Delayed NH₃ and N₂ O uptake by maize leaves

¹⁵ N was used to give evidence of NH₃ and N₂ O absorption by maize leaves. A short-term labelling method (90 min) was chosen with high NH₃ concentration (40 μ1 1^-1 ) to assess uptake mechanisms. Two initial entry pathways were suggested for NH₃ : fast uptake with immediate metabolism and fast storage with progressive metabolism. A storage compartment delayed NH₃ absorption after exposure. Similar mechanisms might be involved in N₂ O uptake.