Emission of volatile organic compounds from ozone-exposed plants

Plants produce a number of volatile organic compounds (VOCs), and this rele ase plays a significant role in atmospheric chemistry. Although certain fac tors controlling the emission rates of VOCs from plants are reasonably well understood, the influence of abiotic stress, such as elevated ozone concen trations, is unknown. Therefore, the emission of VOCs from tobacco plants ( Nicotiana tabacum L. cv. Bel B and Bel W3) and Scots pine (Pinus sylvestris L.) were studied in continuously stirred tank reactors under ozone exposur e. A pulse treatment (5 h) with 120-170 nmol/mol ozone induced visible dama ges in the ozone-sensitive tobacco cv. Bel W3, while the more tolerant cv. Bel B seemed to be unaffected. The total amount and dynamics of the emissio n were studied. Both cultivars emitted methyl salicylate and a series of se squiterpenes after the ozone treatment, but the response was less pronounce d for Bel B plants. C-6-volatiles that are thought to be derived from the l ipoxygenase pathway were emitted only from Bel W3 plants. The results give further support to the hypothesis that the ozone-induced reactions of the o zone-sensitive Bel W3 plants resemble the hypersensitive response found aft er pathogen attack. Longterm ozone treatment (50 nmol/mol, 8 h/d) of pine l ed to 40% increased emissions of monoterpenes, while no damage was visible on the needles. Since VOCs are precursors of ozone, an increased VOC emissi on as a consequence of elevated ozone concentrations in the troposphere may lead to feedback mechanisms in photooxidant formation.