Phytosterol of Potamogeton maackianus and Its Change under the Stress of Microcystis aeruginosa

The phytosterol in Potamogeton maackianus was identified and quantified. From the hexane extracts analysis of unsaponifiable fraction ofP. maackianus by gas chromatography - mass spectrometry（GC-MS）, campesterol, stigmasterol and β-sitosterol were the main phytosterols in P. maackianus with the contents of 0.368, 1.17 and 0.824 mg·g^1, respectively. After 7 days＇ exposure under M. aeruginosa, the contents of campesterol, stigmasterol and β-sitosterol in P.maackianus increased by 23.1%, 40.4% and 40.8%, respectively. Both the contents of 24-ethyl sterols （sitosterol and stigmasterol） and 24-methyl sterol （campesterol） in macrophytes increased, but the percentage of total sterol composition did not change significantly. This result indicated that the content of 4-demethyl sterols and the second alkylation of the phytosterol side-chain at C-24 in P. maackianus were affected by M, aeruginosa.

The compromising foraging of a clonal submerged plant in variable environments of substrate type and light condition: a simulation study

Aims Foraging behavior was concerned less in plants especially for clonal aquatic species.The goal of this study was to test the foraging behav-ior and the function of phenotypic plasticity of a clonal submerged plant,Potamogeton maackianus A.Benn in variable manipulative environments.Methods To explore the foraging behavior of a clonal submerged plant,clones of P.maackianus were cultivated in variable environments of different substrate types and light conditions.We measured bio-mass,specific root area(SRA),specific root length(SRL),branch-ing angle of the ramet,chlorophyll content of apical leaves(CCAL),Fv/Fm(chlorophyll fluorescence parameter that indicates maximal photosystem II(PS II)efficiency)and biomass distribution in soil and light contrast treatments after harvest.Important Findings We found that the atypical non-clonal-like foraging behavior homogenized the performance of the stoloniferous clonal spe-cies,P.maackianus,in the measurement of biomass in our study.Substrate type had significant effects on most traits of P.maackianus,except on total biomass,shoot biomass distribution and CCAL.Patchy substrate mediated more root distribution into sand patch rather than into clay patch.Increase of SRA,SRL and Fv/Fm might be adaptive to substrate heterogeneity.Moreover,substrate hetero-geneity induced‘sidewalk’stolon lineage on the edge of sand patch along the patch border.Light condition only had significant effects on branching angle,shoot biomass distribution and Fv/Fm.Shade led to more shoot assignment in light-rich zone than in light-poor zone.Potamogeton maackianus adjusted the branching angle of ramet rather than clonal exploitation in heterogeneous substrates with patchy shade.Moreover,shade led to higher Fv/Fm.A com-promising foraging strategy promoted P.maackianus to escape unfa-vorable environments.Phenotypic plasticity,which maximized the performance of P.maackianus in the measurement of biomass in variable environments,may explain its domination in some shallow lakes of the middle and lower reaches of Yangtze River.