Staying Overnight at
Xiaosha Stream
Trees, laced in
mountain mist,
patch broken clouds;
the wind scatters a
rainstorm of fragrant petals.
The green willows, it
is said, are without feeling-
why then do they try
so hard to touch the traveler
with their catkins?
Poem by Yang Wanli
(1127-1206)
Translated by
Jonathan Chaves
Plants can seem simple and
inanimate. They are rather silent and
seem to sway passively in the evening wind.
When winter comes it is hard to tell if the deciduous trees are dead,
alive, aware, or unconscious without their leaves.
Through my studies in
biology, however, I’ve realized that complexity found is proportional to how
closely and attentively one looks. That
which seems “lesser, simpler or primitive” in passing, in reality, is just
different upon closer observation.
I began reading a book by Dr. Daniel
Chamovitz, director of the Manna Center for Plant Biosciences @ Tel Aviv
University in Israel (http://en.wikipedia.org/wiki/Tel_Aviv_University),
called "What a Plant Knows" (http://www.whataplantknows.com/)
and came to realize that though plants are different from us in how they
survive and thrive, there is an eerie complexity to their behavior.
A good example from the
book is a plant called Cuscuta pentagona (http://en.wikipedia.org/wiki/Cuscuta),
commonly known as dodder. It lacks the
ability to use the sun’s energy to make food—it has little or no chlorophyll to
perform photosynthesis. Rather, Cuscuta gets its energy from other
plants—it is a parasite of other plants!
Not only is Cuscuta a parasite, but it
also has its preferences; when given choices it chooses consistently. When amongst wheatgrass and tomato plants—tomato
plants being the favorite—Cuscuta moves its stem about in circles not just to
feel its surroundings, but also to “sniff” its surroundings until it picks up
the scent of its beloved tomato plant at which point it will grow towards it to
feast. How it can distinguish between
different species of plants is not well understood, but it is known that when
tomato plant extract is put on a stick at any position in a room the dodder
will seek it out; the volatile chemicals of its victim acting as an attractant,
probably, amongst other signals.
When it has found a host Cuscuta begins
winding its way around and up the stem putting spigot-like haustoria (http://www.thefreedictionary.com/haustoria)
in along the way to obtain nutrients to grow.
When the haustoria are in place and a steady flow of nutrients are
coming from the host, Cuscuta’s roots die though it continues to grow upward
and onward, potentially, to many other hosts.
To get a feel for just how active and
deliberate dodders are check out this video:
Plants lack a nervous system, but that
doesn’t mean that they can’t sense their environment. On the contrary plants, as exemplified by
Cuscuta pentagona, act upon the information they obtain with complex
behavior. They can “smell” their
neighbors and move toward or away from them; they can feel what they touch and
in the case of dodder can accurately pierce their haustoria to where the
nutrient-rich sap of their host is.
Plants are also known to be responsive to light and shadow, time,
temperature, gravity, touch, chemicals from insects and other plants, and
probably many other stimuli not yet discovered.
One departing, unscientific
thought/question that arose in my head while reading “What a Plant Knows”: Just as animals exhibit behavior and
communicate through movement, do plants exhibit similar behaviors and
expression through growth?
Post by: Seth Commichaux
Sources used:
Chamovitz, Daniel. What a Plant Knows. New York: Scientific American, 2012.
“Cuscuta.”
Wikipedia. 12 Feb. 2013.
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