Absorption Spectrum Of Chlorophyll Research Articles

Determination of chlorophyll content of small water bodies (kettle holes) using hyperspectral airborne data

This study presents an approach for chlorophyll content determination of small shallow water bodies (kettle holes) from hyperspectral airborne ROSIS and HyMap data (acquired on 15 May and 29 July 2008 respectively). Investigated field and airborne spectra for almost all kettle holes do not correspond to each other due to differences in ground sampling distance. Field spectra were collected from the height of 30–35cm (i.e. area of 0.01–0.015m2). Airborne pixels of ROSIS and HyMap imageries cover an area of 4m2 and 16m2 respectively and their spectra are highly influenced by algae or bottom properties of the kettle holes. Analysis of airborne spectra revealed that chlorophyll absorption near 677nm is the same for both datasets. In order to enhance absorption properties, both airborne hyperspectral datasets were normalized by the continuum removal approach. Linear regression algorithms for ROSIS and HyMap datasets were derived using normalized average chlorophyll absorption spectra for each kettle hole. Overall accuracy of biomass mapping for ROSIS data was 71%, and for HyMap 64%. Biomass mapping results showed that, depending on the type of kettle hole, algae distribution, the ‘packaging effect’ and bottom reflection lead to miscalculations of the chlorophyll content using hyperspectral airborne data.

Theoretical reconsideration on the hydrogen bonding and coordination interactions of chlorophyll a in aqueous solution

In the present work, explicit water molecule and solvent-field effects on the absorption spectrum of chlorophyll a have been studied using time-dependent density functional theory (TDDFT) method. Calculated results show that the one complex and two water coordinated complexes formed by concerted coordination and hydrogen-bonding interactions would be the most preferable conformations of chlorophyll a in aqueous surroundings. Moreover, four obvious absorption bands are assigned by comparing the theoretically simulated absorption spectra with the experimental ones. The theoretical study shows that the explicit water molecule interactions slightly influence the first absorption band. However, the water coordination and hydrogen-bonding interactions can significantly affect the second absorption band which has a strong red-shift. The solvent-field effect due to the polarity of water on absorptions in Q-bands is relatively smaller than that on absorptions in B-bands. As a consequence, our theoretical study on the absorption spectra in the 350–400 nm region presents that the absorption strength in this region was influenced by the explicit coordination and hydrogen bonding interactions from water molecules, significantly.

Controllable spectrum artificial sunlight source system using LEDs with 32 different peak wavelengths of 385–910 nm

This study developed a lighting system that produces an approximate spectral irradiance (SI) of ground level sunlight in the wavelength range of 385-910 nm (GLS₃₈₅₋₉₁₀) using 547 light-emitting diodes (LEDs) with 32 different peak wavelengths. The produced SI can be modified over an arbitrary wavelength band. The SI at the light outlet reached up to 1/2 of the GLS₃₈₅₋₉₁₀ of a sunny April day, although the produced SI deviated from the GLS₃₈₅₋₉₁₀ at some wavelengths. For subsequent experiments, the reference SI was defined as 1/4 GLS₃₈₅₋₉₁₀ of a sunny April day. The SI produced from the lighting system was adjusted to approximate the reference SI. The ratios of the produced SI and the reference SI were within 0.72-1.28. As an application of the lighting system for biological studies, the transmitted SI of a green leaf of perilla (Perilla frutescens L.) was investigated. The curve shape of the transmitted SI, which had characteristically low transmission percentages of blue and red light, reflected the characteristics of the absorption spectra of chlorophylls. The lighting system is therefore potentially beneficial for use in diagnosing physiological conditions of plant leaves, although its application is not limited to plant physiological studies.

Effects of Clinorotation on Growth and Chlorophyll Content of Rice Seeds

Microgravity, as a different environment, has been shown to affect plant growth and development (Sievers et al. 1996; Sack 1997). In the present study, effects of slow clinorotation (2 rpm) on growth and chlorophyll content in rice (variety: PRH-10) seedlings were investigated. Rice seeds were clinorotated continuously for 3, 5 and 7 days under ambient conditions. Root and shoot lengths and weights of rice seedlings were measured on the third, fifth and seventh day. Chlorophyll was extracted using N, N-Dimethylformamide (DMF). Absorption and fluorescence spectra of chlorophyll were recorded. Chlorophyll a, chlorophyll b and total chlorophyll contents were calculated from absorption spectra using Arnon’s method. Results showed an increase in root and shoot lengths in clinorotated samples. Similar results were obtained for root and shoot weights. Absorption spectra of chlorophyll showed no shift in the absorption peaks. Chlorophyll content was increased in clinorotated samples as compared to the controls. Interestingly, the difference between chlorophyll content in control and clinorotated samples decreased as the number of days of clinorotation increased. Chlorophyll a/b ratio was lowered in clinorotated samples as compared to the controls. These results suggest that slow clinorotation (2 rpm) affects plant growth and chlorophyll content in rice seedlings.

Investigation of Eu–Mn energy transfer in A3MgSi2O8:Eu2+, Mn2+ (A=Ca,Sr,Ba) for light-emitting diodes for plant cultivation

We report a plant growth lamp utilizing near-ultraviolet light-emitting diode and A3MgSi2O8:Eu2+, Mn2+ (A=Ca,Sr,Ba) phosphors with emission spectra consisting of blue and red bands, which conform well to the action spectra of plants and absorption spectra of chlorophylls. Either peak positions of the two bands or intensity ratio of red to blue band can be tailored by tuning the compositions of the cations. Eu–Mn energy transfer in the phosphors was investigated on the bases of photoluminescence, life decay time, and microstructure. This functional solid-state lighting provides a simple, compact, and efficient solution to illuminator for plant cultivation.

Excited state absorption spectrum of chlorophyll a obtained with white-light continuum

The study of excited state properties of chlorophyll a is a subject of foremost interest, given that it plays important roles in biological process and has also been proposed for applications in photonics. This work reports on the excited state absorption spectrum of chlorophyll a solution from 460 to 700 nm, obtained through the white-light continuum Z-scan technique. Saturation of absorption was observed due to the ground state depletion, induced by the white-light continuum region that is resonant with the Q band of chlorophyll a. The authors also observed reverse saturation of absorption related to the excitation from the first excited state to a higher energy level for wavelengths below 640 nm. An energy-level diagram, based on the electronic states of chlorophyll a, was employed to interpret their results, revealing that more states than the ones related to the Q and B bands participate in the excited state absorption of this molecule.

Two-Step Mechanism of Photodamage to Photosystem II: Step 1 Occurs at the Oxygen-Evolving Complex and Step 2 Occurs at the Photochemical Reaction Center

Under strong light, photosystem II (PSII) of oxygenic photosynthetic organisms is inactivated, and this phenomenon is called photoinhibition. In a widely accepted model, photoinhibition is induced by excess light energy, which is absorbed by chlorophyll but not utilized in photosynthesis. Using monochromatic light from the Okazaki Large Spectrograph and thylakoid membranes from Thermosynechococcus elongatus, we observed that UV and blue light inactivated the oxygen-evolving complex much faster than the photochemical reaction center of PSII. These observations suggested that the light-induced damage was associated with a UV- and blue light-absorbing center in the oxygen-evolving complex of PSII. The action spectrum of the primary event in photodamage to PSII revealed the strong effects of UV and blue light and differed considerably from the absorption spectra of chlorophyll and thylakoid membranes. By contrast to the photoinduced inactivation of the oxygen-evolving complex in untreated thylakoid membranes, red light efficiently induced inactivation of the PSII reaction center in Tris-treated thylakoid membranes, and the action spectrum resembled the absorption spectrum of chlorophyll. Our observations suggest that photodamage to PSII occurs in two steps. Step 1 is the light-induced inactivation of the oxygen-evolving complex. Step 2, occurring after step 1 is complete, is the inactivation of the PSII reaction center by light absorbed by chlorophyll. We confirmed our model by illumination of untreated thylakoid membranes with blue and UV light, which inactivated the oxygen-evolving complex, and then with red light, which inactivated the photochemical reaction center.

Photochemical Competence of Assembled Photosystem II Core Complex in Cyanobacterial Plasma Membrane

Cyanobacterial cells have two autonomous internal membrane systems, plasma membrane and thylakoid membrane. In these oxygenic photosynthetic organisms the assembly of the large membrane protein complex photosystem II (PSII) is an intricate process that requires the recruitment of numerous protein subunits and cofactors involved in excitation and electron transfer processes. Precise control of this assembly process is necessary because electron transfer reactions in partially assembled PSII can lead to oxidative damage and degradation of the protein complex. In this communication we demonstrate that the activation of PSII electron transfer reactions in the cyanobacterium Synechocystis sp. PCC 6803 takes place sequentially. In this organism partially assembled PSII complexes can be detected in the plasma membrane. We have determined that such PSII complexes can undergo light-induced charge separation and contain a functional electron acceptor side but not an assembled donor side. In contrast, PSII complexes in thylakoid membrane are fully assembled and capable of multiple turnovers. We conclude that PSII reaction center cores assembled in the plasma membrane are photochemically competent and can catalyze single turnovers. We propose that upon transfer of such PSII core complexes to the thylakoid membrane, additional proteins are incorporated followed by binding and activation of various donor side cofactors. Such a stepwise process protects cyanobacterial cells from potentially harmful consequences of performing water oxidation in a partially assembled PSII complex before it reaches its final destination in the thylakoid membrane.

Spectroscopic and quantum chemical study of pressure effects on solvated chlorophyll

Hydrostatic pressure effects up to 907 MPa on absorption spectra of chlorophyll a molecules dissolved in diethyl ether have been studied at ambient temperature both experimentally and theoretically using quantum chemistry methods. The fluorescence spectra are studied only experimentally. The data suggest that coordination interactions between the central Mg atom of the chlorophyll and solvent molecules along with interactions that modify the porphyrin skeleton of the solute are responsible for the observed differences of pressure dependence of the Q y , Q x , and Soret spectral bands. The coordination number of the Mg atom changes from five to six between 400 and 600 MPa.

Effect of gamma-irradiation on the biophysical and morphological properties of corn.

The effects of gamma-irradiation on the biophysical and morphological properties of corn plants were investigated. The irradiation doses were 0, 1, 1.5, 2.5, 5, and 10 krad. Corn grains exposed to 1.5 and 2.5 krad showed highly significant changes in all growth parameters. Fluorescence and light absorption spectra of chlorophyll attributed to different doses treatments of corn grains clearly confirmed the superiority of 1.5 krad irradiation dose in stimulating corn plants. Furthermore, the frequency dependence of the relative permittivity and the electric conductivity of the treated samples have been performed and discussed. The obtained results give another support via the biophysical properties for the 1.5 krad irradiation dose to be the most favorable one to improve the plant growth characteristics.

Phytol as one of the determinants of chlorophyll interactions in solution.

Optical absorption and fluorescence parameters of chlorophyll a and the phytol-free chlorophyllide a, as well as of their Mg-depleted derivatives, were compared in a series of organic solvents. In contrast to prevailing opinion, the spectral properties of chlorophyll are not indifferent to the removal of phytol. The electronic absorption spectra of chlorophyll a and chlorophyllide a differ and display a different dependence on the nature of the solvent, which cannot be explained solely by the location of a charged carboxylic group in the proximity of the pi- electron system. In fact, measurements in media of varying basicity show that deprotonation of the free carboxylic group in chlorophyllide, i.e., the presence of a negative point charge near the macrocycle, has no effect on pigment absorption spectra. Analysis of the solvent effect on the Q(Y) energies in terms of solvent polarity reveals that the phytyl moiety perturbs the spectral features of chlorophyll, mainly due to its interactions with the pigment solvation shell. The phytyl residue might also be thus partly involved in controlling the central metal ligation in chlorophylls. This influence of phytol on the spectral features of chlorophyll should be taken into account when comparing the spectra in solution with various spectral forms of chlorophyll in vivo.

The Calculated In Vitro and In Vivo Chlorophyll a Absorption Bandshape

The room temperature absorption bandshape for the Q transition region of chlorophyll a is calculated using the vibrational frequency modes and Franck–Condon (FC) factors obtained by line-narrowing spectroscopies of chlorophyll a in a glassy (Rebane and Avarmaa, Chem. Phys. 1982; 68:191–200) and in a native environment (Gillie et al., J. Phys. Chem. 1989; 93:1620–1627) at low temperatures. The calculated bandshapes are compared with the absorption spectra of chlorophyll a measured in two different solvents and with that obtained in vivo by a mutational analysis of a chlorophyll–protein complex. It is demonstrated that the measured distributions of FC factors can account for the absorption bandshape of chlorophyll a in a hexacoordinated state, whereas, when pentacoordinated, reduced FC coupling for vibrational frequencies in the range 540–850 cm −1 occurs. The FC factor distribution for pentacoordinated chlorophyll also describes the native chlorophyll a spectrum but, in this case, either a low-frequency mode ( ν < 200 cm −1) must be added or else the 262-cm −1 mode must increase in coupling by about one order of magnitude to describe the skewness of the main absorption bandshape.

Absorption spectra of chlorophyll a and b in Lhcb protein environment.

The spectral forms of the two chlorophyll species in higher plant Photosystem II antenna proteins have been experimentally determined within their protein environment. Recombinant CP29 and LHC II antenna proteins missing individual chromophores were obtained by over-expression in bacteria without any changing of the primary protein sequence and in vitro reconstitution. Difference absorption spectroscopy with respect to the corresponding proteins binding the complete pigment complement yielded the spectral shape and extinction of single chlorophyll a and b. A functional relation of their absorption was given by Gaussian subband decomposition covering the entire Q(x) and Q(y) optical region together with the absolute value of the molar extinction coefficient. With respect to analogous determinations reported in the literature for organic solvents, this information is valuable for further understanding the in-protein chlorophyll excited states and excited state dynamics: in particular, for the calculation of Förster transfer rates by means of chlorophyll-chlorophyll overlap integral employing the Stepanov relation for emission and single chromophore transition energies according to the results of mutational analysis of chlorophyll binding sites [Bassi et al. (1999) Proc Natl Acad Sci USA 96: 10056-10061; Remelli et al. (1999) J Biol Chem 274: 33510-33521].

Spectroscopic properties of Mg-chlorin, Mg-porphin and chlorophylls a, b, c1, c2, c3 and d studied by semi-empirical and ab initio MO/CI methods

The semi-empirical and ab initio molecular orbital/configuration interaction (MO/CI) methods were used to study spectroscopic properties of chlorophylls a, b, c1, c2, c3 and d and magnesium porphin and magnesium chlorin. Energy minimisation at the PM3 level of all chlorophylls put the magnesium atom away from the centre and above the porphyrin ring and the atomic charges on the nitrogen atoms became positive. At the ab initio HF/6-31G* level of calculation the magnesium is centrally located in the porphyrin plane and the atomic charge on the magnesium atom is positive and that on the surrounding nitrogens negative. Three CI methods used, ZINDO/S CIS (15,15), PM3 CISD (5,5) and ab initio CIS (5,5)/6-31G*, obeyed linear correlation between the experimentally observed and calculated spectroscopic transition energies. The PM3 CISD (5,5) method gave best estimates of Qy, Qx and the Soret transition energies, but predicted oscillator strengths poorly. The ZINDO/S CIS (15,15) method gave best results in the overall simulation of the absorption spectra of chlorophylls, both intensities and wavelengths. The effect of solvent co-ordination on the excited states of chlorophyll a and chlorophyll b was also studied. Calculations predict solvent induced spectroscopic shifts of the Qx and Soret transitions but leave the Qy transition almost unshifted. This is a result of solvent-induced energy level shifts and charge redistribution on the magnesium atom of chlorophylls in the excited states. The results are discussed with reference to spectroscopic properties of chlorophylls in solution, chlorophylls in aggregates and in photosynthetic light-harvesting antenna.

SLOP: A Revised Version of the Stochastic Model for Leaf Optical Properties

SLOP (stochastic model for leaf optical properties) is a revised version of the stochastic model for leaf optical properties. It calculates the reflection, transmission, and absorption of light by leaves in the spectral region from 400 nm up to 2.5 μm. The model treats the radiative transfer of diffuse light as transitions of light with weighted probabilities according to the theory of homogeneous Markov chains. The leaves are divided in several compartments analogous to the well-known leaf structure. As the specific absorption coefficients of chlorophylls are one of the main parameters of the model, special attention has been paid to derive the specific absorption spectra of chlorophyll a and b in vivo. A comparison of modeled with measured leaf spectra from the LOPEX campaign shows good agreement. With this model also, the reflectance both of the upper and lower side of a dicotyledon leaf was calculated with the same parameters, demonstrating the typical differences observed by measurements.

Effects of Simulated Acid Rain on Pinus densiflora: Inhibition of Net Photosynthesis by the Pheophytization of Chlorophyll

This research addressed the effects of simulated acid rain on the chlorophyll contents of leaves of Pinus densiflora, on the net photosynthetic rate on a unit chlorophyll basis, and on chlorophyll degradation. When NO3- concentrations in rain water increased, the chlorophylla+b contents of the leaves increased in parallel, even though the pH of the simulated rain decreased. The nitrogen content of the rain was sufficient to stimulate the production of chlorophyll and was able to override any degradative effect expected due to the H+ input from acid rain. The absorption spectrum of chlorophyll extracted from the leaves exposed to acid rain showed peaks at 665, 606 and 535 nm, characteristic of pheophytin a, indicating degradation of chlorophyll to pheophytin. Net photosynthetic rate on the basis of chlorophyll content was reduced by acid rain, even though the total chlorophyll content of the leaves was increased. The acid rain does, therefore, simultaneously increase chlorophyll content and reduce the efficiency of the use of chlorophyll in photosynthesis. This reduced efficiency may be linked to the increase in the rate of degradation of chlorophyll to pheophytin.

Spectrophotometric Analysis of Carotenoids in Plant Extracts Based on Elimination of Chlorophyll Absorption

Subtraction of the absorption spectra of chlorophyll(s) from the total spectra of plant cell extracts reveals the carotenoid absorption spectra in both the ultraviolet and visible regions, from which the total carotenoid content can be easily evaluated. The applications of this method to Spirulina platensis cells treated with the herbicide norflurazon and to Anabaena siamensis cells grown under high light irradiation are demonstrated. The possibility of subtraction of the absorption of both chlorophyll a and b is demonstrated in an extract of the leaves of a higher plant (grape).

AUTHENTIC in vivo ABSORPTION SPECTRA FOR CHLOROPHYLL IN LEAVES AS DERIVED FROM in situ AND in vitro MEASUREMENTS*

AbstractOn the basis of a comprehensive treatment of light propagation in plant tissue the first authentic in vivo absorption spectrum of chlorophyll in a leaf (of Catalpa bignonioides) has been elucidated. An experimental‐theoretical procedure is described, which permits derivation of the authentic chlorophyll spectrum by purifying the in vivo absorption spectrum of a leaf from the distortions of optical origin: multiple scattering and distributional error. The procedure involves measurements of internal and external light fluxes, spatial characterization of tissue layers, cells, chloroplasts and grana stacks. Furthermore, one has to determine the local chlorophyll concentrations. The theories of radiation transfer and absorption statistics make up the theoretical basis of the procedure. The derived authentic chlorophyll spectrum differs both from the in vivo spectrum of the leaf and (although to a smaller degree) from the in vitro spectrum of chlorophyll‐protein complexes extracted from the same leaf.

Regulation of nitrogenase activity by light in the azolla-anabaena symbiosis

Nitrogenase activity and the rate of photosynthesis were measured simultaneously in Azolla by a continuous gas flow system. The mode of interaction between light, photosynthesis and nitrogenase activity was analysed. Nitrogenase activity dropped off when either Azolla plants or the cyanobiont Anabaena were transferred from light to dark. This decline was immediate and was independent of length or intensity of the prior light phase. Reillumination restored nitrogenase activity. Nitrogenase activity did not depend on the rate of photosynthesis at light intensities below 10 μE m −2 s −1. Its activity was saturated at 200 μE m −2 s −1 while CO 2 fixation was saturated at a light intensity of 850 μE m −2 s −1. Azolla photosynthetic activity followed the absorption spectrum of chlorophyll a, while nitrogenase activity markedly increased between 690 and 710 nm. Inhibition of photosynthesis by DCMU was accompanied by an increase in nitrogenase activity. These results suggest direct light regulation of nitrogenase activity in Azolla independent of CO 2 fixation, and a possible inhibition of nitrogenase activity by the oxygen produced in photosynthesis.

EFFECT OF LIGHT QUALITY ON THE in vitro THYLAKOID PROTEIN PHOSPHORYLATION IN THE GREEN ALGA Scenedesmus obliquus

Abstract Thylakoid protein phosphorylation was assayed in vitro with isolated thylakoids of Scenedesmus obliquus by irradiation with monochromatic light of different wavelengths and equal photon fluences. The action spectrum for light‐activated protein phosphorylation showed two maxima at 450 and 679 nm. A minimum of activity was reached around 580 nm. At this wavelength, the level of protein phosphorylation barely differed from that of dark‐incubated samples. The action spectrum of thylakoid protein phosphorylation resembled the chlorophyll absorption spectrum obtained in vivo. The results show that chlorophyll is the photoreceptor for thylakoid membrane phosphorylation.