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1.
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
2.
Effects of light flux density (LFD) during growth and uptakeassay on induction of transport system and kinetics of transport were studied using the Azolla pinnata-Anabaena azollae association (Azolla). Theinduction and uptake kinetics of the transport system were determined using an automated system that measuredthe NO3 concentration in the growth medium as a function oftime, using an on-line high performance liquid chromatograph(HPLC) with a UV-VIS detector. Full induction of the transport system required about 1.5 to 2.0 h and occurred without any apparent lag phase,regardless of the LFD provided. The level of induction of transport of Azolla grown at 600 µmol m2s1 LFD was higher than for that grown at 100 µmolm2 s1. Similarly, 600 µmol m1 s1LFD during the assay resulted in a higher level of inductionthan did 100 umol m2 s1. An increase in the LFDeither during the growth or the assay period increased the uptake rate; however, an increase in LFD duringthe latter period had greater effect. Azolla grown and assayedat 600 umol m2 s1 had the highest uptake rate. The uptake rate at 50 cm3 m3ambient CO2 concentration was initially higher than at 305 cm3m3, but the uptake rate decreased rapidly with time andeventually dropped below that at 305 cm3 m3 CO2. Thesedata suggest that the energy required for transport in Azolla may bypass the photosynthetic CO2 fixationand carbon-cycling. Key words: carbon dioxide, concentration dependence, light flux density, uptake 相似文献
3.
Growth of Ceratium hirundinella in a subtropical Australian reservoir: the role of vertical migration 总被引:3,自引:0,他引:3
Whittington John; Sherman Bradford; Green Damian; Oliver Roderick L. 《Journal of plankton research》2000,22(6):1025-1045
A study into the photophysiology, growth and migration of Ceratiumhirundinella in Chaffey Reservoir in subtropical northern NewSouth Wales, Australia, revealed that a proportion of cellsformed subsurface accumulations at depths that optimized lightintensity (212552 µmol photons m2 s1)for photosynthesis and cell growth. At high incident irradiance,Ceratium migrated downwards from the near-surface waters, avoidinghigh-light-induced, slow-recovering non-photochemical quenchingof photosystem II. Overnight deepening of the surface mixedlayer by convective cooling produced homogeneous distributionsof Ceratium with a significant proportion of the populationbelow the depth where light saturation of photosynthesis occurred.Ceratium migrated towards the surface from suboptimal lightintensities, at a velocity of 1.62.7 x 104 m s1.Subsurface accumulations occurred under a variety of turbulenceintensities; however, accumulation was significantly reducedwhen the turbulent velocity scale in the mixed layer was >5x 103 m s1, beyond which turbulent diffusion dominatedadvection by swimming. The formation of subsurface accumulationswith increased computed water column integral photosynthesisby 35% compared to a uniform cell distribution. 相似文献
4.
Smith, J. R., Smith, F. A. and Walker, N. A. 1987. Potassiumtransport across the membrane of Chara. I. The relationshipbetween radioactive tracer influx and electrical conductance.J.exp. Bot. 38:731751. The 42K influx () and the electrical conductance (Gm) were measured simultaneously for the membraneof internodal cells of Chara australis as a function of theexternal [KCl] (K?. In bathing solutions of pH = 5?0, progressively increased from 20?5to 430?60 nmol m2 s1 and Gm increased from 0?36?0?02to 3?8?0?8 S m2 when K? was increased from 0?1 to 10mol m3. The resting membrane potential difference (p.d.)was approximately -135 mV for low K? and approached the expectedNernst equilibrium p.d. for K+ ions when K? > 1?0 mol m3.Measurements of 36Cl influx suggested that the 42K influx waspredominantly electrogenic. The equivalent Goldman permeabilityto K+ ions (Pk) was approximately 2030 nm s1 anddid not vary significantly with increasing K?. The equivalentconductance attributable to the electrogenic transport of K+ ions was calculated from assuming passive, independent diffusionof K+ ions and the ratio was found to be typically close to one. It was also found that themagnitudes of and Gm measuredsimultaneously for each individual cell were also well correlatedfor K? 1?0 mol m3, and that the slope of the line ofbest fit was close to one. For each K? it was found that theconductance not attributable to K+ translocation and presumablyassociated primarily with the transport of protons or theirequivalents was typically 0?20?5 Sm2. For K? >1?0 mol m3 the results indicated that the transport ofK+ ions was essentially independent, i.e. there was no evidencefor flux interactions. The results also indicated that the equivalentconductance derived from the measured 42K influx could usefullyindicate the fraction of the electrical conductance attributableto the translocation of K+ ions. Key words: Potassium, conductance, influx 相似文献
5.
The effect of locomotor activity on respiration rate was studiedin the food-deprived copepod Calanus euxinus tethered to a forcesensor. The power generated by mouth appendages during cruisinglocomotion, with a frequency of 40 Hz, accounted for 0.026 and0.0031 W for metabolic and mechanical processes, respectively.To overcome total hydrodynamic drag during foraging with a meanswimming speed of 3.2 cm s1, the copepods need 0.4 x103 W, equating to 1.3% of total metabolism. The lossesof mechanical energy for body propulsion amounted to 1.3 x 103W, whilst the cost of feeding current generation run up to 1.8x 103 W, or 58% of the total. Changing of locomotor activityand respiration rate during feeding was examined separatelyin tethered and free-swimming copepods. At algal concentrationof 300 µg C L1, the magnitude of specific dynamicaction (SDA) averaged 1.2 ± 0.44 nL O2 µg C1h1 in copepodites V and females, with similar movingactivity before and during feeding. The contribution of SDAinto total metabolism varied from 23 to 85% in C. euxinus withlow activity level and constituted only 10% in active animals.In starved copepods, with low locomotor activity, feeding eventsstimulated the increase in frequency and total duration of locomotionwhich resulted in elevated energy expenditure enhancing theapparent SDA. 相似文献
6.
The Osmotic Pressure of Concentrated Solutions of Polyethylene Glycol 6000, and its Variation with Temperature 总被引:1,自引:0,他引:1
The vapour pressures of aqueous solutions of polyethylene glycol6000 have been measured (by equilibration with sucrose solutions)up to the saturation point at 25 °C (1.45 g g1 water).The reduced-osmotic-pressure (/c), when plotted versus concentration(c), rapidly and linearly increased up to a concentration ofabout 0.8 g g1 (crossing the similar plot for sucrose).Above this concentration, the reduced-osmotic-pressure rosemore slowly, but still more rapidly than sucrose. The maximumosmotic pressure achieved at saturation was nearly 18 MPa. Usingthe virial equation: /c= RT/M + RTA2c, the calculated secondvirial coefficient (A2) for the linear part is 4.5 x 103mol g1, a value slightly greater than most literaturevalues at 25 °C. Data are cited showing that A2 varies linearlyfrom 56 x 10x3 at 0 °C, to zero at 8090 °C 相似文献
7.
Root Hydraulic Conductivity of Two Cactus Species in Relation to Root Age, Temperature, and Soil Water Status 总被引:6,自引:1,他引:5
The effects of root age, temperature, and soil water statuson root hydraulic conductivity (LP) were investigated for twocactus species, Ferocactus acanthodes and Opuntia ficus-indica.The volumetric flux density of water was measured for excisedroot segments, either using negative hydrostatic pressures appliedto the proximal end or using reverse flow of water from theroot to the soil. For both species, LP at 20 ?C increased withroot age, average values reaching a maximum of 3.9 ? 107m s1 MPa1 for F. acanthodes and 5.2 ? 107m s1 MPa1 for O.ficus-indica at 11 to 17 weeksof age; LP subsequently declined with increasing root age forboth species. LP was maximal at a temperature of about 10 ?Cfor the youngest roots (13 weeks), this optimum shiftingto 40 ?C for 8-week-old roots of both species. For older roots(up to 1.5-years-old), LP increased with temperature from 0?C to 50 ?C, with a Q10 of 1.3 between 20 ?C and 30 ?C. At asoil water potential (soil) of 0.016 MPa, root LP wasindependent of the direction of water flow for both species.Depending on root age, LP declined 45- to 500-fold for F. acanthodesand 90- to 800-fold for O.ficus-indica as soil was reduced from0.016 to 1.06 MPa, consistent with a rectifier-likebehaviour with respect to water movement between soil and roots.Incorporation of such responses into water uptake models shouldlead to a better understanding of root function. Key words: Ferocactus acanthodes, Opuntia ficus-indica, water potential, tension, reverse flow 相似文献
8.
Fisher Tamar; Shurtz-Swirski Revital; Gepstein Shimon; Dubinsky Zvy 《Plant & cell physiology》1989,30(2):221-228
Exponentially growing cultures of the chlorophyta Tetraedronminimum were allowed to photoadapt to low (50µmole quantam2s1) and high (500µmole quanta m21)irradiance levels. In these cultures, various aspects of theorganization of the photosynthetic apparatus and related differencesin its performance were studied. In this organism, the observed five-fold increase in pigmentationof low-light adapted cells was due to increases in the numbersof PSU's, while their sizes remained constant. Using radioimmunoassay technique, we found that high-light adaptedalgae had over five times more Rubisco per PSU than their low-lightadapted counterparts. The high-light adapted algae also exhibited far higher (x2.3)light saturated photosynthetic rates per chl a. This increasewas the result of a reduction of tau, , the turnover time ofPS II reaction centers. We propose that the increase in Rubisco per PSU in high-lightadapted algae explains the reduction in , which results in thehigher Pmax rates per chl a in these algae. The relationship is non linear, since the increase in Rubiscoper PSU was x5.3 whereas that in PmM per chl a was only x2.3. (Received July 30, 1988; Accepted December 2, 1988) 相似文献
9.
In situ light measurements were used to obtain information oninherent and apparent optical properties. The average verticalattenuation coefficient Kd(ave) varied from 1.1 to 4.6 In unitsm1 During three periods the variation in Kd(ave) correlatedwith changes in chlorophyll a concentration and specific attenuationcoefficients Ks, of 0.013, 0.014 and 0.022 m2 mg Chl a1were calculated. Chlorophyll-specific diffuse absorption coefficients(A,) for these periods were 0.012. 0.013 and 0.017 m2 mg Chla1 and only varied significantly from estimates of Ksin the period when scattering was intense. Absorption coefficientsa(zmid) and scattering coefficients b(zmid) calculated for themid-point of the euphotic zone ranged between 0.45 and 2.9 mand 3.552.0 m respectively. Chlorophyll-specific absorptioncoefficients Ka, of 0.005, 0.006 and 0.007 m2 mg Chl a1and scattering coefficients Kb of 0.05. 0.09 and 0.191 m2 mgChl a1 were measured during the three periods. The highKb value occurred when gas-vacuolate cyanobactena were dominant.Algal photosynthesis and light absorption were related throughthe maximum quantum yield m which varied between 0.019 and 0.11mol C Einstein1 while average quantum yields a, variedbetween 0.006 and 0.024 with a mean of 0.013 mol C Einstein1A comparison of changes in the mean irradiance of the mixedzone and chlorophyll concentration indicated that growth waslight limited below 0.040.05 Einsteins absorbed mg Chla1 day1. 相似文献
10.
Yield stress threshold (Y) and volumetric extensibility () arethe rheological properties that appear to control root growth.In this study they were measured in wheat roots by means ofparallel measurement of the growth rate (r) of intact wheatroots and of the turgor pressures (P) of individual cells withinthe expansion zone. Growth and turgor pressure were manipulatedby immersion in graded osmoticum (mannitol) solutions. Turgorwas measured with a pressure probe and growth rate by visualobservation. The influence of various growth conditions on Yand was investigated; (a) At 27 °C.In 0.5 mol m3 CaCl2 r, P, Y and were20.7±4.6 µm min1, 0.77±0.05 MPa,0.07±0.03 MPa and 26±1.9 µm min1MPa1 (expressed as increase in length), respectively.Following 24 h growth in 10 mol m3 KC1 these parametersbecame 12.3±3.5 µm min1, 0.72±0.04MPa, 0.13±0.01 MPa and 21±0.7 µm min1MPa1. After 24 h osmotic adjustment in 150 mol m3mannitol/0.5 mol m3 CaCl2 r= 19.6±4.2 µmmin1, P = 0.68±0.05 MPa and Y and were 0.07±0.04MPa and 30±0.2 µm min1 MPa01, respectively.After 24 h growth in 350 mol m3 mannitol/0.5 mol m3CaCl2 r= 13.3±4.1 µm min1, P= 0.58±0.07MPa, Y=0.12±0.01 MPa and ø 32±0.2 tim min1MPa1. During osmotic adjustment in 200 mol m3mannitol/0.5 mol m3 CaCl2, with or without KCl, the recoveryof growth rate corresponded to turgor pressure recovery (t1/2approximately 3 h). (b) At 15 °C. Lowered temperature dramatically influencedthe growth parameters which became r= 8.3±2.8 um min1,P=0.78 MPa, r=<0.2 MPa and =15±0.1 µm min1MPa1. Therefore, Y and are influenced by 10 mol m3 K+ ionsand low temperature. In each case the effective pressure forgrowth (P-Y) was large indicating that small fluctuations ofsoil water potential will not stop root elongation. Key words: Yield threshold, cell wall extensibility, wheat root growth, temperature, turgor pressur 相似文献
11.
Occurrence of mycosporine-like amino acids in the red-tide dinoflagellate Alexandrium excavatum: UV-photoprotective compounds? 总被引:1,自引:0,他引:1
Carreto J.I.; Carignan M.O.; Daleo G.; Marco S.G.De 《Journal of plankton research》1990,12(5):909-921
Water extracts of the red-tide dinoflagellate Alexandrium excavatumgrown at high light intensity (200 µE m2s1) show a broad absorbance maximum in the UV regionof the spectrum (310360 nm). Using TLC and reverse-phaseHPLC a series of mycosporine-like amino acids have been characterized:mycosporine-glycine (max = 310 nm), palythine (max = 320 nm),asterina-330 (max = 330 nm), shinorine (max = 334 nm), porphyra-334(max= 334 nm), palythenic acid (max = 337 nm) and the isomericmixture of usujirene and palythene (max = 359 nm). From theobserved spectral changes during transference from low(20 µE m2 s1) to high (200µE m2 s1) light intensities and vice versa,the series of compounds are supposed to be biogenically relatedto one another. The presence of these compounds in A.excavatumis discussed in relation to their possible role in the photoprotectionto deleterious UV radiation. 相似文献
12.
Five inbred strains (129/J, BALB/cByJ, C3HeB/FeJ, C57BI/6J andDBA/2J) were examined with two-bottle (48 h) preference ratiotesting across concentrations of sodium saccharin (3 x 104M, 103 M, 3 x 103 M and 102 M), d-phenylalanine(103 M, 102 M and 101 M), and l-glutamine(102 M, 3 x 102 M, 101 M and 3 x 101M). Three consistent groupings of strains were observed acrosssubstances and concentrations:
- C57BI/6J (preference at low andhigh concentrations);
- BALB/cByJ and C3HeB/FeJ (preferenceat high concentrations);
- 129/J and DBA/2J (preference at highconcentration for sodiumsaccharin and indifference to d-phenylalanineand l-glutamine).
13.
Primary production was measured for 7 years, using the in situ14C-method in hypertrophic Hartbeespoort Dam, South Africa,to examine the influence of light and water temperature on theupper limit of Microcystis aeruginosa production. Water temperaturesvaried from 11 to >25°C and chlorophyll concentrationsreached 6500 mg m3. The maximum volumetric rate of production(Amax) was 12->8800 mg C m3 h1 with areal productions(A) of 69->3300 mg C m2 h1 for euphotic zonedepths of <0.58.4 m. The intrinsic parameters of phytoplanktonproduction (, Amax/B, Ik) indicated that the phytoplankton populationwas adapted to high light levels. Both Amax/B and Ik were correlatedwith temperature. Under optimal conditions, , the theoreticalupper limit of A, was calculated to be 2.8 g Cm2 h1,while the measured rate was 2.5 g Cm2 h1. Measuredareal rates exceeding were overestimated due to methodologicalproblems when working with Microcystis scums. Light and watertemperature interacted to yield high production rates: watertemperature through its direct effect on photosynthetic ratesand indirectly in the formation of diurnal mixed layers; lightindirectly through water temperature and directly through itsattenuation and induction of light-adapted physiology in Microcystis. 相似文献
14.
Horizontal distribution of Thetys vagina Tilesius (Tunicata, Thaliacea) in the Japan Sea during spring 2004 总被引:2,自引:0,他引:2
The occurrence of the salp Thetys vagina was observed in theJapan Sea during spring 2004. Catches up to 187 kg wet weight(WW) per 2.18 x 105 m3 (equal to 0.9 g WW m3) were collectedwith 10-m diameter surface-water otter trawl nets. The horizontaldistribution indicated that the high biomass was related tothe area with high chlorophyll a (Chl a) concentration, whichwas located around the subarctic front with the warm TsushimaCurrent. Five prey taxa were identified from the gut contentsof individuals from the high Chl a area. The diatom Coscinodiscusspp. (1355 µm in diameter) dominated numerically.Another significant prey was the large diatom Coscinodiscuswailesii (219313 µm) that is an indicator of thespring bloom in this area. The mass occurrence of T. vaginathus appears related to phytoplankton availability, though themechanisms remain uncertain. 相似文献
15.
《Journal of plankton research》1986,8(5):1009-1010
Due to an apparent fault in the telex system, a number of mistakeswere not corrected in this paper. The corrected lines are givenbelow p. 539: line 17In vivo fluorescence action spectra of chl a p. 541: Figure 2 legend, line 92.5 µW cm2 at 550nm (0.12 µE m2 s1 p. 542: Figure 3 legend, line 5( 89 µE m2 s1).Monochromatic beam intensity was 6 µW cm2 at 550nm (0.28 µE m2 s1), Figure 3 legend, lines 8 and 9with intensity of 3 mW cm2( 179 µE m2 s1) Monochromatic beam intensitywas 7 5 µW cm2 at 550 nm (0.35 µE m2s1). line 6tivity. The match between the spectra of chl a fluorescenceand PSII O2 evolution is lines 2325fluorescence increasingly deviate from thoseof PSII O2 evolution. We attribute this discrepancy to selectivelight scattering by the algae. This scattering increases substantiallywith decreasing wavelength at that region when using a standardspectrofluorometer p. 543: Figure 4 legend, lines 3 and 4as in Chroomonas, withintensity of 2 mW cm2 ( 120 µE m2 s1).Monochromatic beam intensity was 15 µW cm2 at 550nm ( 0.7 µE m2 s1). line 7:ment types in the oceans. While all photoautotrophicorganisms have chl a (the bulk lines 12 and 13:and Barrett (1983). Our spectral data reflectthe great variability in pigment composition and functionalassociation in the major groups of algae. lines 25 and 26:Hiller, 1983). However, blue-violet and redPSII activity is much lower in cryptomonads than might be expectedfrom their absorption spectra (Haxo and Fork, 1958; Haxo, 1960), p. 544: Table I, column 3, entry 6:R-phycocyanin Table 1 legend, lines 1 and 2:aHaxo and Blinks (1950); bFork(1961); cHaxo et al. (1955); dO'Carra and O'hEocha (1976); cresemblesDelesseria decipiens, Haxo and Blinks (1950, Figure 20); fHaxoand Fork (1969), like lines 1 and 2:I) indicates that these pigments are affiliatedwith PSII, perhaps exclusively, as in the red algae. In Rhodomonas,the peak of activity at 465 nm may be due to chl c absorp- p. 545: line 2:xanthophyll (fucoxanthin in diatoms, peridininin dinoflagellates and chl c. The ac line 7:shown to be similar to those of the much-studied Chlorella(Vidaver, 1966; Ried, 1972). line 14:tivity of PSII in algae. Spectrofluorometers, with theirsuperior sensitivity and stability, line 34:of natural populations, making these spectra more similarto the PSII photosynthesis lines 36 and 37:Large differences between the values of FIIfor different components within the algal population can distortfluorescence spectra, if they do not correspond with dif lines 41 and 42:different components are not similar to eachother. The necessary handling procedures of natural samples,such as filtration (Yentsch and Yentsch, 1979; Neori et al.,1984), p. 546: lines 20 and 21:DOE contract DE-AT03-82ER60031, anda grant to A.N., O.H.H. and F.T.H. from the Foundation for OceanResearch. Travel to the IInd GAP workshop was facilitated by lines 25 and 26:the culture of Chroomonas, J.Lance for helpwith cultures, J. and E.Yguerabide for the use of their spectrofluorometer,C.R.Booth, Y.Blatt and L.Petrosian for technical line 28:This study was in partial fulfilment for a Ph.D. degreeby A.N. line 42:Dutton.H.J., Manning.W.M. and Duggar.B.M. (1943) Chlorophyllfluorescence and energy transfer in the 相似文献
16.
Diurnal series of fluorescence and photosynthesis assays wereconducted in high altitude (3803 m), tropical (16°), LakeTiticaca (Peru/Bolivia). Near-surface diurnal thermoclines formedon typical days of high photon flux density (PFD, {small tilde}2000 µE m2 s1). In the depth range of diurnalstratification profiles of in vivo fluorescence, both without(Fa and with (Fb DCMU, exhibited a mean decrease of 64% frommorning to mid-day, but little change (mean increase of 1.5%)through the afternoon. Three times during the day surface, mid-depth(35 m) and deep (1520 m) phytoplankton sampleswere incubated with H14CO3 under short (<2 h) exposuresto a range of in situ PFDs. Comparison of phytoplankton in differentsamples (ANOVA) showed identical photosynthetic response insunrise (isothermal) samples but a significant drop in surfaceand mid-depth photosynthesis at all PFDs during times of diurnalstratification. Similarly, both low-light () and light-saturated(P2 max photosynthetic parameters were lower in mid-day surfacesamples compared to deep samples. In addition, previously photoinhibitedsamples had a higher threshold intensity for photoinhibition,IT. These results, together with diurnal time series of fluorescencefrom in situ incubations, demonstrate that recovery from extendedepisodes of photoinhibition during diurnal stratification isslower than suggested by previous observations in vitro. Photosynthesisby near-surface phytoplankton is different in light increasingup to IT than light decreasing from IT. This effect can be modeledby reducing and Pmax as a function of the maximum photoinhibitingPFD in the diurnal light history.
1Present address: Division of Molecular Plant Biology, Universityof California, Berkeley, Berkeley, CA 94720, USA 相似文献
17.
The influence of irradiance on growth, photosynthesis and respiration of Gyrodinium cf. aureolum 总被引:1,自引:0,他引:1
The bloom-forming marine dinoflagellate Gyrodinium cf. aureolumwas grown in batch cultures over a range of irradiances (35380µmolm2 s1 and growth, photosynthesis and respirationrates determined. Saturation of growth occurred at irradiancesof 100µmol m2 s1 Below this light level,decreases in growth rates and cell size, and a relative increasein carbon specific respiration rates, were observed. On theother hand, photosynthesis-irradiance relationships determinedfrom dissolved oxygen incubations showed that on a cellularand carbon basis, cultures grown at low irradiances had higherrates of light-limited and light-saturated photosynthesis, mainlyas a result of large increases in cell chlorophyll content.This adaptation strategy enables low-light-grown organisms toexploit available high irradiance through a relatively highphotosynthetic capacity. In cells grown at higher light levels(>100µmol m2 s1), excess photosynthatemay be diverted to storage rather than used for growth. 相似文献
18.
Responses of Soybean Leaf Angle, Photosynthesis and Stomatal Conductance to Leaf and Soil Water Potential 总被引:2,自引:0,他引:2
The hypothesis that soil water potential (s) is better correlatedto heliotropic leaf orientation, photosaturated photosyntheticCO2 assimilation and stomatal conductance during periods oflimited water availability than is bulk leaf water potential(1) was examined in greenhouse-grown soybean (Glycine max) plants,submitted to a progressive drought. Paired plants were exposedto either 1000 or 100 µmol m2 s1 photonflux densities (PFD) for 4560 mins. The higher irradianceinduced short-term decreases in 1, due to increased transpiration,while l in the plant exposed to low PFD did not decrease. Thesechanges in 1 occurred independently of changes in soil waterstatus. Concurrent to the light treatments, a single attachedleaf from each of the two plants was isolated from the restof the plant by shading, and the pulvinus of its terminal leafletwas exposed to a perpendicular PFD of 500 µmol m2S1. Leaf movement of this leaflet was recorded in responseto this light, until a stable leaflet angle was achieved. Valuesof s and l (before and after light treatment), and photosaturatedrates of photosynthesis and stomatal conductance, were thenmeasured on these leaves. Leaflet angle and gas exchange werebetter correlated with s (r2 = 0.50, 0.50 and 0.57 for angle,photosynthesis and conductance, respectively) than with l especiallywhen l was the result of short-term, high-light induced changesin leaf water status (r2 = 0.36, 0.32 and 0.49, for the sameparameters). Leaflet angle was also correlated with stomatalconductance (r2 = 0.61) and photosynthetic rate (r2 = 0.60),suggesting a close association between leaf orientation, leafmetabolism and soil water availability. Glycine max (L.) Merr. cv. Essex, soybean, heliotropism, water potential, photosynthesis, stomatal conductance, solar tracking 相似文献
19.
The development of taurine uptake into the unicellular greenalga Chlorella fusca 211-8b was characterized as a specificresponse to either nitrate or sulphate limitation. Taurine transportunder nitrogen starvation was stimulated by low pH and showeda biphasic kinetics with Km-values of 1.1 x 103 mol dm3and 1.0 x 102 mol dm3. Uptake was substantiallyinhibited by all - and ß-amino acids tested, whereassulphonate analogues failed to diminish taurine accumulation.Thus, uptake seemed to be mediated by a general aminoacid permease, unable to discriminate between carboxyland sulphonyl groups. However, Chlorella fusca could not catabolizethis unusual ß-amino acid and mobilize the amino-boundnitrogen for growth. Only a small group of -amino acids supportedthe growth of Chlorella fusca as an efficient nitrogen source. Key words: Taurine uptake, nitrogen starvation, amino acid uptake, Chlorella fusca. 相似文献
20.
Grande Karen D.; Bender Michael L.; Irwin Brian; Platt Trevor 《Journal of plankton research》1991,13(1):1-16
In vitrorates of gross and net oxygen production were measuredas a function of light intensity in some plankton communitiescollected from Bedford Basin, Nova Scotia, and in a monoclonalculture of Synechococcus. The rate of gross oxygen productionwas measured by a technique in which the stable oxygen isotope,18O, serves as a photosynthetic tracer Net oxygen productionwas measured by automated Winkler technique. The rate of communityrespiration in the light was then determined by the differencebetween gross and net rates of oxygen production. In the naturalpopulations examined, neither gross nor net oxygen productionrates were significantly inhibited at the highest light intensitymeasured (500800 µE m2 s1) In a samplein which the dark respiration rate was small relative to themaximal rate of production [Pmax;sensu Platt et al (1980) JMar. Res., 38, 687701] the rates of lightrespiration were 3 times greater. In two other communities,with high rates of dark respiration relative to Pmaxthe ratesof light respiration were closer to rates of darkrespiration. In the Synechococcus clone, both gross and netoxygen production rates were inhibited at high light intensities.Rates of light respiration were found to varyas a function of light intensity. The greatest rates of respirationwere measured in samples incubated at light intensities thatwere just saturating (100 µE m2 s1). Therates of 14C production were also measured as a function oflight intensity The photosynthetic quotients, based on 14C productionrates and gross oxygen production rates, average 1 9 相似文献