Can plants be altruistic? You bet, says new CU-Boulder-led study
Condensed by Native Village
Unselfishly concerned for or devoted to the welfare of
A study led by the University of Colorado
Boulder suggests some plants are altruistic.
The researchers looked at corn, in which each fertilized seed
contained two “siblings.” The siblings are an embryo and a corresponding bit of
tissue called endosperm, which feeds the embryo as the seed grows.
They compared growth
and behavior of embryos and endosperm in seeds sharing the same
mother and father, vs those that had genetically different parents.
"...embryos with the same mother and father as
the endosperm in their seed weighed significantly more than embryos
with the same mother but a different father,” said
Professor Pamela Diggle from CU-Boulder. “...endosperm that does not share the same father as the
embryo does not hand over as much food. It appears to be acting
Their findings were published in
the Proceedings of the National Academy of Sciences. Co-authors included Chi-Chih Wu, a CU-Boulder doctoral student, and Professor William
Friedman, a professor at Harvard University.
Previous research indicated that plants
may prefer to withhold nutrients from inferior offspring when
resources are limited. “Our study is the first to specifically test
the idea of cooperation among siblings in plants,” Diggle said.
“One of the most fundamental laws of nature is that if you are going
to be an altruist, give it up to your closest relatives,” said
Friedman. “Altruism only evolves if the benefactor is a close
relative of the beneficiary. When the endosperm gives all of its
food to the embryo and then dies, it doesn’t get more altruistic
When corn reproduces, male flowers at the top of the plants
distribute pollen grains two at a time.
The pollen travels down through tubes to
tiny cobs on the stalks covered by strands known as silks. This
process is known as double fertilization.
When the two pollen grains
touch an individual silk, they produce a seed
containing an embryo and endosperm.
Each embryo results in just a single kernel of corn..
Wu cultivated the corn and harvested more than 100 ears over a
three-year period. He removed, mapped and weighed every individual
kernel out of each cob from the harvests. Most kernels had an
endosperm and embryo of the same color. That indicates they shared
the same mother and father. Less than 1% had different colors, such as a purple outer kernel with yellow
embryo. This meant they had two different fathers.
Wu was searching for
those rare 1% as a way to assess cooperation
between the embryo and endosperm.
“It was very challenging and
time-consuming research,” said Friedman. “It was like looking for a
needle in a haystack, or in this case, a kernel in a silo.”
Endosperm -- in the form of corn, rice, wheat and other crops -- is
critical to humans. They provide about 70% of calories we
consume annually worldwide.
“The tissue in the seeds of flowering
plants is what feeds the world,” said Friedman. “If flowering plants weren’t here,
humans wouldn’t be here.”
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