Photoinduced toxicity of PAHs to the foliar regions of Brassica napus (canola) and Cucumbis sativus (cucumber) in simulated solar radiation.

Simulated solar radiation and natural sunlight can enhance polycyclic aromatic hydrocarbon (PAH) toxicity, previously reported in terms of inhibited production of Lemna gibba leaves and diminished growth of Brassica napus seedling roots. This work has been extended to examine the photoinduced impact of PAHs on the foliar regions of terrestrial plants. To carry out these experiments two crop species, B. napus (canola) and Cucumbis sativus (cucumber), were chosen to test the photoinduced toxicity of six PAHs (anthracene, phenanthrene, benzo(a)anthracene, benzo(a)pyrene, flouranthene, and pyrene). Aqueous solutions containing PAHs were sprayed on the foliage of the plants. It was found that all the PAHs tested had negative impacts on the foliage of the plants and the concentrations that induced toxicity were consistent with those observed for inhibition of growth of L. gibba. The impacts were observed as diminished biomass accumulation, induction of chlorosis, and inhibition of photosynthesis. It may be concluded from this work that PAHs in rain and surface waters could be harmful to photosynthetic tissues of terrestrial plants.