Abstract: To clarify the relationships between phenolic compounds and continuous cropping obstacle of Rehmannia glutinosa, the accumulation amounts of ferulic acid, vanillic acid, vanillin, and β-hydroxybenzoic acid in continuously cropped R. glutinosa soil were measured, and the effects of these four phenolic acids on R. glutinosa growth were studied with water culture. The results showed that in the growth period of R. glutinosa, soil ferulic acid, vanillic acid, and vanillin contents had a persistent increase, while β-hydroxybenzoic acid content increased first but decreased then. The addition of ferulic acid (8 μg·ml-1), vanillic acid (08 μg·ml-1), vanillin (12 μg·ml-1), and β-hydroxybenzoic acid (30 μg·ml-1) in water culture had stronger inhibitory effects on R. glutinosa root length, root mass, fresh plant mass, and plant height. Treating with test phenolic acids except β-hydroxybenzoic acid increased leaf chlorophyll content significantly, compared with the control. After treated with test phenolic acids, plant SOD and POD activities decreased after an initial increase, and plant malondialdehyde (MDA) content increased. In the treatment of ferulic acid, root SOD and POD activities were the lowest, and roots were rotted and dead. It was suggested that the test four phenolic acids might be the allelomechemicals of R. glutinosa.

Key words: Road traffic pollution, Environmental elements, Phytoindication