Cellulose microfibrils are crucial for many of the remarkable mechanical properties of primary cell walls. Nevertheless, many structural features of cellulose microfibril organization in cell walls are not yet fully described. Microscopy techniques provide direct visualization of cell wall organization, and quantification of some aspects of wall microstructure is possible through image processing. Complementary to microscopy techniques, scattering yields structural information in reciprocal space over large sample areas. Using the onion epidermal wall as a model system, we introduce resonant soft X-ray scattering (RSoXS) to directly quantify the average interfibril spacing. Tuning the X-ray energy to the calcium L-edge enhances the contrast between cellulose and pectin due to the localization of calcium ions to homogalacturonan in the pectin matrix. As a consequence, the chemical-specificity of RSoXS enables the study of the interplay between cellulose and matrix polysaccharides, by revealing the average center-to-center distance between cellulose microfibrils or microfibrilbundles of about 20 nm.

Resonant soft X-ray scattering for chemically-specific structural characterization of plant primary cell walls

2019 Spring National Meeting

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