Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)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 72 h 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 24 h test for the Hg series and just in the first 6 h for the NaF series. (C) 2012 Elsevier B.V. All rights reserved.1187476Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CEPOF research centerFOTONICOM research centerFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [11/10763-6]CNPq [552258/2009-1]