Effect Of Main Environmental Factors On Photosynthesis Of Three Submerged Macrophytes From Taihu Lake

The ability of three freshwater macrophytes species, Potomageton crispus L., Potomageton malaianus Miq. and Vallisneria spiralis L., to adapt to light irradiance, temperature and inorganic carbon for photosynthesis were assessed by a series of experiments, which may provide a sound basis for genus selection for restoration of submerged macrophytes in shallow lakes.The effect of different irradiance on the photosynthesis activity and spatial variation of three species were investigated. The dependence of fluorescence parameters on the actinic irradiance, pigmentation, photohibition under high radiation and recovery at darkness for three species were examined. The results showed that short-terms performance was consistentand with ability of long-terms light acclimation. Under high irradiance, P. crispus can drive its non-photosynthetic quenching quickly, and the degree of photoinhibition was lowest and time for dark recovery was shorter than other two species. The tendency of the Car/T(Chl) value and qN in P. crispus were correlated to the increase of induced light without significant change of the Chla/Chlb value. However, the photosynthetic activity in terms of ETR and Yield in P. crispus deceased and membrane permeability enhanced greatly under the 5% and 100% natural light intensities, which showed P. crispus can adapt medium high irradiance. The ability of light acclimation of P malainus was similar with P. crispus. But the photopretection ability of P. malainus at high irradiance was lower than P. crispus, and its dark recovery time was slower than P. crispus. Unlike them, the tendency of the Chla/Chlb value in V. spiralis was correlated to the increased treatment light and membrane permeability did change little under 5% natural light intensity, which showed it has excellent adaptive capability to low light. But the photosynthetic activity in terms of ETR was deceased above 70% natural light intensity, and the degree of photoinhibition was severe and photosynthetic activity was not recover completely after 3h dark adaption. Thus, these three species showed a different distinct acclimation to irradiance, which was accordant with the spatial variation of three species in natural waters.Photosynthesis at different temperature especially stability to high temperature were...