A Root-Shoot Partitioning Model Based on Carbon-Nitrogen-Water Interactions and Munch Phloem Flow

A root-shoot model of partitioning during vegetative plant growth is described, which simulates the transport of water, labile nitrogen (N) and labile carbon (C) through the xylem and phloem, and in which C, N and water interact to determine growth. It is assumed that a fraction (λ) of the N taken up by the root passes upwards in the xylem to the shoot where it is transferred to the phloem. The remaining fraction (1-λ) is transferred directly to the root phloem. Phloem translocation of labile C and N downwards from the shoot to the root is driven by a shoot-root gradient of labile C concentration, in accordance with the Munch flow hypothesis. Shoot and root growth rates are assumed to be functions of local water potentials and of the local concentrations of labile C and N (...)