Absence of rapid terpene turnover in several diverse species of terpene-accumulating plants.

Terpenes are commonly believed to undergo rapid metabolic turnover in plants, but the evidence for this process comes largely from studies that used detached organs or applied radiolabeled precursors in unnatural ways. When 14CO2 pulse labeling experiments were carried out with intact plants of four taxonomically distant, terpene-accumulating species, no significant turnover of monoterpenes, sesquiterpenes or diterpenes was detected in young foliage over a two week period after exposure to 14CO2. These results are consistent with those of other investigations performed under physiologically realistic conditions, and caution against the uncritical incorporation of turnover into models or theories concerning plant chemical defense.