Abstract:Influences of rare earth Ce3+ on calcium-regulated photosynthesis in Eichhornia crassipes were investigated. When cultured in Ce3+-containing nutrient solution without Ca2+, the chlorophyll produced in Eichhornia crassipes was found to decrease by 8.31% compared to that of counterparts cultured in Ca2+-containing nutrient solution (control experiment). The corresponding fluorescence quantum yields of chloroplast at 440and 480nm were also decreased by 6.14% and 3.82%, respectively. Additionally, the activities of Mg2+-ATP enzyme and Ca2+-ATP enzyme, and the amount of proteins were also decreased by 1.93%, 5.05% and 3.94%, respectively. However, the above parameters related to the calcium-regulated photosynthesis increased by 9.89%, 15.21%, 3.05%, 8.08%, 10.26% and 10.16%, respectively, when compared with those of Eichhornia crassipes cultured in nutrient solution without Ca2+. The photosynthesis activity of Eichhornia crassipes cultured in the absence of Ca2+ had been significantly improved by the use of rare earth Ce3+. The experimental results have shown that compared with Ca2+, Ce3+ exhibited similar regulation functions on the growth of Eichhornia crassipes. In the absence of Ca2+, a suitable amount of Ce3+ will promote the photosynthesis of plant by increasing the plant biomass, thus resulting in positive catalytic effects on the process of eutrophication.