"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 study co-author Pamela Diggle of the University of Colorado in a press release.
The different-daddied embryos were runts event though the endosperms sharing their kernels were of roughly equal weight to those in kernels with a single father.
"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."
The authors suggested that the interaction between embryo and endosperm was a form of altruism. The genetic favoritism however means that when a nutrition-granting endosperm is stingy, the other kernels that likely do share the same father will have a greater chance of survival.
Endosperms don't just give up their energy to plant embryos. Humans depend on the carbohydrate-rich endosperms of grains for sustenance.
"The tissue in the seeds of flowering plants is what feeds the world," said co-author William Friedman of Harvard University. "If flowering plants weren't here, humans wouldn't be here."