Dormancy is modulated by seed structures in palms of the cerrado biome V. S. Carvalho A , L. M. Ribeiro A,C , P. S. N. Lopes B , C. O. Agostinho A , L. J. Matias A , M. O. Mercadante-Simões A and L. N. F. Correia A A Departamento de Biologia Geral, Universidade Estadual de Montes Claros, Montes Claros, Minas Gerais 39401-089, Brazil. B Instituto de Ciências Agrárias, Universidade Federal de Minas Gerais, Montes Claros, Minas Gerais 39404-547, Brazil. C Corresponding author. Email: leomrib@hotmail.com Abstract. The aim of the present study was to evaluate the influence of the seed structures on the dormancy of the palms Attalea vitrivir Zona, Butia capitata (Mart.) Becc. and Acrocomia aculeata (Jacq.) Lodd. ex Mart., which are found in the cerrado biome (Brazilian savanna). The effects of seed structures on the imbibition and effects of the operculum on germination were evaluated. The effects of the collection area on the seed biometric characteristics and influence of the embryo mass and length on their germination capacity and vigour were also evaluated. The operculum was anatomically characterised, and the effects of the operculum thickness on seed germination were evaluated. The seed structures partially restricted water absorption by the embryos, but this did not affect germination; however, removing the operculum promoted germination. The mass of A. vitrivir and A. aculeata embryos positively influenced their germination capacity and vigour, and the thicknesses of the opercular seed coat and operculum negatively controlled the germination capacity of B. capitata. The greater thickness and rigidity of the operculum of A. aculeata increased the intensity of seed dormancy and possibly contributed to the wider distribution pattern of this species. The interaction between the embryo and operculum structures modulate the dormancy and possibly influence the distribution patterns of the palms in the cerrado biome. Additional keywords: Arecaceae, embryo, operculum, seed coat. Received 5 September 2014, accepted 16 April 2015, published online 22 May 2015 Introduction Palm trees (Arecaceae) contain more than 240 genera and ~2700 species and are primarily distributed in humid tropical and subtropical regions (Orozco-Segovia et al. 2003; Judd et al. 2007). In Brazil, there are ~300 native palm species that are predominantly distributed in the Amazon and Atlantic forest biomes (Lorenzi et al. 2010). However, the cerrado biome (Brazilian savanna), which has a well defined climatic seasonality, is home to over 50 species of palm trees, many of which are of great economic interest (Lorenzi et al. 2010; Neves et al. 2013; Oliveira et al. 2013; Pires et al. 2013). The propagation of palm trees occurs mainly through seeds (Lorenzi et al. 2010); however, dormancy hinders this method of propagation for many species in savanna environments (Orozco- Segovia et al. 2003; Ribeiro et al. 2011; Oliveira et al. 2013). Morphophysiological or morphological dormancies are considered a major cause of germination difficulties in Arecaceae (Baskin and Baskin 2014a), and these types of dormancy are related to the immaturity of embryos (Orozco-Segovia et al. 2003; Pérez et al. 2008; Baskin and Baskin 2014b), wherein the embryonic axis is of microscopic dimensions and internal to the cotyledonary petiole (Panza et al. 2004; Ribeiro et al. 2012a) and the radicle may be undifferentiated (DeMason 1988; Orozco-Segovia et al. 2003). However, recent studies on palm trees that were conducted in the cerrado biome have shown that Acrocomia aculeata (Jacq.) Lodd. ex Mart. (Ribeiro et al. 2011), Attalea vitrivir Zona (Neves et al. 2013) and Butia capitata (Mart.) Becc. (Oliveira et al. 2013) seeds experience non-deep physiological dormancy (Baskin and Baskin 2004) (in this case, the same that coat-imposed dormancy (Bewley et al. 2013)) and this state is determined by the inability of the embryo to overcome the resistance of the adjacent tissues. Non-deep physiological dormancy is controlled by an interaction between two structural components, namely, the morphoanatomy of the embryo, which includes its size and/or histo-morphodifferentiation is related to the amount of stored reserves, and structure of the adjacent tissues, which provides resistance and, in the case of palm trees, corresponds to the operculum formed by the opercular seed coat and micropylar endosperm. Dormancy is usually considered as a trait of a seed lot; nevertheless, the modulating effect determined by the behaviour of individual seeds has an important ecological role CSIRO PUBLISHING Australian Journal of Botany http://dx.doi.org/10.1071/BT14224 Journal compilation Ó CSIRO 2015 www.publish.csiro.au/journals/ajb