Abstract
Equisetaceae has been of research interest for decades, as it is one of the oldest living plant families, and also due to its high accumulation of silica up to 25% dry wt. Aspects of silica deposition, its association with other biomolecules, as well as the chemical composition of the outer strengthening tissue still remain unclear. These questions were addressed by using high resolution (<1 microm) Confocal Raman microscopy. Two-dimensional spectral maps were acquired on cross sections of Equisetum hyemale and Raman images calculated by integrating over the intensity of characteristic spectral regions. This enabled direct visualization of differences in chemical composition and extraction of average spectra from defined regions for detailed analyses, including principal component analysis (PCA) and basis analysis (partial least square fit based on model spectra). Accumulation of silica was imaged in the knobs and in a thin layer below the cuticula. In the spectrum extracted from the knob region as main contributions, a broad band below 500 cm(-1) attributed to amorphous silica, and a band at 976 cm(-1) assigned to silanol groups, were found. From this, we concluded that these protrusions were almost pure amorphous, hydrated silica. No silanol group vibration was detected in the silicified epidermal layer below and association with pectin and hemicelluloses indicated. Pectin and hemicelluloses (glucomannan) were found in high levels in the epidermal layer and in a clearly distinguished outer part of the hypodermal sterome fibers. The inner part of the two-layered cells revealed as almost pure cellulose, oriented parallel along the fiber.
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Claims 9
Claim · model-written summary
Raman imaging visualized compositional differences in Equisetum cross sections.
- Taxon
- Equisetum hyemale
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Equisetum hyemalet0 - Outcome
- direct visualization of differences in chemical compositione0
- Comparator
- defined regionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
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Verbatim
t0“Equisetum hyemale”
e0“This enabled direct visualization of differences in chemical composition and extraction of average spectra from defined regions”
Claim · model-written summary
Silica accumulated in knobs and a thin layer below the cuticula.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Organ / stage
- knobs and in a thin layer below the cuticulae0
- Outcome
- Accumulation of silicae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“Accumulation of silica was imaged in the knobs and in a thin layer below the cuticula”
Claim · model-written summary
Knob spectra showed a broad band below 500 cm(-1) attributed to amorphous silica.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Outcome
- broad bande0
- Value
- below 500 cm(-1)e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“a broad band below 500 cm(-1) attributed to amorphous silica”
Claim · model-written summary
Knob spectra showed a 976 cm(-1) band assigned to silanol groups.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Outcome
- bande0
- Value
- 976 cm(-1)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“a band at 976 cm(-1) assigned to silanol groups”
Claim · model-written summary
The knobs were interpreted as nearly pure amorphous hydrated silica.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Organ / stage
- knobe1
- Outcome
- almost pure amorphous, hydrated silicae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“these protrusions were almost pure amorphous, hydrated silica”
e1“knob region”
Claim · model-written summary
No silanol group vibration was detected in the silicified epidermal layer.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Organ / stage
- silicified epidermal layere0
- Outcome
- No silanol group vibratione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“No silanol group vibration was detected in the silicified epidermal layer below”
Claim · model-written summary
Silicified epidermal layer was associated with pectin and hemicelluloses.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Organ / stage
- silicified epidermal layere1
- Outcome
- association with pectin and hemicellulosese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“association with pectin and hemicelluloses indicated”
e1“silicified epidermal layer below”
Claim · model-written summary
Pectin and hemicelluloses were high in epidermis and outer hypodermal sterome fibers.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Organ / stage
- epidermal layer and in a clearly distinguished outer part of the hypodermal sterome fiberse0
- Outcome
- Pectin and hemicelluloses (glucomannan)e0
- Direction
- high levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“Pectin and hemicelluloses (glucomannan) were found in high levels in the epidermal layer and in a clearly distinguished outer part of the hypodermal sterome fibers”
Claim · model-written summary
Inner parts of two-layered cells were nearly pure cellulose aligned parallel to the fiber.
- Taxon
- Equisetum hyemaleEquisetum hyemalet0
- Organ / stage
- inner part of the two-layered cellse0
- Outcome
- almost pure cellulose, oriented parallel along the fibere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Equisetum hyemale”
e0“The inner part of the two-layered cells revealed as almost pure cellulose, oriented parallel along the fiber”