The Interaction Between Water Movement, Solute Uptake, and Respirational Energy in Plant Roots

Author

Mohamed Sadek Tawakol, Utah State University

Date of Award:

5-1967

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Soil Physics

Committee Chair(s)

Sterling A. Taylor

Committee

Sterling A. Taylor

Committee

H. H. Wiebe

Committee

D. A. Walker

Committee

G. L. Ashcroft

Abstract

Sunflower plants (Helianthus annus, var. Russian mammoth) were grown in Hogland nutrient solution. The roots (after being subjected to treatments with either respiratory inhibitors or respiratory stimulators) were used to measure the flux of water J_w, flux of solute J_s , and the rate of respiration Jo.

The thermodynamic theory of irreversible processes was used to examine the interaction between fluxes, and the changes in conductivity under different treatments. The rate equations for a root membrane of unit thickness were developed as:

J_w = L_wwV_w∆p + L_wsRT ln C¹_s/C²_s +L_woRT ln C¹_o/C²_o

J_s = L_swV_x∆p + L_ssRT ln C¹_s/C²_s + L_soRT ln C¹_o/C²_o

J_o = L_owV_w∆p + L_os RT ln C¹_s/C²_s + L_ooRT ln C¹_o/C²_o

Where: L_ww, L_ss, L_oo are the direct transfer coefficients for water, solute , and oxygen; and L_ws, L_sw, L_wo, L_ow, L_so, L_os are the interaction or linked transfer coefficients; V_w partial molal volume (or specific volume) of water , ∆p the difference in pressure between the external solution and xylem: C¹_s and C²_s , C¹_o and C²_o are the salt and oxygen concentration in external solution and xylem respectively.

The results showed that: 1. The nonlinearity of the flux of water through the root system of sunflower is due to causes associated with the membrane (mainly the permeability). 2. The increase in respiration did not increase the permeability of the membrane. 3. The uptake of water due to solute potential under transpiring conditions is small, but important. 4. The uptake of solute in normal root systems is by active process from solutions to the zylem and then moves passively to the leaves. 5. An increase in passive water uptake might cause an increase of respiration of the root.

Checksum

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Recommended Citation

Tawakol, Mohamed Sadek, "The Interaction Between Water Movement, Solute Uptake, and Respirational Energy in Plant Roots" (1967). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 3605.
https://digitalcommons.usu.edu/etd/3605