Effect Of N Application On The P Accumulation Of Polygonum Hydropiper In High P Condition

Due to a large number of phosphorus?P?fertilizers and animal manures application,excess P accumulated in soil,resulting in the potential risk of environmental,for example eutrophication.The phytoextraction,using P-accumulating plants,was a common approach to extract excess P from soil.However,the phytoextraction efficiency of P-accumulating plants is poor for their low shoot P accumulation.Some studies have used nitrogen?N?fertilizer to enhance P accumulation of P-accumulating plants.Thus,the pot experiments were carried out to investigate the effect of N application on P accumulation characteristics in a mining ecotype?ME?of P.hydropiper with a non-mining ecotype?NME?as contrast.The following is a summary of the primary results:?1?Shoot biomass,P concentrations and P accumulation of the ME reached the maximum at 100mg kg^-1 N application.Shoot P concentrations and P accumulation of the ME were significantly higher than those of NME.Root Biomass,P concentrations and P accumulation of two ecotypes increased with increasing N application.However the ME presented lower root P concentrations and P accumulation,and root P accumulation was only 39.5%-77.7%of NME.Under the condition of N application,the bioaccumulation coefficient and translocation rate of the ME reached the maximum at100 mg kg^-1 N application.The bioaccumulation coefficient and translocation factor of P in the ME were significantly higher than the NME.N application improved P availability in rhizosphere soil of the ME,thus promoting its P accumulation.?2?With optimum N application(100 mg kg^-1),biomass and P accumulation of the ME reached the maximum at 12 weeks,in which the shoot P accumulation was 389.52 mg plant^-1.The best periods to harvest the ME was 12 weeks.After 8 weeks,the ME had higher shoot biomass,P concentrations and P accumulation than the NME,but lower root P accumulation.With increasing growth periods,shoot P accumulation rates of the ME increased and the largest increase was in 6 to 8 weeks.8 weeks was rapid P accumulation periods.The ME performed higher shoot P accumulation rates than the NME.In leaf P fractions,the concentrations of inorganic P and ester P increased first and then decreased.At 10 and 12 weeks,the ME showed higher inorganic P and ester P concentrations than the NME.?3?With optimum N application(100 mg kg^-1),rhizosphere H₂O-Pi?Pi,inorganic P?,NaHCO₃-Po and NaOH-Po?Po,organic P?decreased with increasing growth periods,while H₂O-Po,NaHCO₃-Pi and HCl-Po increased.The ME had lower rhizosphere H₂O-Pi and higher rhizosphere H₂O-Po than the NME after 8 weeks.In addition,acid phosphomonoesterase?ACP?and phosphodiesterase?PDE?activities were increased with increasing growth periods,while alkaline phosphomonoesterase activities?ALP?increased first and then decreased.The ME showed higher ACP and ALP activities than the NME in each period,while PDE activities were higher than the NME in 12 weeks.?4?With optimum N application(100 mg kg^-1),the greatest biomass,P concentrations,P accumulation and shoot P extraction ratios of ME were found at N3.The greatest shoot P accumulation of the ME was 537.67 mg plant^-1 and the greatest shoot P extraction ratios of ME was20.58%.Shoot biomass,P concentrations,P accumulation and P extraction ratios of the ME were higher than that of the NME.But the ME had lower root biomass,P concentrations and P accumulation than the NME at N3.Root P concentrations of the ME were significant positive correlations with P concentrations,while shoot P concentrations of the ME were significant negative correlations with Ca,Fe,Mg and B concentrations.Increasing N top dressing can reduce shoot micronutrients concentrations,which is beneficial to improve P accumulation capacity of the ME.