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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

Raman spectroscopy results for bilobate phytoliths from treatments A–F, and S, and trapezoidal phytoliths from M. Variability in peak locations and relative intensities, designated by vertical bars, indicate locations of Raman band disparities. Spectrum averages (heavy line) and variability (gray area, ±1 standard deviation) within each sample (n = 30) in the fingerprint region (A) and the CH region (B) are shown. Samples B, F, S, and M exhibited the largest standard deviation from their average spectra.
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Figure 3: Raman spectroscopy results for bilobate phytoliths from treatments A–F, and S, and trapezoidal phytoliths from M. Variability in peak locations and relative intensities, designated by vertical bars, indicate locations of Raman band disparities. Spectrum averages (heavy line) and variability (gray area, ±1 standard deviation) within each sample (n = 30) in the fingerprint region (A) and the CH region (B) are shown. Samples B, F, S, and M exhibited the largest standard deviation from their average spectra.

Mentions: Raman bands and intensities varied between sample treatments (Figure 3). In the fingerprint region (1250–1800 cm−1), overlapping modes are present and can be assigned to various CH bonds especially in the 1350–1450 cm−1 range (Table 2). A strong peak at 1356 cm−1 in Sample S is also present in Sample E (Figure 3, highlighted) and could represent tertiary CH groups or NO bonds. The peak at 1500 cm−1 (not highlighted) is present in the glass sample (i.e., originating from the microscope slide on which the phytoliths were mounted) and is not attributed to OM. A band corresponding to aromatic ring stretching at 1603 cm−1 (highlighted) is seen clearly in Samples A and E, and is also present in Samples C and D to a lesser extent. In the CH stretching vibrational region (2700–3150 cm−1), all samples exhibited peaks indicative of some OM (highlighted region 2900–3000 cm−1), although the relative intensities and the overall shape of the spectra varied indicating different OM contributions. Samples B and F appeared to be most distinct from the others and both exhibited a strong peak at 2850 cm−1 (highlighted) that is not present in the other samples. A Raman band at 3073 cm−1 that is present in both samples A and E can be assigned to the carbon-hydrogen stretching mode of the CH = CH- group, and signifies the presence of unsaturated hydrocarbons.


Plant growth conditions alter phytolith carbon.

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

Raman spectroscopy results for bilobate phytoliths from treatments A–F, and S, and trapezoidal phytoliths from M. Variability in peak locations and relative intensities, designated by vertical bars, indicate locations of Raman band disparities. Spectrum averages (heavy line) and variability (gray area, ±1 standard deviation) within each sample (n = 30) in the fingerprint region (A) and the CH region (B) are shown. Samples B, F, S, and M exhibited the largest standard deviation from their average spectra.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Raman spectroscopy results for bilobate phytoliths from treatments A–F, and S, and trapezoidal phytoliths from M. Variability in peak locations and relative intensities, designated by vertical bars, indicate locations of Raman band disparities. Spectrum averages (heavy line) and variability (gray area, ±1 standard deviation) within each sample (n = 30) in the fingerprint region (A) and the CH region (B) are shown. Samples B, F, S, and M exhibited the largest standard deviation from their average spectra.
Mentions: Raman bands and intensities varied between sample treatments (Figure 3). In the fingerprint region (1250–1800 cm−1), overlapping modes are present and can be assigned to various CH bonds especially in the 1350–1450 cm−1 range (Table 2). A strong peak at 1356 cm−1 in Sample S is also present in Sample E (Figure 3, highlighted) and could represent tertiary CH groups or NO bonds. The peak at 1500 cm−1 (not highlighted) is present in the glass sample (i.e., originating from the microscope slide on which the phytoliths were mounted) and is not attributed to OM. A band corresponding to aromatic ring stretching at 1603 cm−1 (highlighted) is seen clearly in Samples A and E, and is also present in Samples C and D to a lesser extent. In the CH stretching vibrational region (2700–3150 cm−1), all samples exhibited peaks indicative of some OM (highlighted region 2900–3000 cm−1), although the relative intensities and the overall shape of the spectra varied indicating different OM contributions. Samples B and F appeared to be most distinct from the others and both exhibited a strong peak at 2850 cm−1 (highlighted) that is not present in the other samples. A Raman band at 3073 cm−1 that is present in both samples A and E can be assigned to the carbon-hydrogen stretching mode of the CH = CH- group, and signifies the presence of unsaturated hydrocarbons.

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