Skin colour in north Indian populations

The skin colour of six endogamous groups of north India has been studied reflectometrically. The percentage reflectance at upper arm and forchead of 650 adult males (20–25 years) is described and discussed using 601 (425 nm), 605 (545 nm) and 609 (685 nm) filters of the “EEL” spectrophotometer. The inter-group heterogeneity is revealed by variance-ratio test. The t-test has been applied to study inter-group differences in pigmentation. Some correspondence has been found in skin colour with caste hierarchy, which holds only when the populations living in the same region are compared. These differences are assigned to adaptive adjustments superimposed by caste endogamy and assortative mating for skin colour.     

Spectroscopic studies on origination of the peak at 730 nm in delayed fluorescence of chloroplasts.

The origination of the peak at 730 nm in the delayed fluorescence (DF) spectrum of chloroplasts was studied using various optical analysis methods. The DF spectrum showed that the main emission peak was at about 685 nm, with a small shoulder at 730 nm when the chloroplast concentration was < 7.8 microg/mL. The intensity of the peak at 685 nm decreased, while the intensity of the peak at 730 nm increased, when the chloroplast concentrations were increased from 7.8 to 31.2 microg/mL. With the concentration increasing, the peak at 730 nm became dominant while the peak at 685 nm finally disappeared. The DF decay kinetic curves showed that the intensity of the peak at 730 nm decayed as the same speed as the intensity of the peak at 685 nm during the entire relaxation process (0.5-30.5 s). With the excitation wavelength at 685 nm, the emission intensity was stronger in the excitation spectrum at 730 nm. The absorption spectrum demonstrated that the ratio A(685):A(730) remained almost constant when the chloroplast concentration increased. The results suggest that the peak at 730 nm appearing in DF is mainly contributed by the fluorescence of photosystem I (PSI), generated by the re-absorption of 685 nm band DF.     

A reflectometric study of the skin in Dutch families

In the period February–May 1968 the reflectances of the exposed (forehead) and unexposed (inside upper arm) skin, were measured at nine wavelengths (430, 470, 490, 520, 550, 580, 600, 660 and 685 mμ), using an “EEL” Reflectance Spectrophotometer in 100 Dutch families. The reflectance curves of upper arm and forehead show the shape usually found in white persons. The skin colour of the upper arm is lighter than that of the forehead in males and females. A difference in skin colour between males and females is observed. The forehead reflectances of males are lower than of females, and the upper arm reflectances of females are lower than those of males. A similarly directed sex difference in skin colour at the forehead has been found in other white groups. If no difference in reaction on exposure exists between both sexes, then the skin colour of the male upper arm will be lighter than that of females, although males in general are more exposed to radiation, because male arms are less uncovered than female arms. No change in skin colour at the upper arm is observed during ageing. As judged from the wavelengths concerned the changes in skin colour at the forehead during ageing result for the greater part both from a regular accumulation of melanin, and an increase in the blood flow of the skin, particularly during the years 11–25.Intrafamilial reflectance resemblances are investigated by means of correlations computed from the upper arm reflectance values measured at wavelengths 550 and 685 mμ. Significant positive correlations between the parents, 0·299 (wavelength 550 mμ) and 0·226 (wavelength 685 mμ) respectively, indicate positive assortative mating. The pattern of intrafamilial correlation coefficients suggests a role of X-chromosomal genes in the causation of the variability in the reflectances measured at wavelength 685 mμ (a measure of melanin deposition). Intrafamilial correlation computations of reflectances measured at wavelength 550 mμ (a measure of vascular response) show some positive correlations, but the role of genes in the causation of the variability in these reflectances remains unclear.     

Fluorescence emission spectra of chloroplasts and subchloroplast preparations at low temperature.

A study was made of the chlorophyll fluorescence spectra between 100 and 4.2 K of chloroplasts of various species of higher plants (wild strains and chlorophyll b mutants) and of subchloroplast particles enriched in Photosystem I or II. The chloroplast spectra showed the well known emission bands at about 685, 695 and 715--740 nm; the System I and II particles showed bands at about 675, 695 and 720 nm and near 685 nm, respectively. The effect of temperature lowering was similar for chloroplasts and subchloroplast particles; for the long wave bands an increase in intensity occurred mainly between 100 and 50 K, whereas the bands near 685 nm showed a considerable increase in the region of 50--4.2 K. In addition to this we observed an emission band near 680 nm in chloroplasts, the amplitude of which was less dependent on temperature. The band was missing in barley mutant no. 2, which lacks the light-harvesting chlorophyll a/b-protein complex. At 4.7 K the spectra of the variable fluorescence (Fv) consisted mainly of the emission bands near 685 and 695 nm, and showed only little far-red emission and no contribution of the band at 680 nm. From these and other data it is concluded that the emission at 680 nm is due to the light-harvesting complex, and that the bands at 685 and 695 nm are emitted by the System II pigment-protein complex. At 4.2 K, energy transfer from System II to the light-harvesting complex is blocked, but not from the light-harvesting to the System I and System II complexes. The fluorescence yield of the chlorophyll species emitting at 685 nm appears to be directly modulated by the trapping state of the reaction center.     

Fluorescence emission spectra of chloroplasts and subchloroplast preparations at low temperature

A study was made of the chlorophyll fluorescence spectra between 100 and 4.2 K of chloroplasts of various species of higher plants (wild strains and chlorophyll b mutants) and of subchloroplast particles enriched in Photosystem I or II. The chloroplast spectra showed the well known emission bands at about 685, 695 and 715–740 nm; the System I and II particles showed bands at about 675, 695 and 720 nm and near 685 nm, respectively. The effect of temperature lowering was similar for chloroplasts and subchloroplast particles; for the long wave bands an increase in intensity occurred mainly between 100 and 50 K, whereas the bands near 685 nm showed a considerable increase in the region of 50-4.2 K. In addition to this we observed an emission band near 680 nm in chloroplasts, the amplitude of which was less dependent on temperature. The band was missing in barley mutant no. 2, which lacks the lightharvesting chlorophyll a/b-protein complex. At 4.7 K the spectra of the variable fluorescence (F_v) consisted mainly of the emission bands near 685 and 695 nm, and showed only little far-red emission and no contribution of the band at 680 nm.From these and other data it is concluded that the emission at 680 nm is due to the light-harvesting complex, and that the bands at 685 and 695 nm are emitted by the System II pigment-protein complex. At 4.2 K, energy transfer from System II to the light-harvesting complex is blocked, but not from the light-harvesting to the System I and System II complexes. The fluorescence yield of the chlorophyll species emittting at 685 nm appears to be directly modulated by the trapping state of the reaction center.     

Photosynthetic vesicles with bound phycobilisomes from Anabaena variabilis.

Photosynthetically active vesicles with attached phycobilisomes from Anabaena variabilis, were isolated and shown to transfer excitation energy from phycobiliproteins to F696 chlorophyll (Photosystem II). The best results were obtained when cells were disrupted in a sucrose/phosphate/citrate mixture (0.3 : 0.5 : 0.3 M, respectively) containing 1.5% serum albumin. The vesicles showed a phycocyanin/chlorophyll ratio essentially identical to that of whole cells, and oxygen evolution rates of 250 mumol O2/h per mg chlorophyll (with 4 mM ferricyanide added as oxidant), whereas whole cells had rates of up to 450. Excitation of the vesicles by 600 nm light produced fluorescence peaks (-196 degrees C) at 644, 662, 685, 695, and 730 nm. On aging of the vesicles, or upon dilution, the fluorescence yield of the 695 nm emission peak gradually decreased with an accompanying increase and final predominant peak at 685 nm. This shift was accompanied by a decrease in the quantum efficiency of Photosystem II activity from an initial 0.05 to as low as 0.01 mol O2/einstein (605 nm), with a lesser change in the Vmax values. The decrease in the quantum efficiency is mainly attributed to excitation uncoupling between phycobilisomes and Photosystem II. It is concluded that the F685 nm emission peak, often exclusively attributed to Photosystem II chlorophyll, arises from more than one component with phycobilisome emission being a major contributor. Vesicles from which phycobilisomes had been removed, as verified by electron microscopy and spectroscopy, had an almost negligible emission at 685 nm.     

Photosynthetic vesicles with bound phycobilisomes from Anabaena variabilis

Photosynthetically active vesicles with attached phycobilisomes from Anabaena variabilis, were isolated and shown to transfer excitation energy from phycobiliproteins to F696 chlorophyll (Photosystem II). The best results were obtained when cells were disrupted in a sucrose/phosphate/citrate mixture (0.3 : 0.5 : 0.3 M, respectiely) containing 1.5% serum albumin. The vesicles showed a phycocyanin/chlorophyll ratio essentially identical to that of whole cells, and oxygen evolution rates of 250 μmol O₂/h per mg chlorophyll (with 4 mM ferricyanide added as oxidant), whereas whole cells had rates of up to 450. Excitation of the vesicles by 600 nm light produced fluorescence peaks (?196°C) at 644, 662, 685, 695, and 730 nm. On aging of the vesicles, or upon dilution, the fluorescence yield of the 695 nm emission peak gradually decreased with an accompanying increase and final predominant peak at 685 nm. This shift was accompanied by a decrease in the quantum efficiency of Photosystem II activity from an initial 0.05 to as low as 0.01 mol O₂/einstein (605 nm), with a lesser change in the V_max values. The decrease in the quantum efficiency is mainly attributed to excitation uncoupling between phycobilisomes and Photosystem II. It is concluded that the F685 nm emission peak, often exclusively attributed to Photosystem II chlorophyll, arises from more than one component with phycobilisome emission being a major contributor. Vesicles from which phycobilisomes had been removed, as verified by electron microscopy and spectroscopy, had an almost negligible emission at 685 nm.     

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; )     

赤潮异弯藻在铁限制条件下的光谱特性

由活体吸收光谱可见,赤潮异弯藻在叶绿素c靠近红光区的吸收峰处,由铁丰富条件下的632nm向蓝漂移2nm．由于类胡萝卜素相对于叶绿素a的比值在铁限制的细胞内增大,因而受铁限制的细胞活体吸收光谱在480nm左右类胡萝卜素的吸收峰处增加了一个吸收峰．赤潮异弯藻细胞低温荧光发射光谱在685nm处有一明显的发射峰。与铁丰富条件(10μmol.L-1)相比,缺铁(5nmol·L-1)和低铁(100nmol·L-1)细胞在685nm处的荧光得率分别升高了2倍和1．4倍．补铁48h后荧光得率则明显降低。表明细胞在铁限制条件下存在大量能量耗散,降低了细胞光合作用效率．     

Anisotropy of the emission and absorption bands of spinach chloroplasts measured by fluorescence polarization and polarized excitation spectra at low temperature

Spectra of fluorescence polarization were measured between 4 and 120 K of spinach chloroplasts, oriented in a magnetic field. At least seven emission bands were observed. The well known bands near 685 nm (‘F-685’) and 735–740 nm (‘F-735’) and the band near 680 nm (‘F-680’) were strongly polarized parallel to the plane of the thylakoid membrane, whereas emission bands near 695 nm (‘F-695’), 710, 730–735 and 760 nm showed perpendicular polarization. Assuming perfect orientation of the thylakoid membranes, we calculated orientation angles of 64, 47 and 66.5° for the emission dipoles of F-685, F-695 and F-735, respectively, with respect to the normal of the membrane. Excitation spectra of F-695 and F-735 in polarized light at 4 K provided information about the orientation of the absorption dipoles of chlorophylls a and b. The spectra thus obtained were in very good agreement with the linear dichroism spectrum. Moreover, they allowed us to distinguish between the pigments associated with Photosystems I and Ii, which is not possible from measurement of linear dichroism alone. The results indicate that a high degree of orientation is not confined to the long-wave absorbing bands, but also bands at shorter wavelength show a clear anisotropy. The calculated orientations were in quantitative agreement with the hypothesis that F-685 and F-735 are associated with chlorophylls absorbing at 676 and 710–715 nm, respectively.     

Fluorescence and energy transfer in phycobiliprotein-containing algae at low temperature

Fluorescence emission spectra of Anacystis nidulans, Porphyridium cruentum and Cyanidium caldarium, three phycobiliprotein-containing algae, were measured at temperatures between 4 and 120 K in the absence and in the presence of quinones as quenchers of chlorophyll fluorescence. In all species three major emission bands were observed in the chlorophyll a region, near 685 nm (F-685), 695 nm (F-695) and between 710 and 730 nm. Additional bands were observed at shorter wavelengths; these were preferentially excited by light absorbed by the phycobiliproteins and are presumably due to phycocyanins and allophycocyanins.

The amplitudes of F-685, F-695 and the long-wave emission showed a distinct increase upon cooling. For F-685 and F-695 the temperature dependence was similar to that earlier observed with spinach chloroplasts, for the long-wave emission it appeared to depend on the location of the emission bands, which was different for different species. All three bands were strongly quenched by quinones. These and other data suggest that the origin of these bands is the same as in higher plants, and that the fluorescence increase upon cooling can be explained by a lowering of the efficiency of energy transfer between chlorophyll molecules. It is concluded that at most a small percentage of the emission at 685 nm can be ascribed to allophycocyanin B, and that the efficiency of energy transfer between allophycocyanin B and chlorophyll a probably exceeds 99% both at 77 and 4 K. Experiments with isolated phycobilisomes suggest that energy transfer from allophycocyanin to allophycocyanin B occurs with an efficiency of about 90% at low temperature.

The effect of quenchers can be understood by the assumption that the quenching is caused by the formation of non-fluorescent traps in the bulk chlorophyll. Of three quinones tested, the strongest quenching was observed with dibromothymoquinone, which quenched F-685, F-695 and the long-wave emission approximately equally. Menadione and 1,4-naphthoquinone, however, preferentially quenched the long-wave bands, indicating a stronger interaction with Photosystem I than with Photosystem II chlorophylls.     

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; )     

The influence of pH on the absorption spectrum of arsenazo III.

The absorption spectrum of arsenazo III in media containing K+, Mg2+ and Ca2+ is sharply influenced by pH in the range of 7.5--5.0. The effect of pH is particularly pronounced in the wavelength range 532--602 nm due to the large pH dependence of the dissociation constant of Mg-arsenazo III complex. Therefore absorption changes at these wavelengths during muscle contraction cannot be used as reliable indicators of free ionized Ca2+ concentration in the cell. The effect of pH is less pronounced, but still noticeable at the wavelength pairs 575--650 or 660--685 nm. Multiple layers of muscle cells grown on polystyrene coils permit measurement of absorption changes of arsenazo III, introduced into the cells, by equilibration with 0.5 mM arsenazo III under routine culture conditions. The absorbance changes recorded at 660--685 nm are probably related to changes in intracellular free Ca2+ concentration.     

Phosphorylation of the light-harvesting chlorophyll-protein regulates excitation energy distribution between photosystem II and photosystem I

The kinetics of thylakoid membrane protein phosphorylation in the presence of light and adenosine triphosphate is correlated to an incease in the 77 °K fluorescence emission at 735 nm (F735) relative to that at 685 nm (F685). Analysis of detergent-derived submembrane fractions indicate phosphorylation only of the polypeptides of Photosystem II, and the light-harvesting chlorophyll-protein complex serving Photosystem II (LHC-II). Although several polypeptides are phosphorylated, only the dephosphorylation kinetics of LHC-II follow the kinetics of the decrease of the $\text{F735}\text{F685}$ fluorescence emission ratios. The relative quantum yield of Photosystem II was significantly lower in phosphorylated membranes compared to dephosphorylated membranes. Reversible LHC-II phosphorylation thus provides the physiological mechanism for the control of the distribution of absorbed excitation energy between the two photosystems.     

Changes in the chlorophyll fluorescence characteristics of chloroplasts from intact pumpkin cotyledons,caused by organ excision and kinetin treatment

The chlorophyll (Chl) fluorescence emission as well as excitation and polarization characteristics of chloroplasts from intact cotyledons were determined in pumpkin seedlings after removal of one cotyledon (co-cotyledon) or apical bud or primary root, or after kinetin treatment of derooted seedlings. Qualitatively, the fluorescence emission and excitation spectra of chloroplasts were similar. The fluorescence emission spectra showed a maximum at 685 (F685) and a hump at 735 nm (F735), whereas the excitation spectra showed peaks at 439, 471, 485, and 676 nm. The fluorescence intensities at F685 and F735 differed in various groups of seedlings, as indicated by changes in their ratios. Similarly, the ratios of 471/439, 485/439, and 676/439 nm were also different. Variability in the Chl fluorescence intensity values and the fluorescence polarization of chloroplasts prepared from various seedling types may suggest a different degree of binding between the pigment complexes and light-harvesting Chl-protein (LHCP), resulting in different rates of photoexcitation energy loss in the form of fluorescence emission. Kinetin treatment improved the coupling of pigment complexes with reaction centre, as indicated by low polarization values in derooted and kinetin-treated seedlings, which suggests the development of a suntype chloroplast.     

Time-resolved fluorescence spectroscopy of spinach chloroplast

Picosecond fluorescent kinetics and time-resolved spectra of spinach chloroplast were measured at room temperature and low temperatures. The measurement is conducted with 530 nm excitation at an average intensity of 2 · 10¹⁴ photons/cm², pulse and at a pulse separation of 6 ns for the 100 pulses used. The 685 nm fluorescent kinetics was found to decay with two components, a fast component with a 56 ps lifetime, and a slow component with a 220 ps lifetime. The 730 nm fluorescent kinetics at room temperature is a single exponential decay with a 100 ps lifetime. The 730 nm fluorescence lifetime was found to increase by a factor of 6 when the temperature was lowered from room temperature to 90 K, while the 685 and 695 nm fluorescent kinetics were unchanged. The time-resolved spectra data obtained within 10 ps after excitation is consistent with the kinetic data reported here. A two-level fluorescence scheme is proposed to explain the kinetics. The effect of excitation with high light intensity and multiple pulses is discussed.     

Ultraviolet vision in birds: the importance of transparent eye media

Ultraviolet (UV)-sensitive visual pigments are widespread in the animal kingdom but many animals, for example primates, block UV light from reaching their retina by pigmented lenses. Birds have UV-sensitive (UVS) visual pigments with sensitivity maxima around 360–373 nm (UVS) or 402–426 nm (violet-sensitive, VS). We describe how these pigments are matched by the ocular media transmittance in 38 bird species. Birds with UVS pigments have ocular media that transmit more UV light (wavelength of 50% transmittance, λ_T0.5, 323 nm) than birds with VS pigments (λ_T0.5, 358 nm). Yet, visual models predict that colour discrimination in bright light is mostly dependent on the visual pigment (UVS or VS) and little on the ocular media. We hypothesize that the precise spectral tuning of the ocular media is mostly relevant for detecting weak UV signals, e.g. in dim hollow-nests of passerines and parrots. The correlation between eye size and UV transparency of the ocular media suggests little or no lens pigmentation. Therefore, only small birds gain the full advantage from shifting pigment sensitivity from VS to UVS. On the other hand, some birds with VS pigments have unexpectedly low UV transmission of the ocular media, probably because of UV blocking lens pigmentation.     

Isolation and Photosynthesis of Spheroplasts in Spirulina platensis

Spirulina platensis is a nonheterocystic filamentous blue-green alga (cyanobacterium). Large quantity of highly qualified spheroplasts were obtained by improved isolation method. The spheroplast has a wrinkled and porous surface. Their diameter ranged from 3.8 btm to 4. 6 μm. The activity of photosynthetic oxygen evolution in the spheroplasts was about 40 % of the intact cell. The absorption spectra of the filaments and spheroplasts at room temperature revealed that they had the same pigments, Chla, PC, PEC and carotenoid. In spheroplasts the relative content of PC and carotenoid decreased, and that of PEC increased. It implicated that the light absorption of Spirulina platensis could be influenced by the cell wall. Some differences existed between the original cells and spheroplasts in the low temperature fluorescence emission spectra. F757 of spheroplasts excited by 436 nm was reduced obviously and that excited by 580 nm was disapeared. F728/F685 and F640/F685 enhanced, and F693/F685 was reduced. F728/F640 was lower than that of the original cells. These results indicated that removing the cell wall may inhibit the PS Ⅱ activity and influence the F695 from core antenna pigment system.     

Changes in the chlorophyll fluorescence characteristics of chloroplasts from intact pumpkin cotyledons, caused by organ excision and kinetin treatment

The chlorophyll (Chl) fluorescence emission as well as excitation and polarization characteristics of chloroplasts from intact cotyledons were determined in pumpkin seedlings after removal of one cotyledon (co-cotyledon) or apical bud or primary root, or after kinetin treatment of derooted seedlings. Qualitatively, the fluorescence emission and excitation spectra of chloroplasts were similar. The fluorescence emission spectra showed a maximum at 685 (F685) and a hump at 735 nm (F735), whereas the excitation spectra showed peaks at 439, 471, 485, and 676 nm. The fluorescence intensities at F685 and F735 differed in various groups of seedlings, as indicated by changes in their ratios. Similarly, the ratios of 471/439, 485/439, and 676/439 nm were also different. Variability in the Chl fluorescence intensity values and the fluorescence polarization of chloroplasts prepared from various seedling types may suggest a different degree of binding between the pigment complexes and light-harvesting Chl-protein (LHCP), resulting in different rates of photoexcitation energy loss in the form of fluorescence emission. Kinetin treatment improved the coupling of pigment complexes with reaction centre, as indicated by low polarization values in derooted and kinetin-treated seedlings, which suggests the development of a suntype chloroplast. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dependence of fluorescence spectra of chloroplasts from the activity of photosystem 2]

By means of high sensitive spectrofluorometer the fluorescence spectra have been measured of normal chloroplasts and those with blocked photosystem 2 activity due to photoinhibition or treatment with 0.6 M tris-buffer. At room temperature fluorescence spectra of inactivated chloroplasts are similar to the spectrum of normal chloroplasts measured at low light intensity. Under excitation by intense light a decrease of intensity at 685 nm is appeared (about 3-4 times) in the fluorescence spectra of inactivated chloroplasts as compared to the spectrum of normal chloroplasts. The sharp intensity decrease of maxima at 685 and 695 nm (3-4 times) and small decrease at 680 and 730 nm (by 30-50%) are observed in low temperature fluorescence spectra of inactivated chloroplasts. Thus, the damage of photosystem 2 reaction centres is not accompanied by the preferential decrease of the only fluorescence band. The similarity of fluorescence difference spectra of chloroplasts distinguished by the state of photosystem 2 reaction centre, and the complex structure of difference spectra indicate that the variable fluorescence of chloroplasts during the induction is due to the emission of bulk chlorophyll alpha of the photosystem 2.