Water transport in plants: Role of the apoplast

Abstract

The present state of modelling of water transport across plant tissue is reviewed. A mathematical model is presented which incorporates the cell-to-cell (protoplastic) and the parallel apoplastic path. It is shown that hydraulic and osmotic properties of the apoplast may contribute substantially to the overall hydraulic conductivity of tissues (Lpr) and reflection coefficients (Crsr). The model shows how water and solutes interact with each other during their passage across tissues which are considered as a network of hydraulic resistors and capacitances ('composite transport model'). Emphasis is on the fact that hydraulic properties of tissues depend on the nature of the driving force. Osmotic gradients cause a much smaller tissue Lpr than hydrostatic. Depending on the conditions, this results in variable hydraulic resistances of tissues and plant organs. For the root, the model readily explains the well-known phenomenon of variable hydraulic resistance for the uptake of water and non-linear force/flow relations. Along the cell-to-cell (protoplastic) path, water flow may be regulated by the opening and closing of selective water channels (aquaporins) which have been shown to be affected by different environmental factors.

Water extraction and implications on soil moisture sensor placement in the root zone of banana

“…This fact should be related to a higher growth rate of banana roots at this stage (Silva et al, 2015). roots (Steudle and Frensch, 1996;Barrowclough et al, 2000;Watt et al, 2008;Draye et al, 2010). The association between the variability of water extraction in the root zone of banana and the variability in soil water availability is shown in Figure 3.…”

Mercuric Chloride Effects on Root Water Transport in Aspen Seedlings

“…An inhibition of water transport by mercury was reported in cell membranes isolated from higher plants Niemietz and Tyerman, 1997) and in whole root systems (Maggio and Joly, 1995;Carvajal et al, 1996). However, the effects of mercury reagents on E a have not been investigated in intact higher plants.Based on the composite transport model (Steudle and Frensch, 1996), water transport is via three parallel pathways, apoplastic, symplastic, and transcellular. Both symplastic and transcellular pathways are often referred to as the cell-to-cell pathway (Steudle and Frensch, 1996).…”

“…Based on the composite transport model (Steudle and Frensch, 1996), water transport is via three parallel pathways, apoplastic, symplastic, and transcellular. Both symplastic and transcellular pathways are often referred to as the cell-to-cell pathway (Steudle and Frensch, 1996).…”

“…Both symplastic and transcellular pathways are often referred to as the cell-to-cell pathway (Steudle and Frensch, 1996). In the present study, we use the term symplastic transport to describe the cell-to-cell transport of water involving both the transmembrane transport and that through the plasmodesmata.…”

A model for hydraulic redistribution incorporating coupled soil-root moisture transport

“…Further, studies have reported the soil moisture dependence of root conductivity (e.g. Nobel et al, 1990;Lopez and Nobel, 1991;Wan et al, 1994;Huang and Nobel, 1994;Steudle and Frensch, 1996). Taking all these into consideration, the root hydraulic conductivity in i th soil layer is assumed to be a function of the total root conductivity of the root system K root, total , the root fraction in that layer F root, i , and the relative soil saturation of that layer [θ θ sat ] i .…”