The growth, photosynthesis and antioxidant defense responses of five vegetable crops to phenanthrene stress

Polycyclic aromatic hydrocarbons (PAHs) are global environmental problem. To better understand the growth and physiological responses to atmospheric PAHs, we investigated biomass, photosynthetic machinery and antioxidant system in pakchoi, cucumber, flowering chinese cabbage, tomato and lettuce under various levels of phenanthrene (PHE) stress. Foliar exposure to PHE for 14 d resulted in a dose dependent decrease in growth, photosynthesis and chlorophyll contents. With few exceptions, antioxidant enzymes (superoxide dismutase, guaicol peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were upregulated following exposure to PHE. Dose dependent increase in malondialdehyde contents together with H2O2 accumulation suggested an occurrence of oxidative stress following PHE exposure. However, to some extent, growth and antioxidant defense responses differ from species to species. Difference in defense capacity might result in different tolerance and phytotoxicity among the studied vegetables. Taken together, phytotoxicity of PHE to five vegetables could be sequenced in the following order: pakchoi>cucumber>lettuce>tomato>flowering chinese cabbage.

► Phenanthrene foliar application reduced biomass and photosynthesis in a dose dependent manner.
► Phenanthrene decreased chlorophyll contents and induced chlorosis.
► Phenanthrene induced photoinhibition, lipid peroxidation and H2O2 accumulation.
► Antioxidant enzyme responses to phenanthrene vary from species to species.
► Phytotoxicity order is as follows: pakchoi>cucumber>lettuce>tomato>flowering chinese cabbage.