Acute stress in seedlings detected by ultra-weak photon emission

► Wheat seeds germinating under chemical stress by Hg and NaF solutions were studied. ► Seedlings’ ultra-weak photon emission (UWPE) acquired at the 4th day of germination. ► Two photon detectors counting photons from control and stressed samples for 24h. ► Germination parameters plotted against angular coefficient of linear fitting of UWPE. ► Analysis of the plots is a viable method to be applied in water and soil assurance. The ultra-weak photon emission (biophoton) patterns of wheat germination tests under chemical stress (mercury and fluoride solutions) are presented in comparison to respective control groups run simultaneously in two similar, automatic photon-count chambers. Solutions of Hg (EC50 and EC100) and NaF (EC50) were applied at the fourth day, after the first 72h of imbibition in water, with photon-count experiments in controlled conditions. Seedlings’ growth performance were checked by total mass increase as well as root development, and plotted against the respective angular factor of photon-count curve’s linear regression. Both Hg and NaF series presented very distinguishable patterns when compared to each respective control groups. Higher counts appear all over the 24h test for the Hg series and just in the first 6h for the NaF series.