Abstract: In a pot culture experiment, Potamogeton crispus was planted at the water depths 30, 60, 90, 120, 150, and 180 cm, with its growth response to the water depth gradient was studied. The stem length of P. crispus had a significant correlation with water depth (P<001), and the appropriate water depth for P. crispus growth was 90〖KG-*2〗-〖KG-*7〗150 cm. Around May 7th, the leaf numbers of P. crispus in all treatments except at the water depth 180 cm decreased, indicating that the plant became senescent. The difference in water depth had no significant effects on the photosynthetic pigment content of P. crispus. At the water depths 30 and 60 cm, the Fv/Fm and photosynthetic electron-transport rate (ETR) of P. crispus were lower, illustrating that a water depth less than 60 cm had certain inhibitory effects on the photosynthetic electron-transport rate during the mid- or late growth period of P. crispus. It was suggested that water depth less than 60 cm or more than 150 cm was not beneficial to the P. crispus during its mid or late growth period.

Key words: Cinnamomum burmannii, Restriction of photosynthesis, Elevated temperature, Elevated CO₂ concentration