Plants "remember" information about light, and a certain type of cell transmits that information, much like nerves do in animals.
In the study, which has not yet been published, the researchers found that light shone on one leaf of an Arabidopsis thaliana plant caused the whole plant to respond. The response lasted even after the light source was taken away, suggesting the plant remembered the light input.
Different wavelengths of light produce a different response, suggesting the plants use the information to generate protective chemical reactions -- like pathogen defense or food production.
As reported by the BBC July 14, scientists found that light shining on a leaf cell triggered a cascade of events that was immediately signaled to the rest of the plant via a type of cell called a bundle sheath cell. Those cells exist in every part of a plant. The researchers, led by Stanislaw Karpinski from the Warsaw University of Life Sciences in Poland, measured the electrical signals from those cells, and compared it to finding a central nervous system for plants.