The variation in the longitudinal and radial direction of the R/T ratio which is the ratio of the radially
maximum length (R) to the tangentially maximum width (T) of a vascular bundle and area ratio of vascular
bundles, which are cross-sectional image features of bamboo, and the relationships between the R/T ratio or
area ratio and relaxation behavior were investigated. These image features varied characteristically in the
longitudinal and radial directions. Relationships between these image features and relaxation behavior were
evaluated using the instantaneous creep compliance ln[J (0)] and the creep intensity ln [J(3×104)−J (0)].
Although both instantaneous compliance and creep intensity decreased as density increased, their
dependence properties were remarkably different. Instantaneous compliance was strongly correlated with
R/T ratio and density, which was related to the area ratio, whereas creep intensity was weakly correlated with
density in a given range. The results indicate a difference between the two relaxation properties, because
creep intensity depends more on microstructures, such as the conformation of molecular chains in the
substance, or interactions among cells than on R/T ratio and area ratio image features.