Seasonal variation in foliar and bud monoterpenes in Sitka spruce

Abstract

As part of a study on the relationship between the monoterpene composition of Sitka spruce, Picea sitchensis (Bong.) Carr., and resistance to the white pine weevil, Pissodes strobi Peck, seasonal differences in the relative monoterpene content of developing buds and 1-year-old foliage were followed. In 2nd-year foliage of four trees from the University of British Columbia Research Forest, Maple Ridge, B.C., α-pinene and camphene levels increased in May and returned to their original levels by September. Myrcene, isopentenyl isovalerate, and camphor levels decreased in May. Isopentenyl isovalerate and camphor levels increased over the summer, but myrcene continued to decline, offsetting rising levels of 3-carene and β-pinene. To obtain representative monoterpene distributions, foliar samples should be taken after September 30, when trees are dormant for the winter. There was significant developmental variation in buds from 20 trees from Say ward, B.C. α-Pinene and β-pinene were prominent initially and then declined, while myrcene increased to become the major volatile component of the elongating buds. β-Phellandrene levels declined and then increased as the season progressed. There was no significant difference in percent monoterpene composition between buds from resistant and susceptible trees.