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1.
Dry weights of individual Daphnia galeata and D. hyalina, whichcoexist in Lake Constance, were determined weekly during a twoyear investigation. From each sample and each species a lengthweightrelationship (LWR) was calculated resulting in 54 (65) regressionequations based on N=2466 (3032) in D. galeata (D. hyalina).The constants (Ln(A)) and (B) of the LWRs showed a marked seasonalvariability, ranging from Ln(A)=1.07842.4740(1.01522.3860)and B=2.144.20 (2.114.15). The seasonal variabilityof the LWR was estimated with four different models. Condensingthe 54 (65) equations into one seasonal cycle resulted in amodel with an explained variance of r2=0.873 (0.869). Threemore models were established by calculating multiple regressionswith take stratification, average fecundity (E), and food concentrationas determining variates. Differences in LWRs of the two Daphniaspecies were significant (p <0.001). As the most useful approximationduring the period of stratification, LWRs are recommended forD. galeata: Ln(W)=(1.5674+0.0287*(E))+Ln(L)*(3.3611+0.0111*(E)) as a generalized LWR for an epilimnetic daphnid, and for D.hyalina: Ln(W)=(1.5593+0.0613*(E))+Ln(L)*(3.2709+0.0017*(E)) as LWR for a daphnid which migrates diurnally between epi andhypolimnion. The explained variance of this model is r2=0.843(0.826). The influence of food concentration in the epilimnionon LWRs was found to be significant on Ln(A) but not on (B).
*This research project was supported by the Deutsche Forschungsgemeinschaft 相似文献
2.
Effects of light intensity and quality on the relative N and P requirement (the optimum N:P ratio) of marine planktonic algae 总被引:2,自引:0,他引:2
The relative requirement of N and P (the optimum N:P ratio)by Dunaliella tertiolecta, Phaeodactylum tricornutum, Prymnesiumparvum and Thalassiosira pseudonana was studied under variouslight intensities and spectra. The ratio was determined as theratio of the minimum cell N and P concentrations (q0N and q0pwhen either nutrient was limiting. The ratio varied widely amongspecies; under light-saturation for growth (116 µEin m2s1 it ranged from 11.8 in D. tertiolecta to 36.6 in P.tricornutum. The ratio appeared to be higher at a sub-saturatingintensity (24 µEin m2 s1 in all except P.tricornutum, mainly because of higher qoN with little changein qoP. In T. pseudonana QoP also increased, resulting in aninsignificant change in the ratio. The ratio varied little withinthe range of saturation intensity. Light quality affected qoNand qoP as well as the ratio, and the pattern of change variedfrom species to species. The optimum ratio of individual specieswas linearly correlated to their qoN except in P. tricornutum.qoN for all species showed a linear correlation with cell proteinconcentrations irrespective of light conditions. The changeof optimum N:P ratios in the three species thus appears to berelated to changes in cell protein contents. The ratio of carbohydratesto protein remained constant regardless of light intensity orquality and was higher in P-limited cultures. We conclude thatchanges in light regime can strongly influence algal nutrientrequirements and species interrelationships by altering theoptimum cellular N:P ratio. 相似文献
3.
Effect of Photoperiod on Growth of Sugar Beet 总被引:1,自引:0,他引:1
Sugar beet grown in controlled environments were given similardaily amounts of visible radiation during three different photoperiodtreatments. Plants were given (a) 115 W m2 visible irradiancefrom fluorescent and tungsten lamps for 12 h; (b) 88 W m2of the same light for 16 h or (c) 115 W m2 from fluorescentand tungsten lamps for 12 h extended to 16 h with low intensity(3 W m2) incandescent light from the tungsten lamps only.Plant growth was increased similarly in both long day treatments[(b) and (c)] and dry weights were 25 per cent greater thanin the 12 h photoperiod (a) after 6 weeks. Leaf area was increasedby 18 per cent and net assimilation rate by 10 per cent in the16 h photoperiod at 88 W m2 (b). By contrast, extendingthe photoperiod with 4 h of incandescent light (c) triggereda photomorphogenic increase in leaf expansion which increasedleaf area per plant by 47 per cent and leaf-area ratio by 12per cent. 相似文献
4.
Growth and Nitrogen Fixation of Phaseolus vulgaris L. at Two Irradiances II. Nitrogen Fixation 总被引:1,自引:0,他引:1
Phaseolus vulgaris cv. Glamis plants grown at 7 and 28 W m228 W m2 in controlled environment cabinets showed copiousnodulation and high levels of acetylene reducing activity. Earlydifferences in nodulation were apparent before differences inphotosynthesis and were attributed to an effect of far-red lighton nodule development. Total plant nitrogen content was greater at 28 W m2 thanat 7 W 2 but nitrogen content as a percentage of d. wtwas greater at the lower irradiance level. Total acetylene reducing activity (nmol. min1 root1)was greater at 28 W m2 than at 7 W 2, but therewas no irradiance effect on specific activity (nmol. min1g d. wt of pink nodules1 or nmol. min1 pink nodule1). Transfer of 40-day-old plants from 7 W m2 to 28 W m2resulted in increased nodulesize(due toincreased size of infectedcells), accompanied by increased total, but not specific, acetylenereducing activity. Transfer of plants from 28 W m2 to 7 W m2 resultedin a fall of total acetylene reducing activity within 24 h,and senescence of large nodules. Specific acetylene reducingactivity was unaffected The results are interpreted as an effect of light on the productionof nitrogen fixing tissue, rather than on nitrogenase activity. 相似文献
5.
Effects of Soil Nutrients and Moisture on Root/Shoot Ratios in Lolium perenne L. and Trifolium repens L 总被引:1,自引:0,他引:1
The dry weights of foliage and roots (excluding stembases) werecompared in a 33x22 factorial experiment with Lolium perenneL. and Trifolium repens L. grown in pots with three nitrogen(0300 ppm N), phosphorus (0300 ppm P), and soilmoisture (pF 3.2, pF 2.4, and waterlogged) treatments, eachduplicated. Root/shoot ratios were influenced significantly (P < 0.001)by N, P, and W (soil moisture), but these main effects werequalified by highly significant first-order interactions andsecond-order interactions which included N and P. The lowestR/S ratios occurred where N, P, and W were all non-limiting,and the highest where there was an imbalance of these factors. The explanation suggested is that a decrease in the availabilityof N, P, or W causes an increase in the relative weight of roots,but in the presence of N, P, or W deficiency an increase inany one of these factors causes a further increase in the R/Sratio by increasing the relative efficiency of the foliage. 相似文献
6.
The rates of CO2 assimilation by potted spray carnation plants(cv. Cerise Royalette) were determined over a wide range oflight intensities (45450 W m2 PAR), CO2 concentrations(2003100 vpm), and leaf temperatures (535 °C).Assimilation rates varied with these factors in a way similarto the response of single leaves of other temperate crops, althoughthe absolute values were lower. The optimal temperature forCO2 assimilation was between 5 and 10 °C at 45 W m2PAR but it increased progressively with increasing light intensityand CO2 concentration up to 27 °C at 450 W m2 PARand 3100 vpm CO2 as expressed by the equation TOpt = 6.47-h 2.336 In G + 0.031951 where C is CO2 concentration in vpmand I is photo-synthetically active radiation in W m2.CO2 enrichment also increased stomatal resistance, especiallyat high light intensities. The influence of these results on optimalization of temperaturesand CO2 concentrations for carnation crops subjected to dailylight variation, and the discrepancy between optimal temperaturesfor growth and net photosynthesis, are discussed briefly 相似文献
7.
Plants of Phaseolus vulgaris grown at 7 and 28 W m2 showedno differences in rate of development of leaves or flowers.At 7 W m-Z plants had longer internodes, more succulent stemsand leaves, higher ratios of shoot:root and greater leaf areasthat those at 28 W m2. These differences were establishedprior to detectable differences in photosynthesis and couldpartly be attributed to an increased proportion of far-red light. Although the final d. wt, carbon content, and fruit yield werehigher at 28 W m2, plants at 7 W m2 apparentlyhad similar relative growth rates and greater photosyntheticefficiency. Dry weight differences are most easily interpretedas resulting from the establishment of an earlier net carbongain at 28 W m2 than at 7 W m2. 相似文献
8.
Loliun perenne L. (cv.S. 23) was grown on vermiculite in winterin a heated greenhouse for 8 weeks under factorial combinationsof two potassium regimes (nominally 6 parts/106 and 156 parts/106in Hewitt's solution) and three densities of artificially supplementedvisible radiation flux (36.1, 7.3, and 2.2 W m2). Growthand potassium uptake were studied through the calculation ofvarious growth functions from fitted curves. There was little effect of potassium treatment but the experimentalmaterial responded markedly to light. Leaf-area ratio in thethree treatments showed extreme plasticity in increasing from23 x 102 through 6 x 102 to 89 x102 m2 g1 as light intensity decreased. Correspondingdecreases in unit leaf rate, however, caused over-all reductionsin relative growth rate. Specific absorption rates for potassium (AK, dry-weight basis)were strongly reduced at the lower light intensities but alsodisplayed complex ontogenetic drifts. Values of the allometricconstant, k (the ratio of root and shoot relative growth rates),decreased from c. 0.7 at 36.1 W m2 through c. 0.3 at7.3 W m2 to a value not significantly different fromzero (P < 0.05) at 2.2 W m2. In material grown under the two higher light intensities a constantinverse relationship was found between the mass ratio of rootand shoot and the corresponding activity ratio. The resultsconform to this model: Mass ratio = 0.001+45.0 (1/activityratio) where activity ratio is expressed as specific absorptionrate for potassium (in µg g root1 h1)/unitshoot rate (rate of increase of whole-plant dry weight per unitshoot dry weight, in mg g shoot1 h1). The implicationsof this relationship are discussed. 相似文献
9.
Existing data on feeding, growth rate, fecundity, absorptionefficiency, respiration and excretion rates in the South Africanabalone Haliotis midae Linnaeus are converted to energy equivalentsand utilised to compile individual energy budgets. About 63%of the energy content of the food consumed (C) is lost as faeces(F) and a further 32% expended on respiration (R). Energy lossesin the form of ammonia excretion are negligible, accountingfor less than 1% of consumption. Some 5% of energy intake, or13% of absorbed ration (Ab) is thus available for growth andreproductive output (Pg & Pr). In juveniles (<100mm)this is all allocated towards somatic growth, while in adultsan increasing proportion of production is expended on reproductiveoutput. Although feeding, respiration and excretion rates allincrease with temperature the proportions of energy allocatedto the various components of the energy budget appear to beconsistent. Population energy budgets are calculated from densityand size distribution surveys at two study sites. At MarcusIsland, on the Cape west coast, the population has a standingstock of 82 g (wet flesh weight) m2,.consumes about 3260KJm2y1 algae and has a P/B ratio of 0.46, whereasat Cape Hangklip, on the Cape south coast, the population biomassis_133gm2, consumes 8613KJm2y1 and hasa P/B ratio of 0.70. These figures indicate that a high proportionof kelp bed primary production is directly consumed by grazingabalone in areas where populations have not been reduced byhuman exploitation (Received 16 March 1987; 相似文献
10.
COMPARATIVE LIFE-CYCLE, BIOMASS AND SECONDARY PRODUCTION OF THREE SYMPATRIC FRESHWATER GASTROPOD SPECIES 总被引:1,自引:0,他引:1
The life cycles, biomass and secondary production of three sympatricfreshwater basommatophoran snails, Lymnaea palustris (MÜller),Physa fontinalis Linnaeus and Anisus rotundatus (Poiret) werestudied during two years in a freshwater ditch. L. palustrisexhibited an iteroparous life-cycle whereas the two other speciespresented a semelparous life-cycle, adults died just after oviposition.L. palustris secondary production (dry weight) value was higher(P = 11 298.4 mg 0.1 m1 yr1) than those of P.fontinalis (P = 846.3 mg 0.1 m2 yr1) and A. rotundatus(P = 1192 mg 0.1 m2 yr1). (Received 16 March 1992; accepted 30 June 1992) 相似文献
11.
Changes in regulation of sodium/calcium exchanger of avian ventricular heart cells during embryonic development 总被引:1,自引:0,他引:1
Shepherd N Graham V Trevedi B Creazzo TL 《American journal of physiology. Cell physiology》2007,292(5):C1942-C1950
It has been suggested that the sodium/calcium exchanger NCX1 may have a more important physiological role in embryonic and neonatal hearts than in adult hearts. However, in chick heart sarcolemmal vesicles, sodium-dependent calcium transport is reported to be small and, moreover, to be 312 times smaller in hearts at embryonic day (ED) 45 than at ED18, the opposite of what would be expected of a transporter that is more important in early development. To better assess the role of NCX1 in calcium regulation in the chick embryonic heart, we measured the activity of NCX1 in chick embryonic hearts as extracellular calcium-activated exchanger current (INCX) under controlled ionic conditions. With intracellular calcium concentration ([Ca2+]i) = 47 nM, INCX density increased from 1.34 ± 0.28 pA/pF at ED2 to 3.22 ± 0.55 pA/pF at ED11 (P = 0.006); however, with [Ca2+]i = 481 nM, the increase was small and statistically insignificant, from 4.54 ± 0.77 to 5.88 ± 0.73 pA/pF (P = 0.20, membrane potential = 0 mV, extracellular calcium concentration = 2 mM). Plots of INCX density against [Ca2+]i were well fitted by the Michaelis-Menton equation and extrapolated to identical maximal currents for ED2 and ED11 cells (extracellular calcium concentration = 1, 2, or 4 mM). Thus the increase in INCX at low [Ca2+]i appeared to reflect a developmental change in allosteric regulation of the exchanger by intracellular calcium rather than an increase in the membrane density of NCX1. Supporting this conclusion, RT-PCR demonstrated little change in the amount of mRNA encoding NCX1 expression from ED2 through ED18. NCX1; chick embryo; allosteric regulation; sodium/calcium exchange current 相似文献
12.
FARADAY CHRISTOPHER D.; QUINTON PAUL M.; THOMSON WILLIAM W. 《Journal of experimental botany》1986,37(4):482-494
Faraday, C. D., Quinton, P. M. and Thomson, W. W. 1986. Ionfluxes across the transfusion zone of secreting Limonium saltglands determined from secretion rates, transfusion zone areasand plasmodesmatal frequencies.J. exp. Bot. 37: 482494. The epidermal salt-secreting glands of Limonium (Plumbaginaceae)are enclosed in a cuticular envelope. Ions and metabolites enterthe glands from the mesophyll through gaps in the cuticularenvelope, the transfusion zones. Net influxes of ions acrossthe transfusion zone were calculated from measurements of secretionrates and transfusion zone areas. When leaves of L. pereziiF. T. Hubb. were treated with 300 mol m3 NaCl, transfusionzone influxes of Na+ K+, Ca++ and Cl as high as 7?0?105,1.7?105, 5?8?107 and 8.5?105 mol m2s1 respectively, were calculated. Assuming a transmembranepathway, these fluxes would be some of the highest reportedfor ions in plant cells. Key words: Salt glands, ion fluxes, ultrastructure 相似文献
13.
In situ bacterial net production and growth yield were measuredusing thymidine, leucine incorporation and dark oxygen consumptiontechniques in marine enclosures and in the Bay of Aarhus, Denmark.Bacterial respiration was significantly correlated with thymidine(r2 = 0.42, P < 0.01, y = 0.l2x + 0.054) and leucine (r2= 0.45, P < 0.01, y = 0.09x + 0.043). The range of bacterialgrowth yield, calculated from the relationship net production/netproduction + respiration, was 0.070.77 with 74% of theobservations lying in the 0.150.45 growth yield interval.Substrate was an important determinant of growth yields. A significantdifference was found between growth yields obtained from anenclosure with added glycine (mean 0.32±0.096) and onewith added inorganic nutrients (mean 0.16±0.051) (P <0.01, t-test). Growth yield showed a weak but significant negativecorrelation with temperature (r2 = 0.0.35, P < 0.001, y =0.017 + 0.52). No correlation between chlorophyll a andgrowth yield was found (r2 = 0.25, P > 0.05). The resultssuggest that thymidine and leucine techniques reflect the levelsof bacterial production to better than an order of magnitude.The variations found in the growth yield support the notionthat relying on fixed growth yields reduces the accuracy ofestimating gross bacterial production. 相似文献
14.
The Relationship Between Shoot Weight, Plant Density and Time During the Propagation of Four Vegetable Species 总被引:3,自引:1,他引:2
Lettuce, cauliflower, leeks and celery were grown from seedin a glasshouse at four widely-differing densities on severaloccasions over a 15-month period, under conditions of amplewater and nutrients. For each sowing there were four early harvests.The reciprocal of mean shoot dry weight was found to be linearlyrelated to plant density at any particular harvest as in theShinozakiKira equation. The reciprocal of the slope ofthis relationship, representing the ceiling yield m2was roughly proportional to mean daily radiation during theperiod of 14 d before harvest: the reciprocal of the interceptwas logarithmically related to accumulated heat units, modifiedfor daily radiation. Hence mean plant weight could be expressedas the following function of environmental variables and plantdensity: w2 = w0pep. 相似文献
15.
The effect of shading a single tiller to below its compensationpoint for a period of 5 weeks in vegetative plants of Loliumperenne L. cv. S23, was studied in two different experimentseach employing two light regimes, one of which was common toboth experiments. In the first experiment tillers in the axils of the first leafwere shaded three weeks from appearance at both 40 and 70 Wm2. None of the shaded tillers died and they continuedto produce new leaves and increase in dry weight but at a reducedrate. In the second experiment, tillers with one emerged leafin any leaf axil position were shaded at 70 W m2 andin a treatment in which light was reduced to 13 W m2after initial growth at 70 W m2. As in the first experimentall shaded tillers survived at 70 W m2 but in the 70 13 W m2 transfer regime all shaded tillers died. In the second experiment shaded tillers in both light regimeswere supplied with 14C-assimilate by translocation from theremainder of the plant but in the 70 13 W m2 the initialsupport was withdrawn within 5 weeks of shading. The results are discussed in terms of the physiological relationshipsbetween the tillers of the grass plant. Lolium perenne L., growth of tillers, survival of tillers, effect of light 相似文献
16.
Summer nutrient dynamics in the Middle Atlantic Bight: primary production and utilization of phytoplankton carbon 总被引:2,自引:0,他引:2
Falkowski P.G.; Vidal J.; Hopkins T.S.; Rowe G.T.; Whitledge T.E.; Harrison W.G. 《Journal of plankton research》1983,5(4):515-537
In late summer, production and utilization of carbon in thestratified water of the Middle Atlantic Bight appears to approachsteady-state conditions. In the euphotic zone there is a paniculateorganic carbon (POC) pool of {small tilde}6000 mg Cm2.Primary production adds {small tilde}350 mg C m2 d1,while zooplankton ingestion removes {small tilde}450 mg C m2d1, of which {small tilde}135 mg C m2 d1are returned to the POC pool as feces. Sinking of POC averages{small tilde}240 mg C m 2 d1. Thus, there is anet loss from the euphotic zone of {small tilde}200 mg C m2d1, which represents a removal rate from the POC poolof {small tilde}3%d1. However, sinking losses of phytoplanktoncarbon from the POC pool were small ({small tilde}12 mg C m2d1), which suggests that most of the primary productionenters the pelagic food chain. This is in sharp contrast tothe conditions in early spring, when the POC pool increasessubstantially, and the main loss is sinking rather than heterotrophicconsumption.
*This research was supported by the U.S. Department of Energyunder Contract No. DE-AC02-76CH000I6. 相似文献
17.
Measuring the Canopy Net Photosynthesis of Glasshouse Crops 总被引:3,自引:0,他引:3
HAND D. W.; CLARK G.; HANNAH M.A; THORNLEY J. H. M.; WILSON J. WARREN 《Journal of experimental botany》1992,43(3):375-381
A null balance method is described for measuring net photosynthesisof mature canopies of cucumber and other protected crops overperiods of 10 min in a single-span glasshouse (c. 9m x 18m inarea). Accuracy of control of the CO2 concentration in the greenhouseatmosphere is within ±10 vpm of the normal ambient level(c. 350 vpm). The amounts of CO2 used in canopy net photosynthesisare measured with linear mass flowmeters accurate to within±0.80g. The total errors incurred in measuring canopynet photosynthesis at an ambient CO2 level are estimated tobe of the order of ± 1·2% in bright light (350W m2, PAR)and ±3·6% in dull light (100W m2, PAR). Measurements of the rates of net photosynthesis of a maturecanopy of a cucumber crop were made at near-ambient CO2 concentrationsover a range (0350 W m2) of natural light fluxdensities. A model of light absorption and photosynthesis applicableto row crops was used to obtain a net photosynthesis versuslight response curve for the cucumber crop. At a light fluxdensity of 350 W m2 the fitted value of canopy net photosynthesiswas 2.65 mg CO2 m2s1 (equivalent to over 95 kgCO2 ha1h1). The results are discussed in relationto the need for CO2 supplements to avoid depletion in both ventilatedand unventilated glasshouses during late spring and summer. Key words: Glasshouse crops, cucumber, measurement, canopy photosynthesis, light, CO2 相似文献
18.
Maximum fixation rates of 120 and 60 pmol cm2 s 1wereobtained when exogenous carbon was supplied as 1CO2 and H14CO3respectively. These values are considerably higher than thosepreviously reported for this species. A kinetic analysis wasperformed on this data. Substrate saturation in the concentrationrange 1.01.5 mM was observed for both CO2 and HCO3 In the presence of exogenous CO2, a linear relationship wasobserved between light intensity and fixation while the HCO3relationship was slightly sigmoidal. Fixation saturated at intensitiesof 1520 W m2 and 1315 W m2 for exogenous14CO2 and H14CO3respectively. The presence, in this species, of an extremely active HCO3transport system, situated in the plasmalemma, demonstratesthat when alkaline solutions are employed the involvement ofthis ion cannot be ignored during electrical studies on thismembrane. The maximum H14CO3 influxes obtained duringthis study are the largest ionic fluxes measured for any Characeanspecies. It was demonstrated that CO2 for fixation can be supplied simultaneouslyby gaseous diffusion and HCO3 transport (cf. Raven, 1968).Inhibition of H14CO3 influx was observed in the presenceof Tris, Tricine, and borate buffers, and CO32 alsoappeared to act as a strong inhibitor. The possible mechanism(s)by which this inhibition occurs is discussed. 相似文献
19.
In the stoichiometric study of phytozooplankton interactions,a controversy exists about how Daphnia species regulate theirfeeding rate when submitted to low-quality food (i.e. high dietarycarbon:phosphorus [C:P] ratio). In this study, we gathered dataover 3 years on in situ clearance rates of a Daphnia galeatapopulation, by conducting grazing experiments from April 1998to October 2000 in the Esch-sur-Sûre reservoir (Grand-Duchyof Luxembourg). Observed clearance rates (2.513.5 mLindividual1 day1, mean 7.0 mL individual1day1) were correlated with population and environmentalvariables. Mean body size of Daphnia individuals was the bestpredictor of clearance rate (r2 = 0.639), followed by watertemperature (r2 = 0.262) and P concentration in the seston (r2 相似文献
20.
The growth of juvenile Bithynia tentaculata (Proso-branchia,Bithyniidae) was measured under controlled laboratory conditionsover 18 months. The animals were fed with different concentrationsof suspended food (Chlamydomonas reinhardii at 2, 000 cells.ml1and at 10, 000 cells.ml1), solid food (lettuce) and combinationsof both (lettuce with 2, 000 cells.ml1 and with 10, 000cells.ml1 Chlamydomonas). The growth of all animals wasmeasured weekly, and after 1 years final shell sizes, shelldry weights and ash-free dry weights, as well as soft body dryweights and ash-free dry weights were determined. Survival rateof the animals increased from 20% when fed with 2, 000 algalcells.ml1 to 75% with lettuce and 10, 000 cells.ml1as food. Final shell sizes and shell weights were not influencedby food, but soft body dry weights were significantly reducedwhen animals were fed on suspended food only. Reproduction (i.e.egg laying) was observed at the end of the second summer whenlettuce (with or without algal addition) was given as food.The ecological consequences of these results are discussed. (Received 7 April 1993; accepted 9 August 1994) 相似文献