The behavior and mechanism of longitudinal liquid permeation in Moso bamboo (Phyllostachys edulis)

Bamboo exhibits exceptional longitudinal permeability under applied pressure, primarily due to its metaxylem vessels (MVs). However, the structural and compositional origins for its relatively high permeability under ambient pressure remain unclear. This study relates the multiscale 3D structure of cells in vascular bundles to the permeability of bamboo using in situ X-ray computed tomography (μCT) and focused ion beam-scanning electron microscopy (FIB-SEM), while mass spectrometry imaging (MSI) is employed to correlate the microscale spatial distribution of chemical components with permeability. The study reveals a previously unknown behavior and mechanism of liquid permeation in bamboo, with sieve tubes (STs) and small vessels serving as the main pathways. Capillary effects are significantly more pronounced in small vessels than in MVs. The small vessels have an average length of 147.87 ± 45.17μm with a shape factor of 1.18 ± 0.22. The reduction in flow resistance caused by the presence of long cavities and smooth cell walls in the small vessels results in an increase in flow rate. High hemicellulose and low lignin content of STs enhance water interaction, thus promoting liquid permeation in bamboo. The mechanism of liquid permeation in bamboo provides valuable insights for the biomimetic design of engineering materials. • The liquid 3D distribution in bamboo during penetration was tracked over time by μCT. • Nanoscale 3D structures of parenchyma in vascular bundle were obtained by FIB-SEM. • Long cavities and smooth walls of small vessels enhance flow. • Sieve tubes, rich in hemicellulose and low in lignin, facilitate liquid permeation.