The researchers at Paranormal Investigation(1) have prepared an interactive Flash demonstration based on the work of Cleve Backster. Using a sensitive EEG device, Backster discovered that plants had a measurable reaction when the researcher merely thought about harming them, and could also "remember" the person who threatened them. Read more at here(2).

1. http://www.paranormal-investigation.com/
2. http://www.paranormal-investigation.com/research/plant_ekg/plant_ekg.htm