Question on plant excretion

Gary Cote gcote at
Fri Jul 9 11:23:58 EST 1999

Bill Williams gave an excellent reply to this.  Two further comments:

While animals get way more N than they need from food and hence have to
excrete, plants get their N (mostly) in inorganic forms from the soil,
nitrates and ammonia.  This costs energy, and so plants recycle their
nitrogen to the greatest extent possible.  Moral: if it's expensive
(energy-wise) re-use it; if it's cheap, toss it.

Second, who says plants don't excrete?  Plants generate enormous amounts of
solid waste with which they litter the ground each year--old leaves, bud
scales, flower parts, aborted fruits, entire above-ground portions (for
perennials that overwinter underground), etc.  It has been suggested that
any unwanted and/or toxic substance that was too expensive (energy-wise) or
impossible to chemically break down could be moved into these parts before
they were dropped.  As far as I know no research has been done on this.  I
would love to hear of any references.

Dr. Gary Coté
Assistant Professor
Department of Biology
Box 6931
Radford University
Radford, VA 24142-6931

Ph: 540-831-5630
Fax: 540-831-6615
email: gcote at

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