Plant shoots may be a significant source of N loss in crops. Ammonia volatilization and C0 2 exchange rates from 'Otar spring wheat (Triticum aestivum L.) plants exposed to low-and high-N treatments were observed from heading through the hard kernel phenological stages. The plants were grown in growth chambers (Nunn clay loam soil [Aridic Argiustoll)) where whole-plant gas-exchange measurements were made using a plexiglass cuvette. Plants lost NH 3 at fairly constant rates (60-120 ng NH 3 -N m-2 s-1 ) during the pre-senescence time period (before milk ripe stage), but the loss rate increased to 200 to 300 ng NH 3 m-2 s-1 during final plant senescence. A reverse pattern was observed in C0 2 exchange rates. Rates of C0 2 .exchange ranged from 0.13 to 0.42 mg C0 2 s-1 during heading, but dropped off (gradually in the high-N treatment, abruptly in the tow-N treatment) as the plants began to senesce. The NH 3 loss rates on a leaf-area basis were similar for the low-and high-N plants despite significantly higher N concentrations in high-N plants. Twice the leaf area was attained by the high-N plants, resulting in NH 3 volatilization rates per plant roughly twice those observed in the !ow-N plants. The results suggest that significant amounts of NH 3 can be lost from wheat shoots.