Translocation and recovery of 15N-labeled N derived from the foliar uptake of 15NH3 by the greenhouse tomato (Lycopersicon esculentum Mill.)

In order to completely evaluate ammonia emission from greenhouse vegetable fields, crop canopy absorption should not be neglected. The foliar uptake of NH3 applied at two growth stages and the subsequent 15N-labeled N translocation to other plant components were investigated under greenhouse conditions using chambers covered with the soil of a tomato field. Treatments comprised three NH3-N application rates (70, 140, and 210 mg/plot) using 15N-labeled ammonium sulfate. Plants were harvested immediately after exposure for 24 h, and the total N concentrations and 15N/14N ratios were determined. With increased NH3 concentration, total 15NH3-N absorption increased considerably, whereas the applied 15NH3-N uptake decreased gradually. The tomato plants absorbed 33–38% and 24–31% of the 15NH3-N generated at the anthesis and fruit growth stages, respectively. A total of 71–80% of the recovered NH3 was observed in the leaves and 20–30% of the recovered NH3 was remobilized to other components. Among them, an average of 10% of the absorbed 15NH3-N was transferred into the tomato fruits. All these results indicated the potential of the tested tomatoes for the foliar uptake of atmospheric 15NH3 and the distribution of 15N-labeled vegetative N among different plant components. The results are of great importance for the complete evaluation of nitrogen use efficiency in the greenhouse tomato fields.