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Plants leaning toward Sun.

A. Cary ac25 at cornell.edu
Fri Sep 3 14:20:56 EST 1999

   This is an interesting question.  One factor that really influences
this is that the light indoors is usually quite low.  Plants grown under
low light generally grow more,i.e. have more elongation, and so have a
greater magnitude of directional(tropic) growth response than when grown
under high light. The low light in houses is one reason why a lot of the
best house plants come from the understory/bottom of jungles where there
is also very low light.  Secondly, like Alfred Falk said,the light source
outside would not be from one direction and would effectively cancel out
or summ up to just vertical growth. 
    However the best explination of this is that the amount and quality of
light  a plant resieves changes the way the plant responds to light. I
think under high light condtions the influence of phototropic (light
directional) growth would be less important to the plant and that
gravitopism might be the dominating factor.  The growth of the plant also
responds to the presence of nearby plants as competitors for light and
grows faster to grow over them or away from them.  Some plants, and I
think particularly some artic plants, growing under high light do orient
their leaves to capture the most sunlight, effectively tracking the dayly
solar path.  So showing that they 'know' where the light is coming from. 
I think I saw time-lapse movies of this in the PBS series 'The Secret
Lives of Plants'.    

In article <7qp33o$d1d$1 at iceman.tac.net>, falk at arc.ab.ca (Alfred Falk) wrote:
> Anyhow, if a plant were to lean toward the sun it would have to lean in 
> different directions through the day, and so the effect generally 
> cancels.  On the other hand, I find that many plants close to my house 
> or fence tend to lean away from the house because the sun necessarily 
> comes from that direction, being shaded by the house or fence.

> Robert Clark <rgclark at my-deja.com> wrote in message
> news:7pu61e$u7t$1 at nnrp1.deja.com...
> >
> >
> >  Plants indoors will lean toward the Sun because the sunlight streams
> > in from that location in the room. But suppose you have a plant or tree
> > on the outside. Presumably it couldn't follow the Sun across the sky,
> > so do they try to lean toward the Sun outdoors? I was thinking that in
> > high latitudes such as the artic the Sun is low on the horizon even at
> > noon. So would plants lean over at an angle to point to that position
> > in the sky?

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