An integrated approach to water transport in a plant over long distances

Abstract

Speaking about long-distance water translocation in plants we mean its displacement across the root (stage I), xylem transport (stage II), permeation of water across leaf apoplast and evaporation to the atmosphere (stage III), and phloem transport (stage IV). Certain biophysical mechanisms are responsible in each of these stages for water transport. The most important of them are included in the theory of root pressure, transpiration-cohesion theory, graviosmotic theory and Munch's theory modified recently. Based on these theories a theoretical model of a plant is developed. It integrates all the above-mentioned stages of water translocation. This model, referred to as the integrated model, is described mathematically using the Kedem and Katchalsky formalism. It is shown that thanks to this description the long-distance water translocation can be considered in a quantitative way and it can take into account interrelationships of these translocations on particular stages.