Astrans-2-nonenal (T2N) acts as an insect repellent, an insecticide, and a flavor compound, it would be desirable to manipulate its concentration in plants. Simple, rapid, and accurate trapping on cartridges of activated charcoal detected T2N in headspace over carrot roots and regenerants. Concentrations ranged from 0.07 to 0.43 ppm total volatiles over the homogenized roots of a range of European carrot cultivars with the following statistically significant differences: Long Chantenay > Sytan > Vertou > Touchon Prima. This suggests that the expression of T2N is determined genetically. Given the potential for genetic manipulation byin vitro techniques, the release of T2N and other terpenoids was monitored in carrot cell suspensions and in "hairy" root cultures of cv. Gelbe Rheinische. T2N concentrations were 6.23 ppm and 0.005 ppm, respectively, as compared with 0.15 ppm over the homogenized root of the same cultivar. Two terpenoids additional to T2N were detected from cell suspension cultures as compared with 14 from "hairy" root cultures. The ready detection in regenerants of this significant aldehyde indicates that its presence could be monitored in derivatives of otherin vitro manipulations.