MODELING NITROGEN UPTAKE IN INGESTAD UNITS USING MICHAELIS-MENTEN KINETICS

The concept of nutrient flux density was developed to grow plants at a controlled and stable relative growth rate whilst maintaining a const ant internal concentration of a limiting nutrient. The method requires frequent and exponentially increasing additions of nutrients to reple nish uptake. In developing this approach there has been little referen ce to Michaelis-Menten-like nutrient uptake kinetics for characterisin g uptake by roots. This paper applies a simple model of nitrogen-limit ed plant growth using Michaelis-Menten uptake kinetics to data from pr eviously published experiments based on the nutrient flux density appr oach. It is shown that the model can indeed reproduce key features of experiments: (1) plant relative growth rate equals nitrogen relative a ddition rate up to a limit; (2) when nitrogen uptake kinetic parameter s are within the range reported in the literature, this limiting growt h rate agrees with that observed; and (3) solution nitrogen concentrat ions are consistent with those published. We suggest that the understa nding of nutrient uptake and utilisation by plants could be advanced b y jointly considering these two approaches.