Mechanisms Of Irorn-manganese Plaque Formation On Root Surface Of Phytolacca Americana By Iron-manganese Oxidizing Bacteria And Ecological Effects Of Iron-manganese Plaque Thickness

In this study,the mechanism of iron-manganese plaque formation on root surface of P.americana by iron-manganese oxidizing bacteria and ecological effects of iron-manga--nese plaque amounts was investigated with various physio-biochemical parameters.the main results include:High concentration of iron-manganese ions and iron-manganese oxidizing bacteria MN1405 could promote high amouts of iron-manganese plaque formation,iron-manganese plaque thickness could reach to 206.60g·kg-1.thick plaque are primarily filled with a jelly-like substance loaded with root surface.In exocuticle,Fe-Mn oxides surrounds Microbial and penetrate deep into the exodermis or aerenchyma.in P.americana root,cell walls are the main area of iron-manganese ions.Add ing iron manganese oxide bacteria MN1405 can reduce enrichment of iron-manganese ions in the cell walls.Iron and manganese oxide bacteria MN1405,not only functions detoxification of roots,but also increased the relative abundance of resistance iron-manganese endophytes of root.It contribute to improve the tolerance of iron manganese of P.americana,and promote high amounts of iron-manganese plaque formation.Under Pb-Cd combined stress,Results indicated that P.americana with middle plaque and thick plaque had developed lateral roots and more new roots.High Cd concentration significantly inhibited the root elongation.Cd accumulation in P.americana at high Cd concentration was in the order:thick plaque>middle plaque>thin plaque.The accumulation of Cd in P.americana with thick plaque could reach to 86735.63 mg·kg-1.With low Cd concentration,Cd accumulation was decreased in the order:thin plaque>thick plaque>middle plaque.High Pb concentrtation could improve Cd concentration in P.americana with thin plaque and thick plaque,but significantly decreased Cd accumulation in P.americana with mid plaque.Soluble sugar from roots,and soluble protein from both roots and leaves were positively correlated to iron-manganese plaque amounts.Soluble protein from both roots and leaves of P.americana with middle plaque and thick plaque also have positive correlation to the combined stress of different metals.Furthermore,under Pb-Cd combined stress,the soluble protein contents in roots and leaves of P.americana were higher than those in the control group.Under Pb-Cd combined stress,Pb accumulation in P.americana was in the order:thin plaque were significantly higher than middle plaque and thick plaque.The accumulation of Pb in P.americana with thin plaque could reach to 1457464.88 mg·kg-1.Pb accumulation was higher than Cd accumulation in different iron-manganese plaque amounts.thin plaque was no influens Pb translate to aboveground or underground,but middle plaque and thick plaque play a role of "barrier layer" in translocation.SDS-PAGE indicated that:P.americana with different iron-manganese plaque amounts showed most protein molecular weight range of 20KD-60KD.Respectively,major bands was found in the-25KD,-29KD,-35KD,-50KD?Phosphate accumulation in P.americana at different phosphorus concentration was in the order:thick plaque>thin plaque>middle plaque,and thick plaque were significantly higher than middle plaque and thin plaque.But thin plaque were significantly higher than middle plaque just at high phosphorus concentration.The ratio of P in every organs of P.americana showed:iron-manganese plaque was an important part for phosphate retention in P.americana,The accumulation of Phosphate in P.americana with thick plaque could reach to 49201.47mg·kg-1.Thickness may also inhibit iron-manganese plaque translocation to underground.Soluble sugar and Soluble protein from both roots and leaves of P.americana with middle plaque and thick plaque also have positive correlation to the combined stress of different metals.