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Plant growth conditions alter phytolith carbon.

Gallagher KL, Alfonso-Garcia A, Sanchez J, Potma EO, Santos GM - Front Plant Sci (2015)

Bottom Line: Previous work has suggested that plant silica is associated with compounds such as proteins, lipids, lignin, and carbohydrate complexes.These Raman spectra exhibited variability of spectral signatures and of relative intensities between sample treatments indicating that differing growth conditions altered the phytolith carbon.This may have strong implications for understanding the mechanism of phytolith formation, and for use of phytolith carbon isotope values in dating or paleoclimate reconstruction.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Systems Sciences, University of California, Irvine Irvine, CA, USA.

ABSTRACT
Many plants, including grasses and some important human food sources, accumulate, and precipitate silica in their cells to form opaline phytoliths. These phytoliths contain small amounts of organic matter (OM) that are trapped during the process of silicification. Previous work has suggested that plant silica is associated with compounds such as proteins, lipids, lignin, and carbohydrate complexes. It is not known whether these compounds are cellular components passively encapsulated as the cell silicifies, polymers actively involved in the precipitation process or random compounds assimilated by the plant and discarded into a "glass wastebasket." Here, we used Raman spectroscopy to map the distribution of OM in phytoliths, and to analyze individual phytoliths isolated from Sorghum bicolor plants grown under different laboratory treatments. Using mapping, we showed that OM in phytoliths is distributed throughout the silica and is not related to dark spots visible in light microscopy, previously assumed to be the repository for phytolith OM. The Raman spectra exhibited common bands indicative of C-H stretching modes of general OM, and further more diagnostic bands consistent with carbohydrates, lignins, and other OM. These Raman spectra exhibited variability of spectral signatures and of relative intensities between sample treatments indicating that differing growth conditions altered the phytolith carbon. This may have strong implications for understanding the mechanism of phytolith formation, and for use of phytolith carbon isotope values in dating or paleoclimate reconstruction.

No MeSH data available.


Related in: MedlinePlus

Hyperspectral imaging of individual phytoliths from samples A and E shows OM is distributed unevenly throughout the silica matrix. Dark spots visible in optical microscopy do not contain OM and there are no obvious patterns in the OM distribution. (A, B) Show one end-member of the VCA for phytolith A and E hyperspectral imaging. Insert is the corresponding optical image. (C, D) are the Raman spectra in the CH region (solid line is average of all spectra, blue dots are specific SRS intensity measures).
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Figure 2: Hyperspectral imaging of individual phytoliths from samples A and E shows OM is distributed unevenly throughout the silica matrix. Dark spots visible in optical microscopy do not contain OM and there are no obvious patterns in the OM distribution. (A, B) Show one end-member of the VCA for phytolith A and E hyperspectral imaging. Insert is the corresponding optical image. (C, D) are the Raman spectra in the CH region (solid line is average of all spectra, blue dots are specific SRS intensity measures).

Mentions: SRS microscopy was used to acquire chemical maps that revealed the spatial distribution of the OM within a phytolith. Hyperspectral imaging of a phytolith of planters A and E was analyzed by vertex component analysis (VCA). The resulting intensity maps (Figures 2A,B) show that the OM were inhomogeneously distributed throughout the phytoliths. Although the distribution was somewhat irregular, the OM was found to occupy the entire volume of the phytolith with no particular discrete site for OM concentration. The yellow areas correspond to regions of the phytolith with higher concentration of OM, and have Raman spectra (blue dots) similar to the mean Raman spectra (black line) for each group (Figures 2C,D). There was no OM detected in the dark spots visible by light microscopy, supporting previous nanoSIMS work by Alexandre et al. (2015).


Plant growth conditions alter phytolith carbon.

Gallagher KL, Alfonso-Garcia A, Sanchez J, Potma EO, Santos GM - Front Plant Sci (2015)

Hyperspectral imaging of individual phytoliths from samples A and E shows OM is distributed unevenly throughout the silica matrix. Dark spots visible in optical microscopy do not contain OM and there are no obvious patterns in the OM distribution. (A, B) Show one end-member of the VCA for phytolith A and E hyperspectral imaging. Insert is the corresponding optical image. (C, D) are the Raman spectra in the CH region (solid line is average of all spectra, blue dots are specific SRS intensity measures).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585121&req=5

Figure 2: Hyperspectral imaging of individual phytoliths from samples A and E shows OM is distributed unevenly throughout the silica matrix. Dark spots visible in optical microscopy do not contain OM and there are no obvious patterns in the OM distribution. (A, B) Show one end-member of the VCA for phytolith A and E hyperspectral imaging. Insert is the corresponding optical image. (C, D) are the Raman spectra in the CH region (solid line is average of all spectra, blue dots are specific SRS intensity measures).
Mentions: SRS microscopy was used to acquire chemical maps that revealed the spatial distribution of the OM within a phytolith. Hyperspectral imaging of a phytolith of planters A and E was analyzed by vertex component analysis (VCA). The resulting intensity maps (Figures 2A,B) show that the OM were inhomogeneously distributed throughout the phytoliths. Although the distribution was somewhat irregular, the OM was found to occupy the entire volume of the phytolith with no particular discrete site for OM concentration. The yellow areas correspond to regions of the phytolith with higher concentration of OM, and have Raman spectra (blue dots) similar to the mean Raman spectra (black line) for each group (Figures 2C,D). There was no OM detected in the dark spots visible by light microscopy, supporting previous nanoSIMS work by Alexandre et al. (2015).

Bottom Line: Previous work has suggested that plant silica is associated with compounds such as proteins, lipids, lignin, and carbohydrate complexes.These Raman spectra exhibited variability of spectral signatures and of relative intensities between sample treatments indicating that differing growth conditions altered the phytolith carbon.This may have strong implications for understanding the mechanism of phytolith formation, and for use of phytolith carbon isotope values in dating or paleoclimate reconstruction.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Systems Sciences, University of California, Irvine Irvine, CA, USA.

ABSTRACT
Many plants, including grasses and some important human food sources, accumulate, and precipitate silica in their cells to form opaline phytoliths. These phytoliths contain small amounts of organic matter (OM) that are trapped during the process of silicification. Previous work has suggested that plant silica is associated with compounds such as proteins, lipids, lignin, and carbohydrate complexes. It is not known whether these compounds are cellular components passively encapsulated as the cell silicifies, polymers actively involved in the precipitation process or random compounds assimilated by the plant and discarded into a "glass wastebasket." Here, we used Raman spectroscopy to map the distribution of OM in phytoliths, and to analyze individual phytoliths isolated from Sorghum bicolor plants grown under different laboratory treatments. Using mapping, we showed that OM in phytoliths is distributed throughout the silica and is not related to dark spots visible in light microscopy, previously assumed to be the repository for phytolith OM. The Raman spectra exhibited common bands indicative of C-H stretching modes of general OM, and further more diagnostic bands consistent with carbohydrates, lignins, and other OM. These Raman spectra exhibited variability of spectral signatures and of relative intensities between sample treatments indicating that differing growth conditions altered the phytolith carbon. This may have strong implications for understanding the mechanism of phytolith formation, and for use of phytolith carbon isotope values in dating or paleoclimate reconstruction.

No MeSH data available.


Related in: MedlinePlus