At 8:51 PM -0000 3/11/97, David L. Haas wrote:
>Dear Plant edders,
>>I have a question concerning collecting sap from maples for the making of
>maple syurp. Why doesn't the phloem plug up due to callose and p-protein
>when a tree is tapped to collect sap? This normally happens in other
>plants doesn't it? Am I missing something here? Can anyone help answer
>this?
Dave,
That probably does happen in the phloem.
The spring sap runs, however, occur mostly
in xylem. The stored sugar is put into
the vascular cylinder and osmosis brings
water into the hypertonic area. This
generates, in part, root pressure to help
drive liquid up the xylem. Then the flow
is further driven by the expansion and
contraction of the trunk by the daily freeze
and thaw cycles of early spring. At least
that's how I remember it...maybe someone at
University of Vermont can clear it up some
more!
ross
_______________________________________________________________
Ross Koning | koning at ecsu.ctstateu.edu
Biology Department | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA | fax: 860-465-4479
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