Uptake and phytotoxicity of anthracene and benzo[k]fluoranthene applied to the leaves of celery plants (Apium graveolens var. secalinum L.)

• Chronic exposure to anthracene reduces ascorbic acid concentrations in celery plants.
• Plant exposure to PAHs increases the total phenolic content of celery leaves.
• Anthracene and benzo[k]fluoranthene do not exert a cumulative phytotoxic effect.
• Benzo[k]fluoranthene slows down the rate of abiotic changes in anthracene.
• Translocation of PAHs from the aboveground parts of celery plants to the roots is low.

The above-ground parts of celery plants were exposed to two polycyclic aromatic hydrocarbons (PAHs): 3-ring anthracene (ANT) and 5-ring benzo[k]fluoranthene (BkF), and the combination of ANT and BkF. After 43 days of exposure (overall dose of 1325 µg/plant), celery plants retained only 1.4% of the total dose of ANT and 17.5% of the total dose of BkF. After exposure to a combination of ANT and BkF (1325 µg of each compound per plant), the average ANT concentrations were more than twofold higher in/on leaf blades, whereas BkF levels were insignificantly higher. Under natural photoperiod conditions equivalent to a normal day, the combined application of ANT and BkF to the above-ground parts of celery plants slowed down physicochemical transformations of ANT. A similar effect was observed when PAHs were applied to glass surfaces. The combination of both PAHs probably led to stacking interactions, which decreased volatilization, in particular of ANT. Phytotoxicity of ANT and BkF could not be unambiguously established based on the results of this study. In all analyzed treatments, the chlorophyll content of leaf blades remained unchanged. Foliar application of ANT reduced ascorbic acid levels in all analyzed plant parts and increased the total acidity of celery leaves. In all experimental treatments, the total phenolic content of leaves increased up to 15%. Interestingly, ANT and BkF did not produce cumulative effects when applied in combination (when total PAH concentrations per plant were twofold higher).