Arbuscular mycorrhizal fungi and endophytic fungi differentially modulate polyamines or proline of peach in response to soil flooding

Symbiotic fungi are involved in plant flooding tolerance,while the underlying mechanism is not yet known.Since polyamines(PAs)and proline are also associated with stress tolerance,it is hypothesized that the enhancement of stress resistance by symbiotic fungi is associated with changes in PAs and/or proline.The aim of this study was to analyze the effect of inoculation with Funneliformis mosseae and Serendipita indica on plant growth,PAs,and proline and the metabolisms in peach(Prunus persica)under flooding.Two-week flooding did not affect root colonization frequence of F.mosseae,while it promoted root colonization frequence of S.indica.Under flooding,plants inoculated with F.mosseae and S.indica maintained relatively higher growth rates than uninoculated plants.Funneliformis mosseae promoted root ornithine(Orn)contentration and arginine(Arg)and Orn decarboxylase activities under flooding,which promoted putrescine(Put),cadaverine(Cad),and spermidine(Spd)contentrations.Conversely,S.indica decreased contentrations of Arg,Orn,and agmatine and Arg decarboxylase activities,thus decreasing PA contentrations under flooding.Polyamines were negatively correlated with the expression of PA uptake transporter genes,PpPUT1 and PpPUT2,in peach.Polyamine transporter genes of F.mosseae(FmTPO)and S.indica(SiTPO)were regulated by flooding,of which FmTPO1 was positively correlated with Put,Cad,and Spd,along with positive correlations of Spd with SiTPO1,SiTPO2,and SiTPO4.Under flooding,F.mosseae decreased proline concentration,while S.indica increased proline concentration and correlated with expression of a△^(1)-pyrroline-5-carboxylate synthetase gene,PpP5CS2.It was thus concluded that F.mosseae modulated polyamine accumulation,while S.indica induced proline accumulation to tolerate flooding.

Testing mechanisms underlying elevational patterns of lakeshore plant community assembly in Poyang Lake, China

Aims Plant community assembly in wetlands usually changes with eleva-tion gradients,which may be due to the direct effect of flooding and indirect effects such as changes in soil properties and competition.However,the respective importance of each factor remains to be investigated.Methods We investigated patterns of plant diversity,community biomass and soil properties along an elevation gradient of a lakeshore meadow at Poyang Lake,China.Important Findings(i)With increasing elevation,species richness and Simpson diver-sity index decreased.Both aboveground biomass(AGB)and below-ground biomass(BGB)increased with elevation,however,the BGB/AGB ratio also increased,which suggests a significant effect of belowground competition.(ii)Soil N content and soil N:P ratio increased,whereas soil pH decreased with elevation.Other soil properties showed no significant response.(iii)Structural equa-tion modeling showed that variation of plant diversity was mainly explained by BGB.Thus,intensified belowground competition seems to be the primary mechanism causing lower plant diversity at higher elevations.(iv)These findings were further supported by the observed greater response ratio of N and P storage in plant commu-nities than the response ratio of soil N and P content to elevation,suggesting that soil nutrient limitation and belowground nutrient competition increased with elevation.Our study has important implications to wetland management and biodiversity conserva-tion under environmental change(e.g.changes in flooding regimes,eutrophication).