Measurements of stem xylem hydraulic conductivity in the laboratory and field

1. Xylem hydraulic properties play an essential role in supporting growth and photosynthesis and influence sensitivity to environmental conditions such as drought and freezing. Consequently, stem hydraulic conductance can be used as a comparative measure of overall hydraulic adaptation across species and to assess the impact of environmental variation, especially drought, on water transport. 2. We summarize the main methods currently in use for measurements of stem xylem hydraulic properties. Measurements can be accomplished in a number of ways, including using a pipette, an analytic balance or a ‘pressure-drop’ flow meter. We provide new details on the design of a relatively inexpensive and easily field-deployable flow meter that is flexible for a variety of applications. The biological challenges associated with these measurements arise from the difficulties of working with diverse living tissues of variable geometry. 3. We provide a review of best practices and provide technical guidance, emphasizing measurements on detached samples using portable equipment