Brassicaceae are characterised by glucosinolates (GS), which appear to be involved not only in biotic but also in abiotic stress responses of plants. We investigated the effect of O (3) stress on leaf GS concentrations in two lines of BRASSICA NAPUS L., differing in GS content. Ozone fumigation decreased GS concentrations in leaves of B. NAPUS of one line. In control conditions, chlorophyll content, rates of saturating photosynthesis, and quantum yield of photosystem 2 differed between the two BRASSICA lines, but differences were smaller in O (3)-stress conditions, suggesting that the relationship between leaf GS concentration and sensitivity to abiotic stress merits further research. In agreement with other ecophysiological measurements, chlorophyll fluorescence imaging clearly distinguished both lines and in some cases also treatments. A method for analysis of fluorescence images accounting for the two-dimensional leaf heterogeneity is presented.