METHODOLOGICAL ESTABLISHMENT FOR INDIVIDUAL EVALUATIONS OF HYDRAULIC CONDUCTANCES OF NODE, INTERNODE AND LEAF INSERTION IN A NODAL COMPLEX

A pressure flow meter system was newly developed for measuring hydraulic characteristics of plant organs. In the system, the pressurized water flow through plant organs was given at a desired rate by regulating the applied pressure, and hydraulic resistance or conductance of plant organs was determined from the flow rate and the applied pressure at intervals of about 5 minutes. By applying the system, individual evaluations of hydraulic characteristics of node, internode and leaf insertion in a nodal complex were performed on the basis of an analogue circuit of hydraulic resistances, where the hydraulic resistance of the node was divided into halves at the leaf insertion point. From measurements with Epipremnum aureum Bunt., Cucumis sativus L. and Zea mays L., it was indicated that hydraulic conductance of a leaf insertion was significantly lower than those of node and internode. Z. mays with the thickest stem had the highest hydraulic conductance of the internode. On the other hand, the stem-area specific hydraulic conductances of node and internode were the highest in C. sativus with the thinnest stem and the large leaf