Comparation of free radical scavenging activity between seven species of Passiflora L.

Antioxidant capacities of seven species of Passiflora were evaluated through comparation of the free radical DPPH scavenging activity. The studied species included cultivated and traditionally used P. edulis, P. incarnata and P. alata and less common species P. coccinea, P. laurifolia, P. mucronata and P. gardneri. The experimental design was completely randomized with ANOVA and Tukey test as main statistical analyses. The results showed that species of Passiflora had variable antioxidant capacities, ranging from 28 to 95% of free radical DPPH scavenging activity.

Comparation of free radical scavenger activity between seven species of Passiflora L.

Antioxidant capacities of seven species of Passiflora were evaluated through comparation of the free radical DPPH scavenging activity. The studied species included cultivated and traditionally used P. edulis, P. incarnata and P. alata and less common species P. coccinea, P. laurifolia, P. mucronata and P. gardneri. The experimental design was completely randomized with ANOVA and Tukey test as main statistical analyses. The results showed that species of Passiflora had variable antioxidant capacities, ranging from 28 to 95% of free radical DPPH scavenging activity.

Resposta à qualidade de luz como estratégia para estabelecimento de Bidens gardneri

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morfoanatomia comparada e ontogênese do pericarpo de Bidens gardneri Baker e B. pilosa L. (Asteraceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Seed and seedling surface-sterilization for in vitro culture of tillandsia gardneri (Bromeliaceae)

Tillandsia gardneri is a bromeliad with ornamental value and a wide geographical distribution over Brazil. However, due to habitat loss and illegal overcollection in the wild it is included as a vulnerable species in the official list of endangered plants of the State of Rio Grande do Sul, Brazil. The development of a protocol for T. gardneri seed propagation in vitro may be useful for reintroducing plants in their natural habitats, and for germplasm conservation. A difficult problem encountered during the establishment of an in vitro culture is explants disinfection, especially when working with endangered species, from which explant availability is restricted. Thus, the establishment of a sterilization protocol is crucial for the initiation and success of a micropropagation system for T. gardneri. The objective of this study was to evaluate the effect of sodium hypochlorite concentration and exposure time in seed and seedling surface disinfection, tissue sensitivity and development. Sodium hypochlorite solutions (10 or 20%/5, 10 or 15 min; 25%/5 or 10 min; and 50%/5 min) were effective in eliminating seed superficial contaminants. There was no significant difference among the effective sterilization treatments in relation to seed germination (%), and seedling length and number of leaves, after 120 days in vitro. Also, no damage to seed and seedling tissues were observed. Surface sterilization of seedlings, for initiation of an in vitro culture, required higher concentrations of sodium hypochlorite (25%/15 min; 20 or 50%/5, 10 or 15 min; and 40%/5 and 10 min) for controlling fungal and yeast contamination, compared to seed sterilization. No significant differences among these treatments were found in relation to seedling length and number of leaves, after 60 days in vitro.

Growth regulators for in vitro propagation of Tillandsia gardneri (Bromeliaceae)

Tillandsia gardneri Lindi, is a herbaceous perennial with ornamental value. However, in Brazil there is no report about this species' cultivation on a commercial scale. The low multiplication rate of T. gardneri (in average one offshoot/plant/year) leads to illegal over-collection in the wild to meet commercial demands. The development of protocols for in vitro propagation of T. gardneri may be useful for increasing multiplication rate, producing enough plants to supply the ornamental market and also to reduce the pressure over plants collection in the wild. The present study evaluated the effect of growth regulators (6-benzylaminopurine-BA alone or in combinations with naphthaleneacetic acid-NAA) on shoots development from seedlings pre-established in vitro, from seed germination on 1/4 MS medium without growth regulators. Seedlings (with about 1.0 cm long) were re-cultured to solid 1/2 MS media supplemented with growth regulators. After 30 days on the induction medium seedlings were re-cultured to MS basal medium. The experiment was conducted in a complete randomized design with four replications and ten treatments: control (free of growth regulators), BA (0.5, 1.0 and 2.0 mg/L), BA (0.5 mg/L) + ANA (0.1 mg/L), BA (1.0 mg/L) + ANA (0.1 mg/L), BA (1.0 mg/L) + ANA (0.5 mg/L), BA (2.0 mg/L) + ANA (0.1 mg/L), BA (2.0 mg/L) + ANA (0.5 mg/L), and BA (2.0 mg/L) + ANA (1.0 mg/L). The outgrowth of shoots did not occur on medium devoid of growth regulators (control). Regression analysis for some evaluated parameters, such as percentage of seedlings responsive to shoot formation and number of shoots/seedling, and regulators concentrations (BA or ANA) were significant, allowing the establishment of the growth regulators concentration for obtaining the best multiplication rate. Some seedlings maintained in media with ANA (0.5 or 1.0 mg/L) were completely converted into callus masses that turned dark brown leading to seedlings death.

Electronic states of trans-polyacetylene, poly(p-phenylene vinylene) and sp-hybridised carbon species in amorphous hydrogenated carbon probed by resonant Raman scattering

Inclusions of sp-hybridised, trans-polyacetylene [trans-(CH)x] and poly(p-phenylene vinylene) (PPV) chains are revealed using resonant Raman scattering (RRS) investigation of amorphous hydrogenated carbon (a-C:H) films in the near IR – UV range. The RRS spectra of trans-(CH)x core Ag modes and the PPV CC-H phenylene mode are found to transform and disperse as the laser excitation energy ћωL is increased from near IR through visible to UV, whereas sp-bonded inclusions only become evident in UV. This is attributed to ћωL probing of trans-(CH)x chain inhomogeneity and the distribution of chains with varying conjugation length; for PPV to the resonant probing of phelynene ring disorder; and for sp segments, to ћωL probing of a local band gap of end-terminated polyynes. The IR spectra analysis confirmed the presence of sp, trans-(CH)x and PPV inclusions. The obtained RRS results for a-C:H denote differentiation between the core Ag trans-(CH)x modes and the PPV phenylene mode. Furthermore, it was found that at various laser excitation energies the changes in Raman spectra features for trans-(CH)x segments included in an amorphous carbon matrix are the same as in bulk trans-polyacetylene. The latter finding can be used to facilitate identification of trans-(CH)x in the spectra of complex carbonaceous materials.

Are combination forecasts of S&P 500 volatility statistically superior?

Forecasting volatility has received a great deal of research attention, with the relative performances of econometric model based and option implied volatility forecasts often being considered. While many studies find that implied volatility is the pre-ferred approach, a number of issues remain unresolved, including the relative merit of combining forecasts and whether the relative performances of various forecasts are statistically different. By utilising recent econometric advances, this paper considers whether combination forecasts of S&P 500 volatility are statistically superior to a wide range of model based forecasts and implied volatility. It is found that a combination of model based forecasts is the dominant approach, indicating that the implied volatility cannot simply be viewed as a combination of various model based forecasts. Therefore, while often viewed as a superior volatility forecast, the implied volatility is in fact an inferior forecast of S&P 500 volatility relative to model-based forecasts.

The jump component of S&P 500 volatility and the VIX index

Much research has investigated the differences between option implied volatilities and econometric model-based forecasts. Implied volatility is a market determined forecast, in contrast to model-based forecasts that employ some degree of smoothing of past volatility to generate forecasts. Implied volatility has the potential to reflect information that a model-based forecast could not. This paper considers two issues relating to the informational content of the S&P 500 VIX implied volatility index. First, whether it subsumes information on how historical jump activity contributed to the price volatility, followed by whether the VIX reflects any incremental information pertaining to future jump activity relative to model-based forecasts. It is found that the VIX index both subsumes information relating to past jump contributions to total volatility and reflects incremental information pertaining to future jump activity. This issue has not been examined previously and expands our understanding of how option markets form their volatility forecasts.