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Plants leaning toward Sun.

Robert Clark rgclark at my-deja.com
Mon Sep 6 03:54:23 EST 1999

In article <7qp33o$d1d$1 at iceman.tac.net>,
  falk at arc.ab.ca (Alfred Falk) wrote:
> Robert Clark <rgclark at my-deja.com> wrote in message
> news:7pu61e$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?
> Need an astronomy lesson here.  It is true that the as you go higher in
> latitude, the sun appears lower in the sky.  However, it also makes a
> wider arc around the horizon in summer and shorter in winter.  (As not
> much growth takes place in winter, we only need to consider summer.)
> The extreme point is that at the pole the sun rises at spring equinox
> and sets at autumn equinox (assuming idealized point sun and no
> atmospheric effects).  The sun then appears to move all the way around
> the sky in one day.  As you drop in latitude below the arctic circle,
> the sun increasing dips below the horizon on the north side.
> 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.
> ----------------------------------------------------------------
>   A L B E R T A         Alfred Falk               falk at arc.ab.ca
> R E S E A R C H         Information Systems Dept   (780)450-5185
>   C O U N C I L         250 Karl Clark Road
>                         Edmonton, Alberta, Canada
> http://www.arc.ab.ca/   T6N 1E4
> http://saturn.arc.ab.ca/~falk/

 Thanks for the info. I had forgotten that at the North Pole daylight can
last 6 months of the year. And at lower artic latitudes the Sun can stay
visible for several "days" straight ("day" here meaning a 24 hour period.)
This means that the Sun is moving across the sky much more slowly at such
high latitudes and it is conceivable that a plant simply leaning over at
angle (not necessarily moving horizontally) can increase the amount of
sunlight it receives.


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

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