Ozone induced emissions of biogenic VOC from tobacco:: relationships between ozone uptake and emission of LOX products

Volatile organic compound (VOC) emissions from tobacco (Nicotiana tabacum L. var. Bel W3) plants exposed to ozone (O-3) were investigated using proton-transfer-reaction mass-spectrometry (PTR-MS) and gas chromatography mass-spectrometry (GC-MS) to find a quantitative reference for plants' responses to O-3 stress. O-3 exposures to illuminated plants induced post-exposure VOC emission bursts. The lag time for the onset of volatile C-6 emissions produced within the octadecanoid pathway was found to be inversely proportional to O-3 uptake, or more precisely, to the O-3 flux density into the plants. In cases of short O-3 pulses of identical duration the total amount of these emitted C-6 VOC was related to the O-3 flux density into the plants, and not to ozone concentrations or dose-response relationships such as AOT 40 values. Approximately one C-6 product was emitted per five O-3 molecules taken up by the plant. A threshold flux density of O-3 inducing emissions of C-6 products was found to be (1.6 +/- 0.7) x 10(-8) mol m(-2) s(-1).