How Does Water Ascend in Tall Trees and Other Vascular Plants?

Since the Cohesion Theory was first introduced, a series ofincompatible observations has appeared in the literature. Directmeasurements of xylem pressure in single vessels of higher plantsand tall trees by means of the xylem pressure probe techniqueindicate that xylem tension in the leaves of intact, transpiringplants is often much smaller than that predicted for transpiration-drivenwater ascent through continuous water columns. We conclude thatthe available evidence warrants a critical reappraisal of tension-drivenwater transport as the exclusive mechanism of long-distancewater transport in plants.Copyright 1995, 1999 Academic Press Cohesion Theory, higher plants, long-distance transport, trees, water ascent, xylem pressure probe