Physiological Response of Ryegrass and Its Rhizospheric Soil Enzymes under Pyrene Stress and the Phytoremediation

A pot experiment was conducted to study the effects of different soil pyrene contents on the growth of ryegrass root and stem-leaf and the activities of dehydrogenase,hydrogen peroxidase and polyphenol oxidase in rhizospheric soil,and meanwhile the ryegrass phytoremediation for pyrene contaminated soil was investigated.The results showed that the fresh weight of ryegrass root increased at 40 d and 60 d as the pyrene content increasing.The stem-leaf fresh weight of ryegrass decreased at 60 d.The fresh weight ratio of root to the whole plant rose during growth and significantly increased at 40 d and 60 d.The dehydrogenase activities in rhizospheric soil of ryegrass increased as growing and declined as pyrene content increasing during experiment,especially treated by 20,40 mg·kg-1 pyrene.The hydrogen peroxidase activities were significantly higher than control under 100、200、400 mg·kg-1 pyrene stress at 40 d.When treated by 400 mg kg-1 pyrene in test,The polyphenol oxidase activities were higher than other treatments with very significant level.The content of extractable pyrene was lower in the ryegrass pots than in CK(pots without ryegrass and pots without both plant and bacteria).Plant absorption made few loss of pyrene.The pyrene loss rate of rhizospheric soil decreased significantly as the pyrene content increasing.The phytoremediation of pyrene contaminated soil by ryegrass was more complete with less content of pyrene in soil.