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Many heavy metals, such as Cu, are essential for plant growth. However, too much Cu into the water could result in water pollution, which may disturb the normal physiological metabolism of plants, and affect their growth, development and reproduction. Nevertheless, some plant species can grow well and accumulate Cu in the polluted water, showing certain tolerance to Cu.Lemnaceaes have vast latent capacity in disposing polluted water for their wide distribution, fast growing and easily operated. We selected Spirodela polyrrhiza and Lemna minor, which are commonly found, as experiment material. The influence of different concentration Cu on them was studied by the method of system comparison, and the divergences of physiology changes of two lemnaceaes with the consistency of copper treatment were compared. Furthermore, we discussed two lemnaceaes’tolerance to Cu and their using potential. The main results were presented as following:(1) Using S. polyrrhiza and L. minor as phytotoxicty test materials, we found it suitable with 60 as initial culturing number and 4 days as cultivation period. Moreover, the proper concentrations of Cu were 0、0.056、0.1、0.18、0.32、0.56、1.0、1.8、3.2、5.6 mg·L-1. 4d-IC50 of rate of increasing amount of two Lemnaceaes are 0.28 and 0.42 mg·L-1 under Cu solution mentioned above.(2) With the rise of Cu concentration, the growth status and the anatomy structure of leaf epidermis of two Lemnaceaes deteriorated gradually, and the damage symptoms of S. polyrrhiza come about earlier than that of L. minor.(3) With the rise of Cu concentration, both the pigments and the antioxidase system activation of two Lemnaceaes were firstly promoted then restrained. The activities of the superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) all increased first and decreased afterwards with the consistency of copper treatment. To S. polyrrhiza, the activities of each
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