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

为了建立一种快速测量根系吸水和溶质运输能力的方法，我们利用Steudle和Jescke的理论，基于根系作为渗透计的功能，研究了是否可以通过监测根系木质部压力（称为根压探头）来估计根系吸水和溶质运输的特性。研究中得到的结果如下：(1)认为稳态下测得的水力导率是可靠的。用根压探头测量了玉米根系非稳态和稳态下的水力导率。从这两种测量得到的水力导电性之间有密切的线性相关。(2)研究了茎尖根参（Rhizophora stylosa Griff）断根中NaCl的转运。根的反射系数小于0.1，且显著小于以往报道的草本植物。断根渗出液在不同浓度NaCl营养液中的渗透势与营养液的渗透势基本一致。上述结果表明，NaCl随水分在茎尖根内的转运没有受到明显限制。(3)茎尖根参幼苗转入含NaCl溶液后约10 d，根部Na^+和Cl^-浓度与营养液浓度相当，但茎部Na^+和Cl^-浓度仍然较低。这表明Na^+和Cl^-从根到茎部的运输受到了明显的限制。根系蒸腾流中Na+和Cl-in的计算浓度也远低于营养液的浓度。这表明Na^+和Cl^-向根的输运也受到限制。(4)综上所述，本研究所考虑的方法可以用于评价根系的吸水能力，但是否可以用于评价根系的溶质运输特性还需要进一步研究。少

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