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1.
The ability of human subjects to detect -ionone was measuredover a range of concentrations and compared with that of GermanShepherd dogs measured previously under comparable conditions.The mean minimal concentration detected by humans was 4.0x109molecules / cm3 which compares with a mean minimal concentrationof 4.0x105 molecules / cm3 for the dogs. In general, dogs coulddetect -ionone in concentrations 1,000 to 10,000 times lowerthan could human subjects. Concentration-response curves forboth species are similar in form and show a double reversalin their upper ranges. 相似文献
2.
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
3.
The permeability to oxygen of the periderm of the potato tuberhas been measured during its development and storage. When expressedas ml O2, diffusing through 1 cm2 periderm in 1 sec under anO2, pressure of 1 atm, the values for freshly harvested tubersranged from a maximum of 2.4 x 104 in immature tubers,to less than 0.7 x 104 in tubers harvested mature someweeks after the death of the foliage. In every case, after storagefor up to 10 weeks at 10° C, the permeabilities, as expressedabove, were less than 0.7 x 104 (minimum values, c. 0.5x 104 It was shown that the oxygen deficit under theperiderm was unlikely to exceed 0.03 atm during development,and the oxygen status of the developing tuber should thus beadequate for the low oxygen-affinity oxidase system (if present)to function. 相似文献
4.
Translocation in Pteridium 总被引:2,自引:0,他引:2
The distributions of radioactivity with distance have been mappedin the rachis of Pteridium aquilinum at different times afterapplication of 14CO2 to a pinna. Profiles change in shape withtime, from wave to transition and then to diffusion. The apparentdiffusion constant of sucrose may be obtained from transitionand diffusion profiles. Values varied from 2.2 x 103to 3.6 x 102 cm2 sec1. These results are comparedwith those for various angiosperm species. 相似文献
5.
Longitudinal Water Movement in the Primary Root of Zea mays 总被引:1,自引:0,他引:1
The rates of transfer of tritiated water (THO) along lengthsof excised primary roots of Zea mays have been measured undera variety of conditions. The following values of apparentdiffusion coefficients for THO in the root tissue havebeen evaluated: 1.5±0.1x10-5 cm2 sec-1 in roots boiledfor 3 min before use,0.5±0.03x10-5 cm2 sec-1 in rootspoisoned with 10-2 M NaF,0.9±0.07x10-5 cm2 sec-1 in rootspoisoned with 10-2 M NaN3,and 2.1±0.2x10-5 cm2 sec-1in normal roots. The bathing medium in all cases was 1.0 mMKCl/0.1 mM CaCl2 with the addition of the inhibitors where appropriate.Thefourfold increase in the rate of THO transfer in normal rootscompared with poisoned ones is attributed to the existence ofa long-distance convective flow in the first case, which isterminated by the addition of inhibitors. Since experimentsshow that this convective flow must occur both acropetally andbasipetally with equal velocity, it is thought to occur in thephloem.By assuming the streaming transcellular strandsmodel for phloem transport, the rate of movement required togive the observed transfer has been computed as approximately4.5x10-2 cm sec-1 (160 cm h-1).The earlier report of the existenceof a highly impermeable barrier surrounding the xylem vesselshas been further substantiated by the experiments reported here. 相似文献
6.
Activity curves are determined for gibberellins A1 to A0 bythe Avena first-leaf bioassay method. Gibberellins A1, A4 andA5 can be detected at 10-11 or 10-10 g/ml and give optimum activityof approximately 230 per cent elongation (water controls = 100per cent). Gibberellins A2A3, and A9 can be detected at 10-3g/mland give optimum activity of approximately 200 per cent. GibberellinsA6 and A7 can be detected at 10-5g/ml; GA7 gives optimum activityof around 190 per cent. All the gibberellins except GA8 canbe detected by this bioassay method after chromatography inn-butanol: 1.5 N ammonia (3: 1) and benzene: acetic acid: water(4: 2: 1) when applied to the paper at concentrations from O.Ito µg. The sensitivity of the method is compared withthat of other gibberellin bioassay methods. 相似文献
7.
The diffusion of oxyleghaemoglobin, prepared from soybean rootnodules, was measured at 24°C in agar and agarose gels ofvarious strengths, or in 1% agarose containing 0-18% (w/v) bovineserum albumin, to simulate the protein content of the cytoplasmof root nodule cells. Values of Dp, the diffusion coefficient,were unaffected (Dp = 11·8 x 10-11 m2 s-1; s.e.m. 0·3x 10-11) until the protein concentration exceeded 6%, abovewhich Dp declined sharply. With 18% bovine serum albumin, theconcentration of total soluble protein calculated to be presentin the cytoplasm of infected cells, where most of the leghaemoglobinis located in vivo, Dp was 5·9 x 10-11 m2 s-1. Theseresults are discussed in relation to leghaemoglobin-facilitateddelivery of O2 to the respiring N2-fixing bacteroids in rootnodule cells.Copyright 1993, 1999 Academic Press Bacteroids, diffusion, Glycine max, N2 fixation, oxyleghaemoglobin, soybean, root nodules 相似文献
8.
Journal of Plankton Research, 11, 12731295, 1989. The values of P/U0 (Table I) and fluid velocity used to calculatethe energy required for sieving (pp. 12891290) and severalequations (footnote b of Table I; p. 1290, lines 34)are incorrect. The corrected table appears below: Table I. Filter setule measurements (mean and within specimenstandard deviation) of the gnathobases for the cladocerans studiedaGnathobaseof trunklimb number. bP = 8µU0/(b(1 21nt + 1/6(t2) - 1/144(t4))), whereP = pressure drop in dyn cm2, =3.1416, U0 = fluid velocityin cm s1, b = distance between setule centres in cm,t = ( x setule diameter)/b and µ = 0.0101 dyn s1cm2. Formula from Jørgensen (1983). The text (p. 1289, line 19 to p. 1290, line 10) should read: organism. Using a similar argument, a 0.5 mm Ceriodaphnia witha filter area of 0.025 mm2 (Ganf and Shiel, 1985) and pressuredrop P = 2757 dyn cm2 (with fluid velocity of 0.07 cms1) allocates only 2171 ergs h1 to filtrationof a total energy expenditure of 104 ergs h1 [filtrationenergy (ergs h1) = area (cm2) x pressure drop (dyn cm2)x 3600 (s h1) x 1/0.2 (efficiency of conversion of biochemicalinto mechanical work); total energy (ergs h1) = respiration(0.05 µl O2 ind1 h1 consumed; Gophen, 1976)x conversion factor (2 x 105 ergs µl1 O2). Withan estimated 0.034 mm2 in filter area, fluid velocity of 0.041cm s1 and respiration of 1.8 x 104 ergs h1 (calculatedfrom Porter and McDonough, 1984), a 0.5 mm Bosmina uses <4%of its metabolism to overcome filter resistance. The velocities used in the original examples (0.4 cm s1for Ceriodaphnia, 0.2 cm s1 for Bosmina) were derivedfrom literature values of appendage beat rate and estimatesof the distance travelled by the appendages during each beatcycle. This approach unnecessarily assumes that all water movedpasses through the filter. In the new calculations, the flowacross the filter needed for food to be collected by sieving(0.07 cm s1 for Ceriodaphnia and 0.041 cm s1 forBosmina) was determined from the maximum clearance rate/filterarea. The amended energy expenditures, although higher, do notrefute the sieve model of particle collection. 相似文献
9.
L-Leucine Transport in Isolated Protoplasts of Vinca Suspension Culture: Characterization of Uptake 总被引:1,自引:0,他引:1
The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H+ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The Km values of thethree affinity sites were 1.4 x 103 M, 1.3 x 104M, 4.3 x 105 M; the maximum velocity values were 3.3x 108, 4.5 x 109, 1.8 x 109 mol/10 min/4x 106 cells. (Received April 18, 1981; Accepted August 25, 1981) 相似文献
10.
The NADP$-specific isocitrate dehydrogenase was partially purifiedfrom photosynthetically-grown Rhodospirillum rubrum. The pHoptimum is between 7.5 and 9.0 in phosphate buffer. The apparentKm is 3.1x105 M for isocitrate, 5.1x105 M forNADP$, 1.7x105 M for manganese, 1.5x104 M formagnesium, and 3.5x103 M for inorganic orthophosphate.Arsenate exerts a slight inhibition. The Q10 between 17.5°Cand 40°C is 1.62, and the energy of activation at 25°Cis 9.74 Kcal/mole. Glyoxylate and oxalacetate cause concertedinhibition of the enzyme activity. Various nucleotides inhibitthe activity. The kinetics of inhibition by ATP was found tobe mixed type with respect to NADP$ and isocitrate, the Ki valuesbeing 1.17x103 M and 1.10x103 M respectively.The inhibition between ATP and orthophosphate is competitivewith a Ki of 104M. Thiol binding reagents are inhibitory;this inhibition is reversed by cysteine or reduced glutathione. (Received October 1, 1971; ) 相似文献
11.
We investigated the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one(DCEBIO) on the Cl secretory response of the mouse jejunum using the Ussing short-circuit current (Isc) technique. DCEBIO stimulated a concentration-dependent, sustained increase in Isc (EC50 41 ± 1 µM). Pretreating tissues with 0.25 µM forskolin reduced the concentration-dependent increase in Isc by DCEBIO and increased the EC50 (53 ± 5 µM). Bumetanide blocked (82 ± 5%) the DCEBIO-stimulated Isc consistent with Cl secretion. DCEBIO was a more potent stimulator of Cl secretion than its parent molecule, 1-ethyl-2-benzimidazolinone. Glibenclamide or NPPB reduced the DCEBIO-stimulated Isc by >80% indicating the participation of CFTR in the DCEBIO-stimulated Isc response. Clotrimazole reduced DCEBIO-stimulated Isc by 67 ± 15%, suggesting the participation of the intermediate conductance Ca2+-activated K+ channel (IKCa) in the DCEBIO-activated Isc response. In the presence of maximum forskolin (10 µM), the DCEBIO response was reduced and biphasic, reaching a peak response of the change in Isc of 43 ± 5 µA/cm2 and then falling to a steady-state response of 17 ± 10 µA/cm2 compared with DCEBIO control tissues (61 ± 6 µA/cm2). The forskolin-stimulated Isc in the presence of DCEBIO was reduced compared with forskolin control tissues. Similar results were observed with DCEBIO and 8-BrcAMP where adenylate cyclase was bypassed. H89, a PKA inhibitor, reduced the DCEBIO-activated Isc, providing evidence that DCEBIO increased Cl secretion via a cAMP/PKA-dependent manner. These data suggest that DCEBIO stimulates Cl secretion of the mouse jejunum and that DCEBIO targets components of the Cl secretory mechanism. 1-ethyl-2-benzimidazolinone; forskolin; glibenclamide; clotrimazole; H89 相似文献
12.
Equipment is described which delivers air with concentrationsof CO2 and water vapour closely controlled in the ranges 0 to2500 ppm and 5 to 15 mb respectively, at flow rates of up to10 1 min-1, to each four leaf chambers. The leaf temperatureis controlled to ±0.5 °C and, with a light intensityof 0.3 cal cm-2 min-1 visible radiation (0.4 to 0.7 µm)leaf temperature can be maintained at 17.5 °C.The apparatusused to measure the concentration differences between the watervapour and CO2 entering and leaving the leaf chamber (used tocalculate transpiration, photosynthetic, and respiration rates)is described in detail.Results of tests, which show the necessityfor mounting a fan within the leaf chamber, are reported.Typicallight- and CO2-response curves are given for kale leaves (Brassicaoleracca var. acephala) and an attempt is made to quantify theerrors in the measurement of photosynthesis and transpiration. 相似文献
13.
We studied the course of early leaf area expansion and specificleaf area (SLA) in potato (Solanum tuberosum L.) and wheat (Triticumaestivum L.) genotypes and tested whether air temperature explainsdifferences in these courses within different environments.Such knowledge can be used to improve crop growth modelling.The relative rate of leaf area expansion (RL) of potato andwheat decreased with thermal time, but was nearly linear upto a leaf area index (L) of 1.0. TheRL (L < 1; mean: 17.9x 10-3°C-1 d-1) of potato showed an interaction betweengenotype and environment, and varied with year. TheRL (L <1; mean: 7.1 x 10-3°C-1 d-1) of winter wheat was lower thanthat of spring wheat (mean: 10.9 x 10-3°C-1 d-1), and bothvaried with year. SLAof potato increased nearly linearly withthermal time from 5 to 15 m2 kg-1at 50% emergence, to 20 to25 m2 kg-1at 155°Cd, and then decreased slightly. The SLAofboth winter and spring wheat began at 16 to 23 m2 kg-1and inmost cases increased slightly with thermal time. In potato,regression parameters of SLAwith thermal time were affectedby environment (management conditions and year) and genotype;in wheat they were affected by environment (year and site).Treatment effects on RLof potato were not correlated with thoseon SLA , and were only partly correlated for wheat. Thereforewe conclude that the early foliar expansion of potato is associatedwith a strong increase in SLA , and not so for wheat. For bothcrops the course of early leaf area expansion and ofSLA withair temperature is not robust over environments and genotypes.The consequences of these results for modelling are discussed.Copyright 2000 Annals of Botany Company Triticum aestivum, spring wheat, winter wheat, Solanum tuberosum, leaf area expansion, specific leaf area, early growth, genotype, environment, modelling 相似文献
14.
Time-dependent stimulation by aldosterone of blocker-sensitive ENaCs in A6 epithelia 总被引:4,自引:0,他引:4
Helman Sandy I.; Liu Xuehong; Baldwin Kieron; Blazer-Yost Bonnie L.; Els Willem J. 《American journal of physiology. Cell physiology》1998,274(4):C947
To study and define the early time-dependent response (6 h) ofblocker-sensitive epithelial Na+channels (ENaCs) to stimulation ofNa+ transport by aldosterone, weused a new modified method of blocker-induced noise analysis todetermine the changes of single-channel current (iNa) channel open probability(Po), andchannel density(NT) undertransient conditions of transport as measured by macroscopic short-circuit currents(Isc). In threegroups of experiments in which spontaneous baseline rates of transportaveraged 1.06, 5.40, and 15.14 µA/cm2, stimulation of transportoccurred due to increase of blocker-sensitive channels.NT variedlinearly over a 70-fold range of transport (0.5-35µA/cm2). Relatively small andslow time-dependent but aldosterone-independent decreases ofPo occurredduring control (10-20% over 2 h) and aldosterone experimentalperiods (10-30% over 6 h). When thePo of control andaldosterone-treated tissues was examined over the 70-fold extendedrange of Na+ transport,Po was observedto vary inversely withIsc, falling from~0.5 to ~0.15 at the highest rates ofNa+ transport or ~25% per3-fold increase of transport. Because decreases ofPo from anysource cannot explain stimulation of transport by aldosterone, it isconcluded that the early time-dependent stimulation ofNa+ transport in A6 epithelia isdue exclusively to increase of apical membraneNT. 相似文献
15.
Twenty-four hours after leaf 3 of a plant of Lolium multiflorumLam, was supplied with a droplet of 14C-urea and the plant enclosedin a polyethylene bag with an untreated plant, there were significantamounts of radiocarbon recovered from the untreated plant. Theleaf treated with 14C-urea was the major source of 14C leakagebut significant losses were also recorded from other parts ofthe plant. Reducing the humidity within the bag decreased theamount of 14CO2 which escaped. Losses of radiocarbon from CO2-treated plants were very low compared with those from urea-treatedplants but the pattern of assimilate distribution within thetwo types of plants was very similar. The possible causes ofthese effects are considered and the usefulness of 14C-ureaas a source of 14CO2 discussed. 相似文献
16.
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 mm2in the lower epidermis, 38.1 mm2 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 mm2, 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 cm2 which is higher than in Pereskia stemcortex (0.0150 cm2 cm3) but not as high as Pereskia leafpalisade parenchyma (0.0396 cm2 cm3). 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
17.
Water Influx Characteristics and Hydraulic Conductivity for Roots of Agave deserti Engelm. 总被引:4,自引:0,他引:4
NOBEL PARK S.; SCHULTE PAUL J.; NORTH GRETCHEN B. 《Journal of experimental botany》1990,41(4):409-415
Various plant and environmental factors influence the hydraulicproperties for roots, which were examined using negative hydrostaticpressures applied to the proximal ends of individual excisedroots of a common succulent perennial from the Sonoran Desert,Agave deserti Engelm. The root hydraulic conductivity, Lp, increasedsubstantially with temperature, the approximately 4-fold increasefrom 0.5°C to 40°C representing a Q10 of 1.45. Suchvariations in Lp with temperature must be taken into accountwhen modelling water uptake, as soil temperatures in the rootzone of such a shallow-rooted species vary substantially bothdaily and seasonally. At 20°C, Lp was 2.3 x 107 ms{macron}1MPa{macron}1for 3-week-old roots, decreasing to abouthalf this value at 10 weeks and then becoming approximatelyhalved again at 6 months. For a given root age, Lp for rainroots that are induced by watering as lateral branches on theestablished roots (which arise from the stem base) was aboutthe same as Lp for established roots. Hence, the conventionalbelief that rain roots have a higher Lp than do establishedroots is more a reflection of root age, as the rain roots tendto be shed following drought and thus on average are much youngerthan are established roots. Unlike previous measurements onroot respiration, lowering the gas-phase oxygen concentrationfrom 21% to 0% or raising the carbon dioxide concentration from0.1% to 2% had no detectable effect on Lp for rain roots andestablished roots. Lp for rain roots and established roots wasdecreased by an average of 11% and 35% by lowering the soilwater potential from wet conditions (soil=0 kPa) to {macron}40kPa and {macron}80 kPa, respectively. Such decreases in Lp mayreflect reduced water contact between soil particles and theroot surface and should be taken into account when predictingwater uptake by A. deserti. Key words: Gas phase, rain roots, root age, soil, temperature, water potential 相似文献
18.
The effects of the growth in a medium containing NH4NO3 as nitrogensource were studied on cell sap pH, cytoplasmic pH and malatecontent in chl1, an Arabidopsis thaliana mutant impaired inchlorate and nitrate transport. In all the conditions testedthe pH of the cytoplasm in chl1 was more alkaline, and thatof the vacuole was more acidic as compared with those measuredin wt. Treatment with bafilomycin A1, a specific inhibitor ofthe vacuolar H+-ATPase, induced a small alkalinization of thevacuole, and a significant acidification of the cytoplasm, theseeffects being greater in chl1 than in wt. The greater responseof the mutant to bafilomycin Al suggests that, in the absenceof the inhibitor, the activity of the tonoplast H+-ATPase inchl1 is higher than in wt, this diversity being a possible reasonfor the differences in intracellular pH detected between thetwo strains. A possible role for the vacuolar H+-ATPase in regulatingthe cytoplasmic pH is discussed. (Received August 2, 1995; Accepted February 1, 1996) 相似文献
19.
Kitahara Yoshio; Yanagawa Hiroshi; Kato Tadahiro; Takahashi Norindo 《Plant & cell physiology》1972,13(5):923-925
Yellow prisms of asparagusic acid, with a molecular formulaof C4H6O2S2 were isolated from etiolated asparagus tissues (Asparagusofficinalis L.). This acid inhibits growth in lettuce and otherseedlings when applied in concentrations of 6.67x107Mto 6.67xl07M. The extent of activity was very similarto that of abscisic acid.
1 A well known shift reagent in the NMR spectrum (1). (Received April 12, 1972; ) 相似文献
20.
影响叶螨磷酸酯酶活性的四因子数学模型 总被引:1,自引:0,他引:1
应用二次回归通用旋转组合设计,组建了影响叶螨磷酸酯酶(酸性和碱性)活性的四因子(缓冲液Ph值X1、温浴时间X2、反应温度X3、底物浓度X4)数学模型: Y酸性=0.456380+0.107889X2+0.069027X3-0.026836X12-0.030794X32, F=24.98,P<0.01;Y碱性=0.267286-0.200736X1+0.049541X2+0.030930X3-.049063X1X2+0.053585X12-0.049665X22, F=57.68,P<0.01。结果表明,温浴时间是影响叶螨酸性磷酸酯酶活性的关键因子,在缓冲液pH 4.4、底物浓度8.5×10-3 mol/L、42℃温浴40 min测得该酶活性最强。影响碱性磷酸酯酶活性的关键因子则是缓冲液pH值,pH 9.0、37℃恒温30 min、底物7.5×10-3 mol/L的条件下,光密度值最大。两种酶的最大吸收峰波长为405 nm。 相似文献