NOVEL METHODS OF MEASURING HYDRAULIC CONDUCTIVITY OF TREE ROOT SYSTEMS AND INTERPRETATION USING AMAIZED - A MAIZE-ROOT DYNAMIC-MODEL FOR WATER AND SOLUTE TRANSPORT

Steady-state and dynamic methods were used to measure the conductivity to water flow in large woody root systems. The methods were destructi ve in that the root must be excised from the shoot but do not require removal of the root from the soil. The methods involve pushing water f rom the excised base of the root to the apex, causing flow in a direct ion opposite to that during normal transpiration. Sample data are give n for two tropical (Cecropia obtusifolia and Lacistema aggregatum) and two temperature species (Acer saccharum and Juglans regia cv Lara). A hysteresis was observed in the relationship between applied pressure and resulting flow during dynamic measurements. A mathematical model ( AMAIZED) was derived for the dynamics of solute and water flow in root s. The model was used to interpret results obtained from steady-state and dynamic measurements. AMAIZED is mathematically identical with the equations that describe Munch pressure flow of solute and water in th e phloem of leaves. Results are discussed in terms of the predictions of AMAIZED, and suggestions for the improvement of methods are made.