Estimation of ammonium ion distribution between cytoplasm and vacuole using nuclear magnetic resonance spectroscopy

Abstract

Evidence is presented that intracellular ammonium is trapped in vacuoles of maize (Zea mays L.) root tips because of rapid movement of ammonia between cytoplasm and vacuoles. The concentration of cytoplasmic ammonium is estimated to be <15 μM at extracellular ammonium concentrations up to 1 mM. The implications for pathways of ammonium assimilation are discussed.