SummaryCarnivorous Dionaea muscipula operates active snap traps for nutrient acquisition from prey; so what is the role of D. muscipula's reduced root system?We studied the capacity for nitrogen (N) acquisition via traps, and its effect on plant allometry; the capacity of roots to absorb NO 3 À , NH 4 + and glutamine from the soil solution; and the fate and interaction of foliar-and root-acquired N. Feeding D. muscipula snap traps with insects had little effect on the root : shoot ratio, but promoted petiole relative to trap growth. Large amounts of NH 4 + and glutamine were absorbed upon root feeding. The high capacity for root N uptake was maintained upon feeding traps with glutamine. High root acquisition of NH 4 + was mediated by 2.5-fold higher expression of the NH 4 + transporter DmAMT1 in the roots compared with the traps. Electrophysiological studies confirmed a high constitutive capacity for NH 4 + uptake by roots. Glutamine feeding of traps inhibited the influx of 15 N from root-absorbed 15 N/ 13 C-glutamine into these traps, but not that of 13 C. Apparently, fed traps turned into carbon sinks that even acquired organic carbon from roots. N acquisition at the whole-plant level is fundamentally different in D. muscipula compared with noncarnivorous species, where foliar N influx down-regulates N uptake by roots.