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1.
Conditions for measuring fluorescence induction curves (time-scalems) of in vivo chlorophyll a were studied using cultures ofDunaliella tertiolecta Butcher (Chlorophyceae) and of Thalassiosirapseudonana Hustedt (3H) (Bacillariophyceae), and samples ofnatural phytoplankton populations from the Grand Banks. Thearea above the fluorescence induction curve (ADCMU) and themaximum fluorescence intensity (Fmax) measured in the presenceof 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) were computedby microcomputer. Cells must be conditioned oradapted prior to obtaining a fluorescence inductioncurve; dark-adaptation resulted in a lower ADCMU and Fmax thandid adaptation in far-red (720 nm) light, and was the conditioningmethod chosen. ADCMU and Fmax increased linearly with increasingirradiance up to 32.8 W m2 the highest actinic irradianceavailable. Information on the light history of D. tertiolectawas obtained by following the time-course of change in ADCMUand in Fmax for cells exposed for 10 min to far-red or to bluelight. The rise-time of the fluorescence induction curve andvalues of Fmax were greater for samples of D. tertiolecta concentratedonto glass-fiber filters than for liquid samples, however, valuesof ADCMU for filtered and liquid samples were not significantlydifferent. Samples of Grand Banks phytoplankton collected ontoglass-fiber filters and frozen for 28 d exhibited a significantdecrease in Fmax and in ADCMU relative to the same freshly-filteredsamples. Filtration and freezing of samples is not recommended.
*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP). Second International Workshop heldat the National Oceanographic Institute. Haifa. Israel in AprilMay1984. 相似文献
2.
Upadhyay A. P.; Summerfield R. J.; Ellis R. H.; Roberts E. H.; Qi A. 《Annals of botany》1994,74(1):97-101
In soyabean [Glycine max (L.) Merrill] the period between sowingand flowering is comprised of three successive developmentalphasespre-inductive, inductive and post-inductiveinwhich the rate of development is affected, respectively, bytemperature only, by photoperiod and temperature, and then againby temperature only. A reciprocal-transfer experiment (carriedout at a mean temperature of 25°C) in which cohorts of plantswere transferred successively between short and long photoperiodsand vice-versa showed that eight combinations of three pairsof maturity alleles (E1/e1, E2 /e2, E3 /e3) had their greatesteffect on the duration of the inductive phase in long days.This phase was increased with the increasing photoperiod sensitivityinduced by the different gene combinations, and ranged fromabout 27 to 54 d according to genotype. In a short day regime(11·5 h d-1), less than the critical photoperiod, theduration of the inductive phase was briefrequiring about11 photoperiodic cycles in the less photoperiod-sensitive genotypesand only about seven cycles in the more sensitive ones. Thematurity genes also affected the duration of the two photoperiod-insensitivephases; these durations were positively correlated with thephotoperiod-sensitivity potential of the gene combinations.The largest effect was on the pre-inductive phase which variedfrom 3 to 11 d, while the post-inductive phase varied from about13 to 18 d. As a consequence of these non-photoperiodic effectsof the maturity genes, even in the most inductive regimes (daylengthsless than the critical photoperiod) the time taken to flowerby the less photoperiod-sensitive combinations of maturity geneswas somewhat less than in the more sensitive combinationsrangingfrom about 28 to 34 d. The genetic and practical implicationsof these findings are discussed.Copyright 1994, 1999 AcademicPress Glycine max (L.) Merrill, soyabean, maturity genes, isolines, flowering, photoperiod 相似文献
3.
Annual Variation of Environmental Variables, Phytoplankton Species Composition and Photosynthetic Parameters in a Coastal Lagoon 总被引:6,自引:0,他引:6
Physicalchemical variables, phytoplankton biomass, speciescomposition and photosynthesisirradiance (P-I) parameterswere analysed during 1 year in the Santo André Lagoon,SouthwestPortugal a land-locked coastal ecosystem withtemporary connections with the sea. When the lagoon stayed closedthe observed phytoplankton blooms were mainly caused by Prorocentrumminimum, a potentially toxic dinoflagellate. It was dominantduring most of the year but the seawater inflow to the lagoontriggered a decrease in phytoplankton biomass and an abruptshift in species composition. The maximum photosynthetic rate(Pmax) ranged from 2.0 to 22.5 mg C (mg chlorophyll a)1h1 and the light saturation index (Ik), ranged from 5.2to 335.0 µE m2 s1, with winter minima andsummer maxima. Pmax and Ik were both positively correlated totemperature. Abundance ofP. minimum was associated with highnitrate concentrations whereas diatoms appear when ammonium,salinity and wind velocity are high. A mathematical model todescribe photosynthetic rate as a function of irradiance andtemperature [P (I, t)] was applied to the samples in which P.minimum was the dominant species 相似文献
4.
Weihs D 《Integrative and comparative biology》2002,42(5):1071-1078
Porpoising is the popular name for the high-speed surface piercingmotion of dolphins and other species, in which long, ballisticjumps are alternated with sections of swimming close to thesurface. The first analysis of this behavior (Au and Weihs,1980) showed that above a certain "crossover" speed this behavioris energetically advantageous, as the reduction in drag dueto movement in the air becomes greater than the added cost ofleaping. Since that publication several studies documented porpoisingbehavior at high speeds. The observations indicated that thebehavior was more complex than previously assumed. The leapswere interspersed with relatively long swimming bouts, of abouttwice the leap length. In the present paper, the possibilityof dolphins using a combination of leaping and burst and coastswimming is examined. A three-phase model is proposed, in whichthe dolphin leaps out of the water at a speed Uf, which is thefinal speed obtained at the end of the burst phase of burstand coast swimming. The leap is at constant speed and so theanimal returns to the water at Uf, goes to a shallow depth andstarts horizontal coasting while losing speed, till it reachesUi. At that point it starts active swimming, accelerating toUf. It then starts the next leap. Ranges of speeds for whichthis three-stage swimming is advantageous are calculated asa function of animal and physical parameters. Notation CConstant defined in equation (12) CDCoasting drag coefficient DDrag gGravitational acceleration HHeight of jump JEnergy required for jump kRatio of swim length to jump length lDistance LTotal distance (eq. 28) mAdded mass MAnimal mass M1Total mass rCoefficient defined in eq. (22) RRatio of energies, for three-phase swimming R2Ratio of energies, for burst and coast swimming tTime TThrust USpeed VBody volume WWeight 相似文献
5.
Intrathalline and intracellular chlorophyll concentrations togetherwith thallus structure were studied in 12 species of the lichenfamily Umbilicariaceae in order to explore pigment limitationsfor light absorption and for maximum rates of net photosynthesis(Amax). Species from high light environments tended to haverelatively low chlorophyll concentrations and vice versa. Chlorophyllconcentration on a surface area basis of all species studiedwas sufficient to absorb 8099% of the incident light,which led us to believe that chlorophyll concentration was nota limiting factor for Amax. Amaxof Umbilicariaceae was smallerthan Amaxof leaves of vascular plants, both on a dry weightand on a surface area basis. These differences slightly decreasedbut did not disappear when referred to the chlorophyll concentrationof the photosynthetic tissues, but reference units had a confoundingeffect in the comparisons. Differences in Amaxon a dry weightbasis between Umbilicariaceae and vascular plants disappearedwhen comparisons were made with the whole plant and not simplywith the leaf. We found a significant, inverse relationshipbetween amount of alga and chlorophyll concentration withinthe algal cells in the lichens studied. This was interpretedas a mechanism to avoid pigment self-shading within the algallayer, distributing more efficiently the photosynthetic pigmentsover a given surface area, and is the first indication of sucha mechanism in lichens. It is suggested that thallus structureand physiology have a larger influence on the observed low Amaxofthe lichens studied than chlorophyll content. Algal cells; chlorophyll concentration; lichens; light harvesting; net photosynthesis; stereology; thallus structure; Umbilicariaceae 相似文献
6.
Biochemical Limitations to Carbon Assimilation in C3 Plants--A Retrospective Analysis of the A/Ci Curves from 109 Species 总被引:9,自引:0,他引:9
Species-specific differences in the assimilation of atmosphericCO2 depends upon differences in the capacities for the biochemicalreactions that regulate the gas-exchange process. Quantifyingthese differences for more than a few species, however, hasproven difficult. Therefore, to understand better how speciesdiffer in their capacity for CO2 assimilation, a widely usedmodel, capable of partitioning limitations to the activity ofribulose-1,5-bisphosphate carboxylase-oxygenase, to the rateof ribulose 1,5-bisphosphate regeneration via electron transport,and to the rate of triose phosphate utilization was used toanalyse 164 previously published A/Ci, curves for 109 C3 plantspecies. Based on this analysis, the maximum rate of carboxylation,Vcmax, ranged from 6µmol m2 s1 for the coniferousspecies Picea abies to 194µmol m2 s1 forthe agricultural species Beta vulgaris, and averaged 64µmolm2 s1 across all species. The maximum rate ofelectron transport, Jmax, ranged from 17µmol m2s1 again for Picea abies to 372µmol m2 s1for the desert annual Malvastrum rotundifolium, and averaged134µmol m2 s1 across all species. A strongpositive correlation between Vcmax and Jmax indicated that theassimilation of CO2 was regulated in a co-ordinated manner bythese two component processes. Of the A/Ci curves analysed,23 showed either an insensitivity or reversed-sensitivity toincreasing CO2 concentration, indicating that CO2 assimilationwas limited by the utilization of triose phosphates. The rateof triose phosphate utilization ranged from 4·9 µmolm2 s1 for the tropical perennial Tabebuia roseato 20·1 µmol m2 s1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm2 s1 across all species. Despite what at first glance would appear to be a wide rangeof estimates for the biochemical capacities that regulate CO2assimilation, separating these species-specific results intothose of broad plant categories revealed that Vcmax and Jmaxwere in general higher for herbaceous annuals than they werefor woody perennials. For annuals, Vcmax and Jmax averaged 75and 154 µmol m2 s1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm2 s1, respectively. Although these differencesbetween groups may be coincidental, such an observation pointsto differences between annuals and perennials in either theavailability or allocation of resources to the gas-exchangeprocess. Key words: A/Ci curve, CO2 assimilation, internal CO2 partial pressure, photosynthesis 相似文献
7.
Germination of three populations of Kochia indica Wight fromcontrasting soil types were studied under various levels ofsalinity, alkalinity and osmotic stress with a view to evaluatetheir potential to establish through seeds in saline and alkalineenvironments of various magnitudes. The seeds were germinatedunder controlled conditions in Petri dishes using salinizedsolutions of NaCl, Na2SO4, MgCl2 and CaSO4 (electrical conductivity,EC, 416 dsm1), sodium carbonate solutions (pH 8.5ndash;10.0), mannitol solutions ( 2.5 to 10.0 bar) andde-ionised distilled water (control). Inter-population differenceswere very marked, showing selective adaptation of the populationsto a particular stress type. In general, all populations exhibitedsalt tolerance but were rather sensitive to high osmotic stress. Kochia indicaWight (bui), germination, populatio, salinity, alkalinity, osmotic stress 相似文献
8.
Plants of four isolines of soyabean [Glycine max(L.) Merrill]Clark, vizL71-920 (maturity genecomplemente1e2e3 ), L80-5914 (E1e2e3), Clark(e1E2E3), and L65-3366 (E1E2E3), were grown inshort (12.25 h d - 1natural light) and long days (12.25 h d- 1natural light supplemented with 2.75 h d - 1low-irradianceartificial light) from first flowering to maturity in a polythenetunnel maintained at 30/24°C (day/night). Whereas therewere few differences among the isolines grown in short days,in long days the dominant alleles increased crop duration, biomassand seed yield substantially. Increases in biological and economicyield were not solely a consequence of longer crop duration:the dominant alleles also increased crop growth rate and radiationuse efficiency in long days (from 1.3 g MJ - 1total radiationine1e2e3 to 2.8 g MJ - 1inE1E2E3 ). Greater radiation use efficiencyresulted from a relatively longer leaf area duration, betterdistribution and orientation of a larger mass of leaves withinthe canopy, and smaller partitioning of assimilates to reproductivestructures. The work reveals the substantial effects of thethree lociE1 / e1, E2/ e2and E3/e3 on the response of plantgrowth, as well as development, to environment. Their relevanceto crop adaptation is discussed. Copyright 2000 Annals of BotanyCompany Glycine max(L.) Merrill, soyabean, maturity genes, flowering, phenology, growth, yield 相似文献
9.
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
10.
Carbon exchange rates (CER) of individual intact field-grownsoya bean [Glycine max (L.) Merr.] pods were measured continuouslywith a mobile gas analysis laboratory. Conditions in pod chamberssimulated those experienced normally by pods except for experimentalmodification of incident radiation or pod temperature. Undernormal conditions, CER (where positive CER represents CO2 evolution)fluctuated diurnally with a morning rise followed by a slowafternoon and evening decline which was similar among pods whichwere measured simultaneously. The frequency of measurementspermitted detection of rapid CER responses to step changes inlight and pod temperature. CER rapidly decreased and increasedwhen the chamber was alternately exposed to full sunlight andcomplete darkness, respectively. CER responded similarly tosteps up [from ambient to elevated (+ 10°C) temperature]and steps down (from elevated to ambient temperature), respectively.Thus, a temperature sensitive process which regulated pod CERwas located within the pod. CER ranged from less than 0·1to more than 1·2 mg CO2 h1 pod1 over theperiod of rapid dry-matter accumulation. Glycine max (L.) Merr., Soya bean, carbon exchange rate, light, temperature 相似文献
11.
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
12.
Within-night variation in respiratory effort preceding apnea termination and EEG delta power in sleep apnea 总被引:2,自引:0,他引:2
Berry Richard B.; Asyali Musa A.; McNellis Michael I.; Khoo Michael C.K. 《Journal of applied physiology》1998,85(4):1434-1441
We studied the within-night variability of themaximum esophageal pressure deflection before apnea termination(DPmax) in nine patients withsevere obstructive sleep apnea as an index of the arousal threshold andthe mean electroencephalogram (EEG) delta power for each 30 s as anindex of the timing of sleep cycles. Periodicity in the time variationof delta power and DPmax was analyzed by determining their power spectral density and their relationship determined by cross correlation.DPmax and delta power variedcyclically and in phase with a major periodicity (major peak in powerspectral density) of 117.6 ± 8.8 (SE) min. The correlation betweenthe values of DPmax and deltapower was significant (P < 0.001) ineach subject (mean r = 0.47 ± 0.03), and the coherence betweenDPmax and delta power at theirdominant frequency was high. Within cycles of non-rapid-eye-movementsleep, DPmax and delta powerincreased, reaching peak values on average at or after midcycle. Thesefindings suggest that the arousal threshold to airway occlusion inpatients with obstructive sleep apnea varies cyclically during thenight synchronous to the underlying cycles of sleep. 相似文献
13.
The rate of net photosynthesis (P) of whole plant stands oftomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativusL.) and sweet pepper (Capsicum annuum L.) was measured in sixlong-term experiments in large greenhouses under normal operatingconditions and CO2-concentrations between 200 and 1200 µmolmol-1. The objective was to quantify the responses to lightand carbon dioxide and to obtain data sets for testing simulationmodels. The method of measuring canopy photosynthesis involvedan accurate estimation of the greenhouse CO2 balance, usingnitrous oxide (N2O) as tracer gas to determine, on-line, theexchange rate between greenhouse and outside air. The estimatedrelative error in the observed P was about ± 10%, exceptthat higher relative errors could occur under particular conditions. A regression equation relating P to the photosynthetically activeradiation, the CO2 concentration and the leaf area index explained83-91% of the variance. The main canopy photosynthesis characteristicscalculated with the fitted regression equations were: canopyPmax 5-9 g m-2 h-1 CO2 uptake; ratio Pmax/LAI 1·5-3 gm-2 h-1; light compensation point 32-86 µmol s-1 m-2;light use efficiency (quantum yield) at low light 0·06-0·10µmol µmol-1 and CO2 compensation point 18-54 µmolmol-1. The results were related to the prevailing conditions.Copyright1994, 1999 Academic Press Canopy photosynthesis, Capsicum annuum L., carbon dioxide, CO2, CO2 balance, CO2 use efficiency, cucumber, Cucumis sativus L., glasshouse, greenhouse, light use efficiency, Lycopersicon esculentum Mill., sweet pepper, tomato, tracer gas 相似文献
14.
Cross-adaptation has occurred when exposure to an adapting chemicalstimulus (A) reduces the response to a subsequent test stimulus(B). The degree of cross-adaptation between two stimuli is thoughtto reflect the overlap of their neural activation processes.We measured self- (AA) and reciprocal crossadaptation(AB, BA) of the response of the hamster chordatympani nerve with lingual presentations of stimuli elicitingequal unadapted transient responses. Adapting and test stimuliwere 0.1 M NaCl, 0.1 M NaNO3, 0.1 M NaBr, 0.4 M Na acetate (NaAc),0.09 M LiCl and 0.4 M NH4Cl. Nearly complete and symmetricalcross-adaptation was seen for NaCl, NaNO3 and NaBr. Those Nasalts paired with LiCl showed strong but asymmetrical cross-adaptation.Exposure to sodium completely eliminated the response to LiClbut not vice versa, suggesting that lithium and sodium are notcompletely interchangeable taste stimuli for the hamster chordatympani. Relatively little cross-adaptation between NH4Cl andother salts suggested relatively separate neural activationprocesses. Strongly asymmetrical cross-adaptation was foundbetween NaAc and the other sodium salts. Responses to NaCl,NaNO3 or NaBr were eliminated after adaptation to NaAc whereasthe response to NaAc during the reciprocal cross was strong.Asymmetries are discussed in reference to sensitivities of singlenerve fibers for the chorda tympani, effects of adaptation andthe concept of anion inhibition. 相似文献
15.
BORER K.; HARDY R. J.; LINDSAY W. S.; SPRATT D. A.; MEES G. C. 《Journal of experimental botany》1966,17(2):378-389
The results of a systematic attempt to relate the growth-stimulatingfunction of compounds analogous to ethylene-bis-nitrourethaneto their chemical structure and properties showed that, withthe exception of a series of nitraminocarboxylic acids, NO2NH(CH2)COOH,activity was confined to compounds of the form RN(NO2)XN(NO2)R,where X is an alkylene or substituted alkylene chain. It issuggested that active compounds are converted to dinitramines(R = H) in the plant, and that the acidic nature of the NHNO2groups is of importance. The oil/water partition coefficientsand the geometrical structure of the molecules are also shownto influence their growth-stimulating activity. 相似文献
16.
Reactions of birch leaves to changes in light during early ontogeny: comparison between in vivo and in vitro techniques to measure carbon uptake 总被引:1,自引:0,他引:1
Trends in several photosynthetic parameters and their responseto changed growth light were followed for 15 d in leaves ofyoung birch saplings using a rapid-response gas exchange measuringequipment. These in vivo measurements were compared to biochemicalassays that were made from the same leaves after the gas exchangestudies. The measurements were made on leaves that were selectedprior to the study and were at that time of similar age. Forthe first 7 d the photosynthetic parameters were followed fromthe growth conditions of moderate light (200 µmol m2s1; referred to as controls later in the text). On day7 some of the saplings were transferred to grow either underhigh (450 µmol m2 s1; referred to as highlight plants) or low (75 µmol m2 s1; referredto as low light plants) light and the capability of the preselectedleaves for acclimation was followed for 6 d. For comparison,at the end of the experiment the measurements were made on bothcontrols and on young leaves that had developed under high andlow light. Generally the in vivo measured rate of CO2 uptake (gross photosynthesis)both at 310 ppm CO2 and 2000 ppm CO2 corresponded very wellto the biochemically determined CO2 fixation capacity in vitroafter rapid extraction (measured as the initial and total activityof Rubisco, respectively). However, if the flux of CO2 intothe chloroplasts was limited by the closure of the stomata,as was the case of the high light plants, then the in vitromeasured Rubisco activity was greater than the in vivo measuredCO2 uptake. Vmax, calculated from the mesophyll conductanceat 1% O2, exceeded the initial activity of Rubisco (assayedat saturating RuBP and CO2) constantly by 60%. The catalyticactivity of Rubisco in birch leaves was overall very low, evenwhen calculated from the total activity of Rubisco (Kcat 0.631.18 s1), when compared to herbaceous C3 species. Signs of light acclimation were not observed in most of thephotosynthetic parameters and in chloroplast structure whenmature birch leaves were subjected to changes in growth lightfor 6 d. However, the change of the growth light either to highor low light caused day-to-day fluctuations in most of the measuredphotosynthetic parameters and in the case of the high lightplants signs of photoinhibition and photodestruction were alsoobserved (decrease in the amount of chlorophyll and increasein chlorophyll a/b ratio). As a result of these fluctuationsthese plants achieved a new and lower steady-state conditionbetween the light and dark reactions, as judged from the molarratio of RuBP to Rubisco binding site. Key words: Acclimation, photosynthesis, light, Rubisco, birch 相似文献
17.
Bresta Ann-Mari; Ursin Christian; Jensen Lars Moller 《Journal of plankton research》1987,9(2):317-325
An intercomparative study was carried out to investigate possibleeffects on primary productivity measurements when using NaH14C03solutions prepared by different methods. Five different ampoulebatches coded A, B, C, D and E were tested. Three of the batches(A, B and D) had been produced by direct dilution of industriallyproduced NaH14CO3, of high specific activity. A and D were dilutedwith distilled water added carrier, whereas no information onhow batch B was diluted could be obtained. Batch E was preparedby trapping 14CO2, gas released by strong HCl from Ba14CO3 in sodium hydroxide. In the case of batch C, the processof manufacture was not known. The tests were carried out ondifferent phytoplankton material with low algal density. Twobatches (B and C) showed significant inhibitory effects on Pcalc(544%), on the slope of the ascending part ofthe light adaptation curve (), and on Pmax. Batch A showed minor,but still significant effects. The four batches A, B, C andD carried rather high amounts of non-volatile rest activity(between 13 and 194 d.p.m./µCi), which made measurementsof the release of extracellular dissolved organic carbon (EOC)almost impossible. This phenomenon,per se, would if uncor-rectedproduce considerably higher per cent EOC release in low-productivewaters, as has been reported by many authors. As to the standardizationof the working solutions, two batches (C and D) showed a pooraccuracy (16 and 18% deviation, respectively) when tested atthe C14C, and two batches (A and B) showed unacceptably highvariability between ampoules of the same batch. The study indicatesthat it is not recom-mendable to use working solutions preparedby direct dilution of industrially produced NaH14CO3 of highspecific activity without prior testing of possible effectson algal photosynthesis. It is recommended that the specificactivity of the working solution be measured if it is not exactlyspecified by the manufacturer by a Certificate of Quality. 相似文献
18.
Effects of GA3 and CCC application on the sprouting of bulbilsor subterranean dormant organs of 10 species in the genus Dioscoreawere observed. Although the efficiency of both chemicals differedby species, in general GA3 inhibited and CCC promoted the sproutingof the above dormant organs. In some species, however, dilutedGA3 (0.0030.3 µM) has a promotive and diluted CCC(330 µM) has an inhibitive effect on sprouting. Effects of GA3 application on shoot elongation were tested onsprouted bulbils. GA3 promoted elongation when applied directlyto the shoots and inhibited it when applied to the bulbous parts. These results suggest that GA activates two opposing reactionssprouting-promotingand sprouting-inhibitingin these organs. The complicatedrelation between GA3 or CCC concentrations and sprouting wereexplainable by assuming that the two counteractive reactionswere activated by GA in different degrees.
1 Present address: Department of Biology, Faculty of Science,Yamagata University, Yamagata 990, Japan. (Received June 21, 1976; ) 相似文献
19.
The Relation Between the Nitrogen Concentration and Photosynthetic Capacity of Potato (Solanum tuberosum L.) Leaves 总被引:1,自引:0,他引:1
Measurements of the rate of light-saturated photosynthesis (Pmax)were made on terminal leaflets of potato plants growing in cropssupplied with 0, 3, 6, 12, 24 and 36 g N m2. Measurementswere made between 100 and 154 d after planting. Two types ofleaf were selectedthe fourth leaf on the second-levelbranch (L4, B1) and the youngest terminal leaflet that was measurable(LYM). Later, the total nitrogen concentration of each leaflet(NL) was measured. A linear regression between Pmax and NL,common to both leaf positions, explained 68.5% of the totalvariation. With L4, B1 leaves there was a significant improvementin the proportion of variation explained when regressions withseparate intercepts and a common slope were fitted to individualfertilizer treatments. These results suggest that an increasingproportion of leaf nitrogen was not associated with the performanceof the photosynthetic system with increasing nitrogen supply.This separation between nitrogen treatments was not as clearfor LYM leaves. Stomatal conductance to transfer of water vapourwas neither influenced by leaf position nor directly by nitrogensupply. Rather conductance declined in parallel with the declinein photosynthetic capacity. Solanum tuberosum, potato, nitrogen, photosynthesis, stomatal conductance, leaf 相似文献
20.
Seasonal changes in the photosynthesis and primary productionof Microcystis aeruginosa Kütz. were investigated in LakeKasumigaura during 19811982. Microcystis always showeda light-saturated photosynthesis-light curve. Both Pmax andthe initial slope of the photosynthesis-light curve of Microcystisin early summer were very high, so it was concluded that Microcystisutilized both low and high light intensities efficiently. ThePmax of Microcystis was found to be a function of the watertemperature except in August and September. The linear regressionon the temperature-Pmax relationship discontinued at 11°C,where the Pmax value dropped; Microcystis did not photosynthesizebelow 4°C. The initial slope of the curve was also descendingbelow 11°C. It is suggested that Microcystis changes itsphysiological properties below 11°C. The highest value ofgross production calculated for M. aeruginosa was 5.4 gC m2d1 in July; the annual gross production was estimatedto be 300 gC m2year1 (i.e., 40% of the total primaryproduction in this lake). 相似文献