Primary cell wall is a complex heterogeneous mixture of several polysaccharides including cellulose, hemicellulose and pectin. Within these cell walls, cellulose exists as microfibrils forming a crystalline structure that plays an important role in the biological processes of plant growth, conversion of cellulosic biomass into biofuels and in understanding the physical properties of cellulose derivatives. It also holds promise as a source of renewable energy and is an important raw material for paper, textile and construction materials. However, several aspects of crystalline structure of cellulose remain elusive. One such structural parameter is the orientation of cellulose crystallites within the fibrils. This parameter can be an important determinant of the mechanical properties of cell wall as well as cellulose-cellulose and cellulose-matrix interactions. We studied the structure of cellulose in primary cell walls of plants through grazing incidence wide angle X-ray scattering (GIWAXS). It is a morphological characterization tool that can probe the sample surface as well as beneath it. The grazing incidence geometry yields high signal-to-noise ratio and causes lesser radiation damage, making it ideal for plant cell wall samples which are fragile and weakly scattering. We found that the technique could decouple scattering from cellulose and wax crystals. X-ray scattering of different chemical treatments of the cell wall revealed strong texturing of cellulose. The degree of preferred orientation of the crystals was determined through pole figures constructed from the combination of GIWAXS and XRD rocking scans. It was found that the texturing depends on the developmental age of the tissue and also on its source.

Grazing incidence X-ray scattering reveals texturing in primary cell walls

2019 Spring National Meeting

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