Mark Merzlyak - Academia.edu (original) (raw)

Papers by Mark Merzlyak

Research paper thumbnail of The allomerization of chlorophylls a and b with superoxide anion

Journal of Inorganic Biochemistry, 1985

Research paper thumbnail of Non-Destructive Estimation of Anthocyanins and Chlorophylls in Anthocyanic Leaves

The anthocyanin and chlorophyll contents in leaves provide valuable information about the physiol... more The anthocyanin and chlorophyll contents in leaves provide valuable information about the physiological status of plants. Thus, there is a need for accurate, effi cient, and practical methodologies to estimate these biochemical parameters of vegetation. In this study, we tested the performance and accuracy of several nondestructive, refl ectance-based techniques for estimating anthocyanin and chlorophyll contents in leaves of four unrelated species, European hazel ( Corylus avellana ), Siberian dogwood ( Cornus alba = Swida alba ), Norway maple ( Acer platanoides ), and Virginia creeper ( Parthenocissus quinquefolia ), with widely variable pigment content and composition. An anthocyanin refl ectance index, which uses refl ectances in the green and red edge spectral bands, and a modifi ed anthocyanin refl ectance index, employing, in addition, the near-infrared (NIR) band, were able to accurately estimate leaf anthocyanin for all species taken together with no reparameterization of algorithms. Total chlorophyll content was accurately estimated by a red edge chlorophyll index that uses spectral bands in the red edge and the NIR. These approaches can be used to estimate anthocyanin and chlorophyll nondestructively and allow the development of simple handheld fi eld instrumentation.

Research paper thumbnail of Spectral reflectance changes associated with autumn senescence of Aesculus hippocastanum L. and Acer platanoides L. leaves. Spectral features and relation to chrororophyll estimation

Journal of Plant Physiology, 1994

Page 1. J. Plant Physiol. Vol. 143. pp. 286-292(1994) Spectral Reflectance Changes Associated wit... more Page 1. J. Plant Physiol. Vol. 143. pp. 286-292(1994) Spectral Reflectance Changes Associated with Autumn Senescence of Aesculus hippocastanum L. and Acerplatanoides L. Leaves. Spectral Features and Relation to Chlorophyll ...

Research paper thumbnail of Superoxide Mediated Chlorophyll Allomerization in a Dimethyl Sulphoxide-Water Mixture

The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water syst... more The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water system. It was found that O2(-.), directly or via HO2., produces the chlorophyll enolate-ion (Molish's intermediate) that is oxidized to Mg-chlorine(s). The allomerization reaction was found to be inhibited by superoxide dismutase. A possible participation of oxygen radicals in chlorophyll degradation in plants is discussed.

Research paper thumbnail of Stimulation of nadph-dependent lipid peroxidation by 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid and diquat in microsomes isolated from Pisum sativum

Plant Science Letters, 1984

Abstract 2, 4-Dichlorophenoxyacetic acid (2, 4-D), 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T... more Abstract 2, 4-Dichlorophenoxyacetic acid (2, 4-D), 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T) and diquat (DQ) stimulate NADPH-dependent lipid peroxidation (in the presence of ADP-Fe 2+ complex) in microsomes from green leaves and etiolated seedlings. The activity ...

Research paper thumbnail of Detection of Red Edge Position and Chlorophyll Content by Reflectance Measurements Near 700 nm

Pigment contents was determined in and high spectral resolution reflectance measurements were acq... more Pigment contents was determined in and high spectral resolution reflectance measurements were acquired for spring, summer and autumn maple and horse chestnut leaves covering a wide range of chlorophyll content. Consistent and diagnostic differences in the red edge range (680-750 nm) of the reflectance spectrum were obtained for the various leaf samples of both species studied. This included the differences in the wavelength position of the red edge and in the reflectance values in the range of 690 to 710 nm. Both characteristics were found to be dependent on leaf chlorophyll concentration. The nrst derivative of reflectance spectra showed four peaks at 685-706, 710, 725 and 740 nm that were dependent in different degree on leaf age and pigment concentration in the leaves. The position and the magnitude of the nrst peak showed a high correlation with the leaf chlorophyll concentration. Reflectance at 700 nm was linearly dependent on the wavelength of the nrst peak. Variation of inflection point position with change in chlorophyll content was found small for yellow-green to dark green leaves (total chlorophyll in the range above 10 nmollcm 2 ). Reflectance near 700 nm was found to be a very sensitive indicator of the red edge position as well as of chlorophyll concentration. The ratio of reflectances at 750 nm to that near 700 nm (R7S0/R700) was directly proportional (correlation r 2 >0.95) to chlorophyll concentration. The ratio R7S0/R700 as a newly established index for non-invasive in-vivo chlorophyll determination was tested by independent data sets in the range of Chi contents from 0.6 to more than 60 nmol/cm 2 of maple and chestnut leaves with an estimation error of Chi ofless than 3.7nmollcm 2 • Abbreviations: Chi = chlorophyll; Chi a and b = chlorophyll a and b; Car = total carotenoids; red edge = increase in the reflectance spectrum of leaves between 680 and 750 nm; NIR = near infra-red range of the spectrum; A. re = wavelength position of inflection point at red edge of the reflectance spectrum.

Research paper thumbnail of Signature Analysis of Leaf Reflectance Spectra: Algorithm Development for Remote Sensing of Chlorophyll

The goal of the study is to investigate the basic spectral properties of plant leaves to develop ... more The goal of the study is to investigate the basic spectral properties of plant leaves to develop spectral indices more sensitive to chlorophyll concentration than the presently widely used Normalized Difference Vegetation Index. These indices can serve as indicators of stress, senescence, and disease in higher plants. The spectral reflectance of senescing leaves of two deciduous species (maple and chestnut) as well as their pigment content were measured. Spectral indices were developed using reflectances corresponding to wavelengths with maximum and minimum sensitivity to variation in pigment concentration. The signature analysis of reflectance spectra indicated that, for a wide range of leaf greenness (completely yellow to dark green leaves), the maximum sensitivity of reflectance coincides with the maximum absorption of chlorophyll a at 670 nm. However, for yellow-green to green leaves (minimum chlorophyll a as low as 3-5 nmollcm 2 ), the reflectance near 670 nm is not sensitive to chlorophyll concentration due to saturation effects. Therefore, it seems inappropriate to use this spectral band for pigment estimation in yellow-green to green vegetation. The spectral bands ranging from 400 to 480 nm and above 730 nm are not sensitive to chlorophyll concentration as found for 670 nm. The reflectances at these wavelengths could be used as references in the vegetation indices. Maximum sensitivity to chlorophyll a concentration was found at 550-560 nm and 700-710 nm. Reflectances at 700 nm correlated very well with that at 550 nm for a wide range of chlorophyll concentrations for both plant species studied. The inverse reflectance, (R 550 )-1 and (R 700 )-1 are proportional to chlorophyll a concentration; therefore indices R750/R550 and R750/R700 are directly proportional (correlation r 2 >0.95) to chlorophyll concentration. These indices were tested for a wide range of chlorophyll a concentration, using several independent data sets. The estimation error in the derivation of chlorophyll concentration from the indices is assessed to be less than 1.2 nmollcm 2 .

Research paper thumbnail of Destruction of Pigments and Ultrastructural Changes in Cyanobacteria during Photodamage

Russian Journal of Plant Physiology, 2000

Sequential stages of pigment degradation and ultrastructural changes were examined in cyanobacter... more Sequential stages of pigment degradation and ultrastructural changes were examined in cyanobacteria Anabaena variabilis ATCC 29413, Synechococcus sp. PCC 6301 ( Anacystis nidulans ) and S. elongatus B-267 during irradiation of cell suspensions with high-intensity light. Early manifestations of photooxidative destruction were evident as profound changes in ultrastructure of thylakoids; in A. variabilis these changes appeared even before bleaching of pigments. Concomitant to these alterations, the cytoplasmic matrix turned homogenous and the nucleoid was subject to degradation, while ultrastructural changes of cytoplasmic membrane and cell walls became evident in some species. In A. variabilis these changes were related to a subsequent autolysis of cells. Synechococcus strains demonstrated comparatively high resistance to irradiation. The experimental data were compared with previously described behavior of the same species of cyanobacteria cultured under photooxidative conditions. This comparison revealed principal similarity and species-specific features in the destructive changes of thylakoids and other cell components of cyanobacterial cells.

Research paper thumbnail of Hydrogen peroxide- and superoxide-dependent fatty acid breakdown in Phytophthora infestans zoospores

Plant Science, 1990

ABSTRACT Degradation of polyunsaturated (linoleic and eicosapentaenoic) fatty acids induced by hy... more ABSTRACT Degradation of polyunsaturated (linoleic and eicosapentaenoic) fatty acids induced by hydrogen peroxide and superoxide- and hydroxyl radical-generating systems was studied in zoospores of phytopathogenic fungus Phytophthora infestans. Both fatty acids showed sensitivity to the treatments. It was proposed that the oxidative reactions in lipids involve superoxide-mediated formation of hydroxyl radicals. The role of lipid peroxidation as a mechanism of fungicidal activity of oxygen radicals and their possible involvement in production of eicosapolyunsaturated fatty acid metabolites(s) responsible for elicitation of defense reactions in host-plants are discussed.

Research paper thumbnail of Effect of Phytophthora infestans infection on superoxide dismutase dependent cytochrome c—reducing activities of leaves as related to resistance of potato plants to late blight

Plant Science, 1991

ABSTRACT The time-course and phenomenology of superoxide production during compatible and incompa... more ABSTRACT The time-course and phenomenology of superoxide production during compatible and incompatible interactions of the potato, Phytophthora infestans system were studied in the potato plants grown in ‘aseptic’ conditions by assaying superoxide dismutase-inhibited cytochrome c reducing active after fungal penetration were dependent onthe plant susceptibility to P. infestans. Superoxide dismutase-sensitive cytochrome c reducing activity was also found in both leaf tissues and diffusates 17–20 h after infection of potato plants by compatible races of P. infestans. The pattern of O2 ⨪ -production in cultivars having high field resistance to late blight was shown to be similar to that in incompatible interactions. The participation of activated oxygen species in vertical and horizontal resistance of potato plants are discussed.

Research paper thumbnail of Absorption and scattering of light by suspensions of cells and subcellular particles: an analysis in terms of Kramers?Kronig relations

Photochemical & Photobiological Sciences, 2004

An analysis of light scattering from suspensions of pigmented cells and particles is undertaken, ... more An analysis of light scattering from suspensions of pigmented cells and particles is undertaken, and a practicable method, requiring only the experimentally measured extinction spectra, is documented. The analysis is based on two premises: Absorption and selective scattering from a single pool of pigments satisfy the Kramers-Kronig relations, which imply that one can be derived from the other; pigment-free domains contribute only nonselective scattering. This approach succeeds in simulating the spectra of many systems (human erythrocytes, chloroplasts and subchloroplast particles, algal cells) over a wide spectral range. Other, less favourable, cases are also examined, but even here the apparent discrepancy between theory adn experiment provides some clues that cannot be gleaned from absorption data alone.

Research paper thumbnail of Modeling pigment contributions to spectral reflection of apple fruit

Photochemical & Photobiological Sciences, 2006

A simple approach for spectral reconstruction of spectral reflection by whole apple fruit is desc... more A simple approach for spectral reconstruction of spectral reflection by whole apple fruit is described. It is shown that an approximation to the reflection spectrum can be obtained by making a simple assumption on the shape of the featureless scattering and using known spectral properties of the following pigment pools: (i) thylakoid-bound chlorophylls and carotenoids, (ii) cuticular/vacuolar phenolics, (iii) extrathylakoid chloroplasts/chromoplasts carotenoids, and (iv) vacuolar anthocyanins. The in vivo spectra of individual pigment pools estimated in bleaching experiments or as a difference between fruit with high and low pigment content are presented. In most cases simulations based on a linear combination of spectra proved to be effective, but fruit with high chlorophyll content necessitated the use of a non-linear model. The models succeeded in simulating reflection spectra of fruit widely differing in pigment content and composition with relative error lower than +/-4% over the visible range. The estimated relative contributions by the pigment pools into total reflection were found to be sensitive indicators of apple fruit ripening and could be useful in evaluating the light screening efficacy by flavonoids and carotenoids under stress conditions.

Research paper thumbnail of Why and What for the Leaves Are Yellow in Autumn? On the Interpretation of Optical Spectra of Senescing Leaves (Acerplatanoides L.)

Journal of Plant Physiology, 1995

Research paper thumbnail of Effect of Desiccation on Chlorophyll High Temperature Chemiluminescence in Acer platanoides L. and Aesculus hippocastanum L. Leaves

Journal of Plant Physiology, 1992

Research paper thumbnail of Spectral Reflectance Changes Associated with Autumn Senescence of Aesculus hippocastanum L. and Acer platanoides L. Leaves. Spectral Features and Relation to Chlorophyll Estimation

Journal of Plant Physiology, 1994

... The several functions of reflectance were found to be directly propor-tional to Chi (a square... more ... The several functions of reflectance were found to be directly propor-tional to Chi (a square of correlation coefficient of more than C.97); that allows an assessment of the pig-ment concentration ranging from C.5 to 27.5nmol/cnr with an estimation error of less than l.bnmol/ cm2. ...

Research paper thumbnail of Improved solvent system for plant pigment separation on silica gel thin layers

Journal of Chromatography A, 1983

Research paper thumbnail of Reconstruction of microalgal suspension absorption spectra from reflectance spectra of the cells deposited on GF/F filters

Israel Journal of Plant Sciences, 2012

Research paper thumbnail of Remote estimation of chlorophyll content in higher plant leaves

International Journal of Remote Sensing, 1997

Research paper thumbnail of Negative air ions as a source of superoxide

International Journal of Biometeorology, 1992

The physico-chemical characteristics and possible formation mechanisms of negative air ions are c... more The physico-chemical characteristics and possible formation mechanisms of negative air ions are considered. It was found that the products of oxygen and nitrogen negative ionization reduce ferricytochrome c and nitroblue tetrazolium, and that these reactions were inhibited by superoxide dismutase. The interaction of negatively ionized oxygen with water led to hydrogen peroxide accumulation, which was inhibited by tetranitromethane or catalase. Nitrogen ionization under these conditions caused the formation of the hydrated electron e~q and the superoxide anion O]. The data obtained indicate that the biological activity of negative air ions may be dependent on superoxide. The generation of reactive oxygen ions in the gas phase and also at a gas/ water interface is described. A scheme for superoxide production under oxygen and nitrogen ionization is proposed.

Research paper thumbnail of Superoxide Mediated Chlorophyll Allomerization in a Dimethyl Sulphoxide-Water Mixture

Free Radical Research, 1991

The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water syst... more The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water system. It was found that O2(-.), directly or via HO2., produces the chlorophyll enolate-ion (Molish's intermediate) that is oxidized to Mg-chlorine(s). The allomerization reaction was found to be inhibited by superoxide dismutase. A possible participation of oxygen radicals in chlorophyll degradation in plants is discussed.

Research paper thumbnail of The allomerization of chlorophylls a and b with superoxide anion

Journal of Inorganic Biochemistry, 1985

Research paper thumbnail of Non-Destructive Estimation of Anthocyanins and Chlorophylls in Anthocyanic Leaves

The anthocyanin and chlorophyll contents in leaves provide valuable information about the physiol... more The anthocyanin and chlorophyll contents in leaves provide valuable information about the physiological status of plants. Thus, there is a need for accurate, effi cient, and practical methodologies to estimate these biochemical parameters of vegetation. In this study, we tested the performance and accuracy of several nondestructive, refl ectance-based techniques for estimating anthocyanin and chlorophyll contents in leaves of four unrelated species, European hazel ( Corylus avellana ), Siberian dogwood ( Cornus alba = Swida alba ), Norway maple ( Acer platanoides ), and Virginia creeper ( Parthenocissus quinquefolia ), with widely variable pigment content and composition. An anthocyanin refl ectance index, which uses refl ectances in the green and red edge spectral bands, and a modifi ed anthocyanin refl ectance index, employing, in addition, the near-infrared (NIR) band, were able to accurately estimate leaf anthocyanin for all species taken together with no reparameterization of algorithms. Total chlorophyll content was accurately estimated by a red edge chlorophyll index that uses spectral bands in the red edge and the NIR. These approaches can be used to estimate anthocyanin and chlorophyll nondestructively and allow the development of simple handheld fi eld instrumentation.

Research paper thumbnail of Spectral reflectance changes associated with autumn senescence of Aesculus hippocastanum L. and Acer platanoides L. leaves. Spectral features and relation to chrororophyll estimation

Journal of Plant Physiology, 1994

Page 1. J. Plant Physiol. Vol. 143. pp. 286-292(1994) Spectral Reflectance Changes Associated wit... more Page 1. J. Plant Physiol. Vol. 143. pp. 286-292(1994) Spectral Reflectance Changes Associated with Autumn Senescence of Aesculus hippocastanum L. and Acerplatanoides L. Leaves. Spectral Features and Relation to Chlorophyll ...

Research paper thumbnail of Superoxide Mediated Chlorophyll Allomerization in a Dimethyl Sulphoxide-Water Mixture

The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water syst... more The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water system. It was found that O2(-.), directly or via HO2., produces the chlorophyll enolate-ion (Molish's intermediate) that is oxidized to Mg-chlorine(s). The allomerization reaction was found to be inhibited by superoxide dismutase. A possible participation of oxygen radicals in chlorophyll degradation in plants is discussed.

Research paper thumbnail of Stimulation of nadph-dependent lipid peroxidation by 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid and diquat in microsomes isolated from Pisum sativum

Plant Science Letters, 1984

Abstract 2, 4-Dichlorophenoxyacetic acid (2, 4-D), 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T... more Abstract 2, 4-Dichlorophenoxyacetic acid (2, 4-D), 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T) and diquat (DQ) stimulate NADPH-dependent lipid peroxidation (in the presence of ADP-Fe 2+ complex) in microsomes from green leaves and etiolated seedlings. The activity ...

Research paper thumbnail of Detection of Red Edge Position and Chlorophyll Content by Reflectance Measurements Near 700 nm

Pigment contents was determined in and high spectral resolution reflectance measurements were acq... more Pigment contents was determined in and high spectral resolution reflectance measurements were acquired for spring, summer and autumn maple and horse chestnut leaves covering a wide range of chlorophyll content. Consistent and diagnostic differences in the red edge range (680-750 nm) of the reflectance spectrum were obtained for the various leaf samples of both species studied. This included the differences in the wavelength position of the red edge and in the reflectance values in the range of 690 to 710 nm. Both characteristics were found to be dependent on leaf chlorophyll concentration. The nrst derivative of reflectance spectra showed four peaks at 685-706, 710, 725 and 740 nm that were dependent in different degree on leaf age and pigment concentration in the leaves. The position and the magnitude of the nrst peak showed a high correlation with the leaf chlorophyll concentration. Reflectance at 700 nm was linearly dependent on the wavelength of the nrst peak. Variation of inflection point position with change in chlorophyll content was found small for yellow-green to dark green leaves (total chlorophyll in the range above 10 nmollcm 2 ). Reflectance near 700 nm was found to be a very sensitive indicator of the red edge position as well as of chlorophyll concentration. The ratio of reflectances at 750 nm to that near 700 nm (R7S0/R700) was directly proportional (correlation r 2 >0.95) to chlorophyll concentration. The ratio R7S0/R700 as a newly established index for non-invasive in-vivo chlorophyll determination was tested by independent data sets in the range of Chi contents from 0.6 to more than 60 nmol/cm 2 of maple and chestnut leaves with an estimation error of Chi ofless than 3.7nmollcm 2 • Abbreviations: Chi = chlorophyll; Chi a and b = chlorophyll a and b; Car = total carotenoids; red edge = increase in the reflectance spectrum of leaves between 680 and 750 nm; NIR = near infra-red range of the spectrum; A. re = wavelength position of inflection point at red edge of the reflectance spectrum.

Research paper thumbnail of Signature Analysis of Leaf Reflectance Spectra: Algorithm Development for Remote Sensing of Chlorophyll

The goal of the study is to investigate the basic spectral properties of plant leaves to develop ... more The goal of the study is to investigate the basic spectral properties of plant leaves to develop spectral indices more sensitive to chlorophyll concentration than the presently widely used Normalized Difference Vegetation Index. These indices can serve as indicators of stress, senescence, and disease in higher plants. The spectral reflectance of senescing leaves of two deciduous species (maple and chestnut) as well as their pigment content were measured. Spectral indices were developed using reflectances corresponding to wavelengths with maximum and minimum sensitivity to variation in pigment concentration. The signature analysis of reflectance spectra indicated that, for a wide range of leaf greenness (completely yellow to dark green leaves), the maximum sensitivity of reflectance coincides with the maximum absorption of chlorophyll a at 670 nm. However, for yellow-green to green leaves (minimum chlorophyll a as low as 3-5 nmollcm 2 ), the reflectance near 670 nm is not sensitive to chlorophyll concentration due to saturation effects. Therefore, it seems inappropriate to use this spectral band for pigment estimation in yellow-green to green vegetation. The spectral bands ranging from 400 to 480 nm and above 730 nm are not sensitive to chlorophyll concentration as found for 670 nm. The reflectances at these wavelengths could be used as references in the vegetation indices. Maximum sensitivity to chlorophyll a concentration was found at 550-560 nm and 700-710 nm. Reflectances at 700 nm correlated very well with that at 550 nm for a wide range of chlorophyll concentrations for both plant species studied. The inverse reflectance, (R 550 )-1 and (R 700 )-1 are proportional to chlorophyll a concentration; therefore indices R750/R550 and R750/R700 are directly proportional (correlation r 2 >0.95) to chlorophyll concentration. These indices were tested for a wide range of chlorophyll a concentration, using several independent data sets. The estimation error in the derivation of chlorophyll concentration from the indices is assessed to be less than 1.2 nmollcm 2 .

Research paper thumbnail of Destruction of Pigments and Ultrastructural Changes in Cyanobacteria during Photodamage

Russian Journal of Plant Physiology, 2000

Sequential stages of pigment degradation and ultrastructural changes were examined in cyanobacter... more Sequential stages of pigment degradation and ultrastructural changes were examined in cyanobacteria Anabaena variabilis ATCC 29413, Synechococcus sp. PCC 6301 ( Anacystis nidulans ) and S. elongatus B-267 during irradiation of cell suspensions with high-intensity light. Early manifestations of photooxidative destruction were evident as profound changes in ultrastructure of thylakoids; in A. variabilis these changes appeared even before bleaching of pigments. Concomitant to these alterations, the cytoplasmic matrix turned homogenous and the nucleoid was subject to degradation, while ultrastructural changes of cytoplasmic membrane and cell walls became evident in some species. In A. variabilis these changes were related to a subsequent autolysis of cells. Synechococcus strains demonstrated comparatively high resistance to irradiation. The experimental data were compared with previously described behavior of the same species of cyanobacteria cultured under photooxidative conditions. This comparison revealed principal similarity and species-specific features in the destructive changes of thylakoids and other cell components of cyanobacterial cells.

Research paper thumbnail of Hydrogen peroxide- and superoxide-dependent fatty acid breakdown in Phytophthora infestans zoospores

Plant Science, 1990

ABSTRACT Degradation of polyunsaturated (linoleic and eicosapentaenoic) fatty acids induced by hy... more ABSTRACT Degradation of polyunsaturated (linoleic and eicosapentaenoic) fatty acids induced by hydrogen peroxide and superoxide- and hydroxyl radical-generating systems was studied in zoospores of phytopathogenic fungus Phytophthora infestans. Both fatty acids showed sensitivity to the treatments. It was proposed that the oxidative reactions in lipids involve superoxide-mediated formation of hydroxyl radicals. The role of lipid peroxidation as a mechanism of fungicidal activity of oxygen radicals and their possible involvement in production of eicosapolyunsaturated fatty acid metabolites(s) responsible for elicitation of defense reactions in host-plants are discussed.

Research paper thumbnail of Effect of Phytophthora infestans infection on superoxide dismutase dependent cytochrome c—reducing activities of leaves as related to resistance of potato plants to late blight

Plant Science, 1991

ABSTRACT The time-course and phenomenology of superoxide production during compatible and incompa... more ABSTRACT The time-course and phenomenology of superoxide production during compatible and incompatible interactions of the potato, Phytophthora infestans system were studied in the potato plants grown in ‘aseptic’ conditions by assaying superoxide dismutase-inhibited cytochrome c reducing active after fungal penetration were dependent onthe plant susceptibility to P. infestans. Superoxide dismutase-sensitive cytochrome c reducing activity was also found in both leaf tissues and diffusates 17–20 h after infection of potato plants by compatible races of P. infestans. The pattern of O2 ⨪ -production in cultivars having high field resistance to late blight was shown to be similar to that in incompatible interactions. The participation of activated oxygen species in vertical and horizontal resistance of potato plants are discussed.

Research paper thumbnail of Absorption and scattering of light by suspensions of cells and subcellular particles: an analysis in terms of Kramers?Kronig relations

Photochemical & Photobiological Sciences, 2004

An analysis of light scattering from suspensions of pigmented cells and particles is undertaken, ... more An analysis of light scattering from suspensions of pigmented cells and particles is undertaken, and a practicable method, requiring only the experimentally measured extinction spectra, is documented. The analysis is based on two premises: Absorption and selective scattering from a single pool of pigments satisfy the Kramers-Kronig relations, which imply that one can be derived from the other; pigment-free domains contribute only nonselective scattering. This approach succeeds in simulating the spectra of many systems (human erythrocytes, chloroplasts and subchloroplast particles, algal cells) over a wide spectral range. Other, less favourable, cases are also examined, but even here the apparent discrepancy between theory adn experiment provides some clues that cannot be gleaned from absorption data alone.

Research paper thumbnail of Modeling pigment contributions to spectral reflection of apple fruit

Photochemical & Photobiological Sciences, 2006

A simple approach for spectral reconstruction of spectral reflection by whole apple fruit is desc... more A simple approach for spectral reconstruction of spectral reflection by whole apple fruit is described. It is shown that an approximation to the reflection spectrum can be obtained by making a simple assumption on the shape of the featureless scattering and using known spectral properties of the following pigment pools: (i) thylakoid-bound chlorophylls and carotenoids, (ii) cuticular/vacuolar phenolics, (iii) extrathylakoid chloroplasts/chromoplasts carotenoids, and (iv) vacuolar anthocyanins. The in vivo spectra of individual pigment pools estimated in bleaching experiments or as a difference between fruit with high and low pigment content are presented. In most cases simulations based on a linear combination of spectra proved to be effective, but fruit with high chlorophyll content necessitated the use of a non-linear model. The models succeeded in simulating reflection spectra of fruit widely differing in pigment content and composition with relative error lower than +/-4% over the visible range. The estimated relative contributions by the pigment pools into total reflection were found to be sensitive indicators of apple fruit ripening and could be useful in evaluating the light screening efficacy by flavonoids and carotenoids under stress conditions.

Research paper thumbnail of Why and What for the Leaves Are Yellow in Autumn? On the Interpretation of Optical Spectra of Senescing Leaves (Acerplatanoides L.)

Journal of Plant Physiology, 1995

Research paper thumbnail of Effect of Desiccation on Chlorophyll High Temperature Chemiluminescence in Acer platanoides L. and Aesculus hippocastanum L. Leaves

Journal of Plant Physiology, 1992

Research paper thumbnail of Spectral Reflectance Changes Associated with Autumn Senescence of Aesculus hippocastanum L. and Acer platanoides L. Leaves. Spectral Features and Relation to Chlorophyll Estimation

Journal of Plant Physiology, 1994

... The several functions of reflectance were found to be directly propor-tional to Chi (a square... more ... The several functions of reflectance were found to be directly propor-tional to Chi (a square of correlation coefficient of more than C.97); that allows an assessment of the pig-ment concentration ranging from C.5 to 27.5nmol/cnr with an estimation error of less than l.bnmol/ cm2. ...

Research paper thumbnail of Improved solvent system for plant pigment separation on silica gel thin layers

Journal of Chromatography A, 1983

Research paper thumbnail of Reconstruction of microalgal suspension absorption spectra from reflectance spectra of the cells deposited on GF/F filters

Israel Journal of Plant Sciences, 2012

Research paper thumbnail of Remote estimation of chlorophyll content in higher plant leaves

International Journal of Remote Sensing, 1997

Research paper thumbnail of Negative air ions as a source of superoxide

International Journal of Biometeorology, 1992

The physico-chemical characteristics and possible formation mechanisms of negative air ions are c... more The physico-chemical characteristics and possible formation mechanisms of negative air ions are considered. It was found that the products of oxygen and nitrogen negative ionization reduce ferricytochrome c and nitroblue tetrazolium, and that these reactions were inhibited by superoxide dismutase. The interaction of negatively ionized oxygen with water led to hydrogen peroxide accumulation, which was inhibited by tetranitromethane or catalase. Nitrogen ionization under these conditions caused the formation of the hydrated electron e~q and the superoxide anion O]. The data obtained indicate that the biological activity of negative air ions may be dependent on superoxide. The generation of reactive oxygen ions in the gas phase and also at a gas/ water interface is described. A scheme for superoxide production under oxygen and nitrogen ionization is proposed.

Research paper thumbnail of Superoxide Mediated Chlorophyll Allomerization in a Dimethyl Sulphoxide-Water Mixture

Free Radical Research, 1991

The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water syst... more The interaction of chlorophyll a with superoxide anion was studied in an alkaline DMSO-water system. It was found that O2(-.), directly or via HO2., produces the chlorophyll enolate-ion (Molish's intermediate) that is oxidized to Mg-chlorine(s). The allomerization reaction was found to be inhibited by superoxide dismutase. A possible participation of oxygen radicals in chlorophyll degradation in plants is discussed.