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Ithaca, New York
March 19, 2001
Using mathematical equations, a Cornell University
scientist and his colleagues have found evidence of a fourth spatial
dimension in plants.
In short, size matters even in the plant world, suggesting that "universal
scaling laws probably exist," says Karl J. Niklas, the Liberty Hyde Bailey
professor of plant biology at Cornell. In the animal realm, the laws of
scaling have been well known for more than a century. Yet only recently
have plant biologists become aware of these laws' importance throughout
nature.
"You've seen monster movies with giant ants scaled up in a huge size
attacking cars and people. If these larger-than-life ants had the same
proportions as their much smaller counterparts, their legs would break with
the first step. To be much larger than life-size, an ant's exoskeleton
would have to be disproportionately much thicker compared to that of a
smaller ant," says Niklas. "For the same reason, if giant humans were
scaled up as they are in some movies, their hearts wouldn't be able to
circulate blood properly and they would die of a heart attack." This
scaling is known as the fourth spatial dimension because it relates mass to
the other three dimensions, width, length and depth.
Now, Niklas and his colleagues have shown that the same scaling laws known
for animals apply equally to plant life, including trees. Niklas and
co-author Brian J. Enquist, an assistant professor in ecology and
evolutionary biology at the University of Arizona, Tucson, present their
findings in a paper, "Invariant scaling relationships for interspecific
plant biomass production rates and body size," in the online edition of the
Proceedings of the National Academy of Sciences (PNAS). It will be
published in a forthcoming issue of the journal PNAS.
The finding could have profound effects on environmental and ecological
policy, as well as the science of evolutionary biology. In the future,
plant scientists will have the ability to develop mathematical models to
make predictions in such areas as standing forest biomass and growth.
In their paper, Niklas and Enquist show that plant growth increases at
three-fourths the rate of plant body mass, the same scaling relationship as
for animals. For example, as a redwood tree grows in size over centuries,
its rate of growth gradually slows down according to this very precise
mathematical relationship. This relationship was first predicted by
Enquist, Geoffrey B. West of the Los Alamos National Laboratory, Los
Alamos, N.M., and James H. Brown of the University of New Mexico,
Albuquerque, N.M.
The authors of the PNAS paper suspect that their finding in plant biology
has applied since life began on earth. "Because present-day plants and
animals appear to abide by the same or very similar scaling rules, there is
good reason to expect these rules extend into deep geological
(evolutionary) time. … [This] provides a potentially powerful tool for
predicting many important properties for past as well as present day
organisms and the communities in which they live," the researchers say in
their report."
Says Niklas, "Our data say that growth rates are indifferent to other
biological differences across species. In scaling, a tree is a tree is a
tree."
Related World Wide Web sites: The following sites provide additional information on this news release. Some might not be part of the
Cornell University community, and Cornell has no control over their content
or availability.
- The article by Niklas and Enquist in PNAS:
<http://www.pnas.org/cgi/content/abstract/041590298v1>
The web version of this release may be found at
http://www.news.cornell.edu/releases/March01/FourthDim.bpf.html
Contact: Blaine P. Friedlander, Jr.
Office: 607-255-3290
E-mail: bpf2@cornell.edu
Cornell University News Service
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Cornell University news release
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