Ask A Scientist General Science Archive

Question:
This note is from Tom, a 12 old middle student in New Mexico.
He would like information or suggested reference sources about
the effects of gravitional pull on plant growth. Thanks, Armstrong
 
Answer:
It's a very interesting question. I would bet that
this one will be hard to research though. Maybe the
folks at NASA have some information; you might try
linking to them through NEWTON and asking your question there.
Anybody else got some input on this one?

-dr topper

Answer 2:
Using the online Readers' Guide Abstracts, I found some promising titles:
 
"How plants interpret 'signals'", USA Today (periodical) June '91, p. 11-12
 
"How roots respond to gravity", Scientific American, Dec. '86, p. 112-19
 
"Rapid redistribution of auxin-regulated RNAs during gravitropism",
     Science, Jan. 6 '89, p. 91-3
 
"A basic distinction; weight of cytoplasm-filled membrane against cell wall
     triggers gravitional sense in stoneworts", Discover, Nov. '92, p. 18
 
The first one might be difficult to obtain (probably only on microform);
here's the abstract (which probably tells most of what's in the article):
 
"Research by Barbara Pickard, professor of biology at Washington Univer-
sity, and associate Jiu Ping Ding sheds light on plant responses to envi-
ronmental and internal physical signals. Plants convert mechanical signals
into electrical or chemical stimuli, which in turn control biochemical re-
actions that lead, for example, to growth and formation of new leaves and
buds. Studies of onion shoots led the two researchers to discover the first
mechanically activated calcium channels in plants. They believe that the
channels detect gravity and redirect the movement of the growth-controlling
hormone auxin in vegetation. They speculate that the channels convert a
host of other mechanical signals as well. The channels are thought to play
a major role in growth, and further understanding of calcium channels in
gravity sensing may lead to new strategies for breeding plants and for
developing growth regulators and environmentally safe herbicides."
 
In regard to dr. topper's suggestion:
NASA proposed a project called Lifesat that was to study how plants (and
animals) behaved in a microgravity environment (see the Mar. '88 issue
of Space World or the August '87 issue of Omni). It appears that this
project was cut from the budget in 1991.
 
Also, try "geotropism" or "gravitropism" in encyclopedias.
 rcwinther

Answer 3:
I've always heard it as geotropism: roots grow DOWN and stems grow UP.
--- Jade