton research》1986,8(2):341-352
The maximum excretion rate of NH4 (39 nmol mg dry wt1h1) was directly measured for Daphnia pulex by measuringNH4 accumulation in bottles containing D. pulex and dense, satiatingsuspensions of heat-killed algae. Ammonium release rates inthe algal suspensions were compared to those of individual animalsremoved from the suspension and placed in flow cells. Ammoniumrelease rate, R (nmol mg dry wt1 h1). in the flowcell decreased very rapidly with time, t (min), after removalaccording to the relation R = 26 + 25e0.16t. Ammoniumexcretion obtained by the flow cell method after extrapolationto time zero was not significantly different from that obtainedin the bottles. The considerable experiment-to-experiment variationin NH4 excretion was in large part correlated (r2 = 0.73) withthe feeding rate on the algae. 相似文献
7.
The time course of xylem differentiation was determined in explantsof lettuce pith parenchyma (Lactuca sativa L. cv. Romana) culturedon Murashige and Skoog (1962) medium using different concentrationsof auxin (IAA) and one cytokinin (zeatin or kinetin). Increasinglevels of auxin from I mg 11 to 15 mg 11 in thepresence of a constant level of a cytokinin (zeatin or kinetin)yielded up to 10 mg 11 IAA, an increase in the numberof tracheary element formations. Cytokinin concentrations aboveand below o.1 mg 11 interacting with an optimal xylogenicamount of auxin inhibited xylogenesis. The IAA (10 mg 11)-zeatin(0.1 mg 11) treatment produced the greatest number oftracheids, while kinetin compared to zeatin did not producesuch an effect. The different effectiveness of zeatin and kinetinin inducing tracheary element formations was not due to a differentcapacity of the two cytokinins to stimulate cell division butit seems likely that zeatin, because of interaction with IAA,is more active than kinetin in the determination of the dividingcells in a specific type of cytodifferentiation. The IAA (10mg 11)-zeatin (0.1 mg 11) treatment produced about6.9 per cent tracheids with respect to cell division while IAA(10 mg 11)-kinetin (0.1 mg 11) produced 4.2 percent. These results are discussed with reference to the problemsof hormonal control of xylem differentiation. 相似文献
8.
Growth of Ceratium hirundinella in a subtropical Australian reservoir: the role of vertical migration 总被引:3,自引:0,他引:3
Whittington John; Sherman Bradford; Green Damian; Oliver Roderick L. 《Journal of plankton research》2000,22(6):1025-1045
A study into the photophysiology, growth and migration of Ceratiumhirundinella in Chaffey Reservoir in subtropical northern NewSouth Wales, Australia, revealed that a proportion of cellsformed subsurface accumulations at depths that optimized lightintensity (212552 µmol photons m2 s1)for photosynthesis and cell growth. At high incident irradiance,Ceratium migrated downwards from the near-surface waters, avoidinghigh-light-induced, slow-recovering non-photochemical quenchingof photosystem II. Overnight deepening of the surface mixedlayer by convective cooling produced homogeneous distributionsof Ceratium with a significant proportion of the populationbelow the depth where light saturation of photosynthesis occurred.Ceratium migrated towards the surface from suboptimal lightintensities, at a velocity of 1.62.7 x 104 m s1.Subsurface accumulations occurred under a variety of turbulenceintensities; however, accumulation was significantly reducedwhen the turbulent velocity scale in the mixed layer was >5x 103 m s1, beyond which turbulent diffusion dominatedadvection by swimming. The formation of subsurface accumulationswith increased computed water column integral photosynthesisby 35% compared to a uniform cell distribution. 相似文献
9.
Three marine phytoplankton species (Skeletonema costatum, Olisthodiscusluteus andGonyaulax tamarensis) were grown in batch culturesat 15°C and a 14:10 L:D cycle at irradiance levels rangingfrom 5 to 450 µEinst m2 s1. At each irradiance,during exponential growth, concurrent measurements were madeof cell division, carbon-specific growth rate, photosyntheticperformance (both O2 and POC production), dark respiration,and cellular composition in terms of C, N and chlorophyll a.The results indicate that the three species were similar withrespect to chemical composition, C:N (atomic) = 6.9 ±0.4, photo-synthetic quotient, 1.43 ± 0.09, and photosyntheticefficiency, 2.3 ±0.1 x 103 µmol O2 (µgChl a)1 h1 (µEinst m2 s1)1.Differences in maximum growth rate varied as the 0.24power of cell carbon. Differences in growth efficiency, werebest explained by a power function of Chl a:C at µ = 0.Compensation intensities, ranged from 1.1 µEinst m2s1 for S. costatum to 35 forG. tamarensis and were foundto be a linear function of the maintenance respiration rate.The results indicate that interspecific differences in the µIrelationship can be adequately explained in terms of just threeparameters: cell carbon at maximum growth rate, the C:Chl aratio (at the limit as growth approaches zero) and the respirationrate at zero growth rate. A light-limited algal growth modelbased on these results gave an excellent fit to the experimentalµI curves and explained 97% of the observed interspecificvariability.
1Present address: Lamont-Doherty Geological Observatory Columbiaof University, Palisades, NY 10964, USA 相似文献
10.
For Gyrodinium aureolum significant irradiance and daylengtheffects were found on the division rate and on the growth-relevantChla-normalized photosynthetic rate (gPB). Optimum conditionsof irradiance and daylength were found at 230 µmol m2s1 and 14 h for the division rate, and at >260 µmolm2 s1 and <6 h for gPB.gPB showed no photoinhibition,while the division rate decreased markedly at irradiances abovesaturation. This difference and the difference in optimum irradiancebetween the division rate and gPB are explained by a decreasein cellular Chla/carbon ratio with increasing irradiance. Thecellular content of carbon and nitrogen decreased significantlywith increasing irradiance. Total phosphorus was independentof irradiance and daylength. Below the saturation irradiancefor gPB the daily Chla-normalized carbon yield may be describedas an exponential function of the daily irradiance (irradiancex daylength). 相似文献
11.
Whipple Stuart J.; Patten Bernard C.; Verity Peter G. 《Journal of plankton research》2005,27(5):495-501
Using well plates of Phaeocystis pouchetii colonies isolatedfrom experimental mesocosms in western Norway, increases incolony size and division were documented. Median longest lineardimensions increased 07 µm h1; literaturePhaeocystis globosa values are 0.94.7 µm h1.Ten to twelve percent of colonies divided at rates of 0.210.28divisions day1. Daughter colonies were 100 µm smallerthan mother colonies. Colonies delayed 3.54.9 days tofirst division, compared with literature values of 45days for P. globosa. This study provides the first experimentalevidence for colony division of wild P. pouchetii. 相似文献
12.
Soybean [Glycine max (L.) Merrill] seeds and cotyledons weregrown in an in vitro culture system to investigate the relationshipsbetween cell expansion (net water uptake by the seed) and drymatter accumulation. Seeds or cotyledons grown in a completenutrient medium containing 200 mol m3 sucrose continueddry matter accumulation for up to 16 d after in planta seedsreached physiological maturity (maximum seed dry weight). Seedor cotyledon water content increased throughout the cultureperiod and the water concentration remained above 600 g kg1fresh weight. These data indicate that the cessation of seeddry matter accumulation is controlled by the physiological environmentof the seed and is not a pre-determined seed characteristic.Adding 600 mol m3 mannitol to the medium caused a decreasein seed water content and concentration. Seeds in this mediumstopped accumulating dry matter at a water concentration ofapproximately 550 g kg1. The data suggest that dry matteraccumulation by soybean seeds can continue only as long as thereis a net uptake of water to drive cell expansion. In the absenceof a net water uptake, continued dry matter accumulation causesdesiccation which triggers maturation. Key words: Glycine max (L.) Merrill, solution culture, duration of seed growth, water content, dry matter accumulation 相似文献
13.
Malondialdehyde, a product of lipid oxidation, increased graduallywhen Euglena gracilis cells were bubbled with 240 µ1.liter1ozone (delivery rate of 1µmolO3.min1) for 120 min.Simultaneously, the sulfhydryl group content decreased by 36%during the treatment, which was mainly due to oxidation of proteinsulfhydryl groups. The molar amount of SH groups oxidized was3 times higher than that of fatty acid oxidized, indicatingthat sulfhydryl groups were more accessible or more easily oxidizedby O3 than fatty acids. When Euglena cells were allowed to recoverunder autotrophic growth conditions following O3 treatment,viable cells were incapable of dividing during the first 5 hof the recovery period but regenerated SH groups nearly to thecontrol level. The increase of SH content during this periodpreceded the resumption of cell division and the restorationof normal growth. These results suggest that the regenerationof SH groups by Euglena cells is a part of a mechanism involvedin the repair of oxidative damage caused by ozone and is anessential step for the initiation of cell division. (Received July 20, 1987; Accepted December 14, 1987) 相似文献
14.
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
15.
When a dicotyledonous stem is wounded by longitudinally splittinga young internode into halves, cells near the cut surface proliferateto form a callus within which vascular tissues differentiateand tend to restore a vascular cylinder in each half. Threephases of regeneration after wounding were identified and quantifiedin stems of three Solanaceous species. (1) In an initial lagphase, lasting about 2 d, neither cell division nor enlargementwere detected, but mitotic figures were observed within about300 µm of the cut surface. (2) Throughout a second, divisionphase, from about days 210, cell division and enlargementoccurred. Both were initiated mainly in the two cell layersnearest the surface. A mass of callus formed, with new cellwalls mostly parallel to the surface. Cell enlargement laggedbehind cell division for the first few days, so that mean radialcell diameter decreased until day 6, thereafter remaining almostconstant at 3040 µm. Towards the end of this phase,mitoses ceased within the callus except in the positions ofthe future vascular and cork cambia, where radial cell diameterfell towards a constant 1520 µm. (3) During a third,differentiation phase, cell division was restrictedto the cambial zones, and derivatives differentiated into cork,phloem or xylem according to position. The rate of increasein cell number per transect was 1.52.0 cells d1,of which more than half was xylem. Capsicum annuum L., sweet pepper, Lycopersicon esculentum Mill., tomato, cambium, cell division, differentiation, regeneration, wounding of stems, xylem 相似文献
16.
Kato Ryoichi; Nagayama Erina; Suzuki Takashi; Uchida Kenko; Shimomura Tomoko H.; Harada Yoshinori 《Plant & cell physiology》1993,34(6):789-793
In some specified treatments, an epidermal growth factor (EGF)promoted adventitious root formation in epicotyl cuttings ofVigna angularis. The number of the roots induced in cuttingstreated with 0.1 mg liter-1 EGF during the first 24 h and with210-4 M IAA during the second 24 h was 15% greater than thatof the roots in cuttings treated without EGF and with IAA. Analysisof the optimum timing of EGF application was performed by dividingthe first 24 h period into three sequential 8 h periods (08h, 816 h and 1624 h). The most effective timeperiods in terms of the root formation were 816 h and1624 h. The 08 h period was ineffective with respectto the formation. When carrot suspension cells were culturedfor 15 days at a very low cell density (1,000 cells/3 ml Murashigeand Skoog's medium) with more than 0.1 mg liter-1 EGF, cellnumbers were 72% higher than those cultured without EGF. Theseresults suggest that EGF promotes cell division of plants. (Received October 5, 1992; Accepted May 24, 1993) 相似文献
17.
Enhanced suicidal death of erythrocytes from gene-targeted mice lacking the Cl-/HCO(3)(-) exchanger AE1 总被引:2,自引:0,他引:2
Akel A Wagner CA Kovacikova J Kasinathan RS Kiedaisch V Koka S Alper SL Bernhardt I Wieder T Huber SM Lang F 《American journal of physiology. Cell physiology》2007,292(5):C1759-C1767
Genetic defects of anion exchanger 1 (AE1) may lead to spherocytic erythrocyte morphology, severe hemolytic anemia, and/or cation leak. In normal erythrocytes, osmotic shock, Cl removal, and energy depletion activate Ca2+-permeable cation channels with Ca2+-induced suicidal erythrocyte death, i.e., surface exposure of phosphatidylserine, cell shrinkage, and membrane blebbing, all features typical for apoptosis of nucleated cells. The present experiments explored whether AE1 deficiency favors suicidal erythrocyte death. Peripheral blood erythrocyte numbers were significantly smaller in gene-targeted mice lacking AE1 (AE1/ mice) than in their wild-type littermates (AE1+/+ mice) despite increased percentages of reticulocytes (AE1/: 49%, AE1+/+: 2%), an indicator of enhanced erythropoiesis. Annexin binding, reflecting phosphatidylserine exposure, was significantly larger in AE1/erythrocytes/reticulocytes (10%) than in AE1+/+ erythrocytes (1%). Osmotic shock (addition of 400 mM sucrose), Cl removal (replacement with gluconate), or energy depletion (removal of glucose) led to significantly stronger annexin binding in AE1/ erythrocytes/reticulocytes than in AE1+/+ erythrocytes. The increase of annexin binding following exposure to the Ca2+ ionophore ionomycin (1 µM) was, however, similar in AE1/ and in AE1+/+ erythrocytes. Fluo3 fluorescence revealed markedly increased cytosolic Ca2+ permeability in AE1/ erythrocytes/reticulocytes. Clearance of carboxyfluorescein diacetate succinimidyl ester-labeled erythrocytes/reticulocytes from circulating blood was more rapid in AE1/ mice than in AE1+/+ mice and was accelerated by ionomycin treatment in both genotypes. In conclusion, lack of AE1 is associated with enhanced Ca2+ entry and subsequent scrambling of cell membrane phospholipids. annexin; cell volume; osmolarity; phosphatidylserine; energy depletion 相似文献
18.
The amounts of plastid DNA in the primary leaves of 4-d-oldlight- and dark-grown seedlings of Avena sativa were measuredby microspectrofluorometry using the DNA-fluorochrome DAPI (4',6-diamidino-2-phenylindole). In the light-grown primary leaves (4045 mm long) therewas a marked increase in DNA level per plastid from 10.2 to18.5 ? 1015 g between 2.0 mm and 10 mm from the leafbase, resulting from the rate of plastid DNA synthesis beinghigher than the rate of plastid division. Beyond 30 mm the plastidDNA level was reduced to 14 ? 1015g due to chloroplastdivision rates being higher than the rate of plastid DNA synthesis,while from 20 mm plastid DNA levels were constant at 2.2 ? 1012g per cell, which corresponds to 16000 plastome copies per cell. Observations of dark-grown leaves establish that, in Avena,light is not necessary for plastid division and the dark-grownleaf cells accumulate higher amounts of plastid DNA than light-grownleaf cells. Plastid nucleoids showed a change of distribution after completionof plastid DNA synthesis in light-grown leaves. A change inthe distribution of plastid nucleoids was also observed duringthe greening of etioplasts of dark-grown leaves while plastidDNA level remained constant. Such changes in plastid nucleoiddistribution appear to be independent of plastid DNA synthesisand correlate with the formation of grana stacks. Key words: Avena sativa, microspectrofluorometry, plastid DNA 相似文献
19.
Rapid interactions in cell division and cytodifferentiationare induced by hormone treatments in dark-cultured explantsof Jerusalem artichoke. Fusicoccin, at concentrations between106 and 105 M, markedly inhibited the division-promotingactivity induced by plant hormones. Further, fusicoccin-treatedmeristematic root tips of Vicia faba and Allium cepa showeda rapid decrease in the mitotic index. Fusicoccin seems to inhibitsome hormone-sensitive processes required during the inductionand regulation of cell division. (Received March 28, 1979; ) 相似文献
20.
Sexual cell division and activation of gametangial cells forconjugation in Closterium acerosum were induced by light. L200cells conjugated at maximum level under the following conditions;(i) a light intensity higher than 1,000 lux in a 16-hr lightand 8-hr dark regime and (ii) an illumination time longer than12 hr at 3,000 lux. L200 cells also conjugated under continuousillumination at 3,000 lux. The action spectrum for the activation of gametangial cellshad peaks around 450, 611 and 665 nm. 3-(4'-Chlorophenyl)-l,l-dimethylurea (CMU) inhibited the accumulationof carbohydrates and sexual cell division at 105 M andthe activation of gametangial cells for conjugation at 104M. (Received August 15, 1977; ) 相似文献