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Plants leaning toward Sun.

Robert Clark rgclark at my-deja.com
Mon Sep 6 03:59:49 EST 1999

In article <ac25-0309991520560001 at>,
  ac25 at cornell.edu (A. Cary) wrote:
>    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?
> >

  Thanks for the ref. I'll try to look up that PBS show.


"In order for a scientific revolution to occur,
  most scientists have to be wrong"
              -- Bob Clark

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