PLANT PHYSIOLOGY , Vol 104, Issue 1 189-199, Copyright © 1994 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Novel Methods of Measuring Hydraulic Conductivity of Tree Root Systems and Interpretation Using AMAIZED (A Maize-Root Dynamic Model for Water and Solute Transport)
M. T. Tyree, S. Yang, P. Cruiziat and B. Sinclair
Northeastern Forest Experiment Station, Burlington, Vermont 04502 (M.T.T.)
Steady-state and dynamic methods were used to measure the conductivity to
water flow in large woody root systems. The methods were destructive 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 from the excised
base of the root to the apex, causing flow in a direction opposite to that
during normal transpiration. Sample data are given for two tropical
(Cecropia obtusifolia and Lacistema aggregatum) and two temperate 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 roots. 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 the phloem of leaves. Results are discussed in
terms of the predictions of AMAIZED, and suggestions for the improvement of
methods are made.
