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; )     

The Occurrence of Rhodoxanthin in Red-leaved Seedlings of Agathis australis Salisb.

A red carotenoid pigment was isolated by paper chromatographyfrom extracts of leaves of red pigmented Agathis australis seedlings.The position and shape of the absorption spectra of this pigmentin three solvents was identical with those for rhodoxanthinisolated from the arils of Taxus baccata fruit. The behaviourof the red pigment on partitioning between petroleum ether and90 per cent, methanol, its position on sucrose, celite, andmagnesium oxide columns and its solubility in various solventswas consistent with this conclusion. The red leaf pigment andrhodoxanthin could not be separated when co-chromatographedin two solvent systems. The concentration of this pigment inred seedlings was c. 25 times greater than that in green seedlingswhile the chlorophyll content in the former was half that ofthe latter. The implications of these findings are discussed.     

Pigment ingestion and egg production rates of the calanoid copepod Temora longicornisr. implications for gut pigment loss and omnivorous feeding

We examined the relationship between egg production rate (E)and pigment ingestion rate (I, from gut content corrected for33% loss) for adult female Temora longicornis in Long IslandSound on 47 occasions. Linear regression of E on I [both variablesexpressed in mass of nitrogen (N) female^–1 day^–1]was: E_N = 0.0016 + 0.770 x I_N. The slope, 0.77, is the apparentgross efficiency of egg production, equivalent to the grossgrowth efficiency (GGE) assuming that females partition allnitrogen for growth into egg production. Published work suggeststhat a GGE of 0.37 would be expected for herbivorous copepods.The discrepancy between the expected value of 0.37 and observedvalue of 0.77 could result from unquantified losses of gut pigmentor because T.longicomis ingested a significant amount of nitrogenby feeding as a carnivore. We suggest that if T.longicomis femalesderive all of their nitrogen for growth by feeding on phytoplankton,and if no correction for pigment loss is employed, then thegut pigment method underestimates pigment ingestion by no morethan a factor of two.     

A Parallel Study of Pigment Bleaching and Cytochrome Breakdown during Aging of Thylakoid Membranes

Aging of freshly isolated thylakoid membranes from spinach leaves(Spinacia oleracea L.) leads to dramatic alterations in boththe cytochrome (b_{559 (HP)} and f) composition and pigment (chlorophyllsa and b and ß-carotene) content. These changes occurat a faster rate under anaerobic conditions or after heatingthylakoid membranes, and in light as well as in darkness. Inaddition, when thylakoid membranes are heated at 78°C for8 min, or incubated in the presence of an emulsion of linoleicacid, a huge decrease in both cytochrome (particularly cyt.b_{559 (HP)}) and pigment contents occur. Whatever the experimentalconditions, cytochrome b_{559 (HP)} destruction occurs as soonthe aging process starts. Conversely, pigment bleaching is detectableafter an initial lag phase of about 60–70 min. Then, thetwo processes (cytochrome breakdown and bleaching of pigments)appear to take place in parallel. The addition of salicylhydroxamicacid or 8-hydroxy-quinoline, two radical scavenger components,to the aging medium strongly reduces the rate and extent ofcytochrome breakdown and pigment bleaching. On the basis of these results, a tentative scheme accountingfor the bleaching of pigments and the breakdown of cytochromesduring aging in vitro of thylakoid membranes is proposed. Itis suggested that these changes are mediated via a non-enzymaticmechanism in which free radicals could be implicated. The possiblerole of free radicals inducing ultrastructural changes at thelevel of chloroplast membranes in senescent leaves is also considered. (Received October 11, 1985; Accepted January 24, 1986)     

Some properties of the chlorophyll fluorescence of the diatom Phaeodactylum tricornutum

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 (10⁴–10⁵ 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; )     

Further Investigations of Liposoluble Fluorescent Compounds in Senescing Plant Cells

The accumulation of liposoluble fluorescent compounds with excitationand emission fluorescent maxima in the bands of 350–370nm and 410–440 nm respectively has been observed in thedegrading (the late stationary phase) blue-green algae Anabaenavariabilis K?tz and Anabaena cylindrica Lemm. cells, in thedark-senescing cotyledons from Phaseolus vulgaris L., and inmore than 1-year-old leaves of evergreen plants (Ligustrum japonicumThunb. and Osmanthus fortunei Carr.)- Spectral and chromatographicproperties of the compounds are rather similar to those previouslydescribed in the cells of other senescing plant species. Therole of lipid peroxidation in the formation of fluorescent pigmentsand in the ageing of plant cells is discussed. Key words: Fluorescent pigment, Anabaena sp, Senescence     

Ageing of Euglena chloroplasts in vitro I. Variations in pigment pattern and in morphology

Isolated chloroplasts of Euglena gracilis Klebs were kept for10 d in complete darkness at 4 C in a maintenance buffer (pH7.5) without shaking. During incubation, the qualitative andquantitative changes in the pattern of photosynthetic pigmentswere evaluated by the combined use of spectrophotometry in thevisible range of whole chloroplasts and their acetone extracts,of in vivo spectrofluorimetry and of reversed-phase HPLC. Microscopicand submicroscopic modifications were also followed by UV andtransmission electron microscopy. The main findings were as follows: (1) a fast decay of all photosyntheticpigments, chiefly chlorophylls, not accompanied by evident signsof alteration of the thylakoid system during the first 5 d;(2) a higher stability of PSII compared to PSI and of antennacomplexes compared to the relative reaction centres during thefirst 24–48 h; (3) a low accumulation of phaeoderivativecompounds in spite of the marked decrease of chlorophyll content;(4) a lack of dephytylated compounds; (5) a quicker decay ofthe intensity of fluorescence emission with respect to the decreasingchlorophyll a content; and (6) a fast degradation of xanthophyllsand ß-carotene with the consequent lack of defencefrom the ageing oxidative stresses. This accounts for the rapidloss of pigments, although the lack of other antioxidant defencemechanisms is not excluded. The characterization of some of the steps involved in plastiddegradation may render this experimental model viable for furtherstudies on plastid senescence, a multifactorial process stillawaiting definite answers. Key words: Euglena gracilis, ageing, isolated chloroplasts, morphological changes, pigment degradation     

Revision of the genus Stentor Oken (Protozoa, Ciliophora) and description of S.araucanus nov. spec, from South American lakes

Stentor is a heterolrich ciliate which often forms lawn-likecovers on the bottom and/or blooms in the pelagial of lakesworldwide. The species involved in these spectacular eventswere usually either not determined or misidentified becausethe keys are outdated and incomplete. Thus, we have revisedthe nominal species described since the first major revisionby Ehrenberg (1838). Main species characteristics are the presence/absenceof symbiotic algae, the shape of the macronucleus and the colourof the cortical pigment granules. The last character mentionedmust be studied in live cells because the pigment bleaches inchemically fixed specimens. Nineteen valid species are recognizedand dichotomously keyed according to these characteristics.Twenty-seven other species and varieties, described after Ehrenberg'srevision, are synonyms or species indeterminata A new species.S.araucanus, is described from South American lakes. It is asmall, broadly trumpet-shaped Stentor with symbiotic algae,vermiform macronucleus and blue-green cortical granules. Stentoraraucanus is probably euplanktic and restricted to the southernhemisphere. Stentor auriculalus Kahl. 1932 sensu Wang (1934)is recognized as a new species, Condylostoma wangi, and transferredto the genus Condylostoma. New nomenclatural corrections: Stentorbaicalius nom. nov. (pro S.pygmaeus, preoccupied). S loricatiisnom. corr. (for S.loricata), S.ruber nom. corr. (for S.ruhra).     

Accumulation of Pigments during the Greening of Etiolated Seedlings of Hordeum vulgare L.

The pigment changes that occur during transformation of etioplaststo fully developed chloroplasts have been studied in seedlingsof barley (Hordeum vulgare L.) by greening with white lightof low (15–25 µmol m^–2 s^–1) and medium(150 µmol m^–2 s^–1) intensity. At least 24h longer was required in the low light regime for the same concentrationof pigment to be accumulated in the seedlings. The increasein pigment content was mainly due to the synthesis of chlorophyllsa and b. Of the carotenoids present, the increases in the levelsof neoxanthin and, especially, ß-carotene were muchgreater than those observed for the other carotenoids. Levelsof lutein also increased but this change was small by comparisonto those observed for neoxanthin and ß-carotene. Inthe long-term the concentration of violaxanthin remained unalteredalthough significant transient changes were recorded. The levelsof antheraxanthin and zeaxanthin were markedly reduced duringgreening. The rate of pigment synthesis decreased with increasingcell age, i.e. from the base to the tip of the primary leaf.Overall, carotenoid levels increased by approximately 100% atthe base of the seedling but hardly at all at the tip. Key words: Hordeum vulgare, carotenoids, violaxanthin-cycle, etiolation     

Studies on the Hill reaction of membrane fragments of blue-green algae III. Fluorescence characteristics of membrane fragments of Anabaena variabilis and Anabaena cylindrica

Fluorescence spectra of the pigment system at –196°Cin membrane fragments of Anabaena variabilis and A. cylindricawere investigated. The fluorescence spectra of membrane fragments having four emissionbands at 645–655, 685, 695 and 725 nm were basically similarto those reported for intact cells of blue-green algae, thoughthe emission from phycocyanin (645–655 nm) was far strongerwith membrane fragments than with intact algal cells. Incubation of membrane fragments of A. variabilis in a dilutebuffer (10^–2M, pH 7.5) caused an increase in the 645 nmfluorescence and slight decreases in the 685 and 695 nm fluorescences,but had no influence on the 725 nm fluorescence. The decreasein the 685 and 695 nm fluorescences of A. cylindrica was moremarked and had the same kinetics as the inactivation of photosystemII reaction measured by DPIP-photoreduction. When membrane fragments of A. cylindrica were incubated in thebuffer solution at room temperature or in the presence of MgCl₂(10^–3M) at 0°C; phycobilin aggregates, which emittedthe 655 and 685 nm fluorescence, were solubilized. This solubilizationwas not observed with membrane fragments of A. variabilis. (Received August 31, 1972; )     

Studies on flower color in Chrysanthemum morifolium RAMAT. I. Anthocyanins

Isolation and characterization of anthocyanins from the flowersof two cultivars of Chrysanthemum morifolium RAMAT. are reported.The main pigment is a new glucoside of cyanidin. ¹Cultivated at the Kyoto University Agricultural ExperimentalFarm (Received October 25, 1969; )     

Influence of phytoplankton composition and stratification degree on gut pigment content of Ceriodaphnia sp. at dawn

Very short-term feeding activity of the cladoceran Ceriodaphniasp. was investigated in situ in a eutrophic reservoir in thesouth of Spain, using fluorimetric analysis of the gut pigmentcontent in periods when the water column was relatively mixedor strongly stratified. The results obtained in the mixed watercolumn showed a clear increase in gut pigment content at dawn,a period sampled with high frequency. The accumulation of thecladoceran at the depth of maximum concentration of phytoplankton,and the high gut pigment concentration in cladocerans at thatdepth just after dawn, suggested active feeding of Ceriodaphniaon phytoplankton at that time. During stratification, the abundanceof Ceriodaphnia was higher, but the gut pigment contents werevery low and they did not reflect any clear feeding patterns,with either time or depth. Changes in phytoplankton concentrationand composition between the relatively mixed and the stratifiedwater column suggest a shift in feeding activity from herbivorousto.     

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; )     

Pigment Bodies in Fruits of Crimson and High Pigment Lines of Tomatoes

Pigment bodies in fruits of crimson (og^c), high pigment (hp),and crimson-high pigment (og^c hp) lines of tomatoes were observedby electron and light microscopy and compared with those ofnormal red lines and a yellow cultivar. During chloroplast-chromoplasttransformation, two main structurally distinct bodies are produced,their total and relative amounts apparently accounting for theentire range of colours (from very deep red to yellow) characterizingthe mature fruits of these different colour lines. The longnarrow crystalloids, believed to be lycopene, form in associationwith an extended thylakoid system; in senescing (over-ripe)fruit many of these are reduced to shorter irregular forms.The rounded globules are believed to be beta-carotene dissolvedin lipid material derived from membrane lysis. Analytical resultscorroborate microscopic observations that the effect of theog^c gene, as compared with the r⁺ gene for normal red colour,is to increase the lycopene content and lower the beta-carotenecontent. The effect of the hp gene is to increase the levelsof both pigments. The results support the view that the genescontrol the development of fruit pigments which affect chromoplastultrastructure. Lycopersicon esculentum Mill, tomato, fruit, pigment bodies, beta-carotene, lycopene     

Stability of YACs Containing Ribosomal or RCP/GCP Locus DNA in Wild-type S. cerevisiae and RAD Mutant Strains

About 2% of human YAC clones, including tandemly repeated segmentscolor vision pigment DNA, ribosomal DNA and alphoid DNA havebeen reported to be inherently unstable in yeast hosts, producingmore stable deletion products. YACs containing color visionred pigment gene DNA or 1.5 rDNA tandem repeat units were transformedinto hosts bearing lesions at the RAD1, RAD6, RAD51, or RAD52loci. YACs susceptible to deletion during outgrowth of wild-typecells (or in preliminary experiments, in RAD6 transformants)were stable for up to 100 generations or more in the other strains.Thus both the RAD1 and RAD51/RAD52 epistatic pathways are apparentlyinvolved in the instability of YACs containing tandem repeatloci, presumably during recombination-based deletion formation;and a yeast host disarmed in these pathways will likely maintainYACs intact that are otherwise unstable.     

Grazing experiments with two freshwater zooplankters:fate of chlorophyll and carotenoid pigments

In order to evaluate the validity of the gut pigment methodto assess grazing and diet in two freshwater zooplankters, experimentswere carried out to check chlorophyll a and xanthophyll conservationduring feeding. For both animals, two sets of experiments wereconducted by incubating animals in the laboratory, either isolatedfrom a reservoir (the calanoid copepod, Eudiaptomus gracilis)or cultured under high-food conditions (the cladoceran, Daphniagaleata). For both animals, gut pigments and clearance rateson different types of algae were determined from the same incubations.Chlorophyll a and derivatives, as well as major algal carotenoids,were analysed by High Performance Liquid Chromatography (HPLC).In copepods, the pigment profiles from the gut extracts reflectedthe diet of the animals poorly. The animal extracts containedalmost exclusively alloxanthin (or an alloxanthin-like pigment)in large amounts, whereas the other pigments were lost in highproportions (>70% for lutein and fucoxanthin; 57 and 78%for a-phorbins). The cladocerans fed on the main types of algaeabundant in the suspensions, with a preference, however, forsmall cells. Although the main xanthophylls from these algaewere detected in the Daphnia extracts, some destruction of luteinand fucoxanthin may have occurred (18.7 and 30%). The loss ratefor alloxanthin seemed more variable (0 and 68%), possibly dependingon food concentration. As for the transformation of a-phorbins,E.gracilis and D.galeata behaved quite differently. The HPLCprofiles of copepod extracts always showed a very small chlorophylla peak, along with phaeophytin a and pyrophaeophytin a. Thosefrom the cladoceran exhibited a large phaeophorbide a peak,along with some chlorophyll a and phaeophytin a. In fact, D.galeatadid not destroy a-phorbins under our experimental conditionsbut converted chlorophyll a mainly into phaeophorbide. Froma comparison of our results with data from other studies, itseems that in these two zooplankters, use of gut pigment datafor quantitative grazing assessment should be considered withcaution.     

CHLOROPHYLL FORMATION IN ISOLATED PUMPKIN COTYLEDONS IN THE PRESENCE OF KINETIN AND CHLORAMPHENICOL

Investigations have been made on the changes in the levels ofprotochlorophyll, chlorophyll a and chlorophyll b in relationto the kinetin induced expansion of isolated pumpkin cotyledonsin the presence and absence of chloramphenicol. It has been shown that rise in pigment level keeps pace withexpansion growth of the cotyledons. Kinetin markedly promotes the synthesis of protochlorphyll withoutmuch affecting the rate of its photoreduction to chlorophyll. Chloramphenicol strongly inhibits the development of both chlorophylla and b. The inhibition seems to be due to its interferenceboth with the synthesis of protochlorophyll and its subsequentconversion to chlorophyll. The inhibitory effect of chloramphenicol on the formation ofchlorophyll a is greater than on that of chlorophyll b, suggestingthereby the probability of divergent pathways for the formationof the two chlorophylls. (Received December 21, 1966; )     

Somatic Hybrids of the Forage Legumes Medicago sativa L. and M. falcata L.

Protoplasts isolated from embryogenic cell suspensions of tetraploidMedicago sativa cv. Europe (2n= 4? = 32) and M. falcata (2n=4? = 32) were fused using polyethylene glycol (PEG). Heterokaryonswere isolated by micromanipulation and cultured in the presenceof nurse protoplasts from albino or embryogenic cell suspensionsof M. sativa, to give free-floating embryos and embryogeniccalli. Ninety-nine plants were regenerated from somatic embryos.Fifteen of the plants exhibited leaf abnormalities and did notsurvive transfer from culture to the glasshouse. The remainingphenotypically normal plants were established ex vitro and floweredat maturity. Morphological and biochemical analyses confirmedthat 12 of the phenotypically normal plants were somatic hybrids.Morphological characteristics of the hybrids, including plantstature, internode length, leaf size, flower colour, and podshape, were intermediate compared with those of the purple floweredM. sativa and yellow flowered M. falcata parents. Flowers ofthe hybrids were yellow traced with purple-blue veins. Isoenzymebanding patterns for esterase showed bands additional to thoseof M. sativa and M. falcata. The chromosome complements of individualhybrids varied from (2n= 4? = 32) to 58.     

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)     

Mercury Induces Alteration of Energy Transfer in Phycobilisome by Selectively Affecting the Pigment Protein, Phycocyanin, in the Cyanobacterium, Spirulina platensis

Mercury, at a low concentration (3 µM) caused an enhancementin the intensity of room temperature fluorescence emitted byphycocyanin and induced a blue shift in the emission peak ofSpirulina cells indicating the alterations in the energy transferwithin the phycobilisomes. In vitro the isolated intact Spirulinaphycobilisomes from control cells exhibited only a reductionin fluorescence yield with low concentration of HgCl₂ withoutbeing accompanied by changes in the emission features, whereasthe isolated phycobilisomes from mercury treated cells exhibitedthe alterations in the spectral characteristics at the levelof phycocyanin. When isolated phycocyanin and allophycocyaninwere exposed to very low concentrations of Hg²* ions, C-phycocyaninexhibited a large decrease in the absorbance in the longer wavelength(615–620 nm) region, but not allophycocyanin. In addition,mercury also caused a monotonous decrease in the C-phycocyaninemission intensity at 646 nm accompanied by a blue shift to642 nm. These results on isolated C-phycocyanin suggest thatselective bleaching of beta-84 chromophore of phycocyanin isinduced by mercury. The differential effect of mercury towardsC-phycocyanin and allophycocyanin could possibly be due to thedifference in the protein conformation of phycocyanin and allophycocyanin. (Received July 11, 1990; Accepted December 17, 1990)