M. Baranska et al.
6
only as a qualitative technique for identification and verification of unknown pure
substances isolated from extracts or distillates [4]. Nowadays, due to better equipment and modern techniques, Ft-IR spectroscopy has become a powerful tool for
elucidating the structure, physical properties, and interaction of various plant components. Raman spectra support IR analysis however due to weak scattering some
compounds can be difficult to identify.
vibrational spectroscopy methods can be applied for investigation of primary
and secondary plant metabolites. Primary metabolites are defined as those plant
constituents, which are essential for the life of plants. It means that they are directly
involved in plants normal growth, development, and reproduction. the most important representatives of this group are proteins, lipids, and carbohydrates.
Contrary to primary metabolites, secondary plant metabolites are usually unique
to individual plant species and occur in low concentrations. Furthermore, they are
not essential to plant cell survival and their importance is related to ecological aspects such as defense against predators, parasites and diseases, interspecies competition, and reproductive processes (colors, smells, etc.). Among a great number
of secondary metabolites, the most common are phenolic compounds, terpenoids,
alkaloids, polyacetylenes, nitrile compounds, iridoids and chlorophylls. Although
their very low concentration in plant material, resonance Raman and Ft-Raman
spectroscopies provide good spectra with no or little fluorescence [5, 6]. For instance, fruit ripening of various species can be followed by Raman spectroscopy
due to the fact that some carotenoids decline when other are accumulated during
the ripening process.
Apart from identification of primary and secondary plant metabolites, vibrational spectroscopy gives an opportunity to follow distribution of the metabolites
and other plant components simultaneously and directly in plant material ( in situ).
Such distribution studies can be performed using Raman mapping and IR imaging.
By combining these techniques with microscopy, molecular information can be obtained with high spatial resolution. there are numerous examples of the usage of
in situ Raman mapping technique for investigation of plant metabolites distribution
in cells, tissues, and whole parts of plants. one of the first Raman mapping studies
in plant research was performed on flax stem tissue gaining information on major
components (cellulose, lignin, polysaccharides) in different tissue types [7]. the
potential of Raman mapping combined with confocal microscope has been shown
for the components of cell walls of wood with a high spatial resolution (below
1 μm) [8]. Furthermore, application of polarized laser light provided an insight into
changes of orientation of the cell wall constituents [9].
high spatial resolution of Raman microscopy enables characterization of individual compounds in single plant cells. For instance, lipid droplets in xylem [10]
and spherical storage compounds in parenchyma cells [8] have been detected in
woody plants. Raman spectroscopy can be also applied for distribution studies in
single plant cells when imaging techniques are used. moreover, a single carotenoid
crystal has been detected directly in a carrot cell [11]. the cellular distribution of
carotenoids with the focus on the individual compounds (β-carotene or astaxanthin)
in single cells of various algae was performed [12, 13].
6
only as a qualitative technique for identification and verification of unknown pure
substances isolated from extracts or distillates [4]. Nowadays, due to better equipment and modern techniques, Ft-IR spectroscopy has become a powerful tool for
elucidating the structure, physical properties, and interaction of various plant components. Raman spectra support IR analysis however due to weak scattering some
compounds can be difficult to identify.
vibrational spectroscopy methods can be applied for investigation of primary
and secondary plant metabolites. Primary metabolites are defined as those plant
constituents, which are essential for the life of plants. It means that they are directly
involved in plants normal growth, development, and reproduction. the most important representatives of this group are proteins, lipids, and carbohydrates.
Contrary to primary metabolites, secondary plant metabolites are usually unique
to individual plant species and occur in low concentrations. Furthermore, they are
not essential to plant cell survival and their importance is related to ecological aspects such as defense against predators, parasites and diseases, interspecies competition, and reproductive processes (colors, smells, etc.). Among a great number
of secondary metabolites, the most common are phenolic compounds, terpenoids,
alkaloids, polyacetylenes, nitrile compounds, iridoids and chlorophylls. Although
their very low concentration in plant material, resonance Raman and Ft-Raman
spectroscopies provide good spectra with no or little fluorescence [5, 6]. For instance, fruit ripening of various species can be followed by Raman spectroscopy
due to the fact that some carotenoids decline when other are accumulated during
the ripening process.
Apart from identification of primary and secondary plant metabolites, vibrational spectroscopy gives an opportunity to follow distribution of the metabolites
and other plant components simultaneously and directly in plant material ( in situ).
Such distribution studies can be performed using Raman mapping and IR imaging.
By combining these techniques with microscopy, molecular information can be obtained with high spatial resolution. there are numerous examples of the usage of
in situ Raman mapping technique for investigation of plant metabolites distribution
in cells, tissues, and whole parts of plants. one of the first Raman mapping studies
in plant research was performed on flax stem tissue gaining information on major
components (cellulose, lignin, polysaccharides) in different tissue types [7]. the
potential of Raman mapping combined with confocal microscope has been shown
for the components of cell walls of wood with a high spatial resolution (below
1 μm) [8]. Furthermore, application of polarized laser light provided an insight into
changes of orientation of the cell wall constituents [9].
high spatial resolution of Raman microscopy enables characterization of individual compounds in single plant cells. For instance, lipid droplets in xylem [10]
and spherical storage compounds in parenchyma cells [8] have been detected in
woody plants. Raman spectroscopy can be also applied for distribution studies in
single plant cells when imaging techniques are used. moreover, a single carotenoid
crystal has been detected directly in a carrot cell [11]. the cellular distribution of
carotenoids with the focus on the individual compounds (β-carotene or astaxanthin)
in single cells of various algae was performed [12, 13].