Split-root experiment with Arabidopsis thaliana.

Plants were grown on agar plates that were divided into two identical compartments by a plastic rib. The two compartments contained either 1.5 mM glutamine or 3 mM NO3 as N sources. For each plate, one of the N sources (either glutamine or NO3) was 15N-labelled. Bars indicate the fraction of N derived from each source for the shoot and for roots growing in the NO3 compartment and the glutamine compartment. Bars represent average ± SE, n = 5. Different lower-case and capital letters indicate differences at p≤0.05 between plant parts, and between N sources, respectively.