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1.
Pascopyrum smithii (C3) andBouteloua gracilis (C4) are importantforage grasses native to the Colorado shortgrass steppe. Thisstudy investigated photosynthetic responses of these grassesto long-term CO2enrichment and temperature in relation to leafnonstructural carbohydrate (TNC) and [N]. Glasshouse-grown seedlingswere transferred to growth chambers and grown for 49 d at twoCO2concentrations (380 and 750 µmol mol-1) at 20 and 35°C, and two additional temperatures (25 and 30 °C) at750 µmol mol-1CO2. Leaf CO2exchange rate (CER) was measuredat a plant's respective growth temperature and at two CO2concentrationsof approx. 380 and 700 µmol mol-1. Long-term CO2enrichmentstimulated CER in both species, although the response was greaterin the C3,P. smithii . Doubling the [CO2] from 380 to 750 µmolmol-1stimulated CER ofP. smithii slightly more in plants grownand measured at 30 °C compared to plants grown at 20, 25or 35 °C. CO2-enriched plants sometimes exhibited lowerCER when compared to ambient-grown controls measured at thesame [CO2], indicating photosynthetic acclimation to CO2growthregime. InP. smithii , such reductions in CER were associatedwith increases in TNC and specific leaf mass, reductions inleaf [N] and, in one instance, a reduction in leaf conductancecompared to controls. InB. gracilis , photosynthetic acclimationwas observed more often, but significant changes in leaf metabolitelevels from growth at different [CO2] were generally less evident.Temperatures considered optimal for growth (C3: 20 °C; C4:35 °C) sometimes led to CO2-induced accumulations of TNCin both species, with starch accumulating in the leaves of bothspecies, and fructans accumulating only inP. smithii. Photosynthesisof both species is likely to be enhanced in future CO2-enrichedand warmer environments, although responses will sometimes beattenuated by acclimation. Acclimation; blue grama (Bouteloua gracilis (H.B.K.) Lag ex Steud.); leaf nitrogen concentration; nonstructural carbohydrates; photosynthesis; western wheatgrass (Pascopyrum smithii (Rydb.) Love) 相似文献
2.
Vidussi Francesca; Claustre Herve; Bustillos-Guzman Jose; Cailliau Caroline; Marty Jean-Claude 《Journal of plankton research》1996,18(12):2377-2382
A rapid reverse-phase HPLC method is presented for the identificationand quantification of most of the phytoplankton pigments. Thismethod yields the resolution of divinyl-chlorophyll a and chlorophylla, as well as the partial resolution of lutein and zeaxanthin,and of divinyl-chlorophyll b and chlorophyll b. In addition,chlorophylls c1,2 and c3 are well resolved. The analysis timefor one sample is 20 mm, which makes this method particularlysuited when large numbers of samples have to be processed. 相似文献
3.
Mistletoes usually have slower rates of photosynthesis thantheir hosts. This study examines CO2assimilation, chlorophyllfluorescence and the chlorophyll content of temperate hostparasitepairs (nine hosts parasitized by Ileostylus micranthus and Carpodetusserratus parasitized by Tupeia antarctica). The hosts of I.micranthus had higher mean annual CO2assimilation (3.59 ±0.41 µmol m-2 s-1) than I. micranthus(2.42 ± 0.20µmol m-2 s-1), and C. serratus(2.41 ± 0.43 µmolm-2 s-1) showed higher CO2assimilation than T. antarctica(0.67± 0.64 µmol m-2 s-1). Hosts saturated at significantlyhigher electron transport rates (ETR) and light levels thanmistletoes. The positive relationship between CO2assimilationand electron transport suggests that the lower CO2assimilationrates in mistletoes are a consequence of lower electron transportrates. When photosynthetic rates, ETR and chlorophyll a /b ratioswere adjusted for photosynthetically active radiation, hostsdid not have significantly higher CO2assimilation (3.21 ±0.37 µmol m-2 s-1) than mistletoes (2.54 ± 0.41µmol m-2 s-1), but still had significantly higher ETRand chlorophyll a / b ratios. The electron transport rates,saturating light and chlorophyll a / b ratios of sun leavesfrom mistletoes were similar to host shade leaves. These responsesindicate that in comparison with their hosts, mistletoe leaveshave the photosynthetic characteristics of the leaves of shadeplants. Copyright 2000 Annals of Botany Company CO2assimilation, photosynthetic active radiation (PAR), chlorophyll fluorescence, electron transport rate (ETR), photochemical quenching (qp), non-photochemical quenching (qn), sun and shade leaves, chlorophyll content, Ileostylus micranthus, Tupeia antarctica, New Zealand 相似文献
4.
Active oxygen participation in chlorophyll destruction and lipid peroxidation in SO2-fumigated leaves of spinach 总被引:1,自引:0,他引:1
Shimazaki Ken-ichiro; Sakaki Takeshi; Kondo Noriaki; Sugahara Kiyoshi 《Plant & cell physiology》1980,21(8):1193-1204
Chlorophyll a and carotenoids of spinach began to be destroyed2 to 3 hr after fumigation with 2 ppm SO2 under light, whereaschlorophyll b was undamaged during 8 hr of exposure to SO2.Pheophytin a was not affected by the fumigation. When disks excised from leaves fumigated with SO2 at 2 ppm for2 hr were illuminated, chlorophyll a and carotenoids were brokendown, while they were not destroyed in darkness. The destructionof these pigments was suppressed under nitrogen. Chlorophylla destruction was inhibited by l,2-dihydroxybenzene-3,5-disulfonate(tiron), hydro-quinone and ascorbate, but not by l,4-diazabicyclo-[2,2,2]-octane(DABCO), methio-nine, histidine, benzoate and formate. Chlorophylla destruction was inhibited by phenazine methosulfate but stimulatedby methyl viologen. Addition of superoxide dismutase (SOD) tothe homogenate of SO2-fumigated leaves inhibited the chlorophylla destruction. The activity of endogenous SOD was reduced to40% by 2-hr fumigation before the loss of chlorophyll was observed.These results suggest that chlorophyll a destruction by SO2was due to superoxide radicals (O2). Moreover, malondialdehyde (MDA), a product of lipid peroxidation,was formed in SO2-fumigated leaves. MDA formation was inhibitedby tiron, hydroquinone and DABCO but not by benzoate and formate.MDA formation was increased by D2O. These results suggest thatlipid peroxidation in SO2-fumigated leaves was due to singletoxygen 1O2 produced from O2. (Received May 15, 1980; ) 相似文献
5.
Active oxygen participation in chlorophyll destruction and lipid peroxidation in SO2-fumigated leaves of spinach 总被引:22,自引:0,他引:22
Shimazaki Ken-ichiro; Sakaki Takeshi; Kondo Noriaki; Sugahara Kiyoshi 《Plant & cell physiology》1980,21(7):1193-1204
Chlorophyll a and carotenoids of spinach began to be destroyed2 to 3 hr after fumigation with 2 ppm SO2 under light, whereaschlorophyll b was undamaged during 8 hr of exposure to SO2.Pheophytin a was not affected by the fumigation. When disks excised from leaves fumigated with SO2 at 2 ppm for2 hr were illuminated, chlorophyll a and carotenoids were brokendown, while they were not destroyed in darkness. The destructionof these pigments was suppressed under nitrogen. Chlorophylla destruction was inhibited by l,2-dihydroxybenzene-3,5-disulfonate(tiron), hydro-quinone and ascorbate, but not by l,4-diazabicyclo-[2,2,2]-octane(DABCO), methio-nine, histidine, benzoate and formate. Chlorophylla destruction was inhibited by phenazine methosulfate but stimulatedby methyl viologen. Addition of superoxide dismutase (SOD) tothe homogenate of SO2-fumigated leaves inhibited the chlorophylla destruction. The activity of endogenous SOD was reduced to40% by 2-hr fumigation before the loss of chlorophyll was observed.These results suggest that chlorophyll a destruction by SO2was due to superoxide radicals (O2). Moreover, malondialdehyde (MDA), a product of lipid peroxidation,was formed in SO2-fumigated leaves. MDA formation was inhibitedby tiron, hydroquinone and DABCO but not by benzoate and formate.MDA formation was increased by D2O. These results suggest thatlipid peroxidation in SO2-fumigated leaves was due to singletoxygen 1O2 produced from O2. (Received May 15, 1980; ) 相似文献
6.
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
7.
This study investigated how CO2and temperature affect dry weight(d.wt) accumulation, total nonstructural carbohydrate (TNC)concentration, and partitioning of C and N among organs of twoimportant grasses of the shortgrass steppe,Pascopyrum smithiiRydb. (C3) andBouteloua gracilis(H.B.K.) Lag. ex Steud. (C4).Treatment combinations comprised two temperatures (20 and 35°C)at two concentrations of CO2(380 and 750 µmol mol-1),and two additional temperatures of 25 and 30°C at 750 µmolmol-1CO2. Plants were maintained under favourable nutrient andsoil moisture and harvested following 21, 35, and 49d of treatment.CO2-induced growth enhancements were greatest at temperaturesconsidered favourable for growth of these grasses. Comparedto growth at 380 µmol mol-1CO2, final d.wt of CO2-enrichedP.smithiiincreased 84% at 20°C, but only 4% at 35°C. Finald.wt ofB. graciliswas unaffected by CO2at 20°C, but wasenhanced by 28% at 35°C. Root:shoot ratios remained relativelyconstant across CO2levels, but increased inP. smithiiwith reductionin temperature. These partitioning results were adequately explainedby the theory of balanced root and shoot activity. Favourablegrowth temperatures led to CO2-induced accumulations of TNCin leaves of both species, and in stems ofP. smithii, whichgenerally reflected responses of above-ground d.wt partitioningto CO2. However, CO2-induced decreases in plant tissue N concentrationswere more evident forP. smithii. Roots of CO2-enrichedP. smithiihadgreater total N content at 20°C, an allocation of N below-groundthat may be an especially important adaptation for C3plants.Tissue N contents ofB. graciliswere unaffected by CO2. Resultssuggest CO2enrichment may lead to reduced N requirements forgrowth in C3plants and lower shoot N concentration, especiallyat favourable growth temperatures. Acclimation to CO2; blue grama; Bouteloua gracilis ; carbohydrate; climate change; global change; grass; growth; growth temperature optima; nitrogen; N uptake; Pascopyrum smithii; western wheatgrass 相似文献
8.
The capacity for C4 photosynthesis in Panicum milioides, a specieshaving reduced levels of photorespiration, was investigatedby examining the activity of certain key enzymes of the C4 pathwayand by pulse-chase experiments with 14CO2. The ATP$P1 dependentactivity of pyruvate,P1 dikinase in the species was extremelylow (0.140.18 µmol mg chlorophyll1 min1).Low activity of the enzyme was also found in Panicum decipiensand Panicum hians (related species with reduced photorespiration)and in Panicum laxum (a C3 species). The antibody to pyruvate,P1dikinase caused about 70% inhibition of the ATP$P1 dependentactivity of the enzyme in P. milioides. The activity of NAD-malicenzyme and NADP-malic enzyme in P. milioides was equally low(approximately 0.10.2 µmol mg chlorophyll1min1) and similar to the activity in P. decipiens, P.hians and P. laxum. Photosynthetic pulse-chase experiments underatmospheric conditions showed a typical C3-like pattern of carbonassimilation including the labelling of glycine and serine asexpected during photorespiration. During the pulse with 14CO2only about 1% of the labelled products appeared in malate and23% in aspartate. During a chase in atmospheric levelsof CO2 for up to 6 min there was a slight increase in labellingin the C4 acids. The amount of label in carbon 4 of aspartatedid not change during the chase, indicating little or no turnoverof the C4 acid via decarboxylation. The results indicate thatunder atmospheric conditions P. milioides assimilates carbondirectly through the C3 pathway. Photorespiration as indicatedby the CO2 compensation point may be repressed in the speciesby a more efficient recycling of photorespired CO2. (Received June 8, 1982; Accepted July 22, 1982) 相似文献
9.
- The effects of 3-(4'-chlorophenyl)-1, 1-dimethylurea (CMU)onthe fluorescence of photosynthetic pigments in vivo wereinvestigatedin blue-green, red and brown algae and in isolatedspinach chloroplasts.CMU caused an increase in steady statelevel of fluorescenceof chlorophyll a, but did not influencethe fluorescence ofphycobilins. The spectrum of the fluorescenceincrement hada peak at 685 m/µ and a shoulder at 730740mµ.These two bands probably arise from chlorophyll a(Cf684) belongingto pigment system II.
- On excitation of chlorophylla in a red alga, Porphyra yezoensis,a fluorescence band witha peak at 720 mµ was observedbesides a shoulder at 685mµ. The 720 m band is inferredto arise from chlorophylla (probably, Cf-1) in pigment systemI.
- On addition of CMUto the algal cells, the induction of fluorescencewas modifiedto take a simple time course. The induction wasobserved onlywith respect to the fluorescence of chlorophylla, but not inthe fluorescence of phycobilins. The spectrumof the "transient"fluorescence showed two emission bands ofchlorophyll a at 685mµ and 740 mµ, and was quitesimilar in form tothe spectrum of the CMU-caused increase insteady state fluorescence.
- These facts were interpreted in terms of the correlation offluorescence of chlorophyll a and the photochemical reactionsof photosynthesis
10.
Acclimation in Seedlings of a Tropical Tree, Bischofia javanica, Following a Stepwise Reduction in Light 总被引:2,自引:0,他引:2
Acclimation of fully developed leaves of Bischofia javanicaBlume to shadelight was examined. Seedlings were grown undersimulated daylight (1000 µmol m2 s1), thentransferred to a simulated shadelight (40 µmol m2s1). When a high-light leaf was transferred to low light, large negativenet photosynthetic rates (Pm) were recorded. This decrease wasrapid, but within 7 d the rate increased and became equal tothe low-light control leaf. These changes in photosynthesisdid not follow the pattern of changes in stomatal conductance(gs). Transfer to the low light resulted in a dramatic decreasein leaf weight per unit area (Lw), and most of the decreasesin Lw occurred within 3 d of transfer when the Pm of the transferredleaf was well below that of the low-light control leaf. There was a significant decrease in chlorophyll a in the transferredleaf without an appreciable change in chlorophyll b resultingin a large decrease in the chlorophyll a to chlorophyll b ratio.Leaf chlorophylls per unit area were higher in the transferredleaf than the low-light control leaf. Maximum photosyntheticrate in the transferred leaf was decreased by 40% compared tothat for the high-control leaf, but was almost at the same extenthigher than the low-light control leaf The results are discussedin the context of carbon gain capacity of its seedlings underlight-limiting forest understorey habitats. Bischofia, chlorophylls, light, photosynthesis, shade acclimation, tree seedlings, tropical tree 相似文献
11.
The presence of chlorophyll b and the estimation of phaeopigments in marine phytoplankton 总被引:1,自引:0,他引:1
A reverse-phase h.p.l.c. technique was used to estimate theconcentration of chlorophyll b in phytoplankton cultures, fecalpellets of Calanus pacificus, and suspended paniculate matterfrom the Central North Pacific, Oregon coastal waters, and DabobBay (a temperate fjord in Puget Sound, WA, USA). The purposewas to assess the distribution of this pigment in the euphoticzone and its effect on the fluorometnc estimation of phaeopigments.Analyses of natural waters confirm high chlorophyll b concentrations(median mass ratio of b:a > 0.3) at the depth of the chlorophylla maximum in tropical waters while values for temperate planktonare relatively low (median mass ratio of chl b:a = 0.05) andpatchy. Zooplankton fecal pellets showed a significant enrichmentin chlorophyll b, suggesting grazing as a mechanism to explainhigh concentrations of this pigment at the bottom of the euphoticzone. It is estimated that the presence of chlorophyll b couldcause an average overestimation of phaeopigment concentrationby the fluorometnc technique of 38% between 0 and 200 m in theCentral North Pacific. This effect is more pronounced at thelayer of chlorophyll b maximum (120140 m).
1Present address: Marine Biology Research Division, A-002, ScrippsInstitution of Oceanography, La Jolla, CA 92093, USA 相似文献
12.
When grown in pots and well-watered, the relative growth ratesof the above ground parts of two species of Moricandia (M. arvensis,an intermediate C3C4 species, and M. moricandioides,a C3 species) were inferior to those of two cultivated Brassicaspecies (B. campestris and B. napus). The Moricandia specieshad thicker leaves (greater d.wt per unit leaf area) with morechlorophyll than the Brassica species and had slightly greaterrates of photosynthesis per unit leaf area at an irradiance(400700 nm) of 2000 µmol quanta m2 s 1.Leaves of M. arvensis, known to have a CO2 compensation pointbetween that of C3 and C4 species, had a lower ratio of theintercellular to atmospheric partial pressure of CO2 (C1/Ca)and a greater instantaneous water use efficiency (WUE) thanthose of M. moricandioides and the Brassica species. Carbon isotope discrimination ( 相似文献
13.
Denton Jerod; Boahene Derek; Moran William M. 《American journal of physiology. Cell physiology》1998,275(5):C1300
In Aplysia intestine,stimulation of Na+ absorption withluminal alanine increases apical membraneK+ conductance(GK,a), whichpresumably regulates enterocyte volume during stimulatedNa+ absorption. However, themechanism responsible for the sustained increase in plasma membraneK+ conductance is not known forany nutrient-absorbing epithelium. In the present study, we have begunto test the hypothesis that the alanine-induced increase inGK,a inAplysia enterocytes results fromexocytic insertion of K+ channelsinto the apical membrane. We used the fluid-phase marker horseradishperoxidase to assess the effect of alanine on apical membraneexocytosis and conventional microelectrode techniques to assess theeffect of alanine on fractional capacitance of the apical membrane(fCa). Luminalalanine significantly increased apical membrane exocytosis from 1.04 ± 0.30 to 1.39 ± 0.38 ng · min1 · cm2.To measure fCa,we modeled the Aplysia enterocyte as adouble resistance-capacitance (RC) electric circuit arranged in series. Several criteria were tested to confirm application of the model to theenterocytes, and all satisfied the model. When added to the luminalsurface, alanine significantly increasedfCa from 0.27 ± 0.02 to 0.33 ± 0.04 (n = 10)after 4 min. There are two possible explanations for our findings:1) the increase in exocytosis, whichadds membrane to the apical plasma membrane, prevents plasma membranefracture, and 2) the increase inexocytosis delivers K+ channels tothe apical membrane by exocytic insertion. After the alanine-induceddepolarization of apical membrane potential (Va), there isa strong correlation (r = 0.96)between repolarization ofVa, whichreflects the increase inGK,a, andincrease in fCa. This correlation supports the exocytic insertion hypothesis for activation ofGK,a. 相似文献
14.
Hillyard Stanley D.; Cantiello Horacio F.; Van Driessche Willy 《American journal of physiology. Cell physiology》1997,273(6):C1995
Skin from larval bullfrogs was mounted in an Ussing-type chamberin which the apical surface was bathed with a Ringer solution containing 115 mM K+ and thebasolateral surface was bathed with a Ringer solution containing 115 mMNa+. Ion transport was measured asthe short-circuit current(Isc) with alow-noise voltage clamp, and skin resistance(Rm) wasmeasured by applying a direct current voltage pulse. Membrane impedance was calculated by applying a voltage signal consisting of 53 sine wavesto the command stage of the voltage clamp. From the ratio of theFourier-transformed voltage and current signals, it was possible tocalculate the resistance and capacitance of the apical and basolateralmembranes of the epithelium(Ra andRb,Ca and Cb,respectively). With as the anion,Rm decreasedrapidly within 5 min following the addition of 150 U/ml nystatin to theapical solution, whereasIsc increasedfrom 0.66 to 52.03 µA/cm2 over a60-min period. These results indicate that nystatin becomes rapidlyincorporated into the apical membrane and that the increase inbasolateral K+ permeabilityrequires a more prolonged time course. Intermediate levels ofIsc were obtainedby adding 50, 100, and 150 U/ml nystatin to the apical solution. Thisproduced a progressive decrease in Ra andRb whileCa andCb remainedconstant. With Cl as theanion, Isc valuesincreased from 2.03 to 89.57 µA/cm2 following treatment with150 U/ml nystatin, whereas with gluconate as the anionIsc was onlyincreased from 0.63 to 11.64 µA/cm2. This suggests that theincrease in basolateral K+permeability produced by nystatin treatment, in the presence of morepermeable anions, is due to swelling of the epithelial cells of thetissue rather than the gradient for apicalK+ entry. Finally,Cb was notdifferent among skins exposed toCl,, or gluconate, despite the largedifferences inIsc, nor didinhibition of Iscby treatment with hyperosmotic dextrose cause significant changes inCb. These resultssupport the hypothesis that increases in cell volume activateK+ channels that are alreadypresent in the basolateral membrane of epithelial cells. 相似文献
15.
Argyroudi-Akoyunoglou J. H.; Kondylaki S.; Akoyunoglou G. 《Plant & cell physiology》1976,17(5):939-954
The plastids of young dark-grown bean leaves, exposed to periodiclight are agranal, devoid of chlorophyll b and contain primarythylakoids and chlorophyll a. Transfer of these plants to continuousillumination results in synthesis of new chlorophyll a, chlorophyllb and grana. This study was done in order to study whether andhow the grana are formed from preexisting primary thylakoids.14C--aminolevulinic acid was used to label the chlorophyll aof the primary thylakoids, and its fate was studied after transferof the plants to continuous light. It was found that chlorophyll b and grana become 14C-labelled.The total radioactivity of chlorophyll b per bean increasedwith the parallel decrease of that of chlorophyll a. All subchloroplastfractions, obtained after digitonin disruption of chloroplasts,contained chlorophyll a of equal specific radioactivity. Thespecific radioactivity of chlorophyll b was lower than thatof chlorophyll a, and, in addition, it was lower in the granathan in the stroma lamellae fraction. The data suggest that chlorophyll b is formed from chlorophylla; the grana are formed by stacking of preexisting primary thylakoids;chlorophyll b is synthesized faster in the grana than the stromalamellae; the newly formed chlorophyll a molecules are distributedat random throughout the developing photosynthetic membraneand not on specific growing sites. (Received April 24, 1976; ) 相似文献
16.
The amount of total chlorophyll, chlorophylls a and b as wellas the ratio of a to b decreased in chloroplasts isolated fromQuercus rotundifolia leaves, kept for 17 d in a solution of35.5 µM evernic acid in 1 mM Na HCO3, when compared withthe chloroplasts of control leaves (kept in NaHCO3). The chloroplastsin the spongy parenchyma were smaller and the amount of starchand plastoglobuli lower. The number of grana per chloroplastsection, the number of thylakoids per grana and the height ofgrana stacks were also less in the chloroplasts of leaves treatedwith evernic acid. Quantitative ultrastructural differenceswere determined by means of electron microscopy and image analysistechniques. Quercus rotundifolia Lam., chloroplasts, ultrastructure, lichens, evernic acid 相似文献
17.
Light-harvesting capacities of photosystem I (PSI) and photosystemII (PSII) in a wild-type and three chlorophyll b-deficient mutantstrains of rice were determined by measuring the initial slopeof light-response curve of PSI and PSII electron transport andkinetics of light-induced redox changes of P-700 and QA, respectively.The light-harvesting capacity of PSI determined by the two methodswas only moderately reduced by chlorophyll b-deficiency. Analysisof the fluorescence induction that monitors time course of QAphotoreduction showed that both relative abundance and antennasize of PSIIa decrease with increasing deficiency of chlorophyllb and there is only PSIIrß in chlorina 2 which totallylacks chlorophyll b. The numbers of antenna chlorophyll moleculesassociated with the mutant PSII centers were, therefore, threeto five times smaller than that of PSIIa in the wild type rice.Rates of PSII electron transport determined on the basis ofPSII centers in the three mutants were 6070% of thatin the normal plant at all photon flux densities examined, indicatingthat substantial portions of the mutant PSII centers are inactivein electron transport. The initial slopes of light-responsecurves of PSII electron transport revealed that the functionalantenna sizes of the active populations of PSII centers in themutants correspond to about half that of PSII in the wild typerice. Thus, the numbers of chlorophyll molecules that serveas antenna of the oxygen-evolving PSII centers in the mutantsare significantly larger than those that are actually associatedwith each PSII center. It is proposed that the inactive PSIIserves as an antenna of the active PSII in the three chlorophyllb-deficient mutants of rice. In spite of the reduced antennasize of PSII, therefore, the total light-harvesting capacityof PSII approximately matches that of PSI in the mutants. (Received July 29, 1994; Accepted February 7, 1996) 相似文献
18.
The cell quotas of microcystin (Qmcyst), protein (Qprot), chlorophylla (Qchloro) and carbohydrate (Qcarbo), as well as the net productionrates of these parameters, were determined during the exponentialand stationary phases in nine batch cultures of Microcystisaeruginosa (CYA 228) at light regimes from 33 to 53 µmolphotons m2 s1. The following results were obtained.(i) A parallel pattern was found in the changes of Qmcyst, Qprot,Qchloro and Qcarbo during the entire growth cycle and significantcorrelations were recorded between Qmcyst and Qprot, Qchloroand Qcarbo. (ii) The net microcystin production rate (µmcyst)was positively correlated with the specific cell division rate(µc), the chlorophyll production rate (µchloro)and the protein production rate. (iii) A significant inverselinear relationship was found between µc and Qmcyst, i.e.cultures with a positive µc had a Qmcyst between 110 and400 fg microcystin cell1, while declining cultures hadQmcyst values >400 fg microcystin cell1. Maximum variationin Qmcyst within cultures was 3.5-fold. Collectively, the resultsshow that cells produced microcystin at rates approximatingthose needed to replace losses to daughter cells during divisionand that microcystin was produced in a similar way to proteinand chlorophyll, indicating a constitutive microcystin production. 相似文献
19.
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
20.
Perianth MP, gynoecium MG, and androecium MA dry-weight biomass(in g) of 39 species of perfect flowers was measured. Thesedata were pooled with published data from an additional 51 speciesand used to determine size-dependent variations in (MG and MA)in terms of the hypothesis that the quotient of MG and MA exceeds1·0 for out-breeding (xenogamous) species and less than1·0 for in-breeding (autogamous) species. Ordinary leastsquare regression of the pooled data (n = 90) showed MG = 0·118M0·916P (r2 = 0·884) and MA = 0·186 M0·975P(r2 = 0·865), indicating that the biomass of the gynoeciumproportionally decrease as floral size increases. The exponentsof these regressions indicate that the ratio of gynoecial toandroecial biomass decreased with increasing floral size suchthat comparatively small flowers (MP < 0·0021 g) hadMG/MA > 1·0 (predicted for 'out-breeders') while comparativelylarger flowers (MP > 0·0021 g) had MG /MA < 1·0(predicted for 'in-breeders'). Thus, on average, the type ofbreeding system was a size-dependent phenomenon. To test whether the biomass of a floral organ-type is a legitimateindicator of gender reproductive effort, the biomass (in g)of stamen filaments Mm and anther sacs MAS of 39 species wasdetermined. Least square regression of these data showed MAS= 0·188 M0·854fil (r2 = 0·967), indicatingthat species with larger stamen filaments, on the average, boreproportionally smaller anther sacs and thereby cautioning againstthe uncritical use of the allocation of biomass to floral organ-typeas a strict gauge of gender-function investment. To determine whether the loss of one gender-function resultsin proportional reallocation of biomass to the remaining gender-function,the size-dependency of androecial and gynoecial biomass wasdetermined for a total of 33 perfect and imperfect flowers ofCucumis melo. Regression of the data obtained from perfect flowersyielded MA = 0·402 M1·47P (r2 = 0·898)and MG = 4·63 M1·36P (r2 = 0·842). SinceMG/MA M0·11P , the biomass allocation to the gynoeciumrelative to the androecium decreased with increasing floralsize. This result was consistent with the broad interpecificcomparison based on 90 species with perfect flowers . Regressionof the data for imperfect flowers yielded MA = 0·151M1·02P (r2 = 0·675) and MG = 4·68 M1·47P(r2 = 0·996), indicating a near allometric relation forthe androecium and a strong positive anisometry for the gynoecium.Thus, for flowers of comparable size, a loss of female genderobtains a modest to significant again in androecial biomasswhereas the loss of male gender yields only a slight increasein gynoecial biomass. Collectively, the results of these studies indicate that biomassallocation patterns are size-dependent phenomena whose complexitieshave been largely ignored in the literature.Copyright 1993,1999 Academic Press Allometry, floral biomass, reproduction 相似文献