applyparastyle “fig//caption/p[1]” parastyle “FigCapt” Botanical Journal of the Linnean Society, 2019, 189, 353–377. With 13 figures. Comparative study of the inflorescence, spikelet and flower development in species of Cynodonteae (Chloridoideae, Poaceae) Keywords=Keywords=Keywords_First=Keywords HeadA=HeadB=HeadA=HeadB/HeadA VANESA PILATTI1,2,5,*, SEBASTIÁN E. MUCHUT1,2, NORA G. UBERTI-MANASSERO3,4, Downloaded from https://academic.oup.com/botlinnean/article/189/4/353/5420633 by guest on 09 April 2021 HeadB=HeadC=HeadB=HeadC/HeadB ABELARDO C. VEGETTI1,3 and RENATA REINHEIMER3,4,* HeadC=HeadD=HeadC=HeadD/HeadC Extract3=HeadA=Extract1=HeadA 1Morfología Vegetal, Facultad de Ciencias Agrarias, Universidad Nacional del Litoral, Santa Fe, REV_HeadA=REV_HeadB=REV_HeadA=REV_HeadB/HeadA Argentina REV_HeadB=REV_HeadC=REV_HeadB=REV_HeadC/HeadB 2Fellow of Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina REV_HeadC=REV_HeadD=REV_HeadC=REV_HeadD/HeadC (CONICET) REV_Extract3=REV_HeadA=REV_Extract1=REV_HeadA 3Member of Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina BOR_HeadA=BOR_HeadB=BOR_HeadA=BOR_HeadB/HeadA (CONICET) BOR_HeadB=BOR_HeadC=BOR_HeadB=BOR_HeadC/HeadB 4Instituto de Agrobiotecnología del Litoral, Universidad Nacional del Litoral, CONICET, FBCB, Santa BOR_HeadC=BOR_HeadD=BOR_HeadC=BOR_HeadD/HeadC BOR_Extract3=BOR_HeadA=BOR_Extract1=BOR_HeadA Fe, Argentina 5 EDI_HeadA=EDI_HeadB=EDI_HeadA=EDI_HeadB/HeadA Current Address: Instituto Nacional de Tecnología Agropecuaria (INTA), Estación Experimental EDI_HeadB=EDI_HeadC=EDI_HeadB=EDI_HeadC/HeadB Agropecuaria Rafaela, Ruta 34 km 227, CP 2300, Santa Fe, Argentina EDI_HeadC=EDI_HeadD=EDI_HeadC=EDI_HeadD/HeadC EDI_Extract3=EDI_HeadA=EDI_Extract1=EDI_HeadA Received 11 May 2018; revised 23 December 2018; accepted for publication 28 December 2018 CORI_HeadA=CORI_HeadB=CORI_HeadA=CORI_HeadB/HeadA CORI_HeadB=CORI_HeadC=CORI_HeadB=CORI_HeadC/HeadB CORI_HeadC=CORI_HeadD=CORI_HeadC=CORI_HeadD/HeadC Inflorescence morphology in Poaceae subtribes Hilariinae, Monanthochloinae, Boutelouinae, Scleropogoninae CORI_Extract3=CORI_HeadA=CORI_Extract1=CORI_HeadA and Muhlenbergiinae (Cynodonteae, Chloridoideae) has been revisited recently, but inflorescence development ERR_HeadA=ERR_HeadB=ERR_HeadA=ERR_HeadB/HeadA remains largely unexplored. The aim of this study is to contribute additional information on the development of ERR_HeadB=ERR_HeadC=ERR_HeadB=ERR_HeadC/HeadB inflorescences in Cynodonteae by generating data on Distichlis, Bouteloua, Munroa, Erioneuron and Muhlenbergia ERR_HeadC=ERR_HeadD=ERR_HeadC=ERR_HeadD/HeadC and to compare them with results for other grasses. Using scanning electron microscopy images, we identified ERR_Extract3=ERR_HeadA=ERR_Extract1=ERR_HeadA common developmental patterns among grasses and described developmental novelties for Bouteloua, Distichlis INRE_HeadA=INRE_HeadB=INRE_HeadA=INRE_HeadB/HeadA and Muhlenbergia. Novel developmental features are: the amphipetal initiation of second-order branches along INRE_HeadB=INRE_HeadC=INRE_HeadB=INRE_HeadC/HeadB the inflorescence of B. curtipendula, the elongation of the internodes of the inflorescence branches before floral INRE_HeadC=INRE_HeadD=INRE_HeadC=INRE_HeadD/HeadC development in M. asperifolius and ‘Type II’ unisexual flowers in D. acerosa. Variable traits among studied species INRE_Extract3=INRE_HeadA=INRE_Extract1=INRE_HeadA are: inflorescence symmetry, direction of branch and spikelet initiation and differentiation, number of developing App_Head=App_HeadA=App_Head=App_HeadA/App_Head stamens, glume developmental patterns and timing of the arrest of gynoecium development during the formation BList1=SubBList1=BList1=SubBList of unisexual flowers. Our results allow us to postulate that a delicate balance of phytohormones may direct early BList1=SubBList3=BList1=SubBList2 development of grass inflorescence branching system by controlling direction of first-order branch differentiation. SubBList1=SubSubBList3=SubBList1=SubSubBList2 The approach used here provides a link between definitive structures and the underlying genetics. SubSubBList3=SubBList=SubSubBList=SubBList ADDITIONAL KEYWORDS: branching – common patterns – developmental novelties – floret – grasses – spikelet. SubSubBList2=SubBList=SubSubBList=SubBList SubBList2=BList=SubBList=BList INTRODUCTION the tribe, subtribes Hilariinae, Monanthochloinae, Boutelouinae, Scleropogoninae and Muhlenbergiinae Tribe Cynodonteae are a diverse group of grasses form a monophyletic clade with most of their species made up by 839 species grouped into 96 genera growing in the Western Hemisphere (Peterson, and 21 subtribes, mainly distributed in Africa, Romaschenko & Herrera Arrieta, 2015; Soreng et al., Asia, Australia and America (Soreng et al., 2015; 2015; Peterson et al., 2016). The species that make up Peterson, Romaschenko & Herrera Arrieta, 2016). In this lineage show wide variation in their reproductive structures. One major characteristic feature is the *Corresponding authors. E-mail: [email protected], great diversity of spikelets and inflorescences found [email protected] between and in these subtribes. In particular, spikelets © 2019 The Linnean Society of London, Botanical Journal of the Linnean Society, 2019, 189, 353–377 353 354 V. PILATTI ET AL. may be single- or many-flowered and they may enclose spikelet and homogenized first-order branches unisexual, bisexual or both types of flowers (Anton, (evenly branched, Rúa & Weberling, 1998) (Fig. 1B); Anton & Hunziker, 1978; Hunziker & Anton, 1979; panicle of spikelets without a terminal spikelet, with Clayton & Renvoize, 1986; Nicora & Rúgolo de Agrasar, homogenized first-order branches (Fig. 1C); panicle 1987; Watson & Dallwitz, 1992; Peterson, Webster & of spiciform first-order branches without a terminal Valdés-Reyna, 1997; Anton, Connor & Astegiano, 1998; spikelet with homogenized first-order branches (Fig. Negritto et al., 2003; Herrera Arrieta, Peterson & De la 1D) and racemes of spikelets with a terminal spikelet Cerda Lemus, 2004; Peterson, Valdés-Reyna & Herrera and homogenized first-order branches (Fig. 1E). Arrieta, 2007). The inflorescences of this lineage may Comparative studies on inflorescence development be panicles (composed of a main axis bearing ramified shed light on various ontogenetic patterns that lateral branches) or racemes (in which the main determine the formation of definitive structures and axis develops non-ramified first-order branches) of add comprehensive knowledge of the morphology of Downloaded from https://academic.oup.com/botlinnean/article/189/4/353/5420633 by guest on 09 April 2021 spikelets. Recent studies using a comparative approach reproductive structures (Kellogg, 2007). There are classified the inflorescences of the clade into five groups now many studies of the development of reproductive based of the branching patterns and the presence/ structures in Poaceae (e.g. Stür, 1986; Frank, 1998; Le absent of terminal spikelet (Pilatti & Vegetti, 2014; Roux & Kellogg, 1999; Orr et al., 2002; Doust & Kellogg, Pilatti, 2016; Pilatti et al., 2017): panicle of spikelets 2002; Kellogg, Hiser & Doust, 2004; Bess, Doust & with a terminal spikelet and non-homogenized first- Kellogg, 2005; Reinheimer, Pozner & Vegetti, 2005a; Liu order branches (unevenly branched, Rúa & Weberling, et al., 2007; Sajo, Lonhi-Wagner & Rudall, 2007; Kinney, 1998) (Fig. 1A); panicle of spikelets with a terminal Columbus & Friar, 2008; Reinheimer et al., 2009, 2010; Figure 1. A–E, Simplified diagrams of the different inflorescence types found in the studied group as described in Pilatti & Vegetti (2014), Pilatti (2016) and Pilatti et al. (2017). A, Panicle of spikelets with terminal spikelet (at arrowhead) and non- homogenized first-order branches. B, Panicle of spikelets with terminal spikelet (at arrowhead) and homogenized first-order branches. C, Panicle of spikelets without terminal spikelet and homogenized first-order branches. D, Panicle of spiciform first-order branches without terminal spikelet and homogenized first-order branches. E, Raceme of spikelets with terminal spikelet (at arrowhead) and homogenized first-order branches. References and abbreviations for all figures: a = anther; am = apical meristem; b1 = first-order branch; b2 = branch of second order; b3 = branch of third order; br = bract; c = carpel; co = anther connective; dfm = meristem of distal flower; fi = filament; fm = floral meristem; g = gynoecium; l = lemma; l1 = lemma of proximal flower; l2 = lemma of distal flower; lgl = lower glume; lo = lodicule; ov = ovary; pa = inflorescence main axis; pal = palea; pfm = meristem of proximal flower; ra = spikelet rachilla; sp = spikelet; sta = stamen; stam = staminod; stig = stigma; sty = style; t = theca; ts = terminal spikelet; tsb1 = terminal spikelet of first-order branch; ugl = upper glume; vl = vegetative leaf. The asterisks represent the aborted main axis. The stars indicate absence of terminal spikelet. Bars = 100 µm. © 2019 The Linnean Society of London, Botanical Journal of the Linnean Society, 2019, 189, 353–377 INFLORESCENCE DEVELOPMENT IN CYNODONTEAE 355 Sajo et al., 2012; Kellogg et al., 2013), but information Samples of inflorescences, spikelets and flowers at relating to the development of the reproductive systems different stages of development were fixed in FAA in grasses is fragmentary, focusing on some species solution (formalin: acetic acid: 70% ethanol, 10:5:85, in particular,