Crystalline cellulose in hydrated primary cell walls of three monocotyledons and one dicotyledon

The molecular ordering of cellulose, including its crystallinity, in the unlignified primary cell walls of three monocotyledons (Italian ryegrass, pineapple, and onion) and one dicotyledon (cabbage) was characterized by solid-state C-13 NMR spectroscopy. These species were chosen because their primary cell walls have different non-cellulosic polysaccharides and this may affect the molecular ordering of cellulose. Values of the proton rotating-frame relaxation [T-1p(H)] and spin-spin relaxation [T-2(H)] time constants showed that the cellulose in the cell wails of all four species was in a crystalline rather than an amorphous state. Furthermore, a resolution enhancement procedure showed that the triclinic (I-a) and the monoclinic (I-beta) crystal forms of cellulose were present in similar proportions in these cell walls. However, the calculated cross-sectional dimensions of the cellulose crystallites varied among the cell walls (in the range 2-3 nm): the largest were in the Italian ryegrass, the smallest were in the onion and cabbage, and those of intermediate size were in the pineapple. The crystallite dimensions may thus be affected by the non-cellulosic polysaccharide compositions of the cell walls.