Do plants "sleep"?

Thomas Thomas at
Tue Feb 11 16:02:39 EST 1997

In article <32FEBC37.7152 at>, "Rejean Hall, ing."
<hallr at> wrote:

> Hi everyone:
> My grade 5 daughter Micheline took up a class project to 
> answer that question. Any info, ref. or URL? 
> Thanks
> R. Hall

There is something like sleeping in plants, although you wouldn't call it
that way. Plants undergo many daily variations, called rhythms. The leaf
movement rhythms were the first described, but also photosynthetic
activity etc. follow such a rhythm. In amy cases such an rhythm persists
under constant condition which means if you transfer a plant from normal
light dark cycles to constant conditions (constant dark or constant light)
these rhythms will persist. To do so, they must be triggered by an
internal mechanism, called the biological clock.
You will find more information in a book called: RHYTHMIC PHENOMENA IN
PLANTS, edited by B.M. Sweeney, Academic Press, San Diego/New York 1987.
Hope that helps


Thomas Urbig
Email:  Urbig at

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