Vegetative rescue and ex vitro system production of Tibouchina sellowiana clonal plants by cutting and mini-cutting / Resgate vegetativo e sistema ex vitro de produção de mudas de Tibouchina sellowiana por estaquia e miniestaquia

We aimed to evaluate the rooting potential of Tibouchina sellowiana through the experiments: I - Cuttings from current-year shoots and epicormic shoots were submitted to IBA concentrations: 0, 500, 1000, 1500 and 2000mg L-1, in a factorial arrangement 2 x 5 (two types of cuttings x five IBA concentrations), with four replicates and 20 cuttings each; II - mini-stumps of Tibouchina sellowiana were submitted to successive shoots collecting during the four seasons, in a split-plot design, with five replications of ten mini-stumps per experimental unit. From the shoots of mini-stumps, mini-cuttings were produced, which were initially kept in greenhouse and later transferred to full sun, in a 4 x 5 factorial arrangement (four seasons x five collections per season), with four replicates of 12 mini-cuttings. Superiority of epicormic shoots cuttings was reported when compared to the current-year shoots, which showed the highest rooting and leaves maintenance (42.50% and 55.00%, respectively), eliminating the use of IBA. High survival of mini-stumps (over 80%) and the mini-cuttings production (170mini-cuttings m-2 month-1) in clonal mini-garden and the mini-cuttings survival (above 80%) in the greenhouse demonstrated the technical feasibility, with summer as the most appropriate time to collect mini-cuttings.(AU)

Objetivou-se avaliar o potencial de enraizamento de Tibouchina sellowiana por meio dos experimentos: I - Estacas provenientes de brotações do ano e epicórmicas foram submetidas às concentrações de IBA: 0, 500, 1000, 1500 e 2000mg L-1, em arranjo fatorial 2 x 5 (dois tipos de estacas x cinco concentrações de IBA), com quatro repetições de 20 estacas cada; II - Minicepas de Tibouchina sellowiana foram submetidas à coletas sucessivas de suas brotações durante as quatro estações do ano, em modelo de parcelas subdivididas no tempo, com cinco repetições de dez minicepas por unidade experimental. A partir das brotações das minicepas foram produzidas miniestacas, as quais foram inicialmente mantidas em casa de vegetação e posteriormente transferidas para pleno sol, em arranjo fatorial 4 x 5 (quatro estações do ano x cinco coletas por estação), com quatro repetições de 12 miniestacas. Verificou-se superioridade das estacas de brotações epicórmicas em comparação às brotações do ano, as quais apresentaram o maior enraizamento e retenção foliar (42,50% e 55,00%, respectivamente), dispensando o uso de IBA. A elevada sobrevivência das minicepas (superior a 80%) e produção de miniestacas (170 miniestacas m-2 mês-1) em minijardim clonal e sobrevivência (acima de 80%) de miniestacas em casa de vegetação demonstram a viabilidade da técnica, sendo o verão a época mais adequada para coleta de miniestacas.(AU)

Mutations in two non-canonical Arabidopsis SWI2/SNF2 chromatin remodeling ATPases cause embryogenesis and stem cell maintenance defects.

SWI2/SNF2 chromatin remodeling ATPases play important roles in plant and metazoan development. Whereas metazoans generally encode one or two SWI2/SNF2 ATPase genes, Arabidopsis encodes four such chromatin regulators: the well-studied BRAHMA and SPLAYED ATPases, as well as two closely related non-canonical SWI2/SNF2 ATPases, CHR12 and CHR23. No developmental role has as yet been described for CHR12 and CHR23. Here, we show that although strong single chr12 or chr23 mutants are morphologically indistinguishable from the wild type, chr12 chr23 double mutants cause embryonic lethality. The double mutant embryos fail to initiate root and shoot meristems, and display few and aberrant cell divisions. Weak double mutant embryos give rise to viable seedlings with dramatic defects in the maintenance of both the shoot and the root stem cell populations. Paradoxically, the stem cell defects are correlated with increased expression of the stem cell markers WUSCHEL and WOX5. During subsequent development, the meristem defects are partially overcome to allow for the formation of very small, bushy adult plants. Based on the observed morphological defects, we named the two chromatin remodelers MINUSCULE 1 and 2. Possible links between minu1 minu2 defects and defects in hormone signaling and replication-coupled chromatin assembly are discussed.

Conservação e enraizamento in vitro de infalível (Mandevilla velutina K. Schum.), uma planta medicinal do Cerrado / In vitro conservation and rooting of "infalível" (Mandevilla velutina K. Schum.), a medicinal plant of Cerrado

Mandevilla velutina (Apocynaceae) é uma planta medicinal endêmica do Cerrado brasileiro conhecida popularmente como infalível, utilizada pela população em tratamentos de processos inflamatórios e acidentes com serpentes. Atualmente, esta espécie encontra-se em risco de extinção, devido à coleta extrativista. Os objetivos deste trabalho foram otimizar o protocolo para o enraizamento in vitro de M. velutina e introduzir diferentes genótipos em banco de germoplasma in vitro, a fim de se estabelecer a conservação da espécie. Foram realizados cinco experimentos de enraizamento in vitro utilizando ANA, AIB, di e poliaminas, dithiothreitol e floroglucinol. As avaliações foram realizadas aos 30 e 60 dias quanto à porcentagem de enraizamento, número e comprimento de raiz. Para a introdução dos genótipos in vitro, foram utilizados segmentos nodais (1 cm) como explantes, contendo uma gema axilar ou apical, coletados de plantas mantidas em casa de vegetação, submetidos previamente à assepsia. As avaliações foram realizadas durante quatro semanas, quanto à porcentagem de contaminação dos explantes. Os resultados obtidos nas avaliações evidenciaram que a presença de compostos fenólicos no meio de cultura foi importante na promoção do enraizamento adventício in vitro de M. velutina e a metodologia de assepsia para a introdução de diferentes genótipos in vitro foi eficiente.

Mandevilla velutina (Apocynaceae) is a medicinal plant endemic to the Brazilian Cerrado, commonly known as "infalivel" and used by the population for treatments of inflammatory processes and accidents with snakes. This species is currently endangered due to extraction. The aims of this study were to optimize the protocol for in vitro rooting of M. velutina and to introduce different genotypes in the in vitro germplasm bank to establish the species conservation. Five experiments for in vitro rooting were conducted using NAA, IBA, di and polyamines, dithiothreitol and phloroglucinol. Evaluations were performed at 30 and 60 days as to rooting percentage, and root number and length. For the introduction of genotypes in vitro, nodal segments (1 cm) were used as explants; they had an axillary or apical bud and were collected from plants kept in a greenhouse after being subjected to asepsis. Evaluations were carried out for four weeks as to the percentage of explant contamination. Results showed that the presence of phenolic compounds in the culture medium was important to promote in vitro adventitious rooting in M. velutina and that the asepsis methodology for the introduction of in vitro of different genotypes was efficient.

Alterations in core histone variant ratios during maize root differentiation, callus formation and in response to plant hormone treatment.

Although several histone variants have been studied in both animal and plant organisms, little is known about their distribution during processes that involve alterations in chromatin function, such as differentiation, dedifferentiation and hormone treatment. In this study we evaluated the ratio of each histone variant in each of the four core histone classes in the three developmental zones of maize (Zea mays L.) root and in callus cultures derived from them, in order to define possible alterations either during plant cell differentiation or dedifferentiation. We also evaluated core histone variant ratios in the developmental zones of roots treated with auxin and gibberellin in order to examine the effects of exogenously applied plant hormones to histone variant distribution. Finally, immunohistochemical detection was used to identify the root tissues containing modified forms of core histones and correlates them with the physiological status of the plant cells. According to the results presented in this study, histone variant ratios are altered in all the cases examined, i.e. in the developmental zones of maize root, in callus cultures derived from them and in the developmental zones of roots treated either with auxin or gibberellin. We propose that the alterations in linker histone variant ratios are correlated with plant cell differentiation and physiological status in each case.

Alterations in core histone variant ratios during maize root differentiation, callus formation and in response to plant hormone treatment

Although several histone variants have been studied in both animal and plant organisms, little is known about their distribution during processes that involve alterations in chromatin function, such as differentiation, dedifferentiation and hormone treatment. In this study we evaluated the ratio of each histone variant in each of the four core histone classes in the three developmental zones of maize (Zea mays L.) root and in callus cultures derived from them, in order to define possible alterations either during plant cell differentiation or dedifferentiation. We also evaluated core histone variant ratios in the developmental zones of roots treated with auxin and gibberellin in order to examine the effects of exogenously applied plant hormones to histone variant distribution. Finally, immunohistochemical detection was used to identify the root tissues containing modified forms of core histones and correlates them with the physiological status of the plant cells. According to the results presented in this study, histone variant ratios are altered in all the cases examined, i.e. in the developmental zones of maize root, in callus cultures derived from them and in the developmental zones of roots treated either with auxin or gibberellin. We propose that the alterations in linker histone variant ratios are correlated with plant cell differentiation and physiological status in each case.

[In vitro organogenesis in Dalbergia retusa (Papilonaceae)]. / Organogénesis in vitro en Dalbergia retusa (Papilonaceae).

Plants were obtained via organogenesis from hypocotyl explants of Dalbergia retusa from in vitro germinated seedlings. Adventitious bud induction was achieved on Murashige and Skoog medium containing five BA (benzyladenine) concentrations. The best BA concentration for budding induction and budding development was 8.8 microM. Shoot rooting was obtained on half-strength modified MS basal medium, supplemented with 20 g x l(-1) of sucrose and five concentrations of indole-3-butyric acid (IBA). The highest number of shoot rooting was obtained with 19.7 microM IBA but the highest average number of roots for plantlet was achieved with 24.6 microM IBA. Plants were transferred to greenhouse conditions.