Nitrogen oxide fluxes between corn (Zea mays L.) leaves and the atmosphere |
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| Affiliation: | 1. Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada H4B 1R6;2. PROTEO, the FRQ-NT Network for Research on Protein Function, Structure, and Engineering, Québec, QC, Canada;1. Departamento de Química, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Asunción, 2189 Campus Universitario San Lorenzo, Paraguay;2. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata, Argentina;1. School of Public Health, Nanchang University, Nanchang 330006, PR China;2. Institute of Quality Standard and Testing Technology, Yunnan Academy of Agriculture Science, 650223 Kunming, PR China;1. College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China;2. Precision Agriculture Center, Department of Soil, Water and Climate, University of Minnesota, St. Paul., MN, 55108, USA;3. College of Information and Electrical Engineering, China Agricultural University, Beijing, 100083, China;4. School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo, 454000, China;5. Department of Geography, Minnesota State University, Mankato, MN, 56001, USA |
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| Abstract: | In the United States, fertilized corn fields, which make up approximately 5% of the total land area, account for approximately 45% of total soil NOx emissions. Leaf chamber measurements were conducted of NO and NO2 fluxes between individual corn leaves and the atmosphere in (1) field-grown plants near Champaign, IL (USA) in order to assess the potential role of corn canopies in mitigating soil–NOx emissions to the atmosphere, and (2) greenhouse-grown plants in order to study the influence of various environmental variables and physiological factors on the dynamics of NO2 flux. In field-grown plants, fluxes of NO were small and inconsistent from plant to plant. At ambient NO concentrations between 0.1 and 0.3 ppbv, average fluxes were zero. At ambient NO concentrations above 1 ppbv, NO uptake occurred, but fluxes were so small (14.3±0.0 pmol m−2 s−1) as to be insignificant in the NOx inventory for this site. In field-grown plants, NO2 was emitted to the atmosphere at ambient NO2 concentrations below 0.9 ppbv (the NO2 compensation point), with the highest rate of emission being 50 pmol m−2 s−1 at 0.2 ppbv. NO2 was assimilated by corn leaves at ambient NO2 concentrations above 0.9 ppbv, with the maximum observed uptake rate being 643 pmol m−2 s−1 at 6 ppbv. When fluxes above 0.9 ppbv are standardized for ambient NO2 concentration, the resultant deposition velocity was 1.2±0.1 mm s−1. When scaled to the entire corn canopy, NO2 uptake rates can be estimated to be as much as 27% of the soil-emitted NOx. In greenhouse-grown and field-grown leaves, NO2 deposition velocity was dependent on incident photosynthetic photon flux density (PPFD; 400–700 nm), whether measured above or below the NO2 compensation point. The shape of the PPFD dependence, and its response to ambient humidity in an experiment with greenhouse-grown plants, led to the conclusion that stomatal conductance is a primary determinant of the PPFD response. However, in field-grown leaves, measured NO2 deposition velocities were always lower than those predicted by a model solely dependent on stomatal conductance. It is concluded that NO2 uptake rate is highest when N availability is highest, not when the leaf deficit for N is highest. It is also concluded that the primary limitations to leaf-level NO2 uptake concern both stomatal and mesophyll components. |
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