J. Phys. IV France 125 (2005) 853-855  EDP Sciences, Les Ulis DOI: 10.1051/jp4:2005125197 Photoacoustic spectroscopy applied to the study of the influence of laser irradiation on corn seeds C. Hernández Aguilar 1 , A. Carballo C. 2 , A. Cruz-Orea 3 , R. Ivanov 4 , E. San Martín Martínez 5 and A. Michtchenko 1 1 Instituto Politécnico Nacional, Sepi-Esime, Zacatenco, Unidad Profesional “Adolfo López Mateos”, Col. Lindavista, CP 07738, Mexico, DF, Mexico 2 Colegio de Postgraduados, Programa de Semillas (IREGEP), Montecillo, Texcoco, Edo. de Mexico, CP 56180, Mexico 3 Departamento de Física, Centro de Investigación y de Estudios Avanzados–IPN, A.P. 14740. Mexico 07360, DF, Mexico 4 Unidad Académica de Física, Universidad Autónoma de Zacatecas, A.P. 580, Zacatecas, Zac., CP 98068, Mexico 5 Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada-IPN, Legaria 694, Col. Irrigación, 11500 Mexico, DF, Mexico Abstract. In the present study we were interested in the effects of low intensity laser irradiation on hybrid corn seeds CL 1 x CL 4 when these seeds were exposed to different laser intensities and irradiation times. In order to observe qualitative differences in chlorophyll a and b optical absorption spectra of seedling’s leaves, whose seeds were irradiated and non irradiated, were obtained by using photoacoustic spectroscopy (PAS). A randomized complete blocks experimental design with three replications was used. The experimental unit included 10 seeds, from which we randomly choose three seedlings. The variance analysis (ANOVA) for both chlorophylls revealed significant (P< 0.05) differences among treatments. 1. INTRODUCTION The phytochromes are signal-transducing photoreceptors that convert inactive to active forms and vice versa in response to different wavelengths of light. This conversion is used to synchronize plant development to the exigencies of the light environment. Light signals provide information of crucial ecological value at many stages of development. Seed germination, seedling establishment, the proper development of photosynthetic machinery, are all potentially controlled by the reception of environmental light signals through the phytochromes [1]. For example some differences have been observed in the formation of chlorophyll a and chlorophyll b, and also in the content of these pigments, when soybean seeds were exposed to the He-Ne laser irradiation at different times pre- sowing (ranging from 1 to 10 minutes) [2]. In this work we are interested in the effects of GaAsAl laser irradiation on hybrid corn seeds CL 1 x CL 4 , when these seeds were exposed to different laser intensities and irradiation times. The optical absorption spectra of their seedling leaves were obtained using photoacoustic spectroscopy in order to investigate qualitative differences in the optical absorption bands of the chlorophylls a and b. Article published by EDP Sciences and available at http://www.edpsciences.org/jp4 or http://dx.doi.org/10.1051/jp4:2005125197