Culture solutions of the submerged freshwater macrophytes Hydrilla verticillata and Vallisneria spiralis,
separately incubated at 10 g of fresh weight (FW) per liter for three days, were extracted by solid phase extraction
(SPE) followed by liquid liquid extraction (LLE), and the acquired ethyl acetate fractions were analyzed
by
gas chromatograph-mass spectrometry (GC-MS) to identify potential allelochemicals exuded from these
plant
species. Freeze-dried plant tissues were separately methanol-extracted with a similar LLE-GC-MS procedure
to compare allelochemical production and exudation. Four phenolic compounds were identified for
both
species: vanillic acid (VA),
protocatechuic acid (PA),
ferulic acid (FA),
and caffeic
acid (CA).
H.verticillata
produced 179 times the amount of phenolic compounds of V. spiralis. The phenolic contents in
the culture solution were lower than 10% of those in the plant tissues for both submerged species in six of the
eight cases. When evaluating the joint effects of the compounds using the Toxicity Index (TI) model, it was
observed that the four phenolic compounds exerted additive and synergistic inhibition effects on the growth
of Microcystis aeruginosa depending on the mixing ratios. These results indicate that H. verticillata and V. spiralis
could
release some phenolic allelochemicals to inhibit the growth of M.
aeruginosa,
and the joint action
of
multiple allelochemicals may be an important allelopathic pattern of submerged
macrophytes to inhibit the
growth
of noxious cyanobacteria in natural aquatic ecosystems.
Culture solutions of the submerged freshwater macrophytes Hydrilla verticillata and Vallisneria spiralis,separately incubated at 10 g of fresh weight (FW) per liter for three days, were extracted by solid phase extraction(SPE) followed by liquid liquid extraction (LLE), and the acquired ethyl acetate fractions were analyzedbygas chromatograph-mass spectrometry (GC-MS) to identify potential allelochemicals exuded from theseplantspecies. Freeze-dried plant tissues were separately methanol-extracted with a similar LLE-GC-MS procedureto compare allelochemical production and exudation. Four phenolic compounds were identified forbothspecies: vanillic acid (VA),protocatechuic acid (PA),ferulic acid (FA),and caffeicacid (CA).H.verticillataproduced 179 times the amount of phenolic compounds of V. spiralis. The phenolic contents inthe culture solution were lower than 10% of those in the plant tissues for both submerged species in six of theeight cases. When evaluating the joint effects of the compounds using the Toxicity Index (TI) model, it wasobserved that the four phenolic compounds exerted additive and synergistic inhibition effects on the growthof Microcystis aeruginosa depending on the mixing ratios. These results indicate that H. verticillata and V. spiraliscouldrelease some phenolic allelochemicals to inhibit the growth of M.aeruginosa,and the joint actionofmultiple allelochemicals may be an important allelopathic pattern of submergedmacrophytes to inhibit thegrowthof noxious cyanobacteria in natural aquatic ecosystems.
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