ORIGINAL ARTICLE Leaf and inflorescence peduncle anatomy: a contribution to the taxonomy of Rapateaceae Renata Callegari Ferrari • Vera Lucia Scatena • Aline Oriani Received: 3 August 2013 / Accepted: 8 January 2014 Ó Springer-Verlag Wien 2014 Abstract The anatomy of leaves and inflorescence pe- duncles was studied in species of Monotrema (4), Stego- lepis (1) and Saxofridericia (1), aiming to contribute to the taxonomy of Rapateaceae. The form and structure of leaf blade midrib and the form of the inflorescence peduncle are diagnostic characteristics for the studied species. Mono- trema is distinguished by: epidermal and vascular bundle outer sheath cells containing phenolic compounds in both organs; leaf blade with palisade and spongy chlorenchyma, arm-parenchyma, and air canals between the vascular bundles; leaf sheath with phenolic idioblasts in the meso- phyll; inflorescence peduncle with tabular epidermal cells and air canals in the cortex and pith. Such characteristics support the recognition of Monotremoideae, which includes Monotrema. Stegolepis guianensis is distinguished by thick-walled epidermal cells and a plicate chlorenchyma in both organs; leaf blade with subepidermal fiber strands in abaxial surface and a heterogeneous mesophyll; inflo- rescence peduncle with rounded epidermal cells, a hypo- dermis with slightly thick-walled cells, and a pith with isodiametric cells and vascular bundles. Saxofridericia aculeata is distinguished by papillate epidermal cells in both organs; unifacial leaf blade with subepidermal fiber strands in both surfaces and a regular chlorenchyma; leaf sheath with a hypodermis in both surfaces and fiber bun- dles in the mesophyll; inflorescence peduncle with an undefined cortex and a hypodermis with thick-walled cells. S. guianensis shares few characteristics with S. aculeata, supporting their placement in different tribes. Keywords Leaves Á Inflorescence peduncle Á Scape Á Rapateaceae Á Monotrema Á Stegolepis Á Saxofridericia Introduction Rapateaceae comprise 16–17 genera and approximately 100 species that occur mostly in the Guayana Shield and in the Amazon Basin (Maguire 1958; Stevenson et al. 1998; Berry 2004). The only exception is the monotypic Maschalocephalus, which occurs in western Africa (Maguire 1958; Stevenson et al. 1998). In Brazil, there are nine genera and about 39 species (Monteiro 2012) distributed mainly in the Amazon region (Souza and Lorenzi 2012). Based on morphological data, Rapateaceae were grouped with Xyridaceae, Eriocaulaceae, Mayacaceae, and Commelinaceae into the order Commelinales (Dahlgren et al. 1985). However molecular phylogenies revealed a close relationship between Bromeliaceae, Typhaceae, and Rapateaceae, placing Rapateaceae in the order Poales (Givnish et al. 1999, 2006, 2010; Chase et al. 2000, 2006). These three families are considered the earliest divergent in Poales and they appear as successive sister lineages to all other members of the order in the most recent phylogenetic analyses for the monocotyledons (Givnish et al. 2010). Studies on Rapateaceae morphology (Maguire 1958, 1965), anatomy (Carlquist 1966, 1969; Oriani and Scatena 2013), embryology (Venturelli and Bouman 1988), and palynology (Carlquist 1961) have contributed to the tax- onomy of the family. The family was formerly divided into two subfamilies based on reproductive morphological characteristics: Rapateoideae, comprising the tribes Rapa- teeae and Monotremeae; and Saxofridericioideae, com- prising Saxofridericieae and Schoenocephalieae (Maguire 1958; Stevenson et al. 1998). R. C. Ferrari (&) Á V. L. Scatena Á A. Oriani Departamento de Bota ˆnica, Instituto de Biocie ˆncias, Universidade Estadual Paulista, C. Postal 199, Rio Claro, SP 13506-900, Brazil e-mail: renata.callefe@gmail.com 123 Plant Syst Evol DOI 10.1007/s00606-014-0984-1