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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

Comparison of mean non-normalized signal intensities shows variability by sample treatment. Samples A, C, D, and E show common features both in the fingerprint region (A) and the CH stretching region (B). Sample M is less similar but retains some characteristics of the above. Samples B and F show a broad higher intensity set of peaks in the fingerprint region and lower intensities in the CH stretching region from the other samples. (C) is the statistical comparison of peaks 1603, 2907, and 3074 cm−1. Sample A has the highest relative intensity at 2907 cm−1. Asterisks denote statistical differences (*p < 0.05).
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Figure 4: Comparison of mean non-normalized signal intensities shows variability by sample treatment. Samples A, C, D, and E show common features both in the fingerprint region (A) and the CH stretching region (B). Sample M is less similar but retains some characteristics of the above. Samples B and F show a broad higher intensity set of peaks in the fingerprint region and lower intensities in the CH stretching region from the other samples. (C) is the statistical comparison of peaks 1603, 2907, and 3074 cm−1. Sample A has the highest relative intensity at 2907 cm−1. Asterisks denote statistical differences (*p < 0.05).

Mentions: A comparison of non-normalized average peak intensities in the fingerprint region for samples A–F is given in Figure 4A. The aromatic band intensity at 1603 cm−1 is strongest for samples A and E. Samples B and F show a strong and broad contribution in the 1300–1500 cm−1 region, which is not attributed to group vibrations of OM and likely originates from inorganic materials. In the CH region (Figure 4B), the 2907 cm−1 peak intensity for sample A is 2–3 times higher than C, E, and D. Although B and F displayed the highest intensity peaks in the fingerprint region, their peaks in the CH stretching region, though more numerous, were less intense. Only samples E and A show a peak at 3074 cm−1 (unsaturated CH). A graph showing the relative intensities of the assigned bands at 1603, 2907, and 3074 cm−1 is also shown for clarity (Figure 4C). Mann-Whitney U-test (*p < 0.05) reveals groups A and E have a significantly larger mean than the rest of the groups at the 1603 cm−1 Raman band, but not between each other. For the band at 2907 cm−1, the Sample A mean is significantly larger than all the rest, and Samples B and M means are significantly smaller. Sample S shows no peak at this position. Finally, only Samples A and E have a peak at 3074 cm−1, with significantly different means.


Plant growth conditions alter phytolith carbon.

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

Comparison of mean non-normalized signal intensities shows variability by sample treatment. Samples A, C, D, and E show common features both in the fingerprint region (A) and the CH stretching region (B). Sample M is less similar but retains some characteristics of the above. Samples B and F show a broad higher intensity set of peaks in the fingerprint region and lower intensities in the CH stretching region from the other samples. (C) is the statistical comparison of peaks 1603, 2907, and 3074 cm−1. Sample A has the highest relative intensity at 2907 cm−1. Asterisks denote statistical differences (*p < 0.05).
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Related In: Results  -  Collection

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Figure 4: Comparison of mean non-normalized signal intensities shows variability by sample treatment. Samples A, C, D, and E show common features both in the fingerprint region (A) and the CH stretching region (B). Sample M is less similar but retains some characteristics of the above. Samples B and F show a broad higher intensity set of peaks in the fingerprint region and lower intensities in the CH stretching region from the other samples. (C) is the statistical comparison of peaks 1603, 2907, and 3074 cm−1. Sample A has the highest relative intensity at 2907 cm−1. Asterisks denote statistical differences (*p < 0.05).
Mentions: A comparison of non-normalized average peak intensities in the fingerprint region for samples A–F is given in Figure 4A. The aromatic band intensity at 1603 cm−1 is strongest for samples A and E. Samples B and F show a strong and broad contribution in the 1300–1500 cm−1 region, which is not attributed to group vibrations of OM and likely originates from inorganic materials. In the CH region (Figure 4B), the 2907 cm−1 peak intensity for sample A is 2–3 times higher than C, E, and D. Although B and F displayed the highest intensity peaks in the fingerprint region, their peaks in the CH stretching region, though more numerous, were less intense. Only samples E and A show a peak at 3074 cm−1 (unsaturated CH). A graph showing the relative intensities of the assigned bands at 1603, 2907, and 3074 cm−1 is also shown for clarity (Figure 4C). Mann-Whitney U-test (*p < 0.05) reveals groups A and E have a significantly larger mean than the rest of the groups at the 1603 cm−1 Raman band, but not between each other. For the band at 2907 cm−1, the Sample A mean is significantly larger than all the rest, and Samples B and M means are significantly smaller. Sample S shows no peak at this position. Finally, only Samples A and E have a peak at 3074 cm−1, with significantly different means.

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