  The origin of land plants was one of the most important events in
evolutionary history of earth in terms of its broad impact on metazoan life and
the biotic environment. Because vascular tissues enabled land plants to meet
the challenges of terrestrial life, it is important to understand the
mechanistic basis of water transport through these tissues from soil to the
canopy of trees, in some cases almost 100 meters high. The answers to these
questions involve not only the biology of plant vasculature, but also the
physical properties of water that enable such transport. Although early
researchers proposed the hypothesis of cohesion-tension of water as the likely
mechanism for sap ascent, the exact mechanism of transport continues to be a
hotly debated topic in the field of plant physiology. This debate continues to
be enriched with several sophisticated studies on plants of various
morphologies growing in diverse habitats. Although a wealth of evidence has
upheld the cohesion-tension theory as being fundamentally correct, several
important details about how plants deal with vascular stress remain unknown.
Here, we review the recent literature on this topic with the aim of
highlighting how a multi-disciplinary perspective has contributed to our
understanding of the cohesion-tension theory of sap ascent in plants.
