A multi compartments model of nitrate metabolism regulation in plant roots

A new concept illustrated by a corresponding mathematical model of nitrate metabolism regulation is proposed. The model is based on the root nitrate compartmentation in several functional pools: storage, metabolic and mobile (MobP) intended for translocation to shoots. Data on nitrate uptake, compartmentation, reduction in intact roots and translocation to shoots were obtained on steady state wheat seedlings grown at 25 degrees and 12 degreesC in the root zone. The net uptake, influx/efflux ratio, MobP size and translocation changed depending on the medium temperature. The oscillations of the net uptake rate, nitrate tissue concentration and its temperature modification were revealed. The scheme of regulation is based on the idea that net uptake through nitrate influx/efflux is under the control of the nitrate of MobP which size was dependent on the nitrate translocation into shoots. The mathematical model is represented by a system of ordinary differential equations simplified according to the time hierarchy of reactions. It has a limit cycle at definite values of parameters. The model postulates the mechanism of a positive feedback regulation of newly absorbed nitrate transfer into translocated pool formed in the root cortex. Theoretical results are verified experimentally.