sap rise in spring

David R. Hershey dh321 at PGSTUMAIL.PG.CC.MD.US
Thu Oct 3 01:24:09 EST 1996

The famous flow of maple sap is actually considered a stem pressure rather
than a root pressure. It can occur in isolated stem segments. It is driven
by alternating freezing and thawing temperatures and the conversion of
starch stored in xylem into sucrose. The whole process is incompletely
understood. Moore and Clark's text Botany: Plant Form & Function 
discusses the process.

David R. Hershey
Snail mail: 6700 Belcrest Road #112, Hyattsville, MD 20782-1340

Adjunct Professor, Biology/Horticulture Department
Prince George's Community College, Largo, MD 20772-2199

Email: dh321 at

On 30 Sep 1996 SCHMID at wrote:

> What's the current theory on the rise of sap in trees before they
> leaf out and initiate tension/cohesion/adhesion?  Is "root pressure" 
> resulting from release of sugar by stored starch considered enough 
> to account for it? I've also heard theories about pressure from
> carbon dioxide.  This question is about due to pop up in class 
> again....
> Kathy Schmid
> schmid at

More information about the Plant-ed mailing list