Studies of osmo-diffusive and energetic properties of the maize root

This work is concerned with osmotic and diffusive transport of water and solutes across the maize root, and also with ascent of substances in the xylem. The root has been modelled as a one-membrane system. For the root treated in this way (and with the stem cut off) all the transport parameters present in the thermodynamic description of transport (Katchalsky and Curran 1965) were determined using the pressure probe method (Steudle et al. 1987). These parameters include coefficients of filtration Lp, reflection sigma, and permeability omega. Using numerical values of the parameters and the formalism mentioned, detailed calculations were performed of osmotic volume flows Jv, and solute flows js, going across the maize root and pumped by the root up to a certain height h, against the force of gravity. This in turn allowed, with the use of a previously developed analytical method (Kargol 1990) to study the osmo-diffusive conversion of free energy of solutions, and to analyse the root as a free energy converter. In particular, the effective power and energetic efficiency of the root in the radial transport and pumping of water by the root pressure up to a certain height h, were studied. The root pressure has been assumed to be generated osmotically.