Plants are altruistic, sharing more food with the closest relatives

February 01, 2013

Plants are altruistic, sharing more food with the closest relatives

Plants are altruistic, say researchers.

There are plenty of examples of altruism in animals. For example, there’s Samantha, the Erie Zoo gorilla who shares her space and occasionally her food with Panda, a Dutch rabbit. There’s also Sydney, a beagle/terrier mix who cares for five kittens that were rescued from a construction site. Now, Researchers from the University of Colorado-Boulder have found evidence that suggests some plants are altruistic too.

UC-Boulder researchers examined corn, in which each fertilized seed contained an embryo and a matching piece of tissue known as endosperm that nourishes the embryo as the seed grows. They compared the growth and behavior of the embryos and endosperm in seeds with the same mother and father with the growth and behavior of embryos and endosperm that had genetically different parents, according to CU-Boulder Professor Pamela Diggle.

“The results indicated 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 Diggle, a member of CU-Boulder’s ecology and evolutionary biology department, in a statement. “We found that endosperm that does not share the same father as the embryo does not hand over as much food — it appears to be acting less cooperatively.”

Diggle said that the CU-Boulder study is the first to “specifically test the idea of cooperation among siblings in plants.”

“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 Professor William Friedman, a professor at Harvard University. “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 than that.”

Researchers looked for evidence of an extremely rare phenomenon in plants called “hetero-fertilization,” in which two different fathers father individual corn kernels. For ages, scientists have been manipulating corn plant genes, resulting in the generation of multicolored “Indian corn” cobs of dynamic colors. The information obtained from this manipulation helped the researchers in identifying the ancestry of the kernels, according to Diggle.

Chi-Chih Wu, a CU-Boulder doctoral student in the ecology and evolutionary biology department, cultivated and harvested more than 100 ears of corn over a three-year period, and removed, mapped and weighed every individual kernel out of each cob. Most of the kernels had an endosperm and embryo of the same color (a sign that they shared the same mother and father), but some had varying colors.

Wu searched tirelessly for the rare kernels that had two different fathers as a way to evaluate the 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 provides about 70 percent of the calories humans consume annually worldwide.

“The tissue in the seeds of flowering plants is what feeds the world,” added Friedman. “If flowering plants weren’t here, humans wouldn’t be here.”

The study’s findings are described in detail in the journal Proceedings of the National Academy of Sciences.

Photo credit: Ashlyak at ml.wikipedia.


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