The effect of blooming epiphytic algae on the leaf traits and photosynthetic hnction of the submersed macrophyte Potamogeton crispus was investigated under different epiphytic conditions and nutrition levels. Epiphytic algae growth was promoted at a rate of 0.16 chl a pg.cm".d-' on leaf surface area under eutrophic conditions (N: 1 mg.L-'; P: 0.1 mg-L-') and at a rate of 0.004 chl a pg-~m-~.d-' under mesotrophic conditions (N: 0.1 mgL-'; P: 0.01 mg.~-'). In the presence of the algae eaters Macrobrachiurn nipponense and Radix auricularia, the growth of epiphytic algae was markedly suppressed. In the absence of algae eaters, the growth of epiphytic algae for 42 days under the eutrophic and hypereutrophic conditions resulted in 25.2% of decrease of chl a, more than 50% decrease of the electron transport rate, harmful change in content of leaf nitrogen, photosystem I1 activity and photochemical quenching, and a lower production in the plant.

Lanthanum (La) has been used as agricultural inputs in order to enhance yield and improve crop quality. However, little is known about the effect of La on the photosynthesis and growth of Amorphophallus sinensis, a worldwide food source. The effects of La on the photosynthetic and chlorophyll fluorescence parameters, photosynthetic pigments, corm yield, and konjac glucomannan (KGM) of Amorphophallus sinensis were investigated via field experiments. The leaves were sprayed with different concentrations of LaCl3 (20, 80, 160, and 240 mg L-1). The results exhibited an increasing effect of LaCl3 on photosynthetic rate, stomatal conductance, intercellular CO2 concentration, chlorophyll fluorescence parameters, photosynthetic pigments, corm yield, and KGM, when concentration was between 20 and 240 mg L-1 , and the most effective concentration was 160 mg L-1. Therefore, moderate LaCl3 concentration may increase yield of Amorphophallus sinensis by enhancing the photosynthetic efficiency, increasing the corm yield, and KGM contents.

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