New chlorophyll-b forms in a chlorophyll-detergent photosynthetic model system

The absorption spectra of chlorophyll b in Triton X-100 micelles at room temperature are superpositions of components with absorption maxima at 640.8, 648.9, 659.5, 669.6, 682.1 and 695.7 nm, obtained from Gaussian analysis of the spectra. The last four forms strongly overlap the chlorophyll a forms of this system obtained with maxima at 659.3, 667.6, 674.3, 680.8, 686.5, 692.8, 701.9, 713.6 and 722.0 nm.

Since the in vivo chlorophyll a forms practically coincide with the forms found in this system, the possible existence of in vivo overlapping chlorophyll b and a forms eventually should be taken into consideration. In this case, however, the Gaussian analysis of in vivo absorption bands in itself in the proper spectrum range cannot discriminate between chlorophyll a and b components.     

PHOTOSYNTHETIC LIGHT-HARVESTING FUNCTION OF VIOLAXANTHIN IN NANNOCHLOROPSIS SPP. (EUSTIGMATOPHYCEAE)1

Whole cell absorption spectra of the Eustigmatophycean algae Nannochloropsis salina Bourrelly and Nannochloropsis sp. reveal the presence of a distinct absorption peak at 490 nm. The lack of chlorophylls b and c in these species indicates that this peak must be attributed to carotenoid absorption. In vivo fluorescence excitation spectra for chlorophyll a emission show a corresponding maximum at 490 nm. This peak is more clearly resolved than carotenoid maxima in other algal classes due to the absence of accessory chlorophylls. The carotenoid composition of the two Nannochloropsis species shows that violaxanthin and vaucheriaxanthin are the main contributors to 490 nm absorption. Violaxanthin accounts for approximately 60% of the total carotenoid in both clones. We conclude that light absorption by violaxanthin, and possibly by vaucheriaxanthin, is coupled in energy transfer to chlorophyll a and that violaxanthin is the major light-harvesting pigment in the Eustigmatophyceae. This is the first report of the photosynthetic light-harvesting function of this carotenoid.     

Long-wavelength chlorophyll forms in Photosystem I from pea thylakoids

Absorption maximum positions of three LW Chl forms in pea chloroplasts were estimated using 77 K excitation spectra of fluorescence detected in their maxima (720, 732 and 746 nm). The 705, 714 and 723 nm components were revealed in the second derivative plots of the excitation spectra. The same maxima were found in normalized excitation spectra obtained with dividing excitation spectra by absorption spectrum. It was confirmed that the observed maxima belong to absorption of LW fluorescing Chl forms. The same maxima were displayed in an action spectrum of P700 oxidation measured at room temperature. It confirms the energy transfer from LW Chl forms to P700. Close to 50% efficiency of bulk Chl forms in both excitation of LW fluorescence and P700 oxidation was found. Analysis of the shape of normalized excitation spectra suggests that there is no energy exchange among LW Chl forms. Their location and physiological role are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Light Induced Protochlorophyll–Chlorophyll a-Transformation and the Succeeding Interconversions of the Different Forms of Chlorophyll

Curve resolution into Gaussian components of the absorption spectra during the varying stages of the Shibata shift in dark grown, irradiated leaves of barley indicates that the chlorophyll a forms formed after irradiation consist of the same main components which have been reported to be present in all hitherto investigated plant materials (peak values in the red region 662, 670, 677 and 683 nm, respectively) but in varying proportions. The spectra during the Shibata shift proper can be satisfied by a mixture of two single components gradually changing their proportions, although a four component system gives a still better fit to the measured absorption curves. It is also shown that curves taken before and after the shift and added together in the appropriate proportions will match the absorption spectrum measured with peak at the isosbestic point (after ca. 15 min at room temperature).     

Photochemical and spectral properies of the photosystem I reaction centers-enriched particles]

The photosystem I reaction centers-enriched particles (RCP) having the ratio of P700/chlorophyll of 1 : 20--1 :30 were prepared from stroma lamellae photosystem subchloroplast fragments by extraction with water-saturated ether. The EPR signals and light-induced absorption changes indicate that the reaction centers are active in the particles. The spectral properties of the RCP were characterized. The main red absorption maximum is located at 673--674 nm with a "shoulder" at about 684--688 nm. A comparative analysis of the subchloroplast fragments and RCP absorption and fluorescence spectra suggests that the chl. a forms absorbed in the region of 680--695 nm are more closely associated with the reaction center. The most long-wavelength absorbing chl. a forms with maxima around 730--740 nm in the low temperature fluorescence spectra were not found in the RCP.     

Absorption and fluorescence spectra of chlorophyll-proteins isolated from Euglena gracilis

A spectroscopic study of chlorophyll-protein complexes isolated from Euglena gracilis membranes was carried out to gain information about the state of chlorophyll in vivo and energy transfer in photosynthesis. The membranes were dissociated by Triton X-100 and separated into fractions by sucrose gradient centrifugation and hydroxyapatite chromatography. Four different types of chlorophyll-protein complexes were distinguished from each other and from detergent-solubilized chlorophyll in these fractions by examination of their absorption, fluorescence excitation (400–500 nm) and emission spectra at low temperature. These types were: (1). A mixture of antenna chlorophyll a- and chlorophyll ab-proteins with an absorption maximum at 669 and emission at 682 nm; (2) a P-700-chlorophyll a-protein (chlorophyll: P-700 = 30 : 1), termed CPI with an absorption maximum at 676 nm and emission maxima at 698 and 718 nm; (3) a second chlorophyll a-protein (CPI-2) less enriched in P-700, with an absorption maximum at 676 nm and emission maxima at 680, 722 and 731 nm; (4) a third chlorophyll a-protein (CPa₁) with no P-700, absorption maxima at 670 and 683 nm, and an unusually sharp emission maximum at 687 nm. Treatment of CPa₁ with sodium dodecyl sulfate drastically altered its spectroscopic properties indicating that at least some chlorophyll-proteins isolated with this detergent are partially denatured. The results suggest that the complex absorption spectra of chlorophyll in vivo are caused by varying proportions of different chlorophyll-protein complexes, each with different groups of chlorophyll molecules bound to it and making up a unique entity in terms of electronic transitions.     

Analyses of absorption and fluorescence spectra of water-soluble chlorophyll proteins, pigment system II particles and chlorophyll a in diethylether solution by the curve-fitting method.

Absorption and fluorescence spectra in the red region of water-soluble chlorophyll proteins, Lepidium CP661, CP663 and Brassica CP673, pigment System II particles of spinach chloroplasts and chlorophyll a in diethylether solution at 25 degrees C were analyzed by the curve-fitting method (French, C.S., Brown, J.S. and Lawrence, M.C. (1972) Plant Physiol 49, 421--429). It was found that each of the chlorophyll forms of the chlorophyll proteins and the pigment System II particles had a corresponding fluorescence band with the Stokes shift ranging from 0.6 to 4.0 nm. The absorption spectrum of chlorophyll a in diethylether solution was analyzed to one major band with a peak at 660.5 nm and some minor bands, while the fluorescence spectrum was analyzed to one major band with a peak at 664.9 nm and some minor bands. A mirror image was clearly demonstrated between the resolved spectra of absorption and fluorescence. The absorption spectrum of Lepidium CP661 was composed of a chlorophyll b form with a peak at 652.8 nm and two chlorophyll a forms with peaks at 662.6 and 671.9 nm. The fluorescence spectrum was analyzed to five component bands. Three of them with peaks at 654.8, 664.6 and 674.6 nm were attributed to emissions of the three chlorophyll forms with the Stokes shift of 2.0--2.7 nm. The absorption spectrum of Brassica CP673 had a chlorophyll b form with a peak at 653.7 nm and four chlorophyll a forms with peaks at 662.7, 671.3, 676.9 and 684.2 nm. The fluorescence spectrum was resolved into seven component bands. Four of them with peaks at 666.7, 673.1, 677.5 and 686.2 nm corresponded to the four chlorophyll a forms with the Stokes shift of 0.6--4.0 nm. The absorption spectrum of the pigment System II particles had a chlorophyll b form with a peak at 652.4 nm and three chlorophyll a forms with peaks at 662.9, 672.1 and 681.6 nm. The fluorescence spectrum was analyzed to four major component bands with peaks at 674.1, 682.8, 692.0 and 706.7 nm and some minor bands. The former two bands corresponded to the chlorophyll a forms with peaks at 672.1 and 681.6 nm with the Stokes shift of 2.0 and 1.2 nm, respectively. Absorption spectra at 25 degrees C and at --196 degrees C of the water-soluble chlorophyll proteins were compared by the curve-fitting methods. The component bands at --196 degrees C were blue-shifted by 0.8--4.1 nm and narrower in half widths as compared to those at 25 degrees C.     

Red chlorophyll excitation dynamics in Arthrospira platensis photosystem I trimeric complexes as studied by femtosecond transient absorption spectroscopy

Femtosecond absorption spectroscopy was applied to study for the first time excitation dynamics in isolated photosystem I trimers from Arthrospira platensis, which display extremely long-wavelength absorption peaks. Pump–probe spectra observed at 77 K in the timescale of dozens of picoseconds upon 70-fs excitation revealed two maxima near 710 and 730 nm, which correspond to red chlorophyll forms. Bleaching at 680 nm developed in ∼200 fs, whereas the bleaching kinetics at 710 and 730 nm exhibited two components with time constants of 1 and 5.5 ps. Comparison of the kinetics of bleaching development at 710 nm and 730 nm with that of bleaching decay at 680 nm indicated that both long-wavelength forms of trimers are populated mainly via direct energy transfer from bulk chlorophyll.     

Circular dichroism and magnetic circular dichroism spectra of chlorophylls a and b in nematic liquid crystals. II. Magnetic circular dichroism spectra

Absorption and magnetic circular dichroism (MCD) spectra are reported for chlorophyll (Chl) a and Chl b dissolved in nematic liquid crystal solvents. The spectra were measured with the dye molecules oriented uniaxially along the direction of. the magnetic field and measuring light beam. It is significant that under such conditions the MCD spectra recorded in the wavelength region of the Q and Soret bands of the chlorophyll are essentially unchanged with respect to rotation of the sample cell around this axis, even though there is almost complete orientation of the chlorophyll molecules by the liquid crystals. The MCD spectra of Chl a and b in the nematic liquid crystal solvents used in this study are surprisingly similar to the spectra obtained under isotropic conditions. These results illustrate an important technique with which to examine the optical spectra of dyes oriented in liquid crystal matrices in which the anisotropic effects can be reduced the negligible proportions by the application of a strong magnetic field parallel to the direction of the measuring light beam. The first deconvolution calculations are reported that describe the deconvolution of pairs of absorption and MCD spectra, in the Q and B band regions, for both Chl a and b. The spectral analysis to obtain quantitative estimates of transition energies was accomplished by carrying out detailed deconvolution calculations in which the both the absorption and MCD spectral envelopes were fitted with the same number of components; each pair of components had the same hand centres and bandwidth values. This procedure resulted in an assignment of each of the main transitions in the absorption spectra of both Chl a and b. Chl a is clearly monomeric, with Qy, Qx, By and Bx located at 671, 582, 439 and 431 nm, respectively. Analysis of the spectral data for Chl b located Qy, By and Bx, at 662, 476 and 464 nm, respectively.     

Protochlorophyll forms in roots of dark-grown plants

Protochlorophyll was found in roots of dark-grown plants of seven species investigated. It was identified by absorbance and fluorescence spectra of acetone and ether extracts. Chlorophyll was also found in roots of one pea species. The concentration of protochlorophyll was usually highest in young root tips and decreased upwards along the roots. The maxima of the in vivo absorbance spectra of the species studied varied between 634 and 638 nm. Low temperature in vivo fluorescence emission spectra had two maxima, one at ca 633 and the other at ca 642 nm, when the wavelengths of the excitation light were 440 and 460 nm, respectively. In vivo fluorescence excitation spectra displayed a shift of the excitation maximum from 438 to 445 nm, when emission varied from 620 to 647.5 nm. Deconvolution of these three types of spectra into Gaussian components made it possible to identify two spectral forms of protochlorophyll: protochlorophyll_629–633 and protochlorophyll_638–642.     

Excitation energy transfer in the light-harvesting chlorophyll a/b.protein

The "light-harvesting chlorophyll a/b.protein" described by Thornber has been prepared electrophoretically from spinach chloroplasts. The optical properties relevant to energy transfer have been measured in the red region (i.e. 600-700 nm). Measurements of the absorption spectrum, fluorescence excitation spectrum and excitation dependence of the fluorescence emission spectrum of this protein confirm that energy transfer from chlorophyll b to chlorophyll a is highly efficient, as is the case in concentrated chlorophyll solutions and in vivo. The excitiation dependence of the fluorescence polarization shows a minimum polarization of 1.9% at 650 nm which is the absorption maximum of chlorophyll b in the protein and rises steadily to a maximum value of 13.8% at 695 nm, the red edge of the chlorophyll a absorption band. Analysis of these measurements shows that at least two unresolved components must be responsible for the chlorophyll a absorption maximum. Comparison of polarization measurements with those observed in vivo shows that most of the depolarization observed in vivo can take place within a single protein. Circular dichroism measurements show a double structure in the chlorophyll b absorption band which suggest an exciton splitting not resolved in absorption. Analysis of these data yields information about the relative orientation of the So leads to S1 transition moments of the chlorophyll molecules within the protein.     

Analysis of absorption spectra changes induced by temperature lowering on phycobilisomes, thylakoids and chlorophyll-protein complexes.

Using fourth derivative analysis, differences between room and low temperature absorption spectra were studied. The positions of most absorption bands of the water-soluble, accessory pigment complex, the phycobilisome, remained unchanged after cooling. The stability of the wavelength positions of chlorophyll a forms in vivo as a function of temperature (Gulyaev, B.A. and Litvin, F.F. (1967) Biofizika 12, 845--854) was generally confirmed. The wavelength positions of all chlorophyll a forms in the P-700 chlorophyll a protein complex were unchanged when the preparations were cooled to -196 degrees C. Likewise, with other chlorophyll-containing materials: the light-harvesting chlorophyll a/b protein complex and the thylakoids of higher plants, algae, and cyanobacteria, the wavelengths positions of most chlorophyll a forms were stable upon cooling. An exception was a 680 nm chlorophyll a band which was generally split at low temperature into two bands with the materials investigated. An interpretation of the multiplicity of chlorophyll spectral forms and the spectral changes induced by cooling for these forms is given using exciton theory and the energy-coupling variation of chlorophyll a molecules.     

Absorption and fluorescence spectra and molecular organization of bacteriochlorophyll in reaction centers of Rhodopseudomonas spheroides

Second derivative spectroscopy, computer curve analysis and Stepanov's equation show that the absorbance and fluorescence spectra of primary electron donor in reaction center of Rhodopseudomonas sphaeroides are splitting each into two asymmetric Gaussian components. Their absorption maxima at -196 degrees are 880 and 896 nm and emission maxima-906 and 923 nm, respectively. The absorption spectrum of Bchl-800 splits in the near infrared region into two bands with maxima at 790 and 803 nm. These components are ascribed to an exciton coupling in the two dimers of bacteriochlorophyll in the reaction center. The Qy transition moments of the two bacteriochlorophyll molecules of primary electron donor make an angle of 110 degrees and the angle between two Qy transitions of the pigment in Bchl-800 dimer is 150 degrees. The distance between the centers of chromophores in the dimers is estimated to be 8-11 A.     

Characterization of prolamellar bodies, from dark-grown seedlings of Scots pine, containing light- and NADPH-dependent protochlorophyllide oxidoreductase

Cotyledons of conifers have a light-independent pathway for chlorophyll biosynthesis. To investigate whether the prolamellar body of Scots pine ( Pinus sylveslris L.) is similar to the better known prolamellar body of wheat, etioplast membrane fractions were isolated from cotyledons of dark-grown Scots pine. Dark-grown cotyledons contained both chlorophyll and protochlorophyllide, 158 and 10 nmol (g fresh weight)'respectively, and had a chlorophyll a to b ratio of 4.2. The content of glyco- and phospholipids was 7.1 μmol (g fresh weight)¹. About 40 mol % of these lipids were the specific plastid lipids – monogalactosyl diacylglycerol. digalactosyl diacylglycerol and sulfoquinovosyl diacylglycerol in the relative amounts 50, 35 and 7 mol %. The mol ratio of monogalactosyl diacylglycerol to digalactosyl diacylglycerol was 1.7. Low temperature fluorescence emission spectra of intact cotyledons and homogenate showed maxima at 633, 657, 686, 696 nm and a broad peak at 725–735 nm. The maxima at 633 and 657 nm represented different forms of protochlorophyllide and the other emission maxima represented chlorophyll protein complexes. The 657 nm form of protochlorophyllide was phototransformable both in vivo and in the isolated membranes. The phototransformable protochlorophyllide was substantially enriched in the prolamellar body fraction.
The specific activity of light dependent protochlorophyllide oxidoreductase in the prolamellar body fraction was found to be 2 nmol chlorophyllide formed [(mg protein)⁻¹ min⁻¹]. The molecular weight of the enzyme polypeptide was determined as 38 000 dalton with sodium dodecylsulphate-polyacrylamide gel electrophoresis.     

Comparison of chlorophyll a spectra in wild-type and mutant barley chloroplasts grown under day or intermittent light

The absorption (640–710 nm) and fluorescence emission (670–710 nm) spectra (77 K) of wild-type and Chl b-less, mutant, barley chloroplasts grown under either day or intermittent light were analysed by a RESOL curve-fitting program. The usual four major forms of Chl a at 662, 670, 678 and 684 nm were evident in all of the absorption spectra and three major components at 686, 693 and 704 nm in the emission spectra. A broad Chl a component band at 651 nm most likely exists in all chlorophyll spectra in vivo. The results show that the mutant lacks not only Chl b, but also the Chl a molecules which are bound to the light-harvesting, Chl a/b, protein complex of normal plants. It also appears that the absorption spectrum of this antenna complex is not modified appreciably by its isolation from thylakoid membranes.Abbreviations Chl chlorophyll - DL daylight - ImL intermittent light - WT wildtype - LHC light-harvesting Chl a/b protein complex - S.E. standard error of the mean DBP-CIW No. 763.     

Spectral analysis of allophycocyanin I, II, III and B from Nostoc sp. phycobilisomes

Low temperature (-196C) and room temperature (25C) absorption spectra of a family of allophycocyanin spectral forms isolated from Nostoc sp. phycobilisomes as well as of the phycobilisomes themselves have been analyzed by Gaussian curve-fitting. Allophycocyanin I and B share long wavelength components at 668 and 679 nm, bands that are absent from allophycocyanin II and III. These long wavelength absorption components are apparently responsible for the 20 nm difference between the 680 nm fluorescence emission maximum of allophycocyanin I and B and the 660 nm maximum of II and III. This indicates that allophycocyanin I and B are the final acceptors of excitation energy in the phycobilisome and the excitation energy transfer bridge linking the phycobilisome with the chlorophyll-containing thylakoid membranes. These Gaussian components are also found in resolved spectra of phycobilisomes, are arguing against this family of allophycocyanin molecules being artifactual products of protein purification procedures.     

PHOTOSYNTHETIC LIGHT-HARVESTING FUNCTION OF VIOLAXANTHIN IN NANNOCHLOROPSIS SPP. (EUSTIGMATOPHYCEAE)1

Whole cell absorption spectra of the Eustigmatophycean algae Nannochloropsis salina Bourrelly and Nannochloropsis sp. reveal the presence of a distinct absorption peak at 490 nm. The lack of chlorophylls b and c in these species indicates that this peak must be attributed to carotenoid absorption. In vivo fluorescence excitation spectra for chlorophyll a emission show a corresponding maximum at 490 nm. This peak is more clearly resolved than carotenoid maxima in other algal classes due to the absence of accessory chlorophylls. The carotenoid composition of the two Nannochloropsis species shows that violaxanthin and vaucheriaxanthin are the main contributors to 490 nm absorption. Violaxanthin accounts for approximately 60% of the total carotenoid in both clones. We conclude that light absorption by violaxanthin, and possibly by vaucheriaxanthin, is coupled in energy transfer to chlorophyll a and that violaxanthin is the major light-harvesting pigment in the Eustigmatophyceae. This is the first report of the photosynthetic light-harvesting function of this carotenoid.     

Spectral substructure and excitonic interactions in the minor photosystem II antenna complex CP29 as revealed by nonlinear polarization spectroscopy in the frequency domain

CP29 (the lhcb4 gene product), a minor photosystem II antenna complex, binds six chlorophyll (Chl) a, two Chl b, and two to three xanthophyll molecules. The Chl a/b Q(y) absorption band substructure of CP29 (purified from spinach) was investigated by nonlinear polarization spectroscopy in the frequency domain (NLPF) at room temperature. A set of NLPF spectra was obtained at 11 probe wavelengths. Seven probe wavelengths were located in the Q(y) spectral region (between 630 and 690 nm) and four in the Soret band (between 450 and 485 nm). Evaluation of the experimental data within the framework of global analysis leads to the following conclusions: (i) The dominant Chl a absorption (with a maximum at 674 nm) splits into (at least) three subbands (centered at 660, 670, and 681.5 nm). (ii) In the Chl b region two subbands can be identified with maxima located at 640 and 646 nm. (iii) The lowest energy Q(y) transition (peaking at 681.5 nm) is assigned to a Chl a which only weakly interacts with other Chl aor b molecules by incoherent F?rster-type excitation energy transfer. (iv) Pronounced excitonic interaction exists between certain Chl a and Chl b molecules, which most likely form a Chl a/b heterodimer. The subbands centered at 640 and 670 nm constitute a strongly coupled Chl a/b pair. The findings of the study indicate that the currently favored view of spectral heterogeneity in CP29 being due essentially to pigment-protein interactions has to be revised.     

Photochromic pigments in akinetes and pigment characteristics of akinetes in comparison with vegetative cells of Anabaena variabilis

Since akinete germination is triggered by light and the action spectrum for this process has features in common with the spectra of the two photochromic pigments, phycochromes b and d, a search was made for the presence of these phycochromes in akinetes of the blue-green alga. Anabaena variabilis Kützing. Allophycocyanin-B was also looked for, since the action spectrum for akinete germination points to a possible participation of this pigment too. Isoelectric focusing was used for purification of the pigments. The different fractions were investigated for phycochromes b and d by measuring the absorbance difference spectra: for phycochrome b. 500 nm irradiated minus 570 nm irradiated, and for phycochrome d, 650 nm irradiated minus 610 nm irradiated. For determination of allophycocyanin-B. fourth derivative analysis of absorption spectra was made for some of the fractions from the isoelectric focusing column. Phycochrome b was also assayed for by measuring in vivo absorption difference spectra. The assays were positive for all three pigments. The complete photosynthetic pigment systems were also studied by in vivo fluorescence measurements on both akinetes and vegetative cells of Anabaena variabilis. Fluorescence emission and excitation spectra at selected emission wavelengths were measured at room temperature and liquid nitrogen temperature. The energy transfer from phycoerythrocyanin to phycocyanin is very efficient under all conditions, as is the energy transfer from phycocyanin to allophycocyanin at room temperature. At low temperature, however, phycocyanin is partly decoupled from allophycocyanin, particularly in the akinetes; the energy transfer from allophycocyanin to chlorophyll a is less efficient at low temperature in both types of cells, but especially in akinetes. Delayed light emission was measured for both types of cells and found to be very weak in akinetes compared to vegetative cells. From this study it would seem that akinetes lack an active photosystem II, although the 691 nm peak in the 570 nm excited low temperature fluorescence emission spectrum proves the presence of photosystem II chlorophyll, and also its energetic connection to the phycobilisomes.     

Low temperature spectral properties of subchloroplast fractions purified from spinach

Spinach (Spinacia oleracea L.) chloroplasts solubilized by digitonin were separated into five fractions by sucrose density gradient centrifugation. Three of the fractions, F_I, F_II, and F_III, corresponding to photosystem I, photosystem II, and the chlorophyll a/b complex, were purified further by two steps of diethylaminoethyl-cellulose chromatography followed by electrofocusing on an Ampholine column. The polypeptide patterns of the fractions were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the spectral properties of the fractions at −196 C determined by absorption spectra, fourth derivative curves of the absorption spectra, fluorescence emission spectra, and fluorescence excitation spectra. The activity of purified F_II (photosystem II) was also assayed by the photoreduction of dichlorophenol-indophenol at room temperature using 1,5-diphenylcarbohydrazine as the electron donor and by the photoreduction of C-550 at −196 C. The different fractions showed unique polypeptide patterns and unique sets of low temperature-absorbing forms of chlorophyll. The fluorescence emission spectra of F_I, F_II, and F_III at −196 C were also unique with maxima at 734, 685 and 681 nm, respectively. F_I showed negligible emission at wavelengths shorter than 700 nm and the long wavelength tails of F_II and F_III in the 730 nm region were relatively small (approximately 10% of emission of their wavelength maxima). Addition of 0.1% Triton to F_I and F_II caused the longer wavelength absorbing forms of chlorophyll to shift to 670 nm and the fluorescence emission maxima (of both fractions) to shift to 679 nm at −196 C with an increase in the yield of fluorescence especially in the case of F_I.