Influence of different sediment nutrients on growth and photosynthesis fluorescence characteristics of Hydrilla verticillata (L.f)Royle The Effects of Immobilization on Photosynthesis, Growth, Nitrogen Fixation and Ammonium Ion Excretion of Mutant and Wild Type Cells of Anabaena variabilis Comparative Studies on Photosynthetic Fluorescence Spectra and Fluorescence Kinetics of Bryophytes Influence of soil gradual drought stress on Acorus calamus growth and photosynthetic fluorescence characteristics Influence of Cd2+ or Cu2+ stress on the growth and photosynthetic fluorescence characteristics of Hydrilla verticillata Influence of water turbidity on germination of Potamogeton crispus and growth of germinated seedling