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1.
甜菜夜蛾不同世代对氯氟氰菊酯抗性减退及多功能氧化酶系活性变化 总被引:4,自引:0,他引:4
在室内用人工饲料连续饲养和未用药剂筛选条件下,测定了采自田间对氯氟氰菊酯产生高水平抗性甜菜夜蛾Spodoptera exigua (Hübner)种群的抗药性及其多功能氧化酶系活性的变化情况。用点滴法测定不同世代3龄幼虫抗性结果为:室内F1代LD50值为 0.9672 μg/头,抗性倍数为4 836.0倍,以后各世代逐渐降低,至F43代LD50值为0.0325μg/头,抗性倍数为162.5倍,抗性水平下降了29.8倍。用浸叶法测定不同世代3龄幼虫抗性结果为:室内F1代LC50值为185.6 mg/L,抗性倍数为964.7倍,以后各世代也逐渐降低,至F43代LC50值为9.2 mg/L,抗性倍数为47.8倍,抗性水平下降了20.2倍。与敏感品系相比,该田间种群室内饲养至F43代仍处于较高的抗性水平,抗性减退缓慢,很难恢复到敏感水平。测定甜菜夜蛾田间种群室内F2、F20和F41代及敏感品系5龄幼虫中肠微粒体甲氧试卤灵-O-脱甲基酶、乙氧试卤灵-O-脱乙基酶、芳香基羟基化酶及艾氏剂环氧化酶活性,结果表明:与敏感品系相比,田间种群甲氧试卤灵-O-脱甲基酶和艾氏剂环氧化酶的活性仅F2代显著较高,F20和F41代差异不显著,乙氧试卤灵-O-脱乙基酶和芳香基羟基化酶的活性F2、F20和F41代均显著较高。结果提示甜菜夜蛾抗性水平可能与其体内微粒体多功能氧化酶系活性有密切关系。 相似文献
2.
Thomas, H. 1987. Physiological responses to drought of Loliumperenne L.: Measurement of, and genetic variation in, waterpotential, solute potential, elasticity and cell hydration.J.exp. Bot. 38: 115125. Clonally-replicated genotypes of Loiium perenne L. were grownin a controlled environment. Leaf water potential (w) osmoticpotential (s), turgor potential (p = w s), elasticity(E), leaf hydration (g water per g dry matter, H) and numberof green leaves per tiller (NGL) were measured before and duringa 42 d drought treatment. A simplified method of estimating E (at w < 1?0 MPa) usingonly six measurements was developed to permit a measurementrate of 8 leaves per hour. Measurement errors in all characterswere 3% or less. During drought, w and s (at w = 0?5 MPa) decreased significantly,p and E increased significantly, and H decreased slightly. Plantsize during drought was negatively correlated with s, and Hand positively correlated with p, osmotic adjustment, E andNGL. Measurements made on the genotypes before draughting didnot give a reliable indication of their physiological conditionafter adaptation to drought. Genetically controlled variation (broad sense heritability)of drought-adapted plants for E was 15%, w 23%, s, 34%, p, 35%,H 34% and NGL 64%. The possibilities for, and effectivenessof, divergent selection of genotypes with high and low expressionof the characters are discussed. Key words: Water relations, Lolium, genetic variation 相似文献
3.
The study of the kinetics of O2 consumption (o2) at the onsetand offset of constant-load submaximal exercise (o2 on- andoff-kinetics) is useful from a practical point of view (a fasteradjustment of oxidative metabolism following an increased metabolicdemand reduces the need for substrate level phosphorylation,with implications on exercise tolerance and muscle fatigue)and can give valuable insights into the regulation of oxidativemetabolism in skeletal muscle. Measurements have been carriedout both in man and in animals, at the tissue and at the wholebody level. At the tissue level, the o2 on- and off-kineticswere determined: a) Directly, by dynamic solution of the Fickequation throughout the transients; attempts were also madeto obtain similar informations by near-infrared spectroscopy.b) Indirectly, from the kinetics of phosphocreatine hydrolysisand resynthesis, by chemical methods or by 31P magnetic resonancespectroscopy. At the whole body level, o2 on- and off-kineticsare determined from breath-by-breath measurements of pulmonarygas exchange. The o2 = f(t) function is a complex one, particularlyduring the on-transient. The so-called "phase 2" of the o2 on-response,as well as the o2 off-response, yield relevant metabolic informations.In muscle the o2 on- and off-kinetics are characterized by half-times(t) of 1520 sec. At the whole-body level, t of the o2on-kinetics show a wider variability, related to the experimentalprotocol and to other factors. The o2 off-phase is more constant,and its kinetic parameters appear closer to those obtained atthe tissue level. The study of the o2 kinetics is valuable fora functional evaluation of skeletal muscle oxidative metabolism.In ordinary conditions muscle o2 kinetics appears mainly imposedby intrinsic (metabolic) rather than extrinsic (O2 delivery)factors. 相似文献
4.
Flowering (number of flowers) of a short-day duckweed, Lemnapaucicostata 6746, in continuous darkness at 26?C was affectedby a red light pulse in various ways depending on the time ofapplication. A conspicuous inhibition and a slight promotionwere respectively caused by the pulse given at the 7th and 19thhours of the dark period. Of the recently introduced floral parameters (4), a (vegetativegrowth rate) and (flowering ratio) were almost unchanged bythe pulse given at any time. P1 (pre-flower induction period)was extended by one day when the pulse was given at about the7th hour of the dark period. The pulse greatly extended P2 (flowerinduction period) when given at about the 7th hour of the darkperiod. A pulse given earlier or later was increasingly ineffectiveon P2. P4 (flower production period) changed rhythmically (i.e.,was extended or shortened) with the time of the red light pulse,the maximum extension and shortening being induced by the pulsegiven at about the 7th and 19th hours, respectively. Differenttiming mechanisms were suggested as controlling the sensitivitiesto the red light pulse of P1 and P2 or P4. The floral response (number of flowers) vs. the red light pulseapplication time curve was explained in terms of the sum ofthe responses of P2 and P4 to the pulse. Floral parameters P1and P2 were defined more clearly. (Received September 4, 1978; ) 相似文献
5.
Catecholamines, heart rate, and oxygen uptake during exercise in persons with spinal cord injury 总被引:2,自引:0,他引:2
Schmid Andreas; Huonker Martin; Barturen Jose-Miguel; Stahl Fabian; Schmidt-Trucksass Arno; Konig Daniel; Grathwohl Dominik; Lehmann Manfred; Keul Joseph 《Journal of applied physiology》1998,85(2):635-641
The purpose ofthis study was to investigate the influence of different injury levelsin persons with spinal cord injury (SCI) on epinephrine (Epi) andnorepinephrine (NE) at rest and during graded wheelchair exercise andthe related changes in heart rate andO2 uptake(O2). Twenty tetraplegics(Tetra), 10 high-lesion paraplegics (HLPara), 20 paraplegics with SCIbelow T5 (MLPara), and 18 able-bodied, nonhandicapped persons (AB) were examined. Because of thehigher level of interruption of the sympathetic pathways, Tetra personsshowed lower Epi and NE at rest and only slight increases duringexercise compared with all other groups; the Tetra subjects' impairedcardiac sympathetic innervation caused restricted cardioaccelerationand strongly reduced maximalO2. Whencompared with AB persons, HLPara had comparable NE but lower Epi levelsas a result of partial innervation of the noradrenergic system anddenervation of the adrenal medulla. MLPara subjects showed an augmentedbasal and exercise-induced upper spinal thoracic sympathetic activitycompared with AB subjects. The increase in heart rate in relation toO2 was higher in HLParabecause of a smaller stroke volume as a result of venous blood pooling.The different exercise response in persons with SCI is a result of theinterruption of pathways in the spinal cord to the peripheral sympathetic nervous system in addition to the motor paralysis. 相似文献
6.
Superoxide, hydroxyl radical, and hydrogen peroxide effects on single-diaphragm fiber contractile apparatus 总被引:6,自引:0,他引:6
Reactive oxygenspecies contribute to diaphragm dysfunction in certainpathophysiological conditions (i.e., sepsis and fatigue). However, the precise alterations induced by reactive oxygen species orthe specific species that are responsible for the derangements inskeletal muscle function are incompletely understood. In this study, weevaluated the effect of the superoxide anion radical (O2·), hydroxyl radical (·OH), and hydrogenperoxide (H2O2) on maximum calcium-activatedforce (Fmax) and calcium sensitivity of the contractileapparatus in chemically skinned (Triton X-100) single rat diaphragmfibers. O2· was generated using thexanthine/xanthine oxidase system; ·OH was generated using 1 mMFeCl2, 1 mM ascorbate, and 1 mMH2O2; and H2O2 wasadded directly to the bathing medium. Exposure to O2· or ·OH significantly decreasedFmax by 14.5% (P < 0.05) and 43.9%(P < 0.005), respectively. ·OH had no effect onCa2+ sensitivity. Neither 10 nor 1,000 µMH2O2 significantly altered Fmax orCa2+ sensitivity. We conclude that the diaphragm issusceptible to alterations induced by a direct effect of ·OH andO2·, but not H2O2, on thecontractile proteins, which could, in part, be responsible forprolonged depression in contractility associated with respiratorymuscle dysfunction in certain pathophysiological conditions. 相似文献
7.
A low flow of air is passed through a temperature-controlledplant chamber in order to obtain relatively large (300500µl-1) differences in [O2] between influx and efflux streams.These differences are measured with a stabilized O2 electrodesystem incorporating elements of gas conditioning electroniczero suppression and signal amplification. Changes in [O2] of400 µl l-1 can be detected at full scale recorder deflectionagainst a background concentration of 21% O2. The concentrationsof CO2 and H2O within the chamber are held constant by con-trolled-flowCO2-scrubbing and dehumidifying loops. Carbon dioxide, H2O,and O2 fluxes are measured and leaf diffusion resistance andinternal [CO2] are calculated in essentially real time. 相似文献
8.
Recovery of free ADP, Pi, and free energy of ATP hydrolysis in human skeletal muscle 总被引:1,自引:0,他引:1
Wackerhage Henning; Hoffmann Uwe; Essfeld Dieter; Leyk Dieter; Mueller Klaus; Zange Jochen 《Journal of applied physiology》1998,85(6):2140-2145
We measuredsignificant undershoots of the concentrations of free ADP([ADP]) and Pi([Pi]) and the freeenergy of ATP hydrolysis (GATP) belowinitial resting levels during recovery from severe ischemic exercisewith 31P-nuclear magneticresonance spectroscopy in 11 healthy sports students. Undershoots ofthe rate of oxidative phosphorylation would be predicted if the rate ofoxidative phosphorylation would depend solely on free[ADP],[Pi], orGATP. However,undershoots of the rate of oxidative phosphorylation have not beenreported in the literature. Furthermore, undershoots of the rate ofoxidative phosphorylation are unlikely because there is evidence that a balance between ATP production and consumption cannot be achieved if anundershoot of the rate of oxidative phosphorylation actually occurs.Therefore, oxidative phosphorylation seems to depend not only on free[ADP],[Pi], orGATP. Anexplanation is that acidosis-related or other factors control oxidativephosphorylation additionally, at least under some conditions. 相似文献
9.
GORDON A J.; MACDUFF J H.; RYLE G. J. A.; POWELL C E. 《Journal of experimental botany》1989,40(5):527-534
Established, nodulated white clover plants were transferredto eight tanks of a flowing culture apparatus with solutiontemperatures of 5, 11, 17, and 25 ?C (two tanks per temperature).Shoot temperature and light environment were common to all plants.After 7 d, (10 mmol m3) was continuouslysupplied to one tank at each temperature while in the remainingfour tanks (one at each temperature) the plants were completelydependent on nodule N2-fixation. Plants were randomly selected at intervals during the following14 d period in order to measure root and nodule respirationand acetylene reduction activity (ARA) in a flow-through systemset at the adapted root temperature. Additional plants wereassayed for in vitro nitrate reductase activity in leaves, roots,and nodules. Apparent nitrogenase activity (ARA) and respiration associatedwith it were each markedly affected by temperature in two ways;(1) Activity per unit weight of nodule was reduced at lowertemperatures; (2) Development of the plant, and thus also nodulemass, was restricted at lower temperatures which, in turn, restrictedtotal nodule activity per plant. The presence of nitrate significantly reduced ARA of nodules,particularly at higher temperatures. However, significant discrepancieswere found when N2-fixation rates, estimated from the acetylenereduction assay, were compared with N2-fixation rates calculatedfrom curves fitted to N accumulation data (minus the rate of uptake in the case of nitrate-treated plants). Carbon use efficiency (CO2 respired per C2H4 produced) was notsignificantly affected by temperature or the presence of nitrate. Nitrate reductase activity (NRA) developed in all plant partsat the three highest temperatures, but not at 5 ?C. We calculatethat leaf NRA may account for 82, 75, and 68% of total nitratereduction at 11, 17, and 25 ?C respectively. Key words: Trifolium repens, white clover, N2 fixation, root temperature, acetylene reduction assay, nitrate, nitrate reductase 相似文献
10.
Field Studies of Cereal Leaf Growth: III. BARLEY LEAF EXTENSION IN RELATION TO TEMPERATURE, IRRADIANCE, AND WATER POTENTIAL 总被引:1,自引:0,他引:1
A mechanical auxanometer, suitable for measuring hourly ratesof leaf extension of grass and cereal crops, is described. Severalof these instruments were used to monitor leaf extension rates(RE) of a spring barley crop. RE of main stem and first leaftillers responded similarly to environmental factors. DuringMay, when soil water deficits were less than 50 mm, and on dulldays later in the season, RE was directly related to meristemtemperature with night and day measurements responding similarly.During the central 10 h of bright days in late May and June,RE was unrelated to temperature but slowed during bright sunshineand accelerated at the start of cloudy periods. Pressure chambermeasurements of total leaf water potential () showed that brightsun caused to decrease rapidly and that this was associatedwith slow RE. Analysis of 2 h mean values of and RE indicatedthat, at any given temperature, RE slowed in direct proportionto decrease of . 相似文献
11.
Several lines of evidence suggest that, for certain odorants,olfactory signal transduction may be mediated by a stimulatoryG-protein coupled adenylate cyclase cascade. Two stimulatoryG-proteins, Golf and Gs, are expressed in olfactory tissue.To evaluate their relative contributions to the process of odorantsignal transduction, specific antisera were used to determinethe distribution and relative abundance of Golf and Gs in ratolfactory neuroepithelium and olfactory sensory cilia. Theseanalyses demonstrate that (1) Golf is far more abundant thanGs in olfactory neuroepithelium and (2) Golf is essentiallythe only stimulatory G-protein present in olfactory sensorycilia.
1Present address: Gene Expression Laboratory, The Salk Institute,PO Box 85800, San Diego, CA 92138, USA 相似文献
12.
Effects of temperatures ranging from 16 to 31?C on inductionand production of flowers in Lemna paucicostata 6746 were studiedin uninterrupted and interrupted darkness. In uninterrupted darkness, the growth rate (a) and floweringratio () increased and the flower production period (P4) decreasedas the temperature rose. On the contrary, the pre-flower inductionperiod (P1) and the flower induction period (P2) were independentof temperature except that P2 was remarkably extended at 31?C.Thus, a, and P4 may be rate-limited by chemical reactions andP1 and P2 by physical reactions. P2 started at the onset ofdarkness. A red light pulse given 7 hr after the start of the dark periodextended P1, P2 and P4 without modifying a and at any temperature.The pulse extended P1 by one day irrespective of temperature,and the sensitivity of P1 to the pulse was constant at all temperatures.The red light pulse caused obvious extensions of P2 and P4 at2126?C, but no extension at lower and higher temperatures.Thus, the extension of P1 by red light seems to be rate-limitedby a physical reaction and those of P2 and P4 by chemical reactions. (Received September 26, 1978; ) 相似文献
13.
Interaction of cross-sectional area, driving pressure, and airflow of passive velopharynx 总被引:2,自引:0,他引:2
Isono Shiroh; Feroah Thom R.; Hajduk Eric A.; Brant Rollin; Whitelaw William A.; Remmers John E. 《Journal of applied physiology》1997,83(3):851-859
Isono, Shiroh, Thom R. Feroah, Eric A. Hajduk, Rollin Brant,William A. Whitelaw, and John E. Remmers. Interaction ofcross-sectional area, driving pressure, and airflow of passive velopharynx. J. Appl. Physiol. 83(3):851-859, 1997.Previous studies have shown that, when thepharyngeal muscles are relaxed, the velopharynx is a highly compliantsegment of the pharynx. Thus, under these circumstances,cross-sectional area of the velopharynx (AVP), drivingpressure across the velopharynx (P), and inspiratory airflow(I) willbe mutually interdependent variables. The purpose of the presentinvestigation was to describe the interrelation among these threevariables during inspiration. We studied 15 sleeping patients withobstructive sleep apnea/hypopnea when the pharyngeal muscles wererendered hypotonic by applying continuous positive airway pressure tothe nasal airway.AVP, determined by endoscopic imaging, was significantly greater at onset ofI limitationthan at minimum oropharyngeal pressure(P < 0.01). Snoring was neverobserved duringIlimitation. In a subgroup of six patients, values for P,I, andAVP were obtainedat 0.1-s intervals at various levels of mask pressure. For these sixpatients, the mathematical expressionI = 0.657(AVP/Amax) · P0.332,where Amax ismaximal AVP,described the relationship among the three variables(R2 = 0.962) forflow-limited and non-flow-limited inspirations. The impedance of thepassive velopharynx, defined asP0.33/,was inversely related toAVP and increaseddramatically when AVP was <0.3cm2. In summary, we observed aprogressive decrease inAVP during flow-limited inspiration in patients with obstructive sleep apnea. Thisconstriction of the velopharynx contributes to an increase invelopharyngeal impedance that, in turn, counterbalances the increase inP during flow limitation. 相似文献
14.
Potard U. Silke Birlenbach; Leith David E.; Fedde M. Roger 《Journal of applied physiology》1998,84(6):2052-2059
Thoroughbred (TB) and draft horses (DH) havelong been selected for tasks of very different intensities andforce-speed relationships. To study their adaptations, we measuredO2 consumption and related variables in three TB and four DH during progressive exercise tests ona level treadmill. The horses exerted a draft force of 0, 5, 10, 15, or20% of their body weight at speeds that increased by 2 m/s every 3 minuntil they could not maintain that speed. We found that TB could exertthe same draft forces as DH and, at each force, TB achieved about twicethe speed, twice the external power, and twice theO2 consumption as DH; thus the twobreeds had the same gross efficiencies. We also found maximalO2 consumption of TB to be abouttwice that of DH (134 vs. 72 ml · kg1 · min1,respectively), suggesting adaptations to high-intensity exercise. Peakefficiency was reached at lower speeds in DH than in TB, suggestingadaptations to high-force, low-speed exercise. These differencesbetween TB and DH in force-speed and aerobic capacities and in speedfor peak efficiency likely reflect different contraction velocities inlocomotor muscles. 相似文献
15.
Crop load affects assimilation rate, stomatal conductance, stem water potential and water relations of field-grown Sauvignon blanc grapevines 总被引:3,自引:1,他引:2
The effects of two shoot densities (14 and 44 shoots/vine) andtwo crop levels (one and two clusters/shoot) on gas exchangeand water relations of field-grown Sauvignon blanc (Vitis viniferaL.) were studied in a factorial design over 3 years. The two-clustertreatments had 0.14 MPa higher stem water potential (stem),1.4 µmol m2 s1 higher assimilation rate(A), 0.04 mol m2 s1 higher stomatal conductance(gs) and 0.008 mol m2 s1 higher non-stomatal (gm)conductance. The two-cluster treatments had higher gs and transpirationrates than the one-cluster treatments, for similar stem. A quantitativeanalysis suggests that storage capacity cannot account for thesimultaneous increase in gs and stem in the two-cluster treatments.Similar gs-gm responses were found In the one- and two-clustertreatments, regard less of differences between the treatmentsin gs-stem response. Key words: Grapevine, stomatal conductance, assimilation rate, water relations 相似文献
16.
LIGHT-INDUCED REDUCTION OF NITRATE, NITRITE AND HYDROXYLAMINE IN A BLUE-GREEN ALGA, ANABAENA CYLINDRICA 总被引:1,自引:0,他引:1
- Reduction of nitrate, nitrite and hydroxylamine by intact cellsof Anabaena cylindrica was investigated with special referenceto the stimulating effect of light on these processes.
- Itwas found that in light and under anaerobic condition thesecompounds are reduced to ammonia, with the production of extraoxygen. The stoichiometry of the reactions under these conditionscan be represented as follows: HNO2+H2O=NH2+2O2 HNO2+H2O=NH2+1O2 NH2OH+H2O=NH2+O2+H2O
- Reduction of nitrite and hydroxylaminewas markedly suppressedby CMU in the light but not in the dark.KCN inhibited reductionto the same extent both in the lightand in the dark. Reductionin the light was much less sensitiveto the uncoupling agent,DNP, than was that in the dark.
- Atlow light intensities, CO2 was suppressed by 2030per cent by the simultaneous provision of nitrite, but the nitritereduction was not affected at all by CO2. At high light intensities,reduction of nitrate and nitrite was considerably acceleratedby CO2
- On the basis of these findings, a possible mechanismfor thelight stimulation of the reactions in question was brieflydiscussed.
17.
Gas exchange in Clusia rosea has been measured under variousconditions of water status, light and leaf-air vapour pressuredeficit (w, mbar bar1) which produce daytime (C3), night-time(CAM) or 24 h uptake of CO2. At high light levels, at a w of6.6, well-watered plants utilized C3 photosynthesis while CAMand 24 h uptake occurred under lower light levels and with lowto normal water availability and differing w (13.5 and 3.4,respectively). CO2 uptake was highest, stomatal conductanceto water vapour (gH2o) lowest, and water use efficiency (WUE)highest in plants using C3 photosynthesis. This latter factis contrary to the accepted view that CAM is most water useefficient, i.e. it optimizes CO2 uptake with minimal water loss.It is suggested that the low CO2 uptake in CAM photosynthesismay be related not only to the higher w but also to the factthat Clusia species accumulate citrate which may originate fromß-carboxylation of fatty acids (i.e. an internal sourceof CO2) and does not contribute to night-time external CO2 assimilation.Curves of assimilation (A) versus internal partial pressureof CO2 (A/c1) for the three photosynthetic types, under atmosphericconditions, did not produce a single trend. The trends whichwere produced represent the supply function for the interaction,under differing modes of photosynthesis, of the two major enzymesystems involved in CAM. Key words: Clusia rosea, Crassulacean acid metabolism, C3 photosynthesis, internal CO2 concentration, 24 h carbon dioxide uptake, water use efficiency. 相似文献
18.
Muscle capillarization, O2 diffusion distance, and VO2 kinetics in old and young individuals 总被引:1,自引:0,他引:1
Chilibeck P. D.; Paterson D. H.; Cunningham D. A.; Taylor A. W.; Noble E. G. 《Journal of applied physiology》1997,82(1):63-69
Chilibeck, P. D., D. H. Paterson, D. A. Cunningham, A. W. Taylor, and E. G. Noble. Muscle capillarization,O2 diffusion distance, andO2 kinetics in old andyoung individuals. J. Appl. Physiol.82(1): 63-69, 1997.The relationships between muscle capillarization, estimated O2diffusion distance from capillary to mitochondria, andO2 uptake(O2) kineticswere studied in 11 young (mean age, 25.9 yr) and 9 old (mean age, 66.0 yr) adults. O2kinetics were determined by calculating the time constants () forthe phase 2 O2 adjustment to andrecovery from the average of 12 repeats of a 6-min, moderate-intensityplantar flexion exercise. Muscle capillarization was determined fromcross sections of biopsy material taken from lateral gastrocnemius.Young and old groups had similarO2 kinetics(O2-on = 44 vs. 48 s;O2-off = 33 vs. 44 s, for young and old, respectively), muscle capillarization, andestimated O2 diffusion distances.Muscle capillarization, expressed as capillary density or averagenumber of capillary contacts per fiber/average fiber area, and theestimates of diffusion distance were significantly correlated toO2-off kinetics in theyoung (r = 0.68 to 0.83;P < 0.05). We conclude that1) capillarization andO2 kinetics during exerciseof a muscle group accustomed to everyday activity (e.g., walking) arewell maintained in old individuals, and2) in the young, recovery of O2 after exercise isfaster, with a greater capillary supply over a given muscle fiber areaor shorter O2 diffusion distances. 相似文献
19.
A limnological database for Lake Kinneret was used to determinethe period each year when the interaction of mixed depth andlight availability would permit growth of the planktonic cyanobacteriumAphanizomenon ovalisporum. The organism, recorded for 56211days in each of the 7-years, 19942000, was usually distributedthrough the mixed epilimnion and reached a maximum in late October.The mixed depth (zm) was calculated from the temperature profile,wind speed and wind direction. Changes in the total populationwere related to changes in the daily integrals of photosynthesis,calculated from vertical profiles of water temperature () andlight attenuation (Kd), and hourly changes in photon irradiance(E0) each day, using temperature-compensated algorithms basedon measurements of photosynthesis at different irradiances.Net photosynthesis was calculated for different ratios of respiration(R) and maximum photosynthesis (Pm). In a modelling analysis,the daily integral of net photosynthesis fell below zero onthe day of the population maximum, and remained negative duringthe period of population decline, when R was set at -0.08 Pm.Similar modelling, based on the 7-year mean values of , Kd andE0for each day of the year, showed the critical depth for photosynthesisby Aphanizomenon would exceed the mixed depth in Lake Kinneretfrom mid-March to late October. Direct measurements of -R/Pmratios could be used with information in the database to analysethe periods of photosynthetic production by different phytoplanktonspecies in Lake Kinneret. 相似文献
20.
Vertical migration, entrainment and photosynthesis of Peridiniumcinctum were investigated in the Torrens Lake, South Australia.Cell distribution was a function of swimming speed, shear velocityand the surface mixed layer depth. During the morning, whenthe wind speed was low, cells migrated upwards, at a velocityof 2.35 x10-4 m s-1 and accumulated at 0.7 m (827 µmolm-2 s-1 at 13:00 h). After 13:00 h, cells migrated downwardsto 3.33.6 m at 1.85 x 10-4 m s-1. As wind speed increasedin the afternoon, the shear velocity of the surface mixed layerexceeded the swimming speed, leading to a homogeneous cell distributionwithin the surface mixed layer. Below the surface mixed layer,a deep chlorophyll maximum persisted. The observations werefound to fit in an entrainment function (), where if > 1,cells are disentrained, and if < 1, cells are entrained.The maximum effective quantum yield of photosystem II (F'v/F'm)was used as an index to monitor the photosynthetic performanceof P. cinctum and the ratio of bottle (fixed depth) to lakeF'v/F'm indicated whether or not migration or mixing was enhancingphotosynthesis or preventing photoinhibition. A small (0.10.2units) but significant depression in F'v/F'm was observed inP. cinctum in bottle and lake surface samples during stratifiedconditions. However, this recovered to initial values laterin the day. The ratio of bottle to lake F'v/F'm was consistentwith P. cinctum migration patterns. A comparison between modelleddaily photosynthetic rates of the observed migrating and a theoreticalhomogeneous population revealed that migration would not increasephotosynthetic rates within the Torrens Lake. The net ratesof O2 production in the water column from dawn to dusk for themigrating and evenly distributed cell populations were 2574and 3120 mg m-2, respectively. 相似文献