De Novo Terpenes Emitted from Juvenile Leaves of Eucalyptus globulus Labill. subsp. globulus

The contributions of de novo synthesis to terpene emissions from Eucalyptus globulus subsp. globulus were determined by fumigating branchlets with 13 CO 2 in a gas exchange system. Of more than thirty-four terpenes emitted by this species, only four, i.e., isoprene, iso-valeraldehyde, cis -ocimene, and trans-caryophyllene, incorporated 13 C into the terpene carbon skeleton during the ~5–6 h experiment. 13 C incorporation into isoprene and iso-valeraldehyde reached a maximum of ca. 82% of the carbon skeleton, similar to cis -ocimene, with a maximum of 77% 13 C incorporation after ~2.5 h exposure to 13 CO 2 . Only ca. 20% of carbon was labelled in trans-caryophyllene after 5–6 h. the incorporation of 13 C was observed only in compounds emitted from leaves, and was not detected in either individual oil glands or in bulk leaf tissue. The results suggest the de novo synthesis of some terpenes (isoprene, cis -ocimene, trans-caryophyllene, and iso-valeraldehyde) and their emission is independent of emissions of terpenes stored in oil glands.