Format: ORAL

Lingyu Ma1,2, Qiulu Meng1,2, Xiaomei Jiang1,2, Zhedong Ge3, Zixiong Cao4, Yupei Wei1,2, Lichao Jiao1,2, Yafang Yin1,2, Juan Guo1,2

1 Research Institute of Wood Industry, Chinese Academy of Forestry, Dongxiaofu No.1, Beijing, China. 2 Wood Collections (WOODPEDIA), Chinese Academy of Forestry, Beijing, China 3 School of Information and Electrical Engineering, Shandong Jianzhu University, No.1000, Fengming Road, Lingang Development Zone, Jinan, Shandong, China. 4 Object Research Systems (ORS) Inc., 460 Ste-Catherine West, #600, Montreal, Quebec, Canada.

Xylem developed from cambium, consisting of diversified wood cells. Spatial organization and connectivity of wood rays are essential for understanding the wood hierarchical architecture, but the spatial information is ambiguous due to small cell size. Herein, 3D visualization of rays in Pinus massoniana was performed using high-resolution CT. We found brick-shaped rays were 6.5% in volume fractions, nearly twice the area fractions estimated by 2D levels. Uniseriate rays became taller and wider during the transition from earlywood to latewood, which was mainly contributed from the height increment of ray tracheids and widened ray parenchyma cells. Furthermore, both volume and surface area of ray parenchyma cells were larger than ray tracheids, so ray parenchyma took a higher proportion in rays. Moreover, three different types of pits for connectivity were segmented and revealed Pits in both axial tracheids and ray tracheids were bordered, but the pit volume and pit aperture of earlywood axial tracheids were almost 10-fold and over 4-fold larger than ray tracheids. Contrarily, cross-field pits between ray parenchyma and axial tracheids were window-like with the principle axis of 31.0 m, but its pit volume was approximately one third of axial tracheids. Additionally, spatial organization of rays and axial resin canal was analyzed by a curved surface reformation tool, providing the first evidence of rays close to epithelial cells inwards through the resin canal. Epithelial cells had various morphologies and large variations in cell size. Our results give new insights into the organization of radial system of xylem, especially the connectivity of rays with adjacent cells. Furthermore, the diversified structure in the forestry will be better understood and target the goal of carbon neutrality for human society.