Proc. Hernández, J. C., and Rua, G. (1992). (D,E) Centrolepis aristata, showing spiral phyllotaxis. After production of branches, the inflorescence meristem may be converted to a spikelet meristem or may simply abort; this developmental decision appears to be independent of the branching pattern. Arrow head in (B) indicates region enlarged in (C). Phyllotaxis of the inflorescence meristem cannot be determined in all cases, because the term has meaning only if the meristem produces at least two lateral structures. Inflorescences are described by many different characteristics including how the flowers are arranged on the peduncle, the blooming order of the flowers and how different clusters of flowers are grouped within it. (2007). (A–C) Aphelia brizula, showing distichous phyllotaxis. B., Blieck, M., Kusters, E., de Bruin, R. A. M., and Koes, R. (2008). Instead, it originated after the former and well before the latter. Res. Because of the importance of inflorescence architecture, much effort has gone in to describing phenotypic and genetic aspects of inflorescence development, but this work has focused on a few model species (e.g., Arabidopsis thaliana) and a couple of hugely important crops (rice, Oryza sativa, and maize, Zea mays). Each branch bears two rows of homogeneous subunits composed either of one or two consecutive-ordered axes, each one Brachypodium distachyon (Brachypodieae). Science 316, 1452–1456. Inflorescence typology in setaria p.beauv. An Arabidopsis F-box protein acts as a transcriptional co-factor to regulate floral development. doi: 10.1086/428701, Bommert, P., Lunde, C., Hardmann, J., Vollbrecht, E., Running, M., Jackson, D., et al. Floral Initiation in Field Crops: An Atlas of Scanning Electron Micrographs. Scanning electron microscopic observations on morphogenesis of the panicle and spikelet in rice plants. Am. Beitr. 68, 1–52. The apex terminates in a set of increasingly small gynoecia that appear to lack bracts. For example, green spangletop (Leptochloa dubia) would be a panicle of racemose primary branches, blue grama (Bouteloua gracilis) is described as a panicle of spicate primary branches, and windmillgrass (Chloris verticellata) a panicle of digitate spicate branches. The part of the spikelet that bears the florets is called the rachilla. Most bamboos and some Andropogoneae have complex flowering shoots that are extensively branched and bracteate, as though the entire structure is neither fully vegetative nor fully floral. It is unknown whether the distichous inflorescence originated at the base of Pooideae, or whether it appeared several times independently. B. Harder, L. D., and Prusinkiewicz, P. (2013). Avena sativa is included here as typical of the Tribe Poeae. J. Agric. 45, 334–338. However, establishing this correlation requires data on members of the tribes Brachyelytreae, Nardeae, Stipeae, Phaenospermateae, Meliceae, and Diarrheneae, which are successive sister groups to the rest of the subfamily and have not been studied. Macroevolution of panicoid inflorescences: a history of contingency and order of trait acquisition. doi: 10.1242/dev.01441, Suzaki, T., Toriba, T., Fujimoto, M., Tsutsumi, N., Kitano, H., and Hirano, H. Y. Fm, floral meristem; im, inflorescence meristem; pb, primary branch; Scale bars: (A), 100 μm; (B, C), 200 μm; (D), 100 μm. In addition, the interaction of LFY and UFO also appears to be important in bract suppression in Arabidopsis, which may have a direct or indirect effect on phyllotaxy (Hepworth et al., 2006). Funct. ABPHYL1, a two-component response regulator, also regulates meristem size (Jackson and Hake, 1999; Giulini et al., 2004). Assembling the tree of monocotyledons: plastome sequence phylogeny and evolution of Poales. Corresponding Author. Aromatic oils: Certain grasses give aromatic oil (sweet-scented), e.g. Jap. Aberrant panicle organization1 temporally regulates meristem identity in rice. A gene controlling the number of primary rachis branches also controls the vascular bundle formation and hence is responsible to increase the harvest index and grain yield of rice. Zurn. Images were either captured on Polaroid film (Harvard, UM-St. Louis) and then scanned, or captured digitally (all other sources). (2009a). The floral units of this species are clearly arranged in a spiral (Figures 1D,E). b, bract; gy, gynoecium; a, anther; m, meristem; s, seed coat. The first two branches of the inflorescence are separated by an angle of 105° (Figures 2A,D), with subsequent branching establishing spiral phyllotaxis. Functional associations of floret and inflorescence traits among grass species. Grasses shed their seeds as naked caryopsis, florets, spikelets, or entire inflorescences. Nassella filiculmis (Stipeae). While often obvious in figures, this pattern has not been noted by previous authors. doi: 10.1080/0028825X.1993.10419494, McKone, M. J., Lund, C. P., and O'Brien, J. M. (1998). doi: 10.3732/ajb.94.9.1554, Reinheimer, R., Pozner, R., and Vegetti, A. C. (2005). MEGA5: molecular evolutionary genetics analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods. The development of the wheat spike. J. Bot. We also identify a set of taxa that exhibit a character state that we call biased distichous [following the terminology of Ikeda et al. Cymbopogon gives lemon grass oil. Cambridge: Cambridge University Press. A developmental study of wild rice, Zizania aquatica L. Can. Because the development of the spikelet is highly stereotyped and deterministic within most major groups of grasses, investigations of inflorescence architecture treat the spikelet as the terminal differentiated unit of the inflorescence, rather than the flower. doi: 10.1105/tpc.109.073536, Whipple, C. J., Zanis, M. J., Kellogg, E. A., and Schmidt, R. J. Res. Each floral unit (variously interpreted as a flower or pseudanthium) consists of a multicarpellate gynoecium plus a single stamen and a bract [called a “bract-like phyllome” by Sokoloff et al. Development 126, 315–323. Awns may be fused at the base as in Aristida, twisted as in Stipa, or bent or geniculate as in Danthonia. Biol. doi: 10.3732/ajb.0800245. 94, 1554–1569. : 12 The spikelets are further grouped into panicles or spikes. (D) distichous bract formation shortly after the transition to flowering; (E), early development of the terminal spikelet; (F), later stage of spikelet development, with additional branching obscuring the primarily distichous pattern. Landes, A., and Porter, J. R. (1990). One problem is simply that the spikelet itself is a part of an inflorescence and thus is not strictly equivalent to a flower. doi: 10.1073/pnas.0405230101, Doust, A. N. (2001). The involucre encloses a single female flower, represented by a pistil, in the centre, situated on a long stalk. doi: 10.3732/ajb.90.1.93. [Epub ahead of print]. In all the species the inflorescence is polytelic, with main florescence and paracladial zone. The gene FLORAL ORGAN NUMBER1 regulates floral meristem size in rice and encodes a leucine-rich repeat receptor kinase orthologous to Arabidopsis CLAVATA1. In addition, the vascular (hydraulic) architecture of the inflorescence affects the ability of the plant to supply developing seeds with water and photosynthate. Am. Ann. Scale bars: (A–C), 100 μm; (D–F), 200 μm. Morphological, anatomical, and taxonomic studies in Anomochloa and Streptochaeta (Poaceae: Bambusoideae). Int. Appl. J. Bot. (2009). (2010). The evolution of nuclear genome structure in seed plants. The inflorescence ultimately terminates in a spikelet (Figure 7F). (A–C) Hordeum vulgare (Triticeae). Conversely, when APO1 levels are elevated, the shift to spikelet identity is delayed. Thus, “distichous” is a subset of “two-ranked.” The only data for subfamily Danthonioideae come from Chionochloa macra, in which the primary branch primordia are distichous (Martin et al., 1993). 60, 25–37. PreserveArticles.com is an online article publishing site that helps you to submit your knowledge so that it may be preserved for eternity. Data are presented for Nassella filiculmis, but observations for N. manicata (= Stipa formicarum) and N. tenuissima were similar, and we infer that the results are general for the genus. Plant Sci. Higher order branches form from the primary ones. (2009b). doi: 10.1104/pp.106.086736, Chuck, G., Whipple, C., Jackson, D., and Hake, S. (2010). Bot. Finally, we hypothesize that modulation of APO1 levels, perhaps relative to LFY levels, could create the observed phenotypic variation, although variation in the CLV pathway could also be involved. A new species of Centrolepis (Centrolepidaceae, Polaes) from Northern Australia, with remarkable inflorescence architecture. Morphology and development of the gynoecium in Centrolepidaceae: the most remarkable range of variation in Poales. The unit of its inflorescence is called spikelet. b, bract; fm, floral meristem; im, inflorescence meristem; lf, leaf; pb, primary branch; arrows, glumes. (A) Distichous primary branch formation; (B) inflorescence meristem and uppermost branch meristem converted to spikelet meristems; (C–F), successive stages of development, showing differentiation of the terminal spikelet well ahead of the lateral spikelets. 47, 1591–1602. Nonetheless, there are three basic types: the panicle, the raceme, and the spike. UFO in the Arabidopsis inflorescence apex is required for floral-meristem identity and bract suppression. Most often the palea fits within the enrolled edges of the lemma and does not often offer distinguishing characteristics. Biol. So these plants of family poaceae have ornamental significance / importance. Sci. As the inflorescence matures, the apex produces bracts that appear to lack floral structures (Figures 2C,D). Jean, R. V. (1994). All primary branches and the inflorescence axis itself terminate in spikelets. Flora 191, 117–119. doi: 10.2307/3298585, Grass Phylogeny Working Group II. doi: 10.1086/297572, Liu, Q., Peterson, P. M., Columbus, J. T., Zhao, N., Hao, G., and Zhang, D. (2007). However, the fact that it can be stable among groups of species, including the several thousand species of subfamily Pooideae, suggests that it is preserved either by selection or developmental constraint. Mutations in apo1 in rice create a biased distichous inflorescence much like that seen in Diarrhena and Stipeae (Figure 12). The tree was opened in Mesquite (Maddison and Maddison, 2002–2009), and the characters mapped using maximum likelihood. doi: 10.1105/tpc.108.060871, Stevens, P. F. (2012). “The grass inflorescence,” in Grasses: Systematics and Evolution, eds S. W. L. Jacobs and J. Everett. This result is obtained whether using a parsimony or maximum likelihood optimization of character evolution. Sci. Am. In Gramineae/Poaceae, the inflorescence is . doi: 10.1534/genetics.109.112045, Keywords: phyllotaxis, shoot apical meristem, phylogeny, branching, APO1, Citation: Kellogg EA, Camara PEAS, Rudall PJ, Ladd P, Malcomber ST, Whipple CJ and Doust AN (2013) Early inflorescence development in the grasses (Poaceae). Regulation of leaf initiation by the terminal ear1 gene of maize. Rua, G. H., and Weberling, F. (1995). Joinvilleaceae, Ecdeiocoleaceae, and Poaceae (Michelangeli et al., 2003)], the vegetative meristem produces leaves in a distichous pattern (Stevens, 2012). Thus, for example, we represented Paniceae with all species with published data, but Puelioideae and Bambusoideae were included even though no data are available. Biol. doi: 10.1007/s00122-009-1218-8. Copyright © 2013 Kellogg, Camara, Rudall, Ladd, Malcomber, Whipple and Doust. Figure 7. In representatives of both families, the inflorescence meristem produces lateral structures in a spiral. Our mission is to liberate knowledge. Plant Sci. Parsimony optimization of the character indicates that the ancestral state is to produce a terminal spikelet, but within some clades (e.g., Triticeae) the evolution of this character is labile and optimizations are ambiguous (not shown). Wu X(1), McSteen P. Author information: (1)Department of Biology, The Pennsylvania State University, 208 Mueller Lab, University Park, Pennsylvania 16802 USA. Development 132, 1235–1245. Kellogg, E. A., and Bennetzen, J. L. (2004). A floret consists of two bracts, the lemma and the palea, which enclose the grass flower. Since true flower parts in grasses are inconsequential in identification, spikelet arrangement will be used for description of the inflorescence type. Jackson, D., and Hake, S. (1999). Of the families in the core Poales, only Ecdeiocoleaceae and Centrolepidaceae have been studied developmentally. Plant Sci. Brachypodium distachyon (Figure 8). Sci. APO1 is an F-box protein and is homologous to UNUSUAL FLORAL ORGANS1 (UFO1) of Arabidopsis, FIMBRIATA of Antirrhinum, DOUBLETOP of Petunia, PROLIFERATING FLORAL ORGANS of Lotus, and STAMINA PISTILLOIDA of pea, all of which affect inflorescence architecture (Taylor et al., 2001; Zhang et al., 2003; Souer et al., 2008; Ikeda-Kawakatsu et al., 2009). It is thus similar to the lateral branches in many other taxa in which the two ranks of spikelets are both formed on one side of the inflorescence axis, and are separated by an angle appreciably less than 180°. Expression level of ABERRANT PANICLE ORGANIZATION1 determines rice inflorescence form through control of cell proliferation in the meristem. 106, 269–289. Res. Beitr. Nardus (Nardeae) and Phaenosperma (Phaenospermateae). Within the Pooideae with two-ranked inflorescence branching, distichy appears after the divergence of Nardus, but is lost in Diarrhena. More commonly in the grasses, the inflorescence meristem simply terminates blindly, as described for Oryza. 95, 903–913. (1972) “Differentiation in the grass inflorescence,” in The Biology and Utilization of Grasses, eds V. B. Youngner and C. M. McKell (New York, NY: Academic Press), 365–399. Phyton (Horn, Austria) 40 (1): 71-88, 6 figures. The inflorescences ofPaspalum are composed of a main axis and 1 to more than 100 raceme-like lateral branches arranged along it. Characters of Poaceae: Mostly herbs, stem jointed, fistular, cylindrical; leaves simple, alternate, sheathing, sheath open, ligulate; inflorescence compound spike; flowers zygomorphic, hypogynous, protected by palea; perianth represented by 2 or 3 minute scales (lodicules); stamens 3, versatile; carpel one, style 2 or 3, stigmas feathery, basal placentation; fruit caryopsis; testa fused with pericarp. Theor. In addition, the inflorescence meristem itself often shifts from producing branch primordia to producing spikelet primordia; in this case, the spikelet primordia are produced in two ranks.
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