Effect of pinene isomers on germination and growth of maize Vanessa A. Areco a , Silvana Figueroa b, c , María T. Cosa b, c , José S. Dambolena a, c , Julio A. Zygadlo a, c , María P. Zunino a, c, * a Cátedra de Química Orgánica, Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de Córdoba, Instituto de Ciencia y Tecnología de los Alimentos (ICTA), Av. Vélez Sarsﬁeld 1611, Córdoba, Argentina b Cátedra de Morfología Vegetal, Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsﬁeld 299, 5000 Córdoba, Argentina c Instituto Multidisciplinario de Biología Vegetal (IMBIV), Concejo Nacional de Investigaciones Cientíﬁcas y Técnicas (CONICET), Argentina article info Article history: Received 16 May 2013 Accepted 12 February 2014 Available online Keywords: Pinene Isomer Phytotoxicity Allelopathy Maize abstract Terpenes, secondary metabolites that are present in the essential oils of aromatic plants, are responsible for the biochemical interaction between plants, known as allelopathy. Mono- terpenes are a major component of essential oils. Pinene is a monoterpene well-known for its phytotoxic action, but little is known about the allelopathic effect of its isomers. The aim of this study is to determine the effect of pinene’s structural isomers and enantioisomers [()-a-pinene; (þ)-a-pinene; ()-b-pinene and (þ)-b-pinene] at 0.16 mM, on certain physiological parameters (growth, dry weight, phenol, photosynthetic pigments and abscisic acid content) in both the germination and growth of maize (Zea mays L.). In germination bioassays, neither of the a-pinene stereoisomers showed change when compared to the control with respect to seed vigour; but root growth was increased, while b-pinene (racemic mixture) inhibited germination and plant length. In the growth bioassay, all of the pinene isomers decreased the plant length. In general, b-pinene terpene was more phytotoxic than a-pinene in both bioassays. Differences in germination and growth of maize treated with the pinene isomers can be attributed to different action mechanisms which depends both on the growth phases of maize and on the particular pinene isomers. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Allelopathy is a phenomenon whereby secondary metabolites synthesized by fungi, viruses, microorganisms and plants inﬂuence biological and agricultural systems (Farooq et al., 2011). These allelochemicals are released into the environment and thus affect the growth of adjacent plants (Rice, 1984). The terpenoids are considered to have the greatest potential as naturally occurring allelochemicals (Zunino and Zygadlo, 2004; Barney et al., 2005). Monoterpenes, the main constituents of essential oils, constitute a group of compounds with a diverse range of different functional groups as well as optic isomers of speciﬁc compounds. These isomers may exhibit differential properties. For example, Romagni et al. (2000) suggested that two isomers of cineole appear to have different modes of action. Moreover, synergistic and antagonistic actions have been observed between enantiomers in bacteria, seedlings, and insects (Vokou et al., 2003) and more recently in model membranes (Zunino et al., 2011). * Corresponding author. Instituto Multidisciplinario de Biología Vegetal (IMBIV), Concejo Nacional de Investigaciones Cientíﬁcas y Técnicas (CONICET), Argentina. Tel.: þ54 0351 4334141x191; fax: þ54 0351 4334439. E-mail addresses: vecaareco@hotmail.com (V.A. Areco), silﬁgueroa2003@yahoo.com.ar (S. Figueroa), cosa@imbiv.unc.edu.ar (M.T. Cosa), dambolena@ mail.fcq.unc.edu.ar (J.S. Dambolena), jzygadlo@efn.uncor.edu (J.A. Zygadlo), pauzun@efn.uncor.edu, mpzbdv@yahoo.com.ar (M.P. Zunino). Contents lists available at ScienceDirect Biochemical Systematics and Ecology journal homepage: www.elsevier.com/locate/biochemsyseco http://dx.doi.org/10.1016/j.bse.2014.02.013 0305-1978/Ó 2014 Elsevier Ltd. All rights reserved. Biochemical Systematics and Ecology 55 (2014) 27–33