Abstract:In order to ascertain the allelopathy of Parthenium hysterophorus L. flowers on wheat, the greenhouse pot experiments were performed to investigate the effects of aqueous extract on the growth, physiological and biochemical mechanism in wheat. The results showed that aqueous extract of flowers inhibited the germination and growth of wheat, and the inhibition became stronger as the concentration of the extract increased. Some results from physiological and biochemical mechanism of treated wheat indicated that with the increase of extract concentration, photosynthesis, photosynthetic pigment contents and CAT activity decreased, while P and MDA contents increased; N content decreased first and then up to normal, while NR activity decreased first and then increased; GS activity kept normal, while POD and SOD activities increased first and then decreased. The results showed that aqueous extract of P.hysterophorus flower inhibited the photosynthesis, SOD, POD and CAT activities of wheat leaf, but increased the MDA content of wheat.