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 limi ted area, and this technique allows the determination of lignin distri bution throughout an individual cell wall. It is generally accepted th at hardwood lignin is composed mainly of guaiacyl and syringyl moietie s. Our microspectrometric investigations revealed variation of lignin distribution within an annual ring in beech (Fagus crenata). Distribut ion of guaiacyl and syringyl lignins in vessel and fibre secondary wal ls 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 earlyw ood); it is lower in latewood. In contrast, the proportion of syringyl units in the lignin in the vessel secondary wall is quite low in earl ywood, but becomes appreciable in latewood. The content of syringyl un its in the lignin in the fibre secondary wall is high in earlywood, be comes lower in latewood, and again increases in the terminal zone of a n annual ring (last formed latewood). Guaiacyl lignin is present in ap preciable amounts in the terminal zone.