In-situ shrinkage /swelling behavior and displacement based on vascular bundle morphological difference

The swelling/shrinking behavior is a complex process of interactions between multiscale structures, and it is also a major problem affecting the processing and utilization of bamboo. As an important structure connecting macroscopic and cellular scales in bamboo, the analysis of vascular bundles ' swelling/shrinking behaviors is important for revealing the swelling/shrinking laws of bamboo. In this study, in -situ observation technique was used to characterize the swelling/shrinking behaviors of open vascular bundles, open fibers, semi -open vascular bundles and semi -open fibers, and further analyzed the area change and location change of open vascular bundles (OV) and its fibers (OF), semi -open vascular bundles (HOV) and its fibers (HOF), and then analyzed the area and position change. During the swelling/shrinking cycle, the area change patterns of HOV was similar. The shrinkage rate of OV varied little, with a range of 1 -0.74 %. The shrinkage rate of HOV was 1 -0.18 %. The shrinkage ranges for OF and HOF fibers were closer, 1 -0.2 % and 1 -0.18 %, respectively. Swelling/shrinking was accompanied by movement of vascular bundles and fiber, with HOV moving in a radial direction and OV moving in a definite direction. Random forest simulations reveal that the effect of different fiber sheaths on the shrinkage area of the vascular bundle varies, and the HOV is more affected by the fiber sheath ,its factor importance is 0.47. The importance of the fibrous sheath "a " to the OV area is only 0.24. This provides an important reference for the subsequent establishment of multiscale swelling/shrinking relationships for bamboo.