Cellulose crystals in fibrovascular bundles of sugarcane culms: orientation, size, distortion, and variability

Abstract

Cellulose crystals in fibrovascular bundles of sugarcane culms were throughly characterized by X-ray diffraction, with area-detector patterns acquired in fiber geometry. It was observed that microfibril angles are, on average, higher for bundles from pith compared to bundles from intermediate regions and rind, and higher for ratoon canes compared to plant canes. On the other hand, microfibril angles do not differ significantly among sugarcane cultivars, internode positions in the culm, or ratoon cane cut cycles. Broadening analyses of diffraction peaks yield crystal sizes (crystal width from equatorial 200 reflection and apparent crystal lengths from meridional 002 and 004 reflections) similar to other plant species (woods and bamboo). In addition, compared to reference cellulose Iβ, the 200, 110, and 110 diffraction peaks from sugarcane cellulose are notably shifted. These shifts indicate pronounced crystallite distortions, with expanded intersheet spacing d 200 , contracted d 1 1 0 /d 110 , and monoclinic angle γ closer to 90°. Our findings deepen the understanding of the fine structure and variability of sugarcane lignocellulose.