Hydrilla verticillata and Vallisneria spiralis are two
common Hydrocharitaceae submerged macrophytes in
many shallow lakes of the middle-lower reaches of the
Yangtze River, China [7, 8]. Growth of the noxious
cyanobacteria Microcystis aeruginosa could be inhibited in
the presence of V. spiralis or the culture filtrates of H. verticillata
[9, 10], which indicates that the two plants could
release allelochemicals into water environment to exertallelopathic effects on Microcystis aeruginosa. But what
compounds are responsible for the algal growth inhibition
is not clear.