Water in trees

I find Physics Today a good source of information on physics in general. The Quick Study is usually interesting reading. However, the January 2008 Quick Study was an exception.

Granted, the topic of water transport to the tops of trees is a controversial one and the authors’ description of the phenomenon, “life in a metastable state,” pays little attention to the physical constraint of cavitation under high tension. The only reference given was from 1981, but new tools and techniques—for example, nuclear magnetic resonance imaging and pressure-probing techniques—have brought new insights on the topic in the past 27 years.

In a case like this, a warning to readers that scientists hold several different views on the topic and some reference to other perspectives would be welcome. In a more recent publication, Ulrich Zimmermann and coworkers provide access to more than 300 references on the subject. ¹ They also give a well-documented description of a complex, multiforce, multistage, segmented xylem perspective on water ascent in trees.

I hope Physics Today readers will eventually get a broader description than the “realm where water is transported in a metastable state,” as the Quick Study authors call it.