| Abstract: | An apparatus is described for the measurement of water flowin shoots of woody plants by a steady-state heat-flow method.Two thermocouples are set up on either side of a heating elementinserted into the stem. The temperature difference between eachof these thermocouples and the surrounding air is measured.Theoretical considerations show that the logarithm of the ratioof this difference in the ‘downstream’ to that inthe ‘upstream’ position gives a measure of sap flow-rate.The apparatus provides a system that can be used in field orlaboratory conditions to follow water transport in the leafyshoot over periods of at least 24 h. |
