The Micro Drop Recorder; A High Resolution Monitor of the Bleeding Rate of Plant Root Systems

The micro drop recorder is an accurate automatic instrumentwhich can detect within seconds small changes in the bleedingrate of sap. It is based on the micro drop recording technique.The reliability of the micro drop recorder can be proved bycalibration using an accurate pump. We report transient changesin bleeding rate that may not be detected by measurement techniquescurrently in use. Key words: Micro drop recorder, bleeding rate, automatic measurement     

A Two Compartment Model Method for Continuous Determination of Hydraulic Parameters of Higher Plant Cells by Pressure Probe Technique

Zhu, G-L. and Lou, C-H. 1988. A two compartment model methodfor continuous determination of hydraulic parameters of higherplant cells by pressure probe technique.—J. exp. BoL 39:961–971. The new model treats the whole measuring system as two compartments:the vacuole and the cavity of the probe, which are connectedby a microcapillary. Instead of a short injection, a continuousinjection of distilled water is used in this model. The mainprinciple of the calculation method is to estimate cell turgorpressure and hydraulic conductivity continuously from the resistanceof the microcapillary and the probe pressure as well as thecurrent flow through the microcapillary. The model avoids theeffect of membrane potential changes on the measurement of hydraulicparameters in pressure steps. In this model, microcapillarieswith a tip diameter smaller than flow rate-limiting dimensionscan be employed. The present method provides a way to monitorcontinuously cell hydraulic conductivity during the pressurerelaxation process with a time resolution in seconds. The calculationis performed automatically using a microcomputer. Key words: Two compartment model, cell pressure probe, computer