Effect of Sodium Dodecyl Sulfate on Structure and Spectroscopic Characteristics of Water-Soluble Chlorophyll Protein Complex Isolated from Stems of Lepidium virginicum

The relationship between structure and spectroscopic characteristicsof the watersoluble chlorophyll protein complex isolated fromstems of Lepidium virginicum (CP663S) was studied. Additionof 0.08% SDS induced a red shift of the 663 nm absorption maximum.At the same time, under excitation at 435 nm, the maximum offluorescence emission shifted from 672 nm to 675 nm and thefluorescence yield increased. When CP663S was excited at 480nm, the 660 nm emission band of chlorophyll b became more prominent.Fluorescence lifetime of emission from chlorophyll a increasedon addition of SDS. The energy transfer from chlorophyll b tochlorophyll a was decreased by the SDS addition, as judged bythe fluorescence spectra and lifetime measurement. Symmetricalpositive and negative peaks of the circular dichroism (CD) spectrumaround 669 nm, which indicate the interaction between chlorophylla molecules at short distances, disappeared after addition ofSDS. These SDS-induced changes of spectroscopic characteristicsoccurred in similar SDS concentration ranges and were reversible.SDS polyacrylamide gel electrophoresis cleaved CP663S into subunits.Chlorophyll molecules moved with protein moieties. Glutaraldehydetreatment suppressed the effects of SDS on absorption, fluorescenceand CD characteristics. We conclude that chlorophyll moleculesin CP663S are in the hydrophobic region of the protein and theinteraction between chlorophyll a molecules occurs at shortdistances. Changes of spectroscopic characteristics are a resultof cleavage of CP663S. ¹Present address: National Institute for Basic Biology, Okazaki444, Japan. (Received November 22, 1982; Accepted May 31, 1983)     

Time-Resolved Spectroscopy of Chlorophyll-a like Electron Acceptor in the Reaction Center Complex of the Green Sulfur Bacterium Chlorobium tepidum

The absorption changes of chlorophyll (Chl) a-like pigments(C670) were studied by ns-ms laser spectroscopy at 77 K in theuntreated and urea-treated homodimeric reaction center (RC)complex of the green sulfur bacterium Chlorobium tepidum. Theuntreated RC complex contained 9 molecules of C670 in additionto 41 molecules of Bchl a and 0.9 molecules of menaquinone-7per one primary electron donor Bchl a dimer (P840). Upon photo-oxidationof P840, C670 showed an absorption change of a red-shift withan isosbestic wavelength at 668 nm. The absorption change ofP840 decayed with time constants (t_1/e) of 55 and 37 ms at 283and 77 K, respectively, and was assigned to represent the chargerecombination between P840⁺ and FeS^–. In the urea-treatedRC complex, a bleach peaking at 670 nm with a shoulder peakat 662 nm, which is ascribable to the reduced primary electronacceptor A₀^–, was detected after the laser excitationin addition to the shift at 668 nm indicating the formationof the P840⁺A₀^– state. The P840⁺A₀^– state decayedwith a t_1/e of 43 ns at 77 K and produced a triplet state p840^Tdue to the suppression of the forward electron transfer. Theseresults indicate the two different types of C670 species inthe RC complex; the one peaking at 670 nm functions as A⁰, whilethe other peaking at 668 nm shows the electrochromic shift,which presumably functions as the accessory pigment locatedin the close vicinity of P840. (Received May 17, 1999; Accepted July 14, 1999)     

Pigment Composition of a Novel Oxygenic Photosynthetic Prokaryote Containing Chlorophyll d as the Major Chlorophyll

The principal pigment found in the majority of oxygenic photosyntheticorganisms is known to be chlorophyll a. However, we isolateda new oxygenic photosynthetic prokaryote that contained chlorophylld as a predominant pigment with chlorophyll a being a minorpigment. Chlorophyll d had previously been noted but its naturaloccurrence and function remained unclear. Cells of the new prokaryotehad an absorption maximum at red region of 714–718 nmdue to chlorophyll d absorption, but no characteristic absorptionpeak of chlorophyll a around 680 nm was observed. Chlorophylld of the new organism was identified spectrophotometricallyin several solvents and its chemical structure was confirmedby NMR and FABMS analysis. The cell also contained a chlorophyllc-like pigment, zeaxanthin and a-carotene but not chlorophyllb and ß-carotene. The content of chlorophyll d accountedfor more than 2% of the cell dry weight, while the content ofchlorophyll a was less than 0.1%. The chlorophyll a/d ratioremained between 0.03 and 0.09 under different culture conditions.The light absorption characteristics and the high content ofchlorophyll d along with the small content of chlorophyll aindicated the existence of a new light utilization mechanisminvolving chlorophyll d. (Received October 7, 1996; Accepted December 16, 1996)     

Temperature-Induced Change of Chlorophyll a Forms in Phosphatidylcholine Liposomes

Absorption spectra of chlorophyll a in phosphatidylcholine liposomesat different temperatures were analyzed by a curve fitting method.The absorption spectrum was found to be composed of one majorband with a peak at 670–671 nm and minor bands with peaksat 650–652, 662–663 and 684–686 nm. Upon coolingbelow the phase transition temperature of the lipid, the componentabsorbing at 670–671 nm increased significantly at theexpense of the component absorbing at 662–663 nm. No changein the extents of other bands was observed. ¹ CIW-DPB Publication No. 795. ²On leave from the Department of Biology, Faculty of Science,Kanazawa University, Marunouchi, Kanazawa 920, Japan. (Received December 20, 1982; Accepted April 27, 1983)     

Growth of grana from "primary" thylakoids in Phaseolus vulgaris

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; )     

Active oxygen participation in chlorophyll destruction and lipid peroxidation in SO2-fumigated leaves of spinach

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 O_2^–. (Received May 15, 1980; )     

Active oxygen participation in chlorophyll destruction and lipid peroxidation in SO2-fumigated leaves of spinach

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 O_2^–. (Received May 15, 1980; )     

Properties of light-harvesting chlorophyll a/b-protein, and photosystem I chlorophyll a-protein, purified from digitonin extracts of spinach chloroplasts by isoelectrofocusing

A procedure for purifying both light-harvesting chlorophylla/b-protein and photosystem I chlorophyll -protein from digitoninextracts of spinach chloroplasts is described. This procedureuses isoelectrofocusing on Ampholine at the last step and permitsisolating all of the chlorophyll-proteins from the same extractin a better yield and a highly pure state. The purified light-harvesting chlorophyll a/b-protein whichhas an isoelectric point (pi) of 4.35 (?0.1) and a single polypeptideof 24 kilodaltons (kD), shows slightly higher chlorophyll a/Aratio of 1.35 than the values reported for the preparationsobtained by anionic detergents. This chlorophyll-protein exhibitsa markedly high and sharp fluorescence band at 681 nm at 77?Kwhich is not found on the chloroplast emission spectrum. Photosystem I chlorophyll a-protein focuses on Ampholine intotwo bands with pi values of 4.75 (?0.1) and 4.80 (?0.1). Thesetwo fractions show the same absorption spectra (maximum at 678nm at room temperature) and emission spectra (maximum at 734nm at 77?K) and have the same constituent polypeptides: onelarge band at 55–64 kD and six minor bands (21.5, 20,19, 18, 16 and 15 kD). The polypeptide composition and the P-700to chlorophyll a ratio (1 to ca. 80) of this preparation arevery similar to those of the photosystem I reaction center preparationobtained from Swiss chard chloroplasts by Bengis and Nelson(8). (Received October 31, 1978; )     

The Influence of Stress Conditions on Chlorophyll Content of Two Range Grasses with Contrasting Photosynthetic Pathways

The influence of various treatments and temperature regimeson total chlorophylls and on the chlorophyll a:b ratio of westernwheatgrass and blue grama plants was investigated at differenttime intervals during the 120-day growth period. Western wheatgrass,a C₃ species, accumulated greater amounts of chlorophyll thandid blue grama plants, a C₄ species. Maximum concentrations(mg gd wt^–1) of chlorophylls in western wheatgrass andin blue grama were recorded at the lower (13/7°C) and higher(30/18°C) temperature regimes. Nitrogen fertilizer alonedecreased the chlorophyll content in both species. The chlorophylla:b ratio in blue grama ranged from an average of 2·00under irrigated plus fertilized conditions to 3·00 undercontrol and fertilized conditions. On the other hand, the chlorophylla:b ratio in western wheatgrass remained constant at 3·00throughout the growing season under various treatments and temperatureregimes.     

Phase Transition Temperatures Determined for Chloroplast Thylakoid Membranes and for Liposomes Prepared from Charged Lipids Extracted from Thylakoid Membranes of Higher Plants

Lipid phase separation temperatures of intact thylakoid membranesfrom a number of chilling sensitive plants were measured usingchlorophyll a as the intrinsic fluorescent probe. The phospho-and sulfolipids were extracted from the thylakoid lamellae ofthese plants and purified by silicic acid column and thin layerchromatographies. These separated lipids were eluted and recombinedto give a total charged anionic thylakoid lipid fraction thatwas used to prepare liposomes containing purified chlorophylla as the fluorescent probe. The phase separation temperaturesof these liposomes were compared to phase separation temperaturesin intact thylakoid membranes isolated from the same plants. The chilling-sensitive plants—corn, pepper, tomato andwater hyacinth — showed phase separation temperaturesranging from 9 to 19°C for both the liposomes and the thylakoidmembranes. In addition, low temperature phase separations wereseen from –21 to –27°C. Mimulus, which is notas chilling sensitive as the former plants, had a phase separationtemperature near 0 to 2.5°C and at –27°C. In general,there was a good agreement between the phase separation temperaturesof intact thylakoids and the purified anionic lipid fractionextracted from these thylakoids. Similar results were obtained using either trans-parinaric acidor chlorophyll a as the fluorescent probe in liposomes madefrom anionic thylakoid lipids or in liposomes prepared frompure dimyristoyl phosphatidyl choline, distearoyl phosphatidylcholine, or mixtures of equal amounts of these phospholipids. ¹ CIW-DPB Publication # 728. ³ Present address: Laboratory of Experimental Physics, Departmentof Biophysics, State University of Utrecht, Princetonplein 5,Utrecht, The Netherlands. (Received January 18, 1981; Accepted July 2, 1981)     

The use of high-spectral-resolution radiometer data for detection of low chlorophyll concentrations in Lake Kinneret

Chlorophyll distribution in Lake Kinneret was estimated in aperiod of low chlorophyll-a concentrations (3–7 mg m^–3)using remotely sensed data. The data set included high-spectral-resolutionradiometric measurements in the range 400–750 nm, chlorophylland suspended matter concentrations, Secchi disk transparencyand vertical attenuation coefficients at 20 stations. The spectroradiometricdata were used to create the algorithms suitable for quantitativedetermination of chlorophyll content. The present paper presentsexperimental field evidence showing that fluorescence can besuccessfully used for remote monitoring of chlorophyll-a content(with an estimation error <0.5 mg m^–3) in productiveinland waters with a background of variable and relatively highsuspended matter concentration.     

The presence of chlorophyll b and the estimation of phaeopigments in marine phytoplankton

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 (120–140 m). ¹Present address: Marine Biology Research Division, A-002, ScrippsInstitution of Oceanography, La Jolla, CA 92093, USA     

Effects of Light on Degradation of Chlorophyll and Proteins during Senescence of Detached Rice Leaves

Regulatory effects of light on senescence of rice leaves wereinvestigated by measuring degradation of chlorophyll and proteinsin leaf segments which had been kept in the dark or under illuminationwith light of different intensities and colors. When leaveshad been left in total darkness for three days at 30°C,there was an initial long lag that lasted for one whole dayand then chlorophyll was rapidly degraded in the second andthird days. Breakdown of chlorophyll was strongly retarded bycontinuous illumination with white light of intensity as lowas 0.5 µmol photons m^–2 s^–1 but the effectof light decreased at intensities above 10 µmol photonsm^–2 s^–2. The initial lag and subsequent degradationof chlorophyll in the dark were little affected by illuminationwith red or far red light at the beginning of dark treatment.However, a brief illumination with red light at the end of thefirst and/or second day significantly suppressed degradationof chlorophyll during subsequent dark periods and the effectof red light was nullified by a short irradiation with far redlight. Thus, degradation of chlorophyll is regulated by phytochrome.Thylakoid membrane proteins and soluble proteins were also largelydegraded during three days in the dark. Degradation of membraneproteins such as the apoproteins of light-harvesting chlorophylla/b proteins of photosystem II and chlorophyll a-binding proteinsof reaction center complexes showed a long lag and was stronglysuppressed by illumination with weak white light. Thus, theloss of chlorophyll can be correlated with degradation of chlorophyll-carryingmembrane proteins. By contrast, light had only a weak protectingeffect on soluble proteins and ribulose-1,5-bisphosphate carboxylase/oxygenaserapidly disappeared under illumination with weak white light.Thus, breakdown of thylakoid membrane and soluble proteins aredifferently regulated by light. Artifacts which would be introducedby detachment of leaves were also discussed. ¹ Present address: Department of Applied Biology, Faculty ofScience and Technology, Science University of Tokyo, Yamazaki,Noda-shi, Chiba, 278 Japan. ² Present address: Department of Life Science, Faculty of Science,Himeji Institute of Technology, Harima Science Park City, Hyogo,678-12 Japan.     

Can phaeopigments be used as markers for Daphnia grazing in Lake Constance?

The formation of chlorophyll a degradation products was measuredwith natural phytoplankton from Lake Constance and Daphnia magnaand native Daphnia as grazers in grazing experiments duringspring bloom conditions using high-pressure liquid chromatography(HPLC). Chlorophyll a start concentrations were between 1.2and 16.3 µg l^–1; phaeopigment weights constituted5% of chlorophyll a weight. Only phaeophorbide a was a markerfor Daphnia grazing; concentrations of other phaeopigments (phaeophytina, chlorophyllide a and two unidentified phaeopigments) didnot increase during Daphnia grazing. Conversion efficiencies(chlorophyll a to phaeophorbide a) were between 0 and 43% ona weight basis, and between 0 and 65% on a molar basis. Conversionefficiencies were highest at high grazer density (40 Daphnial^–1) and after a 24 h exposure time. Grazing by microzooplanktonprobably led to the formation of the two unidentified phaeopigments.In Lake Constance, Daphnia density was significantly positivelycorrelated with the phaeophorbide a/chlorophyll a ratio whenit was <5000 Daphnia m^–3. However, when higher Daphniadensities were included in calculations, then Daphnia densitywas positively, but insignificantly, correlated with the phaeophorbidea/chlorophyll a ratio. This suggests that when the level offood per Daphnia is low, then grazing is more efficient withless production of phaeophorbide a and a higher production ofcolourless products.     

CHANGES IN EMISSION SPECTRA OF PHOTOSYNTHETIC PIGMENTS IN VIVO

1. 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 730–740mµ.These two bands probably arise from chlorophyll a(C_f684) belongingto pigment system II.
2. 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, C_f-1) in pigment systemI.
3. 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.
4. These facts were interpreted in terms of the correlation offluorescence of chlorophyll a and the photochemical reactionsof photosynthesis

(Received July 20, 1967; )     

Artificial Quinones Replace the Function of Quinone Electron Acceptor (QA) in the Isolated D1-D2-Cytochrome b559 Photosystem II Reaction Center Complex

Various benzo- and naphthoquinone derivatives were introducedinto the purified photosystem II Dl-D2-cytochrome b₅₅₉ reactioncenter complex, which lacks the intrinsic plasto-quinone electronacceptors. Effects of these quinones on the electron transferreactions in nanoseconds to milliseconds time range were studiedat room and cryogenic temperatures. 1) The addition of quinonesto the purified photosystem II reaction center complex suppressedthe nanosecond charge recombination between oxidized reactioncenter chlorophyll a (P680⁺) and reduced pheophytin a (Ph^–),and stabilized P680⁺ up to millisecond time range at 280 K andat 77 K. 2) In the reaction center complex supplemented withdibromothymoquinone (DBMIB), P68O was almost fully oxidizedand cytochrome b₅₅₉ was partially reduced by flash excitation.A semi-quinone-like signal with a peak around 320 nm was alsoinduced but the shift of pheophytin absorption band (C55O) wasnot observed. 3) Halogenated quinones, especially DBMIB, werebetter electron acceptors than unsubstituted or methylated quinones.4) The affinities of quinones to the reaction center complexwere weakly dependent on their molecular structure. (Received July 9, 1991; Accepted August 15, 1991)     

Comparison of main emissions at--196?C from phycobilisomes of two blue-green algae Anabaena cylindrica and Anacystis nidulans

Main emissions at—196?C from phycobilisomes of two blue-greenalgae Anabaena cylindrica and Anacystis nidulans were studiedwith special reference to allophycocyanin (APC) B content. Supplementaryexperiments were done with Anabaena variabilis (M-2 and M-3).The main emission from phycobilisome of Anacystis nidulans richin APC B was located at 681 nm. The location was identical tothat of the main emission from APC B but at a shorter wavelengththan that of in vivo emission (685 nm). Results indicate thatAPC B acts as the energy output of phycobilisomes, but thatthe in vivo 685 nm emission is not attributed to APC B. The main emission of the phycobilisome of Anabaena cylindricawas always located at 685 nm irrespective of the preparationmethod; 0.75 M phosphate buffer [Plant Physiol., 63: 615–620(1979)] or 30% polyethylene glycol [Special Issue of Plant &Cell Physiol., No. 3, p. 23–31 (1977)]. This alga alsocontained a special form of APC, but its content was very low.The location of its emission band (681 nm) was identical tothat of APC B, but shorter than that of the main band of phycobilisomes(685 nm). The 685 nm emitter in phycobilisomes showed a charactersimilar to chlorophyll a but not phycobiliproteins in treatmentsfor aqueous extraction or methanol extraction. Results indicatethat the pigment is probably chlorophyll a as we assumed previously.The 685 nm emission from phycobilisomes of Anabaena variabilis(M-2 and M-3) showed the same character. Results were interpreted as indicating that (i) the contentof the special form of APC varies with the species or strainof blue-green algae and (ii) the energy at the phycobilin levelis transferred directly from APC to pigment system II chlorophylla when the amount of the special form of APC is low. (Received October 24, 1979; )     

Chlorophyll a forms in mesophyll and bundle sheath chloroplasts of Zea mays leaves grown at low light intensity

Mesophyll and bundle sheath chloroplasts were prepared fromleaves of Zea mays grown at light intensities of 1.1 and 240µW/cm², respectively. The mesophyll chloroplasts thatdeveloped at the low intensity and bundle sheath chloroplatsthat developed at both low and high intensities showed higherratios of chlorophyll a/b and P700/chlorophylls compared withthe normal ratios found for the mesophyll chloroplasts thathad developed at the high intensity. Derivative absorption spectrophotometryat 77?K revealed that the low intensity mesophyll chloroplastscontained more of chlorophyll a forms with longer wavelengthred bands than high intensity mesophyll chloroplasts. More ofthe longer wavelength forms of chlorophyll a were also presentin the bundle sheath chloroplasts that had developed at lowand high intensities. All these four types of chloroplasts showedtwo peaks of fluorescence, one at 687 hra and the other at 733or 738 nm. In addition to these peaks, the high intensity mesophyllchloroplasts showed a shoulder at 697 nm, and the two typesof bundle sheath chloroplasts showed a shoulder at 680 nm. (Received June 17, 1974; )     

Photoacclimation in the marine alga Nannochloropsis sp. (Eustigmatophyte): a kinetic study

Exponentially growing cultures of Nannochloropsis sp. were transferredfrom high light (650 µ.mol quanta m^–2 s^–1)to low light (30 (µrnol quanta m^–2 s^–1). Thekinetics of changes in the various parameters of the photoacclimationprocess were followed until steady state was reached. In thisorganism, the observed 4.25 increase in cellular chlorophylla in the low-light-acclimated cells was linearly correlatedwith an increase in the number of photosynthetic units (PSU),while the PSU size remained constant. The new steady state wasreached after a transition period of 87 h and following an initialovershoot in the chlorophyll a concentration. During the processof photoacclimation, harvested and utilized light was increaseddue to a combination of increased cellular chlorophyll and anincrease of the quantum yield. These improvements in efficiencywere coupled with the reduction of respiration. The overalleffect of photoacclimation, therefore, amounted to reducingthe impact of low light on the growth rate of the algae. Ourstudy demonstrates the importance of the photoacclimation processin the context of the planktonic way of life. An index of the'effectiveness of photoacclimation' is proposed.     

Spectral effectiveness in chlorophyll and 5-aminolevulinic acid formation during regreening of glucose-bleached cells of Chlorella protothecoides

Regreening of glucose-bleached cells of Chlorella protothecoidesis stimulated by light. Spectral effectiveness in the processshowed maxima around 370, 440 and 480 nm, suggesting a flavoproteinas primary photoreceptor. Action spectra of ALA synthesis provedto be similar to those of chlorophyll formation, indicatingthat light stimulation of greening in this alga is regulatedat the first step of chlorophyll biosynthesis. ¹ Present address: Institute of Applied Microbiology, Universityof Tokyo, Tokyo 113, Japan. (Received March 27, 1978; )