The dynamics of "dead wood": maintenance of water transport through plant stems.

The lack of mobility in plants is often interpreted as a sign of their passivity in the face of environmental variation. This view is perhaps most firmly entrenched with regard to water transport through the xylem in which water flows through the lumen of cells that are "dead" (i.e., lack any cytoplasm or nucleus) at maturity. However, recent work demonstrates that a number of active, physiological processes may be involved in maintaining the transport capacity of this essential pathway. Here we review work relating to both embolism repair and the effect of ion concentrations on xylem hydraulic properties as examples of such dynamic processes.