fascinating new research ( via an over-the-top report by the bbc, scientific american gives a more balanced treatment ) shows that while plants don’t have memory or thoughts or intelligence as we know it, they’re still pretty smart and have evolved to use light to encode “memories” to help fight against pathogens:

“[So the plant] has a specific memory for the light which builds its immunity against pathogens, and it can adjust to varying light conditions.”

“Plants perform a sort of biological light computation, using information contained in the light to immunise themselves against diseases”

and who knows just what else it might encode?