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An Impasse in Plant Water Relations?
J. B. Passioura,
Corresponding Author
J. B. Passioura
CSIRO, Division of Plant Industry, Canberra, Australia
CSIRO Division of Plant Industry GPO Box 1600 Canberra, 2601 AustraliaSearch for more papers by this authorJ. B. Passioura,
Corresponding Author
J. B. Passioura
CSIRO, Division of Plant Industry, Canberra, Australia
CSIRO Division of Plant Industry GPO Box 1600 Canberra, 2601 AustraliaSearch for more papers by this authorAbstract
Balling and Zimmermann [Planta 182 (1990), 325–338] used a pressure probe to measure directly negative pressures in the xylem of transpiring plants. They obtained data that challenge the standard framework that plant physiologists use when thinking about plant water relations, and, most notably, found a substantial discrepancy between their measurements of xylem pressure and of leaf water potential measured with a Scholander pressure bomb. Their data are critically examined and it is shown that most of them can be accommodated within the established principles of plant water relations. In particular, there are several reasons, consistent with the established principles, why leaf water potential and xylem pressure may differ.
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