Tropisms-HELP!!

Ross Koning koning at ECSUC.CTSTATEU.EDU
Wed Oct 15 07:59:42 EST 1997


At 6:37 PM -0400 10/13/97, Gary wrote:
>Hello, I am a student in 7th grade, and I am working on a large project
>dealing with "skototropisms," or the plant growth towards darkness.
>Although I have found quite enough information on tropisms, I have not
>found any books or articles on skototropisms.  Let me explain my
>project, and maybe you can help me.
>I will construct three "walls," all the same length and height.  These
>walls will be placed in the same place and exactly the same distance
>from a large window.  The first of these three walls will be constructed
>of black construction paper.  The second will be wax paper.  The third
>will be Saran Wrap.  (Keep in mind that there will be a few experimental
>plants that have no wall near them.)  I will have a minimum of 10
>plants, and they will all be in a row, therefore they will also all be
>the same distance from the walls. These plants will get the same amount
>of water, the same type of soil, be put in the same type of pots, and
>have same amount of sunlight. My hypothesis is that the plants will grow
>towards the darkest of the walls.
>My problem with this experiment is the plants.  What types of plants
>grow towards darkness? Why? How does this affect their photosynthesis?
>Please help!

There was one article on this subject that was never
followed up by additional research, so it remains
unsubstantiated.  The article is:

D. R. Strong and T. S. Ray. 1975. Host Tree Location
Behavior of a Tropical Vine (Monstera gigantea) by
Skototropism. Science 190:804-806.

The project showed that these plants grew toward the
black object in spite of the light coming from various
angles to the side.  Thus, it was claimed that they were
indeed growing toward the black object rather than
simply away from the light.  This tantalizing idea begs
the question of how a plant might "see" the black object
as opposed to simply growing away from light.

The trouble with using Monstera is that the seeds are
viable for only a VERY short time...maybe two weeks...
and the skototropic response disappears after the plants
reach a certain condition.  As far as I know, no one has
repeated this work to verify it.

I certainly am NOT recommending this, but the only other plant
I know of that seems to germinate and head straight for the
nearest treetrunk is poison ivy.  Other vines seem to meander
and circumnutate until they "happen" upon an object.  Work
with poison ivy could be a health menace, so please don't
go that way!

Monstera seeds are available from some seed companies, but
their viability is questionable.  I did try to grow some from
one company with 0% germination, so I cannot say I got anywhere
with a verification attempt.  I think if you were staying in
the tropics and had lots of the plants in fruit there, you
could do this project easily.  Strong and Ray were living in
=46lorida at the time and so could do this project.

Good Luck!

ross


_______________________________________________________________
Ross Koning                 | koning at ecsu.ctstateu.edu
Biology Department          | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA   | fax: 860-465-4479
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