Growth and photosynthetic adaptation of two submersed Hydrochariaceae species to irradiance were compared under 4 light intensity gradients by shading. It was found that there is no inherent differences in the photosynthetic adaptation to both low and high light stress between the canopy form Hydrilla verticillata (L. f.) Royle and the benthic form Vallisneria americana Michx. It is concluded that significant differences in photosynthesis and growth rates between these two species are attributed to their different growth forms, i.e., the canopy Hydrilla has most of its leaves to reach the surface water where light intensity is high, therefore obtaining a higher photosynthetic rate than the benthic Vallisneria living mostly near the lower light bottom.
Ni, Leyi; George, Bowes; Wang, Feng.Comparative studies on photosynthetic adaptation of two submersed Hydrochariaceae species to different light intensities using microcosm experiment,Acta Hydrobiologica Sinica,1997,21(SUPPL.):150-165