“…Long term, day-length recordings of spontaneous UPE during the development of seedlings were first presented by Yan in 2006 [13] . Shortly after, UPEs were shown to be analytically useful by the Laboratory of Applied Photonics in Campinas, Brazil [14 , 15] , as light emissions constitute reliable indicators of seed germination and development in chronic toxicological testing conditions, with more developed seedlings presenting more photon counts. Under acute stress, when a chemical stressor is applied after the first days of germination, the response is the opposite, with the more damaged, less developed sprouts presenting higher photon-counts, just after the stress, than the control samples, and the burst lasting for few hours (6–12 h) [16] .…”