Limits...
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

Optical image of bilobate phytoliths and other silica debris from Samples A (A) and E (B). Sample E contains more silica remnants of other tissues. Scale bar = 25 μm.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4585121&req=5

Figure 5: Optical image of bilobate phytoliths and other silica debris from Samples A (A) and E (B). Sample E contains more silica remnants of other tissues. Scale bar = 25 μm.

Mentions: In addition, for Sample A the proportion of bilobate phytoliths to other silica shapes was higher than other samples as exemplified by a qualitative comparison of images from Samples A and E (Figure 5). The relatively high signal intensity in A compared to other samples could represent a concentration effect because the amount of silica in the transpiration stream would be lower in proportion to the organics, or it could relate to speed of precipitation and entrapment of OM into the amorphous silica (Blackman, 1969; Hodson et al., 1985). The bands cannot be assigned to a particular type of organic compound, though the pattern in the CH stretching region is consistent with that of a carbohydrate (Wiley and Atalla, 1987; Pizzini et al., 1988). Enhanced carbohydrate signals from polysaccharides such as cellulose can be related to the mechanism of precipitation. It has been proposed previously that silicification is preceded by lignification of plant cell walls (Zhang et al., 2013; Rudall et al., 2014) which would perhaps result in enriched carbohydrate and lignin signals. We examined the putative carbohydrate peak at 2907 cm−1 and the characteristic lignin peaks at 1603 cm−1 and 3074 cm−1 (Figure 3C), and found different intensities between the samples. The Raman band at 1603 cm−1 consistent with lignin aromatics is corroborated by the unsaturated CH stretching band at 3074 cm−1 (Agarwal and Ralph, 1997).


Plant growth conditions alter phytolith carbon.

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

Optical image of bilobate phytoliths and other silica debris from Samples A (A) and E (B). Sample E contains more silica remnants of other tissues. Scale bar = 25 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: Optical image of bilobate phytoliths and other silica debris from Samples A (A) and E (B). Sample E contains more silica remnants of other tissues. Scale bar = 25 μm.
Mentions: In addition, for Sample A the proportion of bilobate phytoliths to other silica shapes was higher than other samples as exemplified by a qualitative comparison of images from Samples A and E (Figure 5). The relatively high signal intensity in A compared to other samples could represent a concentration effect because the amount of silica in the transpiration stream would be lower in proportion to the organics, or it could relate to speed of precipitation and entrapment of OM into the amorphous silica (Blackman, 1969; Hodson et al., 1985). The bands cannot be assigned to a particular type of organic compound, though the pattern in the CH stretching region is consistent with that of a carbohydrate (Wiley and Atalla, 1987; Pizzini et al., 1988). Enhanced carbohydrate signals from polysaccharides such as cellulose can be related to the mechanism of precipitation. It has been proposed previously that silicification is preceded by lignification of plant cell walls (Zhang et al., 2013; Rudall et al., 2014) which would perhaps result in enriched carbohydrate and lignin signals. We examined the putative carbohydrate peak at 2907 cm−1 and the characteristic lignin peaks at 1603 cm−1 and 3074 cm−1 (Figure 3C), and found different intensities between the samples. The Raman band at 1603 cm−1 consistent with lignin aromatics is corroborated by the unsaturated CH stretching band at 3074 cm−1 (Agarwal and Ralph, 1997).

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