Effect of airborne bromoxynil–octanoate and metribuzin on non-target plants

The present study was conducted to determine the effects of airborne herbicides on the photosynthesis and growth of non-target plants. Sunflowers at different growth stages were used as test plants and exposed for 24 h in a wind tunnel to a range of concentrations of bromoxynil– octanoate and metribuzin. The quantum yield ((phi)PSII) and the dry weight were used as response parameters. Results indicate that young sunflower plants are affected by sublethal concentrations of both herbicides, whereas metribuzin proved to be more phytotoxic. Bromoxynil–octanoate and metribuzin concentrations >0.265 and >0.135 (mu)g/m3 impair the photosynthetic activity of exposed leaves and concentrations >0.780 and >0.641 (mu)g/m3 of leaves developed after exposure. Effects on dry weight indicate that younger plants were more susceptible, whereby the response to metribuzin proved to be more dependent on growth stage. Based on these results and considering herbicide concentrations in ambient air, there is a reasonable probability that non-target plants are temporarily at risk of being affected.