COMPARTMENTAL REDISTRIBUTION AND LONG-DISTANCE TRANSPORT OF ABSCISIC-ACID (ABA) IN PLANTS AS INFLUENCED BY ENVIRONMENTAL-CHANGES IN THE RHIZOSPHERE - A BIOMATHEMATICAL MODEL

Based on experimental data obtained in earlier studies on membrane per meabilities of abscisic acid (ABA) for Cortex and stele cells of roots and on measured compartmental pH shifts after onset or release of dif ferent types of soil-borne stresses, a biomathematical model was devel oped which permits computer analysis of the dynamics of compartmental ABA distribution within different root tissues (cortex, stele) and the ir compartments (apoplast, cytosol, vacuole), and in the xylem sap of the root stele, Metabolism and conjugation of ABA and its export from roots via the xylem and its import into roots via phloem sap flow are also taken into consideration, We want to know which soil-borne stress es can biophysically provoke a root-to-shoot signal of ABA. In this co mmunication we describe the biomathematical structure of the root mode l and present all necessary morphological (volumes, surfaces etc.) and physiological (pH, membrane conductances etc.) parameters of unstress ed roots, This root model and an available leaf model are integrated t o a plant model (rosette plant), Simulations reveal the fundamental ro le of the stele tissues, the rhizospheric ABA concentration and the AB A synthesis in roots (root-to-shoot communication), The shoot-to-root communication strongly depends on ABA synthesis in leaves, but hardly on ABA redistribution effects after stress-induced compartmental pH-sh ifts in leaves.