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.