Submitted to: Biological Systems Simulation Group Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2006
Publication Date: April 20, 2006
Citation: Timlin, D.J., Fleisher, D.H., Yang, Y., Kouznetsov, M., Reddy, V., Pachepsky, Y.A. 2006. Regulation of active and passive nitrogen uptake in response to C02 and nitrogen application rate. 37th Annual Biological Systems Simulation Conference. p. 35.
Active and passive uptake mechanisms are important for nitrogen uptake in plants. Active uptake includes nitrogen entering a plant via a diffusive flow process in the roots. This process is believed to be controlled by the plant and depends on plant demand for nitrogen. Passive uptake includes nitrogen that enters the plant as mass flow mixed with water that enters the root system in the transpiration flow. Little is known about how the plant regulates nitrogen influx or the relative importance of the two processes as nitrogen content varies. The two dimensional water and solute transport model 2DSOIL was modified to simulate active and passive transport. Simulations were carried out using a range of boundary and atmospheric conditions from a nitrogen experiment with potato carried out in sunlit controlled environment chambers. Six nitrogen levels from 2 to 14 mmol per liter N were used. The experimental data showed that nitrogen (N) uptake varied with carbon assimilation rate and the mean carbon to nitrogen ratio of the plant. Total measured N uptake varied from 20 to 90 mg N per plant per day during the exponential growth period and passive N uptake was a small component of total N uptake but increased linearly as N concentration in the soil and transpiration rate increased. The active uptake rate increased asymptotically with nitrogen concentration leveling off at about 6 to 8 umol L-1 N. The asymptotic behavior was related to the decline in demand for N as the N rate increased and carbon assimilation rate also reached a plateau. The simulated data showed similar relationships. These results suggest that active uptake is an important component of total N uptake and that the C/N ratio and carbon assimilation rates can be used to estimate N demand.