Nitrate induction in spruce: an approach using compartmental analysis

Abstract

Using 13NO3−-efflux analysis, the induction of nitrate uptake by externally supplied nitrate was monitored in roots of intact Picea glauca (Moench) Voss. seedlings over a 5-d period. In agreement with our earlier studies, efflux analysis revealed three compartments, which have been identified as surface adsorption, apparent free space, and cytoplasm. While induction of nitrate uptake was pronounced, NO3−fluxes in induced plants were decidedly lower and the induction response was slower than in other species. Influx rose from 0.1 μmol·g−1·h−1 (measured at 100 μM [NO3−o) in uninduced plants to a maximum of 0.5 μmol·g−1h−1 after 3 d of exposure to 100 μM [NO3−o and declined to 0.3–0.4 μmol·g−1h..