Integration of trap‐ and root‐derived nitrogen nutrition of carnivorous Dionaea muscipula

Carnivorous 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 NO₃⁻, NH₄⁺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 NH₄⁺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 NH₄⁺was mediated by 2.5‐fold higher expression of the NH₄⁺transporter DmAMT1 in the roots compared with the traps. Electrophysiological studies confirmed a high constitutive capacity for NH₄⁺uptake by roots. Glutamine feeding of traps inhibited the influx of¹⁵N from root‐absorbed¹⁵N/¹³C‐glutamine into these traps, but not that of¹³C. 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.