1.2 Uptake of N and rhizosphere pH changes NH4+ assimilation: pH(acicl)-often whole root surface NO3 assimilation; pH often alkaline-sometimes in patches, may be also be pH patches elsewhere on same root Maize(in soil agar indicator) NO NH+ low no Marschner Romheld (1983) 60 1D1.2 Uptake of N and Rhizosphere pH changes ▪ NH4 + assimilation: pH  (acid) - often whole root surface ▪ NO3 - assimilation: pH often  (alkaline) - sometimes in patches; may be also be pH  patches elsewhere on same root Maize (in soil & agar + indicator) NO3 - NH4 + low NO3 - Marschner & Römheld (1983)