Lignification of ray parenchyma cells in the xylem of Pinus densiflora. Part II: Microchemical analysis by laser microdissection and thioacidolysis

Abstract

Abstract The lignification of ray parenchyma cells in the sapwood (sW) and heartwood (hW) of Pinus densiflora was investigated by thioacidolysis and the subsequent Raney nickel desulfuration. The samples rich and less rich in ray parenchyma cells were prepared by laser microdissection (LMD). The whole sections burned randomly by the laser served as the controls. Guaiacyl (G) monomers were detected in all the samples, and p-hydroxyphenyl (H) monomers were detectable only in trace amounts, while syringyl (S) units were absent, as expected in softwood. In sW samples rich in ray parenchyma cells, the yields of G monomers are significantly lower than in the other samples. The various types of G-G and one G-H dimers were detected, and the β-1′, β-5′, and 5-5′ dimers were dominant. The relative distributions of lignin interunit linkages were very similar in all the samples regardless of the abundance of the ray parenchyma cells in the sW or hW tissues.