Meiotic Behavior During Microsporogenesis of Alchornea Triplinervia (Sprengel) Müller Argoviensis
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Ciência Rural,Meiotic Santa Maria,behavior v.42, during n.6, microsporogenesisp.1027-1032, jun, of2012 Alchornea triplinervia (Sprengel) Müller Argoviensis. 1027 ISSN 0103-8478 Meiotic behavior during microsporogenesis of Alchornea triplinervia (Sprengel) Müller Argoviensis Comportamento meiótico durante a microsporogênese de Alchornea triplinervia (Sprengel) Müller Argoviensis Sara Mataroli de GodoyI Andréia Rodrigues Alonso PereiraI Mariza Barion RomagnoloII Claudicéia Risso-PascottoI* ABSTRACT de poliploides. Outras irregularidades foram observadas, porém, em baixa frequência, não comprometendo a formação The Alchornea triplinervia specie belongs to the dos grãos de pólen das plantas analisadas. Euphorbiaceae family, one of the main families of the Brazilian flora. In order to contribute to a better understanding of the Palavras-chave: Euphorbiaceae, número cromossômico, specie, a counting of chromosome number and the gametas 2n, meiose, poliploide. microsporogenesis analysis of A. triplinervia were done. The inflorescences were collected in the municipalities of Paranavaí and Diamante do Norte, State of Paraná, Brazil, and the slides were prepared by squashing technique and staining with 1% INTRODUCTION acetic carmine. The analysis were performed using an optical microscope and showed a chromosome number for the specie The Euphorbiaceae botanical family equal to 2n=8x=72. Irregularities in the chromosome comprises around 290 genus and 7,500 species with great segregation process were the main meiotic abnormalities, presenting typical polyploid behavior. Other irregularities were variations, ranging from woody to herbaceous plants. observed; however, at low frequency without compromising In Brazil there are approximately 70 genus and 1,000 the pollen grain formation of the analyzed plants. species, native and exotic ones, representing one of the main families of the Brazilian flora and one of the most Key words: Euphorbiaceae, chromosome number, 2n gametes, meiosis, polyploid. complex ones taxonomically (BARROSO, 1991; SOUZA & LORENZI, 2005). Several species belonging to this family have economic interest and among them are: the RESUMO rubber tree (Hevea brasiliensis), cassava (Manihot A espécie Alchornea triplinervia pertence à família esculenta) and beaver beans (Ricinus communis). There Euphorbiaceae, uma das principais famílias da flora brasileira. are also other species used in ornamentation (LORENZI, Visando a contribuir para um melhor entendimento da espécie, 2002; SOUZA & LORENZI, 2005). foi realizada a contagem do número de cromossomos e a Alchornea triplinervia is a specie of great análise da microsporogênese de A. triplinervia. As Inflorescências foram coletadas nos Municípios de Paranavaí environmental importance because it is indicated for e Diamante do Norte, no Estado do Paraná, Brasil, sendo as reforestation of degraded areas. The aril that involves lâminas preparadas pela técnica de esmagamento e coradas its seeds is used as food by birds and its wood can be com carmim acético 1%. As análises foram realizadas ao used in the making of boxes, doors and crutches microscópio óptico, revelando um número cromossômico para a espécie igual a 2n=8x=72. Irregularidades no processo de (LORENZI, 2002). segregação dos cromossomos foram as principais Cytologically, the Alchornea genus has anormalidades meióticas, mostrando comportamento típico been little studied, and the studies are limited to the IBiotecnologia Aplicada à Agricultura, Universidade Paranaense (UNIPAR), Av. Huberto Brüning, 360, 87706-560, Paranavaí, PR, Brasil. E-mail: [email protected]. *Autor para correspondência. IIUniversidade Estadual de Maringá (UEM), Departamento de Biologia, Maringá, PR, Brasil. Received 07.05.11 Approved 12.30.11 Returned by the author Ciência04.20.12 Rural, v.42, n.6, jun, 2012. CR-5627 1028 Godoy et al. counting of chromosome number. In the Alchornea associated as bivalents, but univalents and tetravalent genus has been cited x= 8, 9, 10 or 11 as basic were also observed in a lower frequency (Figure 1A). chromosome numbers for most species (HANS, 1973). Considering x=9 as the basic number of Cytogenetic data obtained from the observation of chromosomes for the species of the genus, A. triplinervia number and morphology of chromosomes as well as is an octaploid (2n=8x=72). This statement is based on the behavior and meiotic division process, have been the described number of chromosome for the species of utilized to understand chromosome evolution, Alchornea genus, where n=9 are considered the haploid phylogeny and taxonomic relations (GUERRA & chromosome number of Alchornea tiliifolia Müll. Arg. NOGUEIRA, 1990). In order to contribute to a better (HANS, 1973) and Alchornea hirtella Benth. understanding of the species, this study reports the (SCHMELZER & GURIB-FAKIM, 2008), 2n=18 chromosome number and the abnormalities of the chromosomes as the diploid number of the Alchornea meiotic behavior through the analysis of the floribunda (HANS, 1973; SCHMELZER & GURIB- microsporogenesis A. triplinervia. FAKIM, 2008) and Alchornea laxiflora (Benth.) Pax & Hoffm species, and 2n=36 chromosomes for Alchornea MATERIALS AND METHODS cordifolia (Schumach. & Thonn.) Müll. arg. (SCHMELZER & GURIB-FAKIM, 2008). Botanical material and inflorescences at the No records were found in the literature on initial development stage of A. triplinervia were the meiotic behavior of the genus to which A. collected in the Municipal Park of the city of Paranavaí, triplinervia specie belongs, and the few cytogenetic Paraná – Brazil (23º05’S and 52º27’W), and at the studies that were found are restrict to the counting of Ecological Station of Caiuá, located in the municipality chromosome number for some species. In this study, of Diamante do Norte, Paraná State – Brazil (22°41’S the meiotic behavior of four A. triplinervia plants and 52°55’W). during microsporogenesis was analyzed. The number Reproductive and vegetative parts of four of analyzed cells and the percentage of irregularities in plants were collected and herborized according to the each meiosis phase can be observed on table 1. usual techniques (FIDALGO & BONONI, 1989), and In the chromosomes segregation process, are stored at the Herbarium of Maringá State University the observed irregularities were: precocious (HUEM). The inflorescences at the initial development chromosomes migration in metaphases (Figure 1C and stage were collected for meiotic studies and, immediately I), laggard chromosomes in anaphases (Figure 1D and after the collection, were fixed in a mixture of ethanol J), micronuclei in telophases (Figure 1F, K and L), and and acetic acid (3:1 v/v) for 24 hours at room tetrads with microcytes (Figure 2D). These constituted temperature. After the fixation period, the material was the main abnormalities observed in the four studied A. washed in alcohol at 70% and stored in alcohol at 70% under refrigeration. triplinervia plants and according to SINGH (1993) this In the time of the study, the inflorescences is a typical meiotic behavior of polyploids. were dissected with the help of a stereomicroscope for The greater frequency of precocious the withdrawal of anthers that were used to prepare migration in metaphases I (Figure 1C) was observed in semi-permanent slides by squashing technique, and MPP I plant (13.04%) and the lowest frequency in ESC staining with 1% acetic carmine. Microsporocytes were II plant (4.76%). The chromosomes in precocious analyzed under binocular optical microscope Motic, migration in metaphases I may have originated from B1 series, model 220A. Cells from the metaphase I to univalents in diakinesis or have been a result of tetrad phases, besides microspores and pollen grains precocious terminalization of chiasma and the late were observed. Photomicrographies were obtained with terminalization of these chiasmas makes the laggard a digital camera, DCE- 2 Image Driving Soft Ware, and chromosomes in anaphase I (SOUZA-KANESHIMA only contrast and brightness were altered. et al., 2010). Plants collected at the Municipal Park of Laggard chromosomes (Figure 1D and J) Paranavaí (MPP) will be named MPP I and MPP II and were visualized in MPP I and MPP II plants, affecting the plants collected at the Environmental Station of 16.83% of meiocytes in anaphase I and 35.90% in Caiuá (ESC) will be named ESC I and ESC II. anaphase II, respectively. The presence of irregular chromosome behavior in metaphases and anaphases RESULTS AND DISCUSSION in the Euphorbiaceae family was observed by NASSAR (2000) in a cytogenetic and evolutive study Chromosome counting during of Manihot esculenta Crantz, where there was microsporogenesis (Figure 1A) showed that all precocious chromosome migration in metaphase I and analyzed plants presented 2n=8x=72 chromosomes. In II, and laggard chromosomes in anaphase I and II. diakinesis, the chromosomes were predominantly RISSO-PASCOTTO et al. (2005), in an analysis of Ciência Rural, v.42, n.6, jun, 2012. Meiotic behavior during microsporogenesis of Alchornea triplinervia (Sprengel) Müller Argoviensis. 1029 Figure 1 - Aspects of microsporogenesis in Alchornea triplinervia. A) Diakinesis showing 4 univalents chromosomes, 32 bivalents and one quadrivalent (arrow). B) Metaphase I with 2 non-oriented bivalents (arrow). C) Metaphase I with precocious chromosome migration (arrow). D) Anaphase I with laggard chromosome (arrow). E) Anaphase I with chromosome stickiness. F) Telophase I with micronuclei (arrow). G) Telophase I with chromosome stickiness bridge.