At 5:33 PM 9/3/96 -0400, Artplant wrote:
>pilot scheme on the sensual perception of plants
>>from july 4th untill september 21st i, Ute Ihlenfeldt, conduct research on
>the emotional life of plants in my (art-)studio in Bremen (germany). main
>objective is to gain more insight on the socio-asthetical awareness of
>do plants have a sensual-auratic-atmospheric sense? can the perception of
>plants be compared to human feelings? do plants have character and/or
>soul? do they have feelings and memories; do they perceive visual
>stimulation? can there be a physical and emotional relationship between
>plants and humans? are plants intellectual beings? are plants able to
>love? do plants feel fear? Are plants vain?
As a plant physiologist only a few of your questions
can be approached scientifically. The range of behaviors
exhibited by plants is quite limited and interpretations
translating behaviors into underlying emotions would have
no evidential basis. To the extent that "soul" and "emotions"
are not measurable, science must remain silent about their
existence and impact.
Plants respond to the presence of light in several different
ways. The photosynthetic apparatus (the chloroplast) and
associated biochemistry responds strongly to intensity
(photon flux) of light but uses a broad spectrum of wavelengths
(colors) thanks to evolution of antenna pigments. The
orientation of leaves, stems, roots, and other organs to
the direction of light (phototropism) is commonly more specific
to wavelength than is photosynthesis. The behaviors often
respond one way to one wavelength of light and in an opposite
way to a second wavelength of light. Seed germination in some
seeds as lettuce is also a photoreversible response to light.
Plants can also respond to touch. Classics are the studies
on the folding responses in Venus' Fly Trap (Dionea) and
Sensitive Plant (Mimosa pudica). These responses involve
action potentials, calcium ion movements, and turgor pressure
changes. Pea tendrils respond to touch as well...but much
more slowly...in a process called thigmotropism. Thus the
physical contact with an object (it doesn't have to be human)
causes the tendril to coil around the object (or the location
where the object WAS if the object is removed). Could you
say that the tendril "learned" where the object was? Not
based upon evidence. It satisfies Occam's razor that changes
in the tendril at the location of the touch are responsible
for the curvature. There is no equivalent of a nervous system
yet found in plants despite much ultrastructural and physiological
study. It is doubtful that any equivalent will be found at this
Plants have endogenous rhythms...photoperiodism uses such a
biological clock. This clock can be "trained" by manipulating
the length of light and dark intervals. After plants are moved
to an absence of light and dark intervals (continuous light or
continuous dark) plants continue to operate on their "trained"
cycles for at least a short period of time. This does NOT
mean that there is a memory in the human sense; just that the
biochemical oscillator continues to function after the
entraining signal is terminated. In fact, the training usually
decays with time rather rapidly after loss of the entraining
signals. Flowering, bulb formation, and nyctinastic movements
are examples of photoperiodic responses.
The closest thing to plants responding to human "auras" that
I have heard of is in a plant called Desmodium motorium. I was
told that the leaves respond to either humidity or heat of
a non-touching hand nearby with a kind of shaking behavior.
I have not witnessed this, and a recent attempt to grow the
plants from seeds failed for me. The plants I grew may
be the wrong species (lots of seed packets are mislabeled)
or the response is too subtle for this physiologist to detect.
In any case, the existence of plant emotions or souls or
aesthetic appreciation has never been demonstrated and it
seems doubtful that such an interpretation of results
would ever be considered scientific. Plants DO exhibit
a range of behaviors that ARE very interesting and whose
mechanisms are still incompletely understood. Thus there
is much room for continued research and new approaches.
All must submit to Occam's razor, however, in order to
be accepted widely in the scientific community.
Before you put any findings to print, please give us
plant physiologists a break by being sure that what
you print can stand up to scientific scrutiny...especially
to Occam's razor. Unfortunately many people have rushed
to print with findings that fail to meet credibility
standards and these find their way into trade books, then
text books, then lab exercises, science fair projects,
and computer simulations. Examples of pseudoscience
include plant responses to Mozart vs Metallica, to
kind-speech vs expletives, and electrochemical response
to fire (real) interpreted as "emotional" responses.
True science then faces a Herculean task of removing
the myth from the evidence in the minds of students,
teachers, and the public. If emotions and souls can
be demonstrated unequivocally, scientists will accept
the ideas, but, to date, all claims to this have not
In addition to careful interpretation such work requires
careful construction of controls...something missing
in much "emotion" work.
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: 860-465-5213
Plant Physiology is Phun!
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