Three techniques of root pressure probe,pressure chamber and high pressure flow meter were used to measure the hydraulic conductivities(Lpr)of whole root systems of young maize(Zea mays L.)seedlings grown hydroponically under either drought or normal water conditions.Compared to normal water conditions,drought stress simulated by polyethylene glycol 6 000(osmotic potential =-0.2 MPa)reduced Lpr in the root system by over 50%.It indicated that water permeability in the roots decreased significantly when plants suffered from water shortages.Moreover,there was no significant difference(P < 0.05)on the Lpr values in the root systems developed under a given water stress regime among the three techniques used.Therefore,all three methods are acceptable to study the hydraulic conductivity of maize seedling root systems.We have also highlighted some of the technical limitations of each method.It can be inferred that the root pressure probe is preferable for young maize seedlings because it is subtle and has the additional ability to determine solute transport properties,but the method is time consuming.Other advantages and disadvantages of each technique are discussed in order to acquaint researchers with basic information that could contribute to their choice of an appropriate technique for future studies.
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