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1.
禾谷缢管蚜和麦长管蚜玻璃管药膜法敏感毒力基线的建立 总被引:9,自引:0,他引:9
【目的】建立禾谷缢管蚜Rhopalosiphum padi(Linnaeus)和麦长管蚜Sitobion avenae(Fabricius)对常用杀虫剂的相对敏感基线。【方法】从田间采集麦蚜在实验室内饲养30代以上,利用玻璃管药膜法测定其对杀虫剂的敏感度,每条毒力基线为2次以上独立测定数据合并后的计算结果。【结果】用玻璃管药膜法建立了包括新烟碱类、吡啶类、氨基甲酸酯类、有机磷类和拟除虫菊酯类共22个药剂品种对禾谷缢管蚜和麦长管蚜3 h的敏感毒力基线。禾谷缢管蚜对新烟碱类药剂吡虫啉和啶虫脒的LC50值分别为0.02和0.007 μg/cm2;对吡啶类药剂吡蚜酮的LC50值为0.124 μg/cm2;对氨基甲酸酯类药剂丁硫克百威、硫双灭多威、灭多威、抗蚜威、西维因的LC50值为0.0026~0.70 μg/cm2;对有机磷类药剂三唑磷、丙溴磷、氧乐果、乐果、马拉硫磷、辛硫磷、敌敌畏、毒死蜱的LC50值为0.005~0.065 μg/cm2;对拟除虫菊酯类药剂三氟氯氰菊酯、高效氯氰菊酯、溴氰菊酯、联苯菊酯、氰戊菊酯、氯氰菊酯的LC50值为0.033~0.240 μg/cm2。麦长管蚜对新烟碱类药剂吡虫啉和啶虫脒的LC50值分别为0.15和0.12 μg/cm2;对吡啶类药剂吡蚜酮的LC50值为0.41 μg/cm2;对氨基甲酸酯类药剂丁硫克百威、硫双灭多威、灭多威、抗蚜威、西维因的LC50值为0.005~0.76 μg/cm2;对有机磷类药剂三唑磷、丙溴磷、氧乐果、乐果、马拉硫磷、辛硫磷、敌敌畏、毒死蜱的LC50值为0.018~0.36 μg/cm2;对拟除虫菊酯类药剂三氟氯氰菊酯、高效氯氰菊酯、溴氰菊酯、联苯菊酯、氰戊菊酯、氯氰菊酯的LC50值为0.20~2.94 μg/cm2。【结论】建立的两种麦蚜对22种杀虫药剂的相对敏感基线,包括当前所有可能用于防治麦蚜的药剂,可以用于以后麦蚜抗药性监测或其他相关研究的参照;禾谷缢管蚜对药剂的敏感度高于麦长管蚜。 相似文献
2.
Surfacing and water-leaving behaviour (quitting) of aquaticpulmonate snails was investigated in the laboratory. Regressioncoefficients of surfacing rate per hour for 16 snails in 200cm3 of water were 1.28 for L. peregra, 1.35 for B. glabrata(albino form), 0.47 for B. glabrata (pigmented form) and 0.17for B. jousseaumei. Disturbance, snail size and conditioningof the water were relatively unimportant factors; water volumeadjusted by depth was also unimportant up to 50 mm depth. Importantfactors controlling surfacing appeared to be population density,time of year, temperature, water volume adjusted by perimeterand dissolved oxygen concentration. The response to the latterwas not clear and both B. glabrata and L. peregra orientatedalmost as well to a nitrogen/water interface as to an air/waterinterface. Water-quitting regressed on volume, which had beenadjusted by perimeter variation, revealed a curvilinear relationshipfor B. glabrata, with maximum quitting at 1 snail per 7cm3 (1snail per 14cm of climbable perimeter). L. peregra showed anegative exponential curve, with maximum quitting at 1 snailper 3 cm3 of water (1 snail per 8 cm of climbable perimeter).These data could be relevant to design and management of irrigationchannels where bilharzia might occur. (Received 28 November 1990; accepted 22 October 1991) 相似文献
3.
Effects of Elevated Carbon Dioxide Concentration in the Dark on the Growth of Soybean Seedlings 总被引:2,自引:2,他引:0
Previous work has shown that elevated carbon dioxide (CO2) concentrationsin the dark reversibly reduce the rate of CO2 efflux from soybeans.Experiments were performed exposing soybean plants continuallyto concentrations of 350 or 700 cm3 m-3 for 24 h d-1, or to350 during the day and 700 cm3 m-3 at night, in order to determinethe importance of the reduced rate of dark CO2 efflux for plantgrowth. High CO2 applied only at night conserved carbon andincreased dry mass during initial growth compared with the constant350 cm3 m-3 treatment. Long-term net assimilation rate was increasedby high CO2 in the dark, without any increase in daytime leafphotosynthesis. However, leaf area ratio was reduced by thedark CO2 treatment to values equal to those of plants continuallyexposed to the higher concentration. From days 14-21, leaf areawas less for the elevated night-time CO2 treatment than foreither the constant 350 or 700 cm3 m-3 treatments. For the days7-21-period, relative growth rate was significantly reducedby the high night CO2 treatment compared with the 350 cm3 m-3continuous treatment. The results indicate that some functionallysignificant component of respiration was reduced by the elevatedCO2 concentration in the dark.Copyright 1995, 1999 AcademicPress Glycine max L. (Merr.), carbon dioxide, plant growth, respiration 相似文献
4.
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
5.
An attempt has been made to separate constituents of marineseston samples: inorganic material, detritus and the algal species,by density gradient centrifugation, without affecting the physiologicalstate of the algae. A relatively inert gradient material, consistingof Percoll, salt and sucrose, was composed. Since the densitiesof detritus and algae as well as those of different algal speciesoften overlapped, only 10 of the 100 samples processed in thecourse of the year showed a reasonable separation. However,an enrichment with respect to one or more species was oftenachieved. Densities of eleven species of marine diatoms andof one dinoflagellate have been determined at different timesof the year. For eight diatom species and for the dinoflagellatethe following specific density ranges were established: Bidduiphiaaurita: 1.181.23 g cm3, Biddulphia sinensis: 1.031.08g cm3, Cerataulina bergonii: 1.031.06 g cm3,Ditylum brightwellii: 1.071.13 g cm3, Rhizosoleniadelicatula: 1.041.09 g cm3, Skeletonema costatum:1.121.17 g cm3, Streptotheca thamensis: 1.041.10g cm3 , Thalassiosira rotula: 1.051.10 g cm3,Peridinium sp.: 1.081.12 g cm3. No seasonal variationin density was demonstrated. Gradients of different compositiondid not influence density measurements. 相似文献
6.
The microreticulate resting cyst of the potentially toxic, chain-forming,unarmoured neritic dinoflagellate Gymnodinium catenalum Graham1943. the planktonic stage of which is not known from NorthEuropean waters, is reported for the first time from recentGerman coastal sediments of the North Sea and Baltic Sea. Insandy mud sediments of the German Bight, a maximum of 8 5 livingcysts cm3 were found. In Kiel Bight sediments G.catenalumwas found in maximum concentrations of 17.0 living cysts cm3.In surface waters of the German Bight resuspended G catenatumcysts were observed at concentrations of up to 3.6 cysts l1.Successful germination experiments conducted with natural seawatershow that the occurrence of a vegetative form of G.catenatumin northern Europe is very likely. The present study highlightsthat cyst surveys provide an important tool for the evaluationof areas with potential toxicity problems, as they may indicatethe presence of hitherto overlooked species in the water column. 相似文献
7.
The thesis that the minimum cell-phosphorus content of planktonalgae is a light- and temperature-independent species constantwas investigated using the marine plankton diatom Thalassiosirarotula. To what extent the maximum cell-phosphorus content isalso a constant, light- and temperature-independent quantityhas been tested in parallel. At 2.5C and 3.03 nE cm2s1 the minimum and maximum cell-phosphorus contents aregreater than the values for 16C and 8.93 nE cm2 s1by a factor of 5.7. The light intensities were kept near thelight saturation for the growth rate for all experimental temperatures(2.5, 6, 12 and 16C). The light dependence of the phosphoruscontent was tested at 12C. For 1.43 nE cm2 s1the minimum phosphorus content was lower by a factor of 2.5than for 64.28 and 80.36 nE cm2 s1 respectively.The maximum P-content for 2.86 nE cm2 s1 was 3.9times higher than for 64.28 nE cm2 s1 T. rotulais, on the basis of the stored P-content, only capable of betweenthree and five cell divisions. The N/P atomic ratios were, dependingupon light and temperature, between 56:1 and 226:1 for the minimumcell-phosphorus content, which implies a pronounced phosphorusdeficiency. 相似文献
8.
GEHL KATHARINA A.; COOK CATHERINE M.; COLMAN BRIAN 《Journal of experimental botany》1987,38(7):1203-1210
The carbon dioxide compensation point of the unicellular greenalga, Chloretla saccharophila, was determined in aqueous mediumby a gas chromatographic method. Compensation points decreasedmarkedly from 63 cm3 m3 at an external pH of 4.0 to 3.2cm3 m3 at pH 8.0 and were not affected by the O2 concentrationof the medium. The calculated CO2 concentration required tosupport the half-maximum photosynthetic rate of the algal cellsranged from 6.0 mmol m3 at an external pH of 60 to 1.5mmol m3 at pH 8.0 and these values were not affectedby O2 concentration. The Km(CO2) of nbulose-l,5-bisphosphatecarboxylase isolated from cells grown either at pH 4.0 or pH8.0 was determined to be 64 mmol m3. These results indicatethat loss of CO2 by photorespiration does not occur in C. saccharophilacells at acid pH and the disparity between the apparent affinityfor CO2 of the intact cells and that of the carboxylase indicatesthe operation of a CO2 concentrating mechanismin this alga at acid pH. Key words: Acidophilic alga, bicarbonate transport, Chlorella saccharophila, compensation point, CO2 affinity, PH, RuBP carboxylase 相似文献
9.
It is proposed that surface scums of densely packed planktoniccyanobacteria (blue-green algae) which exist for weeks to months,measure several decimeters in thickness and are covered by acrust of photo-oxidized cells, be called hyperscums. Hyperscumsof Microcystis aeruginosa formed during prolonged periods ofcalm weather in wind-protected sites in a hypertrophic lakesubject to low wind speeds (Hart beespoort Dam, South Africa).A hyperscum that extended over 12 hectares and persistedfor 103 days during winter 1983 was studied. Chlorophyll a concentrationsranged from 100 to 300 mg l2 Microcystis cell concentrationsreached 1.76x109 cells ml1 or 116 cm3l1. The hyperscumenvironment was anoxic, aphotic, with a fluctuating temperatureregime and low pH values. The densely packed Microcystis cellssurvived these conditions for more than 2 months. This was shownby comparing the potential photosynthetic capacity of Microcystisfrom the hyperscum with that of Microcystis from the main basinof the lake. However, after 3 months the hyperscum algae losttheir photosynthetic capacity and decomposition processes prevailed.The hyperscum gradually shrank in size until a storm causedits complete disintegration. 相似文献
10.
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
11.
槲栎种子雨进程中昆虫的捕食特征 总被引:2,自引:1,他引:1
为了了解昆虫捕食与槲栎Quercus aliena种子大小和产量的关系以及在栎林更新中的作用,于2008和2009年秋季,分别在暖温带伏牛山系天池山国家森林公园内研究了两个年度槲栎的种子雨过程及昆虫捕食特征。结果表明:(1)种子雨过程从8月中下旬到9月底约经历40 d,存在高峰期且时段较明显,高峰期下落种子量分别占全部种子雨量的78.13%(2008年)和75.91%(2009年);(2)槲栎的种子雨强度年间存在较大差异,2008年明显小于2009年(两年分别为31.75±16.65粒/m2和51.92±29.26粒/m2),但2009年的橡子明显比2008年小(两年分别为1.94±0.61 cm3和2.46±0.57 cm3);(3)种子雨构成比例在两个年份间存在差异,完好种子的量分别为59.05%(2008年)和36.12%(2009年),虫蛀率在大量结实的2009年显著提高;(4)虫蛀橡子(2.29±0.42 cm3)显著大于完整橡子(1.59±0.32 cm3),且虫蛀种子中所含虫卵数与种子大小显著正相关,昆虫有选择大种子产卵寄生的偏好。本研究的结果说明,昆虫对槲栎大种子有寄生选择偏好;大部分槲栎种子遭遇象甲虫蛀而降低生命活力,这可能是影响槲栎林更新的主要因素之一。 相似文献
12.
The duckweeds Lemna gibba L. and Lemna minor L. only grew wellin undisturbed culture under axenic conditions in low lightintensity when provided with a suitable energy source such asglucose. In media containing N03-N gibbosity (a convex ventralsurface) was induced in the presence of the chelating agentethylene-diamine-di-o-hydroxyphenylacetic acid (EDDHA). In nutrientsolutions containing NO3-N as the only N source, but withoutEDDHA, L. gibba occasionally exhibited gibbosity in culturesolutions of 40 cm3 volumes. More fronds were induced to exhibitgibbosity when the volume of the culture medium was increasedfrom 40 cm3 to 200 cm3. Gibbosity was never induced in L. minor,neither was it induced in L. gibba in media containing NH4-N,even in the presence of NO3-N. There was no direct correlationbetween the occurrence of gibbosity and frond growth rate, butgibbosity occurred only when there was good frond growth. In the absence of a sugar, frond growth was enhanced by bubblingair through the culture solution in the light. Increasing theCO2 concentration in the air up to 1% enhanced growth and inducedgibbosity. Carbon dioxide did not induce gibbosity in mediacontaining NH4-N. Key words: Ammonium-N, carbon dioxide, gibbosity, Lemna, nitrate-N 相似文献
13.
Tomato fruit grown in diurnally fluctuating salinities (8 mScm1 during the day and 3 mS cm1 at night; 8/3mS cm1), accumulated the same amount of dry matter andmagnesium (Mg) as those in constant 3 or 8 mS cm1, butan intermediate amount of calcium (Ca). Raising the salinityof the nutrient solution by enriching with macronutrients orby adding NaCl had similar effects. The uptake of 45Ca by tomato plants during the day was greaterthan at night and was reduced by salinity in both periods. Whilethe uptake of 45Ca by 8/3 mS plants at night was similar tothat of 3 mS plants, the daily uptake was less than that in3 and 5.5 mS plants. The Ca content of tomato fruit increased with truss number at3 and 5.5 mS cm1 but not at 8/3 and 8 mS cm1.Within the same truss, the distal fruit had a lower Ca contentbut higher Mg content than the proximal fruit. The reductionin Ca content of the distal fruit at 8/3 mS cm1 was similarto that at 5.5 mS cm1. The Ca content of the tissue atthe distal end of the 8/3 mS fruit was lower than that of the5.5 mS fruit. Similarly, the distribution of 45Ca to the distalhalf of the detached 8/3 mS fruit was less than that of 5.5mS fruit. A reduced uptake and inadequate distribution of Cato the truss and to the distal end of the 8/3 mS fruit werethe main causes of these differences. Lycopersicon esculentum(Mill.), tomato, fruit, calcium, magnesium, diurnal salinity 相似文献
14.
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
15.
In this paper we report measurements concerning the conductivityof water and ions and the interaction between the two in excisedpieces of xylem of red maple stems under various conditions.We have also demonstrated that it is possible to detect theflow of solutions through the stems of maple by measuring thedegree of interaction between the flow of water and ions. Inthis technique we apply voltage pulses of ±V volts acrossa length of stem and detect the unequal current pulses resultingfrom the greater frictional drag when current (which is carriedprimarily by cations) is flowing against the water stream thanwhen flowing with the water stream. The hydraulic conductivityof recent maple sapwood ranges from 30 to 90 cm3 s1 cm2(J cm3)1 cm; in 2 mM KCl the electrical conductivityis roughly 3 x 104 mho cm1 and the electro-kineticcross coefficient is roughly 4x105 A cm2 (J cm3)1cm. 相似文献
16.
Fluorescence transients were investigated with the diatom Phaeodactylumtricornutum. Supplementary experiments were done with Chaetocerossp. Under weak excitation ({small tilde}103 erg/cm2sec), fluorescencetransients were induced simply by die oxidation-reduction reactionof Q, the primary reductant of photosystem II. The action spectraindicated that the electron transfer components between thetwo photosystems were in the most reduced state when fucoxanthinwas excited. The transients were observed with the 681 run emissionand with the 707 nm emission at room temperature. At 196°C,induction due to the reduction of Q. appeared both at the 681and 707 nm emissions. Similar results were also obtained withChaetoceros sp. Under strong excitation (104105 erg/cm2-sec), the fluorescencetransients due to the interconversion between States 1 and 2of die pigment system (cf. ref. 27, 29) were observed. The transientswere induced by die alternate excitation of chlorophyll a andfucoxanthin or chlorophyll c. Conversion from State 2 to State1 was inhibited by DNP and CCCP, indicating that die processwas energy-dependent. Fluorescence spectra at 196°Cwere not altered by die state-conversion of die pigment system. These results suggest diat all die fluorescence bands whichappeared at room temperature and at 196°C were dueto die chlorophyll a of pigment system II in Phaeodactylum andChaetoceros. (Received September 7, 1972; ) 相似文献
17.
Shikimate kinase from Phaseolus mungo seedlings was partiallypurified by DEAEcellulose, hydroxyapatite and Sephacryl S-200column chromatographies. The activity was completely inhibitedby EDTA and the requirement for Mg2+ could be partially replacedby Mn2+, Ca2+; Co2+ and Cd2+. Sulfhydryl inhibitor did not inhibitthe enzyme activity. The apparent Km values for shikimic acidand ATP at pH 8.6 were 0.25 mM and 0.38 mM, respectively. Theactivity appeared to be maximal at pH 8.69.0. Shikimate-3-phosphateand ADP inhibited the activity slightly. Aromatic amino acids,quinic acid and dehydroquinic acid had no significant effecton the activity. (Received January 11, 1979; ) 相似文献
18.
Ipomeamarone 15-hydroxylase activity was mainly recovered inthe pellet fraction between centrifugations at 10,000 and 100,000?gfrom a crude extract of Ceratocystis fimbriata-infected sweetpotato root tissue, whereas cinnamic acid 4-hydroxylase activitywas found between centrifugations at 300 and 10,000?g. Whenparticles in the crude extract were fractionated by sucrosedensity gradient centrifugation, the rough-surfaced microsomeswere distributed over a wide density range from 1.09 to 1.14g cm3, judging from the distributions of protein, RNAand NADPH-cytochrome c reductase activity. Phosphorylcholine-glyceridetransferase activity was only in the lighter half of the microsomalfraction (density: 1.091.11 g cm3). Ipomeamarone15-hydroxylase activity was found in heavier half of the microsomalfraction (density: 1.101.14 g cm3). We proposethat this tissue has two rough-surfaced endoplasmic reticulumspecies, only one of which carries phosphorylcholine-glyceridetransferase, and that the cytochrome P-450 system is localizedon the species lacking the enzyme. Cinnamic acid 4-hydroxylaseactivity was mainly found in a fraction that had densities of1.171.19 g cm3 and contained vesicular particlesof various sizes.
1 Present address: Laboratory of Food Hygienics, Faculty ofAgriculture, Kagawa University, Miki-cho, Kida-gun, Kagawa 761-07,Japan. (Received September 6, 1984; Accepted December 27, 1984) 相似文献
19.
Evoked potentials recorded by implanted electrodes were usedto measure olfactory thresholds of unanesthetized laboratorymice (Mus musculus) to aliphatic carboxylic acids (formic acid,acetic acid, n-propionic acid, n-butyric acid, n-valeric acid,and n-caproic acid). The thresholds conformed to the typicalmammalian pattern, sensitivity to carboxylic acids increasingwith increasing chain length. The highest threshold was thatto formic acid, 7?1011 molecules/cm3 of air; that to caproicacid was lowest, 1.1?108 molecules/cm3. 相似文献
20.
Photosynthetic 14C fixation by Characean cells in solutionsof high pH containing NaH14CO3 gave a measure of the abilityof these cells to take up bicarbonate (H14CO3). Whereascells of Nitella translucens from plants collected and thenstored in the laboratory absorbed bicarbonate at 11.5µµmoles cm2 sec1, rates of 38µµmoles cm2 sec1 were obtained withN. translucens cells from plants grown in the laboratory. Influxesof 56 µµmoles cm2 sec1 wereobtained with Chara australis, 38 µµmolescm2 sec1 with Nitellopsis obtusa, and 15µµmoles cm2 sec1 with Tolypella intricata.It is considered that these influxes represent the activityof a bicarbonate pump, which may be an electrogenic process. In solutions of lower pH, H14CO3 uptake would be maskedby rapid diffusion of 14CO2 into the cells: the four Characeanspecies fixed 14CO2 at maximum rates of 3040 µµmolescm2 sec1 (at 21° C). 相似文献