首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
OBJECTIVE: To compare methods of analyzing changes in red blood cell volume when exposed to osmotic challenge. STUDY DESIGN: The sensitivity of different methods was tested using fish erythrocytes under hypoosmotic stress (80% and 60% saline): hematocrit ratio, Hcto(exp)/ Hcto(ctr); cellular hemoglobin mean concentration; optical density (OD400); water content; surface area estimation; mean corpuscular volume (MCV); and mean cellular hemoglobin (MCH). RESULTS: Cells exposed to both solutions demonstrated a volume increase via hematocrit ratio of 16 +/- 2% and 30 +/- 3% (p < 0.001) when exposed to 80% and 60% saline, respectively. Cellular volume estimation by OD400 revealed a change in volume only at 60% saline (26% increase). Surface area estimation suggested a difference in volume at 60% saline. MCV revealed differences in volume at < 60% saline exposure with a 33% increase and indicated a 19% increase at 80% saline. MCH showed an increase of 48% with exposure to 80% saline. CONCLUSION: The results reveal that Hcto(ctr)/Hcto(exp), MCV, OD400 and MCH yield significant volume changes and that Hcto(ctr)/Hcto(exp) is the most sensitive assay.  相似文献   

2.
The Effect of Light on the Structure and Organization of Lemna Peroxisomes   总被引:1,自引:0,他引:1  
The effect of light on a number of Lemna minor enzyme activitieswas investigated. The levels of activity of glycolate oxidase,catalase and RuBPCase increased with increasing irradiance,paralleling the increase in Lemna growth rate. In contrast withresults obtained for other species, no glycolate oxidase activitycould be detected in etiolated Lemna fronds or when these weretreated with light or glycolate, in vivo or in vitro, for upto 24 h. The number of peroxisome profiles per cell section was determinedin Lemna grown under different light conditions. When frondswere grown under dim light, the number of peroxisome profilesper cell section appeared to increase with increasing irradiance,although no further increase in the peroxisome number was apparentwhen the fronds were grown under higher irradiances. The levelof glycolate oxidase activity per peroxisome was shown to increasewith increasing irradiance, whereas that of catalase remainedrelatively constant, indicating that differential addition ofenzymes to pre-existing peroxisomes is possible. Peroxisomes from Lemna grown under high irradiance were subjectedto serial sectioning and examined under the electron microscope.Some peroxisomes were found to have a three dimensional structuresuggesting either fission and/or fusion or branching of theseorganelles, supporting the hypothesis of a peroxisomal reticulum.The dynamic relationship between the various shapes is discussed. Key words: Peroxisomes, glycolate oxidase, catalase  相似文献   

3.
In order to study a possible application of cerium-based techniquesin plant cells, ATPase and acid phosphatase activities havebeen compared in two cell lines of Pisum sativum calli, onesensitive to NaCI and the other selected to be grown under salinity(85 mM NaCI). ATPase activity was unchanged and localized inthe plasma membrane of both cell lines. Acid phosphatase activitywas significantly increased in the salt-selected line and localizedin the cell walls, Golgi complex, multivesicular bodies andvacuoles. These results indicated a possible involvement ofboth activities in the maintenance of cell growth in the selectedline under saline conditions. Key words: Acid phosphatase, Pisum sativum, plasma membrane ATPase, salt stress, ultrastructure  相似文献   

4.
Dunaliella is a genus of green unicellular algae distributedin all the oceans and saline bodies of water throughout theworld and distinguished by unusual tolerance to salt. Sincethe cells of this genus do not possess a rigid cell-wall, theyrespond to changes in salt concentration by rapid alterationsin cell volume and then return to their original volume as aresult of adjustments in the amounts of intracellular ions andglycerol, this latter being the major organic osmoticum. Thepaper describes the behaviour of a mutant of D. parva 19/9 withreduced capabilities of growth above 0.5 kmol m–3 NaCl.The mutant is unusual in that its abilities to synthesize glyceroland pump out Na+ and Cl do not appear to be impaired;volume changes in the hyperosmotic range also appear to be roughlythe same as in D. parva. The average cell volume of mutant cellsis reduced (206µm3 as opposed to 255 µm3 in D. parva)and their rate of change of cell volume after an increase insalt concentration is lower; it took about 10 min for mutantcells in the light to reach a new cell volume whereas D. parvacells reached their new volume in less than 1 min. Both factorsmay be dependent on components of the cytoskeleton. The mutantthrows light on adaptations necessary to allow Dunaliella cellsto grow at high salt concentrations and demonstrates that halotoleranceincludes, but is not equivalent to, osmoregulation. Key words: Dunaliella, salt tolerance, mutant  相似文献   

5.
Effects of unilateral exposure to anisotonic conditions on diffusional water permeability of the isolated rabbit conjunctiva were determined. A segment of the bulbar-palpebral conjunctiva was mounted between Ussing-type hemichambers under short-circuit conditions. Unidirectional water fluxes (Jdw) were measured in either direction by adding 3H2O to one hemichamber and sampling from the other. Electrical parameters were measured simultaneously. Jdw were determined under control isosmotic conditions and after introduction of either hyper- or hypotonic solutions against the tear or stromal sides of the preparations. In each of these four separate conditions, the anisotonic medium produced an 20–30% reduction in Jdw across the tissue, with the exception that to obtain such reduction with increased tonicity from the stromal side (medium osmolality increased by adding sucrose), conditions presumptively inhibiting regulatory volume increase mechanisms (e.g., pretreatment with amiloride and bumetanide) were also required. All reductions in Jdw elicited by the various anisotonic conditions were reversible on restoration of control tonicity. In experiments in which preparations were pretreated with the protein cross-linking agent glutaraldehyde, anisotonicity-elicited reductions in Jdw were not observed. Such reductions were also not observed in the presence of HgCl2, implying the involvement of aquaporins. However, it is possible that the mercurial may be toxic to the epithelium, preventing the tonicity response. Nevertheless, from concomitant changes in transepithelial electrical resistance, as well as [14C]mannitol fluxes, [14C]butanol fluxes, and Arrhenius plots, arguments are presented that the above effects are best explained as a cell-regulated reduction in membrane water permeability that occurs at the level of water-transporting channels. Presumably both apical and basolateral membranes can downregulate their water permeabilities as part of a protective mechanism to help maintain cell volume. unidirectional water fluxes; net water fluxes; Ussing chamber; short-circuit current; electrolyte transport; cell volume regulation; paracellular mannitol permeability  相似文献   

6.
Isopropyl 3-chlorocarbanilate (chlorpropham) inhibited Chlorellagrowth by 50% at 1.3 µM under non-photosynthetic conditions.Average DNA content per cell was increased 2.5-fold by chlorprophamtreatment at 4.7 µM. Oxygen uptake was not significantlyaffected at 47 µM. Protein synthesis was more sensitiveto chlorpropham than the other biosynthetic processes tested,but it was not inhibited at 1.3 µM. In cell cycle studiesperformed under photosynthetic conditions, 50% inhibition ofgrowth occurred at 4 µM. At 14 µM, growth in termsof cell number was completely suppressed while inhibition ofgrowth in terms of average cell volume was partial, resultingin comparatively larger cell volume. This was accompanied by3.0-fold increase in average DNA content per cell. (Received March 8, 1976; )  相似文献   

7.
Eighteen poplar (Populus) clones, varying in growth capacitywere grown in plastic containers under outdoor conditions. Duringthe first year of growth their net CO2 exchange rate (NCER)was studied by infra-red gas analysis as a function of photosyntheticphoton flux density (PPFD) under controlled environment conditions.Maximal NCER (under saturating PPFD) and the PPFD compensationpoint were significantly correlated with the first year's shootlength and hence with the above ground biomass production ofthe various clones. Key words: Poplar, Shoot growth, CO2 exchange rate  相似文献   

8.
Primary roots of pea (Pisum sativum L. cv. Taichung No. 11)were treated with 0, 10 and 50 mg dm–3 paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(l,2,4-triazol-l-yl)pentan-3-ol]for 1 h at 48 h after germination. Paclobutrazol treatment inhibitedroot extension, promoted swelling (cell expansion was radialrather than longitudinal), and increased cell volume and theactivity of catalase and peroxidase enzymes. Paclobutrazol alsodecreased root respiration and ethylene production. However,under non-stressed conditions, paclobutrazol treatment did notaffect soluble carbohydrate content, water potential, osmoticpotential or water loss. Under osmotic stress with polyethyleneglycol (PEG), paclobutrazol diminished the increase of waterpotential and decreased the rate of water loss caused by theimposed stress, but had no effect on osmotic potential. Catalaseand peroxidase activity were increased in osmotically-stressedroots of treated plants. Key words: Root growth, paclobutrazol, pea, Pisum sativum, water shortage  相似文献   

9.
Food limitation for the cladoceran Daphnia galeta was measuredgrowing them with natural lake seston for one growing seasonunder standardized conditions in the laboratory. Growth rateswere related to several measures of food quantity. Particulateorganic carbon (POC) <30 µm was the best predictorof total food availability measured. It was better than chlorophyll-a(Chl-a) of the same size fraction, algal volume calculated fromcell counts or total particle volume from Coulter Counter measurements.Daphnids were also grown with Scenedesmus acutus under the sameconditions and their growth rates were compared. Sestonic carbonconcentrations were related to Scenedesmus carbon concentrations,that provided equal growth rates. The ratio of the carbon concentrationsof both food types (seston, Scenedesmus) represented the foodquality of seston. Thus, the nutritional quality of naturallake seston relative to a standard alga was determined overone growing season. Growth rates of seston fed animals revealedthat they were food limited during long periods of the year.This was also ascertained by standard clutch sizes of fieldanimals. However, the causes of food limitation varied withinthe duration of the studied period. Whereas during the clear-waterphase the food quantity was limiting (while the quality washigh: 100% Scenedesmus), shortly after on 10 June and 17 Junefood conditions were close to threshold concentrations due tolow food quality. For the remainder of the summer, a POC of0.3–0.6 mg C I–1 with a quality of  相似文献   

10.
The effect of tetraploidy on leaf characteristics and net gasexchange was studied in diploid (2x ) and autotetraploid (4x) ‘Valencia’ sweet orange (Citrus sinensis (L.)Osb.) and ‘Femminello’ lemon (Citrus limon (L.)Burm. f.) leaves. Comparisons between ploidy levels were madeunder high irradiance (I) in a growth chamber or low total Iin a glasshouse. Tetraploids of both species had thicker leaves,larger mesophyll cell volume and lower light transmittance thandiploids regardless of growth I. Mesophyll surface area perunit leaf area of 2x leaves was 5–15% greater than on4x leaves. Leaf thickness and mesophyll cell volume were greaterin high I leaves than low I leaves. In high I, average leafarea was similar for 2x and 4x leaves, whereas in low I it was30% greater in 4x than in 2x leaves. Nitrogen and chlorophyllconcentration per cell increased with ploidy level in both growthconditions. The ratio of chlorophyll a:b was 25% greater in2x than in 4x leaves. When net CO2assimilation rate (ACO2) wasbased on leaf area, 4x orange leaves had 24–35% lowerACO2than their diploids. There were no significant differencesin ACO2between 2x and 4x orange or lemon leaves when expressedon a per cell basis. Overall, lower ACO2per unit leaf area oftetraploids was related to increase in leaf thickness, largermesophyll cell volume, the decrease in mesophyll area exposedto internal air spaces, and the lower ratio between cell surfaceto cell volume. Such changes probably increased the resistanceto CO2diffusion to the site of carboyxlation in the chloroplasts. Cell volume; chlorophyll; irradiance; leaf thickness; nitrogen; photosynthesis; ploidy; Citrus limon ; C. sinensis ; ‘Valencia’ sweet orange; ‘Femminello’ lemon  相似文献   

11.
1) A partially disintegrated cell preparation of Cyanidium caldarium(i.e. the 100G fraction; cells from which the outer parts ofthe cell wall had been removed) was obtained by differentialcentrifugation of a cell suspension treated with a French press.2) The 100G fraction cells had completely lost the outer partsof their cell walls, but retained their subcellular structureunchanged and had Hill activity that was equally as high asthat of the intact cells. 3) The Hill activity of the 100G fractionshowed an optimum at pH 7.0 and at 35°C. This activity waslost under acid and high temperature conditions (e.g. pH 3,50°C) under which intact cells showed high activity. 4)The Hill activity of the 100G fraction was lost by heat treatment(55°C, 10min), acid-treatment (pH 3.0, 10 min) or pre-illumination(3xl05lux, 30 min) though intact cells were not inactivatedby these treatments. However, no remarkable difference in sensitivitytowards inhibitors was found between the 100G fraction and intactcells. 5) We thus concluded that the cell wall plays an importantrole in the acido- and thermo-phily of Cyanidium cells. (Received August 19, 1974; )  相似文献   

12.
The effects of leaf age and of shading on photosynthetic rateand on other leaf parameters of potato (Solanum tuberosum L.)were studied using a portable gas exchange system. A rapid decreasein the rate of photosynthesis during leaf senescence was observed.This was accompanied by an increase in stomatal resistance,and as a result a fairly constant level of sub-stomatal CO2concentration was maintained at all leaf ages. The reductionin the photosynthetic rate in older leaves was therefore assumedto be essentially mesophyllic in origin, whereas the stomatalresponse was probably secondary. Canopy density significantly affected the rate of photosyntheticreduction with leaf age. Leaves maintained under high radiationintensities manifested a slower decline in their photosyntheticrate, especially in the early stages of their senescence, thanleaves kept under shade conditions. The latter leaves were foundto be more adapted to low radiation intensities, as indicatedby changes in their chlorophyll a:b ratio and specific leafweight Solanum tuberosum L, potato, photosynthetic rate, mesophyll, stomata, leaf age, radiation intensity, chlorophyll a:b ratio  相似文献   

13.
The effect of drought and recovery on cellular and spatial parametersof the growth process in tall fescue leaves was studied in twoexperiments. In both experiments plants grown on vermiculiteand maintained in a controlled environment were submitted toa 7 d drought period generated by withholding water. Droughtwas followed by a 3 d recovery period in experiment II. As leafelongation rate (LER) decreased during developing drought boththe growth zone length (initially 40 mm) and the maximum relativeelemental growth rate (initially 0.09 mm mm–1 h–1during the dark period of diurnal cycles) within the growthzone declined. But the growth zone still exhibited a lengthof approximately 15 mm when LER approached 0 under severe drought(–2.0 MPa predawn leaf water potential). The growth potentialof the basal 15-mm-long portion of the leaf was conserved duringthe period when drought effected the complete arrest of leafelongation. A (retrospective) analysis of the position-timerelationships of epidermal cells identified on leaf replicas(experiment II) indicated that the cell flux out of the growthzone responded very sensitively to drought. Before drought theflux was maximum at approximately 3.2 cells (cell file h)–1during the dark period. Flux decreased to 0 when leaf elongationstopped. Flux also varied diurnally both under well-wateredand droughted conditions. In well-watered conditions it wasabout 30% less during the light than the dark period. Cell elongationwas also sensitive to drought. Under well-watered conditionsepidermal cell elongation stopped when cells attained a lengthof approximately 480 µm. During developing drought cellsstopped elongating at progressively shorter lengths. When LERhad decreased to almost nil, cells stopped elongating at a lengthof approximately 250 µn. When drought was relieved followinga 2 d complete arrest of leaf elongation then cells shorterthan 250 µm were able to resume expansion. Following rewateringcell flux out of the growth zone increased rapidly to and abovethe pre-drought level, but there was only a slow increase overtime in the length at which cell elongation stopped. About 2d elapsed until the leaf growth zone produced cells of similarlength as before drought (i.e. approximately 480 µm). Key words: Epidermal cell length, cell flux, (leaf) growth zone, leaf elongation rate, relative elemental growth rate, position-time relationships (path line, growth trajectory), drought, water deficit  相似文献   

14.
This research examined the hypothesis that as cacti evolve tothe leafless condition, the stem epidermis and cortex becomemore leaflike and more compatible with a photosynthetic role.All cacti in the relict genus Pereskia have non-succulent stemsand broad, thin leaves. All members of the derived subfamilyCactoideae are ‘leafless’, having an expanded cortexthat is the plant's only photosynthetic tissue. In Pereskia,leaves have a high stomatal density (mean: 50.7 stomata mm–2in the lower epidermis, 38.1 mm–2 in the upper epidermis),but stems have low stomatal densities (mean: 11.3 mm 2, threeof the species have none). Stems of Cactoideae have a high stomataldensity (mean: 31.1 mm–2, all species have stomata). Theouter cortex cells of stems of Cactoideae occur in columns,forming a palisade cortex similar to a leaf palisade parenchyma.In this palisade cortex, the fraction of tissue volume availablefor gas diffusion has a mean volume of 12.9%, which is identicalto that of Pereskia leaf palisade parenchyma. Pereskia stemcortex is much less aerenchymatous (mean: 5.3% of cortex volume).Cactoideae palisade cortex has a high internal surface density(0.0207 cm2 cm–2 which is higher than in Pereskia stemcortex (0.0150 cm2 cm–3) but not as high as Pereskia leafpalisade parenchyma (0.0396 cm2 cm–3). Pereskia stem cortexhas no cortical bundles, but Cactoideae cortexes have extensivenetworks of collateral vascular bundles that resemble leaf veins. Cactaceae, cactus, intercellular space, stomatal density, internal surface/volume, evolution  相似文献   

15.
Elongation growth of etiolated hypocotyls of cress (Lepidiumsativum L.) was suppressed when they were exposed to basipetalhypergravity at 35 g and above. Acceleration at 135 g causeda decrease in the mechanical extensibility and an increase inthe minimum stress-relaxation time of the cell wall. Such changesin the mechanical properties of the cell wall were prominentin the lower regions of hypocotyls. The amounts of cell wallpolysaccharides per unit length of hypocotyls increased underthe hypergravity condition and, in particular, the increasein the amount of cellulose in the lower regions was conspicuous.Hypergravity did not influence the neutral sugar compositionof either the pectin or the hemicellulose fraction. The amountof lignin was also increased by hypergravity treatment, althoughthe level was low. The data suggest that hypergravity modifiesthe metabolism of cell wall components and thus makes the cellwall thick and rigid, thereby inhibiting elongation growth ofcress hypocotyls. These changes may contribute to the plants'ability to sustain their structures against hypergravity. Key words: Cell wall extensibility, cellulose, hypergravity, Lepidium sativum L., lignin  相似文献   

16.
Increase in cell number, anlage volume and length have beeninvestigated during the overall period of lateral root primordiumdevelopment in excised primaries and in attached roots of Zeamays L. Each of these aspects of anlage growth was found toincrease more or less exponentially during the interval betweenprimordium initiation and subsequent emergence as a lateralin both batches of roots. Values were then determined for celldoubling time (Td), the size of the proliferative fraction (Pf),and for anlage volume (Tv) and length (Tt) doubling times duringthe overall period of primordium development and at intervalsduring this period in both the excised and attached roots. Thepattern of change which took place in Td, Tv, Tl and Pf duringlateral primordium development was found to be similar in bothbatches of roots. However, the overall period of anlage developmentwas shorter in the excised roots than in the attached ones.Moreover, when laterals grew out of the excised roots they didso with fewer cells than comparable laterals emerging from theattached roots. Zea mays L., maize, root primordia, lateral emergence, cell doubling time  相似文献   

17.
The morphology of developing sporangiophores of Peronosporaparasitica from wallflower is described, and morphogenesis maybe divided into the following five stages: the sporangiophoreprimordium, unbranched sporangiophore, branched sporangiophore,spore formation and maturation, and formation of the cross wall.The growth of individual sporangiophores in a humidity chamberwas followed under the microscope, and increase in height andincrease in volume measured. The greatest increase in volumewas during spore formation, when the sporangiophore volume mightquadruple within an hour.  相似文献   

18.
Yeo, A. R., Yeo, M. E., Caporn, S. J. M., Lachno, D. R. andFlowers, T. J. 1985. The use of 14C-ethane diol as a quantitativetracer for the transpirational volume flow of water and an investigationof the effects of salinity upon transpiration, net sodium accumulationand endogenous ABA in individual leaves of Oryza sativa L.—J.exp. Bot. 36: 1099–1109. Oryza sativa L. (rice) seedlings growing in saline conditionsexhibit pronounced gradients in leaf sodium concentration whichis always higher in the older leaves than the younger ones.Individual leaf transpiration rates have been investigated todiscover whether movement of sodium in the transpiration streamis able to explain these profiles from leaf to leaf. The useof 14C labelled ethane diol to estimate transpiration was evaluatedby direct comparison with values obtained by gas exchange measurements.Ethane diol uptake was linearly related to the transpirationalvolume flow and accurately predicted leaf to leaf gradientsin transpiration rate in saline and non-saline conditions. 14C-ethanediol and 22NaCl were used to compare the fluxes of water andsodium into different leaves. The youngest leaf showed the highesttranspiration rate but the lowest Na accumulation in salineconditions; conversely, the older leaves showed the lower transpirationrates but the greater accumulation of Na. The apparent concentrationof Na in the xylem stream was 44 times lower into the youngerleaf 4 than into the older leaf 1. Exposure to NaCl (50 molm–3) for 24 h elicited an increase in endogenous ABA inthe oldest leaf only, but no significant changes occurred inthe younger leaves. Key words: —Salinity, rice, Oryza sativa L., transpiration, volume flow, abscisic acid  相似文献   

19.
Seed proteins of Castanea sativa and C. crenata were extractedby sequential procedures. Albumins accounted for over 20% ofthe total protein. Globulins were the main storage proteinsand represented close to half of the total protein. Additionof 2-mercaptoethanol was essential for maximum extraction ofthe globulins, a fraction with an amino acid composition similarto that of the 1 IS storage protein from legumes. Negligibleamounts of prolamins (<3%) were present in the seeds. Glutelinsrepresented just under 30% of the total protein. The proteinfractions were characterized by electrophoresis in polyacrylamidegels. The glutelin fraction contained unextracted globulinseven when 2-mercaptoethanol was used. Key words: Castanea spp, seeds, storage protein  相似文献   

20.
The expolinear equation for crop growth (Goudriaan and Monteith,Annalsof Botany66: 695–701, 1990; Goudriaan, 1994. In: MonteithJL, Scott RK, Unsworth MH, eds.Resource capture by crops.Nottingham:Nottingham University Press, 99–110) has the potentialto predict growth under specified environmental conditions.The choice of suitable parameters is discussed and tested usingdata from field experiments with faba bean, peas and lentils(Ishag and Dennett,Annals of Botany82: 497–505. 1998).It is suggested that suitable parameters for predicting cropgrowth are the fraction of solar radiation intercepted at emergence,the extinction coefficient for solar radiation, the maximumfraction of radiation intercepted, the maximum relative growthrate and the maximum crop growth rate for a crop interceptingall the incident radiation. In the experiments considered, thedifferences in growth patterns were due mainly to differencesin the maximum relative growth rate associated with differencesin temperature.Copyright 1998 Annals of Botany Company Expolinear equation, grain legumes, crop growth rate, crop density, relative growth rate, growth modelling, faba bean,Vicia fabaL., peas,Pisum sativumL., lentils,Lens culinarsMedic.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号