Development of a method for a quick measurement of the root capacity of water uptake and solute transport

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In order to develop a method for a quick measurement of the root capacity of water uptake and solute transport, we examined whether the root properties of water uptake and solute transport can be estimated by monitoring xylem pressure of a root (referred to the equipment as a root pressure probe) by using the theory of Steudle and Jescke based on the root function as an osmometer or not. The followings are obtained results in the research.(1)Hydraulic conductivity measured under the steady state is considered to be reliable. Hydraulic conductivity measured with the root pressure probe under non-steady state was compared with that measured under the steady state in a maize root. There was a close linear correlation between the hydraulic conductivity obtained from both measurements.(2)NaCl transport was investigated in the excised root of Rhizophora stylosa Griff. The reflection coefficient of the roots was smaller than 0.1 and was smaller remarkably than those previously reported for th … More e herbaceous species. The osmotic potential of the exudated sap from the excised root in the nutrient solutions containing various concentration of NaCl was always equivalent to that of the nutrient solution. These results indicate that NaCl transport accompanied by water is not restricted significantly in the excised root of Rhizophora stylosa Griff.(3)The concentrations of Na^+ and Cl^-became equivalent to that of the nutrient solution in the root about 10 days after the seedlings of Rhizophora stylosa Griff, were transferred to the solution containing NaCl, but the concentration of a shoot remained low. This indicates that Na^+ and Cl^-transport from roots to shoot is restricted significantly. The calculated concentration of Na+ and Cl-in the transpirational stream in roots was also far low compared with the concentration of the nutrient solution. This indicates the transports of Na^+ and Cl^-into roots are also restricted.(4)From the results mentioned above, we conclude that the method, considered in the research, can be employed in evaluating the root capacity of water uptake and, however, it is still required to be investigated whether this method can be adopted for evaluating root properties of solute transport. Less