Use of atomic force microscopy to view ultrastructure of the fiber cell wall in Phyllostachys edulis culms

Bamboo fiber cell wall structure, including cellulose microfibril morphology, endows fibers with excellent and stable mechanical strength and toughness. Due to the imaging resolution limitations, the ultra-structure of bamboo fiber cell walls remains elusive. Here we characterized the fiber cell wall’s inherent structure and the cellulose microfibril’s cross-sectional shape from native and delignified inclined samples, and the tangential sections of moso bamboo using atomic force microscopy. The secondary cell wall sublayer was composed of multiple microfibril layers, 20 nm in thickness each. The 18 nm in diameter spherical particles between microfibrils were lignin. The bamboo fiber cell wall’s microfibrils were composed of various numbers of individual cellulose elementary fibrils (CEFs), including one, two, three, four, and multiple CEFs (up to 7 CEFs). The microfibrils’ dimensions varied from 3.5 to 40 nm. Additionally, branched microfibrils are described for the first time in the bamboo plant. The study provides insight into the nanometer-scale structure of the fiber cell wall in the bamboo plant.