A Model of Assimilate Partitioning and Utilization in Shoots and Roots in the Vegetative Stage of Lolium multiflorum

Abstract With the purpose of improving crop growth simulation, a mechanistic model and its parameters for assimilate partitioning and utilization were developed for vegetative Lolium multiflorum Lam. (cv. Lomi). The model is based on first-order kinetics and on previously determined efficiencies of assimilate utilization. The driving variable is gross photosynthesis. The five state variables are the translocation pool of recently assimilated carbon, and for shoots and roots, the storage pools and the pools of structural material, respectively. The model consists of first-order rate equations with six parameters. These parameters were estimated by analysis of the time course of CO2-exchange rates, separately for shoots and roots, respectively, during prolonged dark periods of two days and prolonged photo-periods of two days. The analysis was based on maintenance coefficients and on utilization efficiences of shoots and roots and on simulation. Due to the differences in carbon utilization between shoots and...