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Twining direction of climbers acquired or sun-dependent?

Clint Wolff clintw at colorado.cirrus.com
Wed May 8 15:22:57 EST 1996

Joop Wolff wrote:
> Second posting plus elaboration plus reaction
> For some time I've been wondering about the twining direction of climbers
> like for instance, Honeysuckle (Lonicera). Honeysuckle always seems to
> twine clockwise and some other climbers always twine counter-clockwise.
> I checked plant books for the answer, but at most they state the twining
> direction, but do not explain the differences or theories on causes of
> this spiraling.
> Watson and Dallwitz in: "The families of flowering plants: Descriptions
> and illustrations" state for instance, matter of factly, as habit of
> Honeysuckle: Twining clockwise.
> I would like to know whether this is a genetic trait that takes effect
> regardless of the hemisphere the plant grows on, or whether it is
> dependent on the direction the sun takes in its dayly path (relatively
> speaking).
> Joop Wolff (jjwolff at noord.bart.nl)

One obvious experiment I could suggest would be to plant two vines,
one on each side of an east-west wall.

Ensure the vine on the north side receives NO direct sunlight, only
sunlight reflected from a mirror (or several probably) to the north 
of the plant.

|                      S
|             www
|           p www P
|           p www P
|           p www P
|           p www P
|           p www P

  | - mirror
  w - wall
  p - shaded plant
  P - unshaded plant
  \/ - dirt
  S - sun

Now, if the plant is reacting to the motion of the sun (S), you will
discover plant p growing one direction, and plant P growing the opposite
direction. If this is the case the plant should be really confused when
it reaches the top of the wall :)


The gene pool could use a little chlorine.

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