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1.
The action spectrum of the positive topo-phototaxis in Cryptomonaswas determined by photometry in the region of 400 to 680 nmat a stimulus intensity of 8.3 ? 1011 Einsteins cm2sec1. The action spectrum had a main peak at about 560nm unlike peaks for most other flagellated algae. Blue lightwas not very effective and red light above 640 nm had not effect. Swimming rates of individual organisms were measured by darkfield photomicrography. We concluded that the photokinetic effectwas negligible. Among the component pigments of this alga, phycoerythrin hadan absorption spectrum whose main peak appeared to coincidewith that of the phototactic action spectrum. (Received October 31, 1973; ) 相似文献
2.
The Response of Bean Plants to UV-B Radiation Under Different Irradiances of Background Visible Light 总被引:14,自引:1,他引:13
Plants of Phaseolus vulgaris L. (cv. Stella) were grown in controlledconditions under three different irradiances of visible lightwith or without UV-B (280320nm) radiation. The biologicallyeffective UV-B radiation (UV-BBE) was 6.17 kJ m2 d1,and simulated a c. 5% decrease in stratospheric ozone at 55.7?N,13.4?E. The photon flux densities of the photosyntheticallyactive radiation (PAR, 400700 nm) were either 700 µmolm21 (HL), 500, µmol m2 s1(ML) or 230 µmol m2 s1 PAR (LL). Under highlight (HL) conditions plus UV-B radiation, bean plants appearedmost resistant to the enhanced levels of UV-B radiation, andresponded only by increasing leaf thickness by c. 18%. A smallincrease in UV screening pigments was also observed. Both thelower irradiances (ML and LL) increased the sensitivity of theplants to UV-B radiation. Changes in leaf structure were alsoobserved. Photosystem II was inhibited under ML and LL togetherwith UV-B radiation, as determined by Chi fluorescence inductionand calculation of the fluorescence half-rise times. Leaf reflectivitymeasurements showed that the amount of PAR able to penetrateleaves of UV-B treated plants was reduced, and that a possiblecorrelation may exist between the reduced PAR levels, loss ofChi and lowered photosynthetic activity, especially for LL +UV-Bgrown plants, where surface reflection from leaves was highest.Changes in leaf chlorophyll content were mostly confined toplants grown under LL + UV-B, where a decrease of c. 20% wasfound. With regard to protective pigments (the carotenoids andUV screening pigments) plants subjected to different visiblelight conditions responded differently. Among the growth parametersmeasured, there was a substantial decrease in leaf area, particularlyunder LL + UV-B (c. 47% relative to controls), where leaf dryweight was also reduced by c. 25%. Key words: Chlorophyll fluorescence induction, bean, flavonoids, Phaseolus vulgaris, reflectance, UV-B radiation 相似文献
3.
Light-induced changes in the period of the circadian rhythm of carbon dioxide output in Bryophyllum leaves 总被引:1,自引:1,他引:0
Summary The period of the rhythm of carbon dioxide output from leaves of Bryophyllum fedtschenkoi R. Hamet et Perrier at 15°C was shorter in continuous white light than in darkness. The period was monitored in leaves exposed to narrow spectral bands of monochromatic radiation at an incident quantum flux density of 4.7×10-11 einsteins cm-2s-1. Bands centred on 660, 600, 730 and 530 nm significantly shortened the period, the greatest effect being achieved at 660 nm and the smallest at 530 nm; those centred on 760 and 450 nm were without effect. None of the bands tested significantly lengthened the period. The period of the rhythm in leaves exposed continuously to monochromatic radiation at 660 nm decreased with increasing quantum flux density. The extent to which a quantum flux density of 4.7×10-11 einsteins cm-2s-1 at wavelength 660 nm shortened the period depended on the ambient temperature. At 15°C a significant reduction of 4.4 h occurred as compared with the dark control, while at 30°C no significant reduction was observed. The transient (the time from the initiation of the rhythm to the first peak) showed a greater dependence on temperature than did the steady-state period. No such difference could be detected in relation to the intensity or quality of irradiation. The reduction of the transient by the various irradiation treatments was, in general, proportional to the reduction of the period. 相似文献
4.
An attempt has been made to separate constituents of marineseston samples: inorganic material, detritus and the algal species,by density gradient centrifugation, without affecting the physiologicalstate of the algae. A relatively inert gradient material, consistingof Percoll, salt and sucrose, was composed. Since the densitiesof detritus and algae as well as those of different algal speciesoften overlapped, only 10 of the 100 samples processed in thecourse of the year showed a reasonable separation. However,an enrichment with respect to one or more species was oftenachieved. Densities of eleven species of marine diatoms andof one dinoflagellate have been determined at different timesof the year. For eight diatom species and for the dinoflagellatethe following specific density ranges were established: Bidduiphiaaurita: 1.181.23 g cm3, Biddulphia sinensis: 1.031.08g cm3, Cerataulina bergonii: 1.031.06 g cm3,Ditylum brightwellii: 1.071.13 g cm3, Rhizosoleniadelicatula: 1.041.09 g cm3, Skeletonema costatum:1.121.17 g cm3, Streptotheca thamensis: 1.041.10g cm3 , Thalassiosira rotula: 1.051.10 g cm3,Peridinium sp.: 1.081.12 g cm3. No seasonal variationin density was demonstrated. Gradients of different compositiondid not influence density measurements. 相似文献
5.
The theory and practice of applying the thermodynamics of irreversibleprocesses to mass-flow theories is presented. Onsager coefficientswere measured on cut and uncut phloem and cut xylem strandsof Heracleum muntegazzimum. In 0.3 N sucrose + 1 mN KC1 theyare as follows. In phloem, LEE = 5 ? 104 mho cm1,LpE = 9 ? 106 cm3 s1 cm2 volt1 cm,and LPP = 0.16 cm3 s1 cm2 (J cm3)1cm. In uncut phloem strands LEE is about 1 ? 103 mhocm1. In xylem in 2 x 103 N KCI, Lpp = 50 to 225,LPE = 2 ? 104, and LEE = 4 ? 103. The measurementsare tentative since the blockage of the sieve plates is an interferingfactor, but if they are valid they lead to the conclusion thatneither a pressure-flow nor an electro-kinetic mechanism envisaginga long distance current pathway can be the majormotive force for transport in mature phloem. Measurementsof biopotentials along conducting but laterally detached phloembundles of Heracleum suggest, nevertheless, that there may bea small electro-osmotic component of at least 0.1 mV cm1endogenous in the phloem. 相似文献
6.
Ipomeamarone 15-hydroxylase activity was mainly recovered inthe pellet fraction between centrifugations at 10,000 and 100,000?gfrom a crude extract of Ceratocystis fimbriata-infected sweetpotato root tissue, whereas cinnamic acid 4-hydroxylase activitywas found between centrifugations at 300 and 10,000?g. Whenparticles in the crude extract were fractionated by sucrosedensity gradient centrifugation, the rough-surfaced microsomeswere distributed over a wide density range from 1.09 to 1.14g cm3, judging from the distributions of protein, RNAand NADPH-cytochrome c reductase activity. Phosphorylcholine-glyceridetransferase activity was only in the lighter half of the microsomalfraction (density: 1.091.11 g cm3). Ipomeamarone15-hydroxylase activity was found in heavier half of the microsomalfraction (density: 1.101.14 g cm3). We proposethat this tissue has two rough-surfaced endoplasmic reticulumspecies, only one of which carries phosphorylcholine-glyceridetransferase, and that the cytochrome P-450 system is localizedon the species lacking the enzyme. Cinnamic acid 4-hydroxylaseactivity was mainly found in a fraction that had densities of1.171.19 g cm3 and contained vesicular particlesof various sizes.
1 Present address: Laboratory of Food Hygienics, Faculty ofAgriculture, Kagawa University, Miki-cho, Kida-gun, Kagawa 761-07,Japan. (Received September 6, 1984; Accepted December 27, 1984) 相似文献
7.
The predatory copepod Mesocyclops edax is an important componentof many zooplankton communities where it typically makes extensivedid vertical migrations. To describe the effect of light onadults we measured their photoresponses in the laboratory. Theresponse spectrum is characterized by a wide plateau of greatestsensitivity from about 480 580 nm. These animals areadapted to perceive light during the day since their regionof maximum sensitivity overlaps the spectral region of highestquantal intensity underwater (575 700 nm). The thresholdintensity for positive phototaxis by dark adapted animals wasabout 5 x 101 Wm2 at 540 nm, and they were positivelyphototactic up to an intensity of 5 x 101 Wm2.Above this intensity phototaxis is no longer observed. Light-adaptedanimals were less sensitive than dark-adapted, but their generalpattern of response to light intensity did not differ. Thereis no rhythm in phototaxis. Their photoresponses may providea mechanism for controlling vertical migration so as to minimizeexposure to planktivorous fish.
1Contribution No. 1375-AEL from UM-CEES, Appalachian EnvironmentalLaboratory. 相似文献
8.
The Cyt f and P700 contents in leaves of three Sorghum, varietieswere measured, in relation to their carbon assimilation, underdifferent light intensities during growth. At the maximum irradiationused (1,800 µE m2 s1) the ratio of P700to Cyt f was close to unity, whereas under low irradiation (450µE m2 s1) the ratio of P700 to Cyt f rangedfrom two to three. A strikingly positive correlation existedbetween the P700 contents of the leaves and their rates of carbondioxide fixation, dry matter production and Cyt f contents,only when the plants were grown under high light intensities.The P700 content of the leaves in plants grown under low irradiationwas unrelated to the contents of Cyt f. Thus, at a high lightintensity there is a close relationship between the Cyt f andP700 levels, but at low intensities the amounts of electroncarriers and the reaction centre are independent. (Received March 7, 1983; Accepted August 24, 1983) 相似文献
9.
This research examined the hypothesis that as cacti evolve tothe leafless condition, the stem epidermis and cortex becomemore leaflike and more compatible with a photosynthetic role.All cacti in the relict genus Pereskia have non-succulent stemsand broad, thin leaves. All members of the derived subfamilyCactoideae are leafless, having an expanded cortexthat is the plant's only photosynthetic tissue. In Pereskia,leaves have a high stomatal density (mean: 50.7 stomata mm2in the lower epidermis, 38.1 mm2 in the upper epidermis),but stems have low stomatal densities (mean: 11.3 mm 2, threeof the species have none). Stems of Cactoideae have a high stomataldensity (mean: 31.1 mm2, all species have stomata). Theouter cortex cells of stems of Cactoideae occur in columns,forming a palisade cortex similar to a leaf palisade parenchyma.In this palisade cortex, the fraction of tissue volume availablefor gas diffusion has a mean volume of 12.9%, which is identicalto that of Pereskia leaf palisade parenchyma. Pereskia stemcortex is much less aerenchymatous (mean: 5.3% of cortex volume).Cactoideae palisade cortex has a high internal surface density(0.0207 cm2 cm2 which is higher than in Pereskia stemcortex (0.0150 cm2 cm3) but not as high as Pereskia leafpalisade parenchyma (0.0396 cm2 cm3). Pereskia stem cortexhas no cortical bundles, but Cactoideae cortexes have extensivenetworks of collateral vascular bundles that resemble leaf veins. Cactaceae, cactus, intercellular space, stomatal density, internal surface/volume, evolution 相似文献
10.
Fluorescence transients were investigated with the diatom Phaeodactylumtricornutum. Supplementary experiments were done with Chaetocerossp. Under weak excitation ({small tilde}103 erg/cm2sec), fluorescencetransients were induced simply by die oxidation-reduction reactionof Q, the primary reductant of photosystem II. The action spectraindicated that the electron transfer components between thetwo photosystems were in the most reduced state when fucoxanthinwas excited. The transients were observed with the 681 run emissionand with the 707 nm emission at room temperature. At 196°C,induction due to the reduction of Q. appeared both at the 681and 707 nm emissions. Similar results were also obtained withChaetoceros sp. Under strong excitation (104105 erg/cm2-sec), the fluorescencetransients due to the interconversion between States 1 and 2of die pigment system (cf. ref. 27, 29) were observed. The transientswere induced by die alternate excitation of chlorophyll a andfucoxanthin or chlorophyll c. Conversion from State 2 to State1 was inhibited by DNP and CCCP, indicating that die processwas energy-dependent. Fluorescence spectra at 196°Cwere not altered by die state-conversion of die pigment system. These results suggest diat all die fluorescence bands whichappeared at room temperature and at 196°C were dueto die chlorophyll a of pigment system II in Phaeodactylum andChaetoceros. (Received September 7, 1972; ) 相似文献
11.
Effects of 3-(3, 4-dichlorophenyl)-l, 1-dimethylurea (DCMU)on photosynthetic oxygen evolution, respiratory oxygen uptake,phototactic response and swimming rate in Cryptomonas sp. weredetermined and compared. Photosynthetic oxygen evolution wascompletely inhibited in the presence of 105 M DCMU. Thetreatment did not significantly affect the rates of respiratoryoxygen uptake, phototaxis, and swimming, indicating that directparticipation of photosynthesis in the phototaxis of this algacan be ruled out. Wavelength dependency of photosynthetic oxygen evolution wasalso determined in the range of 560 to 700 nm. The rate of photosyntheticoxygen evolution at 680 nm was as high as that at 560 nm, butno phototactic activity was seen at 680 nm although it was maximumat 560 nm. This is consistent with the above conclusion. (Received February 16, 1976; ) 相似文献
12.
The thesis that the minimum cell-phosphorus content of planktonalgae is a light- and temperature-independent species constantwas investigated using the marine plankton diatom Thalassiosirarotula. To what extent the maximum cell-phosphorus content isalso a constant, light- and temperature-independent quantityhas been tested in parallel. At 2.5C and 3.03 nE cm2s1 the minimum and maximum cell-phosphorus contents aregreater than the values for 16C and 8.93 nE cm2 s1by a factor of 5.7. The light intensities were kept near thelight saturation for the growth rate for all experimental temperatures(2.5, 6, 12 and 16C). The light dependence of the phosphoruscontent was tested at 12C. For 1.43 nE cm2 s1the minimum phosphorus content was lower by a factor of 2.5than for 64.28 and 80.36 nE cm2 s1 respectively.The maximum P-content for 2.86 nE cm2 s1 was 3.9times higher than for 64.28 nE cm2 s1 T. rotulais, on the basis of the stored P-content, only capable of betweenthree and five cell divisions. The N/P atomic ratios were, dependingupon light and temperature, between 56:1 and 226:1 for the minimumcell-phosphorus content, which implies a pronounced phosphorusdeficiency. 相似文献
13.
Photosynthetic 14C fixation by Characean cells in solutionsof high pH containing NaH14CO3 gave a measure of the abilityof these cells to take up bicarbonate (H14CO3). Whereascells of Nitella translucens from plants collected and thenstored in the laboratory absorbed bicarbonate at 11.5µµmoles cm2 sec1, rates of 38µµmoles cm2 sec1 were obtained withN. translucens cells from plants grown in the laboratory. Influxesof 56 µµmoles cm2 sec1 wereobtained with Chara australis, 38 µµmolescm2 sec1 with Nitellopsis obtusa, and 15µµmoles cm2 sec1 with Tolypella intricata.It is considered that these influxes represent the activityof a bicarbonate pump, which may be an electrogenic process. In solutions of lower pH, H14CO3 uptake would be maskedby rapid diffusion of 14CO2 into the cells: the four Characeanspecies fixed 14CO2 at maximum rates of 3040 µµmolescm2 sec1 (at 21° C). 相似文献
14.
The influence of salinity in the growing media on ribulose-1,5-bisphosphate (RuBP) carboxylase and on CO2 fixation by intactsugar beet (Beta vulgaris) leaves was investigated. RuBP carboxylase activity was mostly stimulated in young leavesafter exposure of plants for 1 week to 180 mM NaCl in the nutrientsolution. This stimulation was more effective at the higherNaHCO2 concentrations in the reaction medium. Salinity also enhanced CO2 fixation in intact leaves mostlyat rate-limiting light intensities. A 60 per cent stimulationin CO2 fixation rate was obtained by salinity under 450 µEm2 s1. At quantum flux densities of 150 µEm2 s1 (400700 nm) this stimulation was280 per cent. Under high light intensities no stimulation bysalinity was found. In contrast, water stress achieved by directleaf desiccation or by polyethylene glycol inhibited enzymeactivity up to fourfold at 1.2 MPa. Beta vulgaris, sugar beet, ribulose-1, 5-bisphosphate carboxylase, salt stress, water stress, carbon dixoide fixation, salinity 相似文献
15.
Spectral response of corn (Zea mays) in root geotropism 总被引:1,自引:0,他引:1
The primary roots of corn (Zea mays, Wisconsin hybrid 64A ?22R) show positive geotropism following exposure to light. Thisconfirms the works of other investigators. The curvature responsebegins at about 1 hr following irradiation and reached a plateauat 5 hr. A study of wavelengths 350760 nm, using energiesof 2.24 ? 1014 photon cm2 and exposure times 60 sec,shows that the most effective light is at 660 nm with lessereffectiveness at 460 and 560 nm. The responses at 660 and 460nm are reversible by a far-red (730 nm) exposure, indicativeof the possible participation of phytochrome. Analyses of freshtips of corn roots with a dual-wavelength difference photometershow the phytochrome content in the root to be about 0.16 (OD) per gram fresh wieght. The requirement of light for thegeotropic growth response of corn roots might be an adaptivephenomenon. The occurrence of photomorphogenic activity in thegreen light should be of concern to those who use green as the"safe" light in "dark" experiments.
1Work supported by U. S. NASA and U. S. ERDA. (Received September 26, 1977; ) 相似文献
16.
Accumulation of dry weight was measured in plant parts of meadowfescue (Festuca pratensis Huds.) that was grown at 16/11 °Cor 26/21 °C and with 20 or 60 nE cm2 s1 photosyntheticallyactive radiation. Plants reached anthesis about 3 weeks laterat 16/11 °C than at 26/21 °C and had then a higher proportionof dry weight in inflorescences and less in leaf blades. Growthtemperature had little effect on CO2 exchange rate (CER) butplants grown at 60 nE cm2 s1 had higher CER thanthose grown at 20 nE cm2 s1. The concentration of water-soluble carbohydrates (WSC) at similargrowth stages was usually higher at 16/11°C than at 26/21°C.High radiation also led to higher WSC in stem and leaf tissue.Root tissue changed least and WSC did not exceed 10% of dryweight during the experiment. In all tissues, when WSC was high,the fructans were distributed into a group with a high degreeof polymerization (DP) and another with a low DP. The low DPgroup included sucrose, reducing sugars and fructans up to about20 units long. An apparent threshold concentration of WSC wasnecessary for synthesis of the high DP fructans. This concentrationwas near 12% for leaf tissue, about 6% for stem base tissue,and 2.5% for root tissue. The average apparent DP of the highDP fructan group was 43 to 50 for leaf tissue, 31 to 93 forstem base tissue, and 27 to 31 for roots. These characteristicsappeared to be mostly tissue dependent with less effect fromtemperature and radiation. Key words: Fructans, Meadow fescue, Environmental effects, Dry weight distribution 相似文献
17.
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
18.
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
19.
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
20.
Nakamura Teruko; Tomita Kaori; Kawanabe Yukiko; Murayama Tadako 《Plant & cell physiology》1982,23(8):1363-1369
Conidial germination in liquid shake culture of Neurospora crassawas affected by the number of conidia in the medium (conidialdensity effect) with the optimum density being around 2?106conidia/ml. The conidial density effect at 2?104 and 2?105 conidia/mlwas eliminated by the addition of auxin, IAA or 2,4-D with theoptimum concentrations of IAA and 2,4-D being around 106M. IAA and 2,4-D had no effect on the effect at 2?107 conidia/ml.An active substance(s) for conidial germination which was relatedto the conidial density effect was detected in the cell-freefiltrate of the germination medium, and was found to be non-dialyzableand thermolabile. At the early stage of germination, the concentrationof active substance(s) in the medium increased in proportionto the conidial density and reached a supraoptimum amount forgermination at 2?107 conidia/ml. IAA (106M) enhancedthe concentration. Endogenous auxin concentrations in filtratesof the germination media containing 2?105, 2?106 and 2?107 conidia/mlwere 5.8?1012, 4.6?1011 and 1.7?1010M IAAequivalent, respectively. The conclusion reached was that auxinmay control conidial germination with mediation by the activesubstance(s). (Received June 8, 1982; Accepted September 27, 1982) 相似文献