Comparison of Contact and Non-Contact Wood Fibers in Some Hardwood

Abstract

The distributions of syringyl lignin and glucuronoxylans in contact and non-contact wood fibers of Pterocymbium beccarii, Paulownia tomentosa, and Albizia julibrissin were investigated using the Mäule color reaction and immunogold labeling, respectively. In the Mäule color reaction, the fibers with small diameters (tip regions of wood fibers) appeared much darker in color than those with larger diameters (body regions of wood fibers), but there were no significant differences in the depth of color between the contact and non-contact wood fibers with similar diameters. This finding suggests that the tips of the wood fibers tend to be richer in syringyl lignin than the bodies, but there is no positive correlation between the content of syringyl lignin and the distance of the wood fiber from the ray. In the immunogold labeling, no essential difference was found in the labeling distribution and density between contact and non-contact wood fibers in all three species. In Albizia julibrissin, moreover, almost all wood fibers regardless of contact or non-contact with the rays, contained starch grains in the outer portion of the outermost annual ring. These findings indicate that the distance of wood fibers from the rays do not affect the transport of photosynthate, so that even the wood fibers far away from the rays are supplied with almost the same amount of photosynthetic products, which are a source of raw materials for cell wall biosynthesis.