Chlorophyll Absorption Band Research Articles

Reflectance Differences Between Target and Torch Rape Cultivars1

AbstractTo characterize and explain leaf and plant reflectance differences between Target (Brassica napus L.) and Torch (Brassica campestris L.) rape cultivars, laboratory spectrophotometric reflectance measurements were made on leaves of the same age, collected from different nodes, and on leaves of different ages, collected from the same node, for both small (five leaves) and large (nine leaves) Target and Torch plants. Spectroradiometric reflectance measurements were made on Target and Torch plants (four and five leaves, respectively) that were growing in 0.09 m2 soil‐containing flats. Torch's spectrophotometric single leaf reflectance was consistently lower than Target's at the 650‐nm chlorophyll absorption band because Torch's chlorophyll concentration was larger than Target's, which caused more red light absorptance. Spectroradiometric measurements indicated that: (1) wet soil strongly absorbed visible light (500 to 700 nm) so that Target's soil‐containing flat with 60% plant cover had less reflectance than Torch's soil‐containing flat with 75% plant cover, (2) Torch (most foliage) had higher near‐infrared (750 to 1,350 nm) reflectance than Target (least foliage), and (3) the 2,200‐nm wavelength is a candidate band to distinguish Target from Torch. The difference in chlorophyll concentrations between Target and Torch, compared with leaf structural differences, is apparently the most important factor that would affect the infrared color film's tonal response to vegetation in the photographic sensitive region (500 to 900 nm).

Influence of chlorophyll a on intermolecular interactions in liquid crystal

Studies of the variability of the spectral properties (linear dichroism, polarized fluorescence and the energetic separation of the absorption and emission bands) of chlorophyll a in a nematic liquid crystal matrix with respect to the effects of solute concentration and the external electric fields were made. A close examination of the above mentioned types of variability suggest that the pigment molecules can influence a high initial order of the liquid crystal matrix. These structural changes of the matrix can be explained by the assumption that two types of chlorophyll with different orientations occur: the surface layers with the high degree of orientation, and a central volume of the sample with disordered molecules. The ordered molecules are sensitive to an reorientation by the external electric field.

Laser-spectroscopic Characterization of the Absorption Behaviour of Chlorophyll in vitro and in vivo

Intensity-dependent transmission measurements were carried out in vitro with chlorophyll solutions and in vivo with leaf segments of primary leaves of Triticum aestivum L. The results are discussed in relation to the size of the primary absorption unit (∼ 10 6 chlorophyll molecules) and the relative homogeneity of the red absorption band of chlorophyll in vivo.

Anisotropy of photosynthetic membranes and the degree of fluorescence polarization

The degree of fluoresence polarization, P, of unoriented and magnetically oriented spinach chloroplasts as a function of excitation (400–680 nm) and emission wavelengths (675–750 nm) is reported. For unoriented chloroplasts P can be divided into two contributions, P IN and P AN . The latter arises from the optical anisotropy of the membranes which is due to the orientation with respect to the membrane plane of pigment molecules in vivo. The intrinsic polarization P IN , which reflects the energy transfer between different pigment molecules and their degree of mutual orientation, can be measured unambiguously only if (1) oriented membranes are used and the fluorescence is viewed along a direction normal to the membrane planes, and (2) the excitation is confined to the Q y (≈ 660−680 nm) absorption band of chlorophyll in vivo. With 670–680 nm excitation, values of P using unoriented chloroplasts can be as high as +14%, mostly reflecting the orientational anisotropy of the pigments. Using oriented chloroplasts, P IN is shown to be +5±1%. The excitation wavelength dependence studies of P IN indicate that the carotenoid and chlorophyll Q y transition moments tend to be partially oriented with respect to each other on a local level (within a given photosynthetic unit or its immediate neighbors).

CURVE ANALYSIS OF THE RED ABSORPTION BAND OF CHLOROPHYLLbIN ULVA LACTUCA

SUMMARY A component absorbing around 655 nm is observed in the approximate red absorption band of chlorophyll b in Uiva lactuca. The results suggest that this component represents a form of chlorophyll a rather than chlorophyll b. Therefore, no indication that chlorophyll b occurs in more than a single form in vivo is obtained.

Chlorophyll b containing liposomes: Effect of thermal transitions on catalytic and spectral properties

1. 1.Chlorophylls a and b were incorporated into saturated and unsaturated phosphatidylcholine liposomes. The red absorption bands of the two chlorophylls were at 671 nm and 651 nm, respectively, both in liposomes containing egg phosphatidylcholine and in liposomes containing saturated lecithins above their transition temperatures. 2. 2.In dipalmitoylphosphatidylcholine liposomes the absorption bands of chlorophyll b show a red shift on cooling below the transition temperature. Chlorophyll b broadens and depresses the transition temperature region of hydrated dipalmitoylphosphatidylcholine. 3. 3.Chlorophyll b containing liposomes catalyse the reduction of cytochrome c by trimethylhydroquinone in a light-sensitive reaction; the catalysis by egg lecithin liposomes has a rate about 60% that of Triton-dispersed chlorophyll and shows no sharp temperature effects, but the catalysis by dipalmitoyllecithin liposomes is only seen above their transition temperature. 4. 4.Chlorophyll b containing dimyristoyllecithin liposomes show a smaller spectral shift and a less marked increase in catalytic activity on passing through their transition temperature. 5. 5.Chlorophyll a containing saturated liposomes show smaller spectral and catalytic responses to temperature than do the chlorophyll b containing liposomes.

Optical Parameters of Leaves of 30 Plant Species

Optical parameters (absorption coefficient k, infinite reflectance Rinfinity, scattering coefficient 8) are tabulated for seven wavelengths and analyzed for statistical differences for 30 plant species. The wavelengths are: 550 nm (green reflectance peak), 650 nm (chlorophyll absorption band), 850 nm (infrared reflectance plateau), 1450 nm (water absorption band), 1650 nm (reflectance peak following water absorption band at 1450 nm), 1950 nm (water absorption band), and 2200 nm (reflectance peak following water absorption band at 1950 nm).Thick, complex dorsiventral (bifacial mesophyll) leaves such as rubber plant, begonia, sedum, and privet had lower Rinfinity values than thinner, less complex dorsiventral leaves (i.e., soybean, peach, bean, rose) or essentially centric (undifferentiated mesophyll) sorghum and corn leaves. Infinite reflectance was negatively correlated with leaf thickness (-0.734(**)).Thick, complex dorsiventral leaves (crinum, oleander, privet, rubber plant, sedum) had higher (p 0.01) k values than thinner, less complex dorsiventral leaves (i.e., soybean, rose, peach) or essentially centric sorghum, sugarcane, and corn leaves. A coefficient of 0.718(**) was obtained for the correlation of k values with leaf thickness values.Complex dorsiventral oleander, orange, and crinum leaves had higher (p 0.01) 8 values than less complex dorsiventral (i.e., onion, begonia, banana) or centric leaves (i.e., corn and sugarcane). The scattering coefficient was not correlated with leaf thickness.

Polarised absorption spectroscopy of chlorophyll-lipid membranes

A technique has been developed for measuring visible absorption spectra of chlorophyll in lipid membranes. An expression is derived which enables the directions of the transition moments of the different absorption bands to be determined from polarisation data. It is found that the transition moments of the principal blue and red absorption bands of chlorophyll a make angles of 26° and 36.5° respectively with the plane of the membrane. On the assumption that these two transitions lie in the plane of the porphyrin ring and are mutually perpendicular, it may be deduced that the plane of the porphyrin ring is tilted at approx. 48° to the membrane surface. For chlorophyll b the transition moments of the blue and red bands are found to make angles of 29.5° and 36.5° with the plane of the bilayer, giving an angle of tilt of the porphyrin ring of approx. 51°. These results are compared with measurements of dichroism in vivo.

The approximate red absorption band of chlorophyll b in Ulva lactuca at 77°K

The approximate red absorption band of chlorophyll b in Ulva lactuca at 77°K

Light-induced shifts in pigment absorption in green, red and blue-green algae

1. 1. Light-induced absorption changes in the region 640–730 nm which were not associated with the oxidation of the primary electron donor of system 1, P700, were observed in green, red and blue-green algae. The shape of the difference spectra, showing alternating negative and positive bands, suggested shifts in the absorption bands of chlorophyll a types and of chlorophyll b. 2. 2. The chlorophyll absorption changes were correlated with changes in the blue spectral region, due to carotenoids. Absorption shifts of phycobilins were not observed. The uncoupler carbonylcyanide- p-trifluoromethoxyphenylhydrazone (FCCP) at low concentration stimulated the carotenoid and chlorophyll changes and inhibited at higher concentration. 3. 3. Difference spectra of the changes brought about by Photosystems 1 and 2 in Scenedesmus obliquus were approximately proportional to each other, indicating that shifts of chlorophyll a and b and carotenoid occur in the same relative proportion, independent of the activating photosystem. 4. 4. The results, together with older evidence, indicate that shifts in absorption spectra of photosynthetic pigments are universal phenomena, probably correlated with an energized state of the photosynthetic membrane. Evidence that the well-known change at 515 nm in green algae and higher plants is due to a carotenoid rather than to chlorophyll b is discussed.

Reflectance of single leaves and field plots ofcycocel-treated cotton (Gossypium hirsutum L.) in relation to leaf structure

Leaves from cotton plants sprayed with 100 g/ha Cycocel in a fieldexperiment were about 40% thicker and 20% larger in surface dimension than non-Cycocel-sprayed leaves. Cycocel-treated leaves had approximately a threefold increase in numbers of intercellular spaces within their mesophylls. Spectrophotometric measurements of spectra of individual leaves over the wavelength interval 500–2500 mμ revealed a 5%. increase in reflectance over the wavelength interval 500–1350 mμ and a 6% decrease in transmittance over the entire 500–2500-mμ interval for treated compared with untreated leaves. Increased reflectance and decreased transmittance over the wave-length interval 750–1350 mμ were mainly associated with Increased numbers of air spaces in leaf mesophylls. Decreased transmittance of Cycocel-treated leaves over wavelength intervals 500–750 and 1350–2500 mμ was due to Increased absorptance caused by Increased chlorophyll and water contents, respectively. The Cycocel treatment increased absorptance 13 % at the chlorophyll absorption band, 550 mμ; only 2–3 % over the wavelength interval 750–1350 mμ; and 10 and 11 % at the water absorption bands approximating 1450 and 1950 mμ, respectively. Near-infrared light reflectance from single leaves, measured with a spectrophotometer, was inversely related and visible light reflectance was directly related to the reflectivity of field plots of cotton recorded on Kodak Ektachrome infrared aero film, type 8443, with a Kodak Wratten No. 15 (G), light-orange filter, during an overflight.

Analysis of the red absorption band of chlorophyll a in vivo.

Abstract A precise and sensitive integrating spectrophotometer has been constructed in the shape of a dodecahedron with one photoelectric cell on each side. With the help of this instrument and a computer, the red chlorophyll a absorption band of algae and chloroplasts was resolved (after subtracting the chlorophyll b band) into two Gaussian components, with peaks at 668 and 683 nm★★. The half-width of the two-band envelope is 32 nm; the half-width of each component, about 18 nm. In the blue-green alga, Anacystis and the red alga, Porphyridium (both containing no chlorophyll b ), the two-component bands seem to be in the same positions, but are considerably wider. (However, preliminary analysis suggests that the red band in Anacystis can be interpreted instead as the sum of three components—two belonging to chlorophyll a , and a third one probably due to allophycocyanin.) The relative heights of the two chlorophyll a components vary, in all plants used, only between 0.7 and 0.9, the 668-nm band always being the weaker one. Broadening of chlorophyll a absorption curves by the so-called “sieve effect” may to some extent change the analysis presented here, by causing the component bands in vivo to deviate from the Gaussian shape; this effect calls for further investigation but is unlikely to affect the qualitative conclusions. A comparison of the absorption spectrum so analyzed with that of the “Pigment systems I and II” ( Duysens, French et al.) suggests that in Chlorella, a large portion of chlorophyll a 668 nm belongs, together with a large part of chlorophyll b , to System II, while a large part of chlorophyll a 683 nm must be identified with System I, although some of it probably belongs to System II. The simple identification of chlorophyll a 668 nm with System II, and chlorophyll a 683 nm with System I, as previously suggested, appears to be untenable. In red and blue-green algae, larger parts of both chlorophyll a 668 nm and chlorophyll a 683 nm seem to belong to System I.

Fractionation of Chlorophyll Forms from Euglena and Measurement of Light-Induced Absorbance Changes

Since the realization that 2 or more light-reactions participate in photosynthesis and that plants contain several absorbing forms of chlorophyll, correlations have been sought between photochemical activity and particular pigment forms. Traditionally, action spectra have been used to identify functional pigments, btut this nmethod fails either when the activity being measured results from several reactions or when the absorption spectra of the pigments overlap strongly. The chlorophyll forms fall into this latter category. Therefore several investigators have been attempting to break-up the photochemical al)paratus of chloroplasts and bacterial chromatophores by the aid of detergents, to fractionate by centrifugation, and then to measure absorption, fluorescence, or some type of photochemical activity in the fractions. A beginning in this type of investigation has been achieved (2, 3, 5, 1 1 ). The alga, Euglena, when grown with dim light has 3 chlorophyll a absorption maxima at approximately 670, 680, and 695 m,u. Aqueous colloidal extracts of this alga have been extensively studied by us in attempts to isolate these forms and to learn about the nature of chlorophyll in vivo (6). In the whole extract chlorophyll a-695 is much more labile than the other 2 forms and always disappears first when the extract is heated, strongly irradiated, acidified, or differentially extracted with organic solvents. No separation of the different absorbing forms was accomplished by differential centrifugation of the aqueous extract. In new experiments we have observed that a low concentration of the detergent, sodium deoxycholate (DOC), does not change the position or height of the chlorophyll absorption bands. By centrifugation of the detergent extract a supernatanit fraction containing Ca670 can be separated from a sedinment with Ca680 and Ca695. We observed 2 types of photoinduced absorbance changes at 419, 518, and 591 mi.t in both fractions but the rate anld degree of the response differed in the 2 fractions. The different responses may be explained by differences in the forms of chlorophyll present and possibly also by a partial separation of photosynthetic electron transfer components.

Studies on the red absorption band of chlorophyll a in vivo.

It was studied whether certain earlier observed weak shoulders on the red absorption band of chlorophyll a in vivo might represent anomalies due to overlap of absorption bands. The results are suggested of the fact that no such anomalies occur. It is therefore concluded that the present study supports the concept holding that, at least, 6 rather than 4 chlorophyll a forms may be present in the state in vivo. The true position of the Ca680 absorption maximum is suggested to occur at a wavelength at least 4 mμ longer than that actually measured in spectra of cells and chloroplast suspensions. The data suggest that Ca667 is likely to function in the Hill reaction with p-benzoquinone as an oxidant at least as efficiently as Ca670. The possible significance of the chlorophyll a forms other than Ca670, Ca680, Ca695 and Ca700 is discussed.

Shape of the red absorption band of chlorophyll A in algae lacking chlorophyll B : Thomas, J. B., Biophysical Research Group, Physics Institute of the State University, Utrecht, The Netherlands, No. 119, extract from Editions du Centre National de la Recherche Scientifique, 1963, 13 pgs.

Shape of the red absorption band of chlorophyll A in algae lacking chlorophyll B : Thomas, J. B., Biophysical Research Group, Physics Institute of the State University, Utrecht, The Netherlands, No. 119, extract from Editions du Centre National de la Recherche Scientifique, 1963, 13 pgs.

ON THE RELATIVE INTENSITIES OF THE "BLUE" AND "RED" ABSORPTION BANDS OF CHLOROPHYLL A.

Abstract Recent suggestions that the ratio of the heights of the “blue” (430 mμ) and “red” (660 mμ) absorption bands of chlorophyll a in diethyl ether solution should be 1.17–1.19 are not compatible with our results for the specific activities or the spectroscopic properties of rigorously purified samples of 14C-labelled chlorophyll a. We have shown that it is possible to obtain values of this ratio significantly lower than the commonly accepted value of 1.31–1.32 as the result of interaction of the pigment molecules with alcohol or water in the diethyl ether. We have shown with the aid of spectroscopic, chromatographic, and radiotracer data that the lower values certainly do not reflect improved freedom of the chlorophyll a preparations from xanthophylls as has been claimed. We also conclude that a limiting value for this ratio must exist and that this value is 1.29.

Fluorescence and Absorption Changes in Chlorella Exposed to Strong Light: The Red Band

The reversible decrease in the apparent intensity of the main red absorption band of chlorophyll a at 680 mnu upon strong illumination of Chlorella cells, described by Coleman and Rabinowitch in 1957, is shown, by a polarization method, to be due to an increase in the fluorescence yield. True absorption changes are observed at 657 mnu (positive) and 648 mnu (negative).

Structure of the red absorption band of chlorophyll a in Aspidistra elatior

The red absorption band of chlorophyll a in chloroplasts of Aspidistra elatior consists of a main maximum and a number of weak shoulders. This number may vary in chloroplast preparations from different leaves. At most, five shoulders were noticed. Heat treatment affects the shoulders in a mutually different way. Upon storage at 23°, the red absorption band changes in two regions: both the main peak and one of the shoulders around 660 mμ shift to the long-wave side. As a rule, the shift of the main maximum needs 1–2 h for completion, while that of the shoulder is finished within 20–30 min. Indication is obtained that the time course of the slow shift parallels that of the loss of ability to perform the Hill reaction with 0.02 M p-benzoquinone as the oxidant. It is concluded that, most probably, at least six forms of chlorophyll a occur in Aspidistra chloroplasts. To what extent their functions may be different remains to be studied.

Photoreduction of Chlorophyll a in the Presence of Ascorbic Acid in Pyridine Solutions.

Over the last decade, Russian investigators?among whom Krasnovsky, Evstigneev, and Gavrilova are most prominent?have published many papers describing the photoreduction of chlorophyll in dilute solutions. Since the photoreduction has been reported to be reversible and energy-storing, the reaction is of great interest because it could be related to the primary photochemical process of photosynthesis. This paper describes experiments carried out after initial attempts by the writer failed to reproduce certain of the Russian findings. Krasnovsky and Brin (5) reported that, when an oxygen-free pyridine solution of chlorophyll a (10~5 M) and ascorbic acid was illuminated with red light, the blue-green color characteristic of chlorophyll faded away and a pink solution was formed: the absorption bands of chlorophyll disappeared and a new absorption band with a maximum at 523 ??? appeared. Lynch and French have confirmed this observation. Krasnovsky et al (3, 4, 5) found that, with a moderate concentration of ascorbic acid (0.05 M ) and in the absence of water, the bleaching was reversible?i.e., in the dark following bleaching, chlorophyll was regenerated and a blue-green color was restored. In solutions containing water or more ascorbate (0.10 M), the bleaching was irreversible since pheophytin a rather than chlorophyll was generated in the dark. The Russian workers apparently regarded the formation of pheophytin as an unimportant secondary process unrelated to the photoreduction. The results of preliminary experiments of the writer differed significantly from those of the Russians'. In dry pyridine solutions, no bleaching was detected at all. When a certain amount of water was added to the samples, a rapid bleaching resulted but colorless rather than pink solutions were formed ; moreover, no reversibility could be demonstrated because the bleached chlorophyll was quantitatively converted into pheophytin in the dark following illumination. These findings thus failed to corroborate the existence of a pink photoreduced chlorophyll and failed also to show any reversible reaction at all. Since the Russian studies were not only convincing in their extent, but also important in providing evidence for the only known, reversible, light-sensitized, energy-storing redox reaction of chlorophyll, a thorough reinvestigation was undertaken. Part of the results of this study are reported in this paper.

THE CHLOROPHYLL-PROTEIN COMPOUND OF THE GREEN LEAF

1. Aqueous extracts of spinach and Aspidistra leaves yield highly opalescent preparations which are not in true solution. Such extracts differ markedly from colloidal chlorophyll in their spectrum and fluorescence. The differences between the green leaf pigment and chlorophyll in organic solvents are shown to be due to combination of chlorophyll with protein in the leaf. 2. The effect of some agents on extracts of the chlorophyll-protein compound has been investigated. Both strong acid and alkali modify the absorption spectrum, acid converting the compound to the phaeophytin derivative and alkali saponifying the esterified groups of chlorophyll. Even weakly acid solutions (pH 4.5) denature the protein. Heating denatures the protein and modifies the absorption spectrum and fluorescence as earlier described for the intact leaf. The protein is denatured by drying. Low concentrations of alcohol or acetone precipitate and denature the protein; higher concentrations cause dissociation liberating the pigments. 3. Detergents such as digitonin, bile salts, and sodium desoxycholate clarify the leaf extracts but denature the protein changing the spectrum and other properties. 4. Inhibiting agents of photosynthesis are without effect on the absorption spectrum of the chlorophyll-protein compound. 5. The red absorption band of chlorophyll possesses the same extinction value in organic solvents such as ether or petroleum ether, and in aqueous leaf extracts clarified by digitonin although the band positions are different. Using previously determined values of the extinction coefficients of purified chlorophylls a and b, the chlorophyll content of the leaf extracts may be estimated spectrophotometrically. 6. It was found that the average chlorophyll content of the purified chloroplasts was 7.86 per cent. The protein content was 46.5 per cent yielding an average value of 16.1 parts per 100 parts of protein. This corresponds to a chlorophyll content of three molecules of chlorophyll a and one of chlorophyll bfor the Svedberg unit of 17,500. It is suggested that this may represent a definite combining ratio of a and b in the protein molecule.