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Getting to the root of the solution

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Hank Hogan

Modified plants could help bring about more efficient paper production or could serve as sources for chemical feedstocks, but what’s needed for these and other commercial applications is a way to determine a plant’s chemical composition without tedious analysis.

Lawrence C. Davis, a biochemistry professor at Kansas State University in Manhattan, and graduate student Kenneth M. Dokken, now a postdoctoral researcher at the University of Texas at El Paso, tackled the problem using synchrotron radiation infrared microspectroscopy.

Davis noted that the original research project involved mapping the location of contaminants in plants. That effort at compositional analysis resulted in a proof of concept of the usefulness of mid-infrared spectroscopy.


Infrared spectroscopy was used to map the functional groups in sunflower (top) and in maize (bottom) root tissue. The root section studied is in the blue rectangle in the visible image, while the intensity of infrared spectral bands versus location is plotted beside them. Such information about how and where plants incorporate chemical constituents when they grow could help produce better plants or better plant-processing methods. Courtesy of Kenneth M. Dokken, University of Texas at El Paso, and of Lawrence C. Davis, Kansas State University.

For the current research, they used the National Synchrotron Light Source in Upton, N.Y., to analyze plant samples with an infrared microspectrometer in reflection mode. They sent the beam into an infrared microscope and collected the reflected signal in a spectrometer and in a mercury cadmium telluride detector. Both instruments were from Thermo Scientific Inc. of Waltham, Mass.

With this equipment, they investigated the feasibility of using infrared spectroscopy for analysis of cellulose, lignin, proteins and other biopolymers found in sunflower and maize root tissue. The two plants are representative of dicot and monocot plants. Monocots, particularly grasses, contain more lignins than dicots.

The researchers collected data from 12 × 12-μm squares in 10-μm steps over the spectral range from 4000 to 650 cm–1. They analyzed the data using principal component analysis, finding a distinct separation of maize and sunflower samples in the infrared spectra of the plant epidermis and xylem. Their results showed that a particular infrared signature associated with hydrocinnamic acid, or H type, lignin conclusively distinguished between maize and sunflower roots. Thus, the infrared spectroscopy technique yielded acceptable results.

Davis noted that the long-range goal of such research is to learn more about plant growth and development. Monitoring this activity using infrared tools could be useful. The knowledge of how the plant grows could provide benefits when it’s time to turn the plant into a product such as paper, he noted.

“If we can understand the assembly process, we may be able to facilitate the disassembly process.”

Journal of Agricultural and Food Chemistry, Dec. 26, 2007, pp. 10517-10530.

Feb 2008
Basic ScienceBiophotonicschemicalsinfrared microspectroscopyMicroscopyNews & FeaturesSensors & Detectorsspectroscopysynchrotron radiation

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