Microfibril orientation of the secondary cell wall in parenchyma cells of Phyllostachys edulis culms

The secondary cell wall of bamboo parenchyma cells is microfibril-based. However, understanding of the microfibril orientation of secondary cell walls in bamboo parenchyma cells is lacking. This study characterized the microfibril orientation of the sub-layers of the secondary cell wall in the parenchyma cells by field-emission environmental scanning electron microscopy and the microfibril angle of the ground parenchyma cell wall with X-ray diffraction. The microfibril orientation of tight-loose alternating layers of the secondary cell wall was in the opposite direction along the longitudinal axis. Near the parenchyma cells’ pit aperture, the microfibril orientation generally bypassed the pits and continued in a flow-like pattern. The mean microfibril angle of ground parenchyma cells was 63.3°. The average microfibril angle of adjacent sub-layers of the secondary cell wall was 60° and − 65° in ground parenchyma cells, and 54° and − 52° in vascular parenchyma cells. A structure model of microfibril orientation of parenchyma cell wall in moso bamboo was firstly constructed. The study provides insight into the anatomical structure of the parenchyma cell wall in the bamboo plant. Moreover, it provides a structural basis for further analysis of the mechanical properties of parenchyma cells.