Clonal variation of wood chemistry variables in radiata pine (Pinus radiata D. Don.) wood

Middle lamella lignin concentration (MLLC) was measured for 10 clones (cuttings) of Pinus radiata D. Don., using interference microscopy. Significant variation was observed among clones suggesting a genetic component to this aspect of lignin distribution. The colonel repeatability, an estimate of broad-sense heritability for MLLC, was 0.70 with a clonal coefficient of variation of 9%. The average MLLC was 69% v/v with a minimum clonal average of 58% and a maximum of 77%. Comparison with chemical analysis data revealed significant correlations between MLLC and both arabinose content and xylose content (r=-0.51). There is tentative evidence of a negative relationship between lignin content and MLLC (r=-0.42, p=0.067) , which is interpreted as a compression wood effect. Th negative correlations with arabinose and xylose suggest that an increased amount of xylan in the middle lamella (arabino-4-O-methyl-glucuronoxylan) is located at higher concentration in the middle lamella region) may be the cause reduced lignification in this cell wall region. Clonal repeatabilities for various chemical components of P. radiata wood range from 0.32 for glucose content to 0.78 for xylose content. All components except glucose show significant variation among clones.