3D Visualization of Bamboo Node’s Vascular Bundle

Abstract

The vascular bundle is an important structural unit that determines the growth and properties of bamboo. A high-resolution X-ray microtomography (μCT) was used to observe and reconstruct a three-dimensional (3D) morphometry model of the vascular bundle of the Qiongzhuea tumidinoda node due to its advantages of quick, nondestructive, and accurate testing of plant internal structure. The results showed that the morphology of vascular bundles varied significantly in the axial direction. In the cross-section, the number of axial vascular bundles reached a maximum at the lower end of the sheath scar, and the minimum of it was at the middle of the diaphragm. The frequency of axial vascular bundles decreased from the lower end of the node to the nodal ridge, and subsequently increased until the upper end of the bamboo node. The proportion of parenchyma, fibers, and conducting tissue was 65.7%, 30.5%, and 3.8%, respectively. The conducting tissues were intertwined to form a complex 3D network structure, with a connectivity of 94.77%. The conducting tissue with the largest volume accounted for 60.26% of the total volume of the conducting tissue. The 3D-distribution pattern of the conducting tissue of the node and that of the fibers were similar, but their thickness changed in the opposite pattern. This study revealed the 3D morphometry of the conducting tissue and fibers of the bamboo node, the reconstruction of the skeleton made the morphology more intuitive. Quantitative indicators such as the 3D volume, proportion, and connectivity of each type of tissue was obtained, the bamboo node was enlarged mainly caused by the particularly developed fibers. This work laid the foundation for a better understanding of the mechanical properties and water transportation of bamboo and revealed the mystery of bamboo node shedding of Q. tumidinoda.

Three-dimensional visualization of the vascular bundle in a branched bamboo node

“…Branching emerged at the node on the upper end of the diaphragm (Figure 4D, yellow arrow), while the TVB was predominantly located on the side of the culm close to the branch (Figure 4D, white circle). However, a significant amount of TVBs were distributed at the diaphragm of the unbranched bamboo node (Li et al, 2021). This indicates that the branch had an impact on the distribution of TVBs in the BN.…”

“…A sequence of slices was acquired and exported as a stack of TIFF images, obtaining 1293 slices with serial numbers 0-1292 (Figure 2A). The thickness of the conducting tissue and fibers in the VB of the bamboo node changed in the opposite pattern (Li et al, 2021). The conducting tissue and fibers were segmented to better visualize and quantify the VB.…”

“…It can also obtain serial sections of the specimen in any direction, thus advantageous in studying the anatomical structure. μCT applied to study the bamboo node enables visualization of the anatomical structure, 3D visualization, quantitative characterization, and numerical simulation (Palombini et al, 2020;Li et al, 2021;Xiang et al, 2021). Peng et al (2014) and Xiang et al (2021) used μCT to study the complex VB network of bamboo nodes but did not separately extract the VB to observe its morphology, thus lacking intuitive visualization.…”

“…Palombini et al (2020) showed that branches from the basal portion to the branching were continuous, without bridges or vascular traces, and were connected with the culm. Li et al (2021) reported that the VB of the unbranched node formed an intricate and highly connected 3D network structure. The morphology and direction of the bamboo VB changed greatly in the node (Li et al, 2021) because of the branch (Xiang et al, 2021).…”

“…Li et al (2021) reported that the VB of the unbranched node formed an intricate and highly connected 3D network structure. The morphology and direction of the bamboo VB changed greatly in the node (Li et al, 2021) because of the branch (Xiang et al, 2021). The VB arrangement in the node and the branch of the BN thus remains unclear.…”