DISTRIBUTION OF GUAIACYL AND SYRINGYL LIGNINS IN JAPANESE BEECH (FAGUS-CRENATA) - VARIATION WITHIN AN ANNUAL RING

Microspectrometry is the most definitive technique for obtaining both ultraviolet (UV) and visible light absorption spectra from a very limited area, and this technique allows the determination of lignin distribution throughout an individual cell wall. It is generally accepted that hardwood lignin is composed mainly of guaiacyl and syringyl moieties. Our microspectrometric investigations revealed variation of lignin distribution within an annual ring in beech (Fagus crenata). Distribution of guaiacyl and syringyl lignins in vessel and fibre secondary walls differs between earlywood and latewood. The proportion of guaiacyl units in the lignin in the vessel secondary wall is high in earlywood, especially in the initial zone of an annual ring (first formed earlywood); it is lower in latewood. In contrast, the proportion of syringyl units in the lignin in the vessel secondary wall is quite low in earlywood, but becomes appreciable in latewood. The content of syringyl units in the lignin in the fibre secondary wall is high in earlywood, becomes lower in latewood, and again increases in the terminal zone of an annual ring (last formed latewood). Guaiacyl lignin is present in appreciable amounts in the terminal zone.