Abstract: Photosynthetic activities of Azolla imbricata, A. caroliniana and A. filiculoides were studies under different root-zone temperatures. A. imbricata and A. caroliniana present maxium photosynthetic activity at 30℃. photosynthetic activity were decreased dramatically when temperatures (with 7-40℃) were lower or higher than 30~C.Whereas A.filiculoides showed similar photosynthetic activity in the range of root-zone temperatures 7-25℃ (Fig.2). The photosynthetic and acetylene reduction activities of the three Azolla species were influenced in different pattern by the pretreatment of 24 hours dark 0℃ or 2 hours dark 40℃ (Fig. 3,4). The methods here reported were suggested using to measure the ecological-physiology parameters Of Azolla germplasms.