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RADIAL PATTERNS OF CARBON ISOTOPES IN THE XYLEM EXTRACTIVES AND CELLULOSE OF DOUGLAS-FIR
Citation:
TAYLOR, A., BROOKS, B. LACHENBRUCH, AND J. J. MORRELL. RADIAL PATTERNS OF CARBON ISOTOPES IN THE XYLEM EXTRACTIVES AND CELLULOSE OF DOUGLAS-FIR. TREE PHYSIOLOGY. Heron Publishing, Victoria, B.C, Canada, 27:921-927, (2007).
Impact/Purpose:
to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood extractives and imported photosynthate in the formation of heartwood extractives
Description:
Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope composition (δ13C) was analyzed to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood extractives and imported photosynthate in the formation of heartwood extractives. Cellulose and extractives from the outer 39 annual rings of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were isolated and their δ13C composition determined. Although the extractives and the cellulose showed different absolute δ13C values, the patterns of change over time (as represented by the annual rings) were similar in most cases. Within an annual ring, carbon isotope ratios of extractives were correlated with the cellulose isotope ratio (R2 = 0.33 in sapwood, R2 = 0.34 in heartwood for aqueous acetone-soluble extractives; R2 = 0.41 in sapwood for hot-water-soluble extractives). These data suggest that some sapwood extractives are formed when the wood ring forms, and remain in place until they are converted to heartwood extractives many years later. Sapwood extractives appear to be important sources of materials for the biosynthesis of heartwood extractives in Douglas-fir.