Changes in Chemical Composition of Wood Cell Walls Associated with Age in Pinus Resinosa

Microsamples of earlywood and latewood from one mature and two young red pine (Pinus resinosa) trees were analyzed for lignin and the five principal wood sugars. Glucose and mannose yields increased with age, whereas yields of galactose, xylose, arabinose, and lignin decreased. Beyond the juvenile wood period (15-20 years), yields of all constituents from latewood were essentially parallel to those of earlywood; the main differences were lower lignin and xylose and higher mannose yields from latewood. Qualitative changes in the composition of compression wood with increasing age were also detected. Some, but by no means all, of the chemical differences encountered in this study could be accounted for by changes in cell wall thickness. It was concluded that definite qualitative changes in wall composition occur with age, which are independent of changes in wall thickness. These changes appear to be inherent and may be typified by the trends expressed in the earlywood. Thus, at any one age, the increase in wall thickness that occurs during latewood formation is superimposed on a predetermined earlywood matrix. It is suggested that interpretations regarding the chemical constituents of wood should take into consideration the age of the wood being sampled.

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