lecture 11Nitrogen fertilzer.ppt

文档介绍：-4%Nand40%+orNO3-.-andNH4+.Someplantsarespecialists:+&aminoacids(,arctictundra北极冻塬,rice)SometakeupmoreNH4+thanNO3-whenbothsuppliedtogetherinequalamounts,butNO3-isprimeformofNinsoilsolutionOver-supplyofNH4+canbetoxictoplantsIPlantnitrogenUptakeofNH4+maybebroughtaboutbythefacilitateddiffusion(bytheelectropotentialdifferenceandcationselectivechannels).WithNH4+nutritionrecyclingofH+backintothecytosolisrestrictedandtheH+/-ismainlyaH+/NO3--+assimilation:pH(acid)-oftenwholerootsurfaceNO3-assimilation:pHoften(alkaline)-sometimesinpatches;maybealsobepHpatcheselsewhereonsamerootMaize(insoil&agar+indicator) NO3-NH4+lowNO3-Marschner&Römheld(1983)NH4+assimilationinroots(andpHregulation)amino-N NH4+ H+O2sucroseshootrootxylemphloempHlight‘Excess’cationuptakeRaven&Smith(1976);modifiedNH4+assimilationinroots(andpHregulation)amino-N NH4+ H+O2sucroseshootrootxylemphloempHlight‘pHnon-perturbing’aminoacids&amidesAmmoniumcytoplasmoutside-vePDNH4+H+)NH4+)H+NH4+[&K+]NH4+[&K+]?NH3?HighAffinityTransportSystems;Km=20-40mmol/m3LowAffinityTS(Diffusionathighconcentrations?)channelH+co-H+efflux,someH+‘re-cycles’byco-transportwithNH4+Energetics,ics,regulation,genes:Forde&Clarkson(1999);Glassetal.(2002)pHpHregulationduringNO3-assimilationinrootsamino-N NO3- 2H+O2sucroseshootrootxylemphloempHlight‘Excess’anionuptake