Plants leaning toward Sun.

Alfred Falk falk at arc.ab.ca
Fri Sep 3 13:13:20 EST 1999


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.

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