In this sea of unknowns, there is at least one take-home message: epigenetic factors appear to be the vehicle by which plants transfer defense memories to offspring. Further evidence for this comes from the finding that the “grandchildren” of exposed plants inherit the defense memory, but the fourth generation does not. “The observation that inherited resistance reverts after three generations suggests the underlying mechanism is not a mutation or another stable genetic change,” says Georg Jander, a biologist at the Boyce Thompson Institute in Ithaca, NY who partnered with Rasmann.
Memory of past insults
Gravitropic 