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. Although direct imaging can provide some information on cell wall organization over limited sample sizes, scattering yields structural information in reciprocal space over large sample areas. Using onion epidermal wall and Arabidopsis hypocotyls, 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 microfibril bundles of about 20 nm to 30 nm. Furthermore, we use grazing-incidence wide-angle X-ray scattering to reveal a texturing of cellulose crystals within the cell wall. We find a degree of preferred orientation of crystals along the thickness of the wall that depends on developmental age and source. Using a combination of Arabidopsis mutants, we can reveal the role of matrix polysaccharides on cellulose crystal texturing and organization.

Using a combination of resonant soft X-ray scattering and grazing-incidence diffraction for the study of plant primary cell walls

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.