Subcellular NH4 flux analysis in leaf segments of wheat (Triticurn aestivum)

Abstract

We report the first use of tracer 13NH4+ (13N-ammonium) efflux and retention data to analyse subcellular fluxes and compartmentation of NH4+ in the leaves of a higher plant (wheat, Triticum aestivum). Leaf segments, 1-2 mm, were obtained from 8-d-old seedlings. The viability of the segments, and stability of NH4+ acquisition over time, were confirmed using oxygen-exchange and NH4+-depletion measurements. Fluxes of NH4+ and compartment sizes were estimated using tracer efflux kinetics and retention data. Influx and efflux across the plasma membrane, half-lives of exchange and cytosolic pool sizes were broadly similar to those in root systems. As the external concentration of NH4+ ([NH4+]o) in..