Energetic potentialities of in vitro cultures of plant cells: Crude oil produced by calli and cells of Euphoria characias

The content of crude oil produced by Euphorbia characias calli vary significantly with the basal medium used. Contrarily to what occurs with in nature growing plants, either calli or suspended cells from this species show a positive correlation between biomass growth and specific crude oil production. Heterotrophic suspended cells from Euphorbia characias at growth exponential phase revealed crude oil contents of 4–5% of dry weight, similar to those found in nature Spring growing plants of this species.     

Estimating ‘Value at Risk’ of crude oil price and its spillover effect using the GED-GARCH approach

Estimation has been carried out using GARCH-type models, based on the Generalized Error Distribution (GED), for both the extreme downside and upside Value-at-Risks (VaR) of returns in the WTI and Brent crude oil spot markets. Furthermore, according to a new concept of Granger causality in risk, a kernel-based test is proposed to detect extreme risk spillover effect between the two oil markets. Results of an empirical study indicate that the GED-GARCH-based VaR approach appears more effective than the well-recognized HSAF (i.e. historical simulation with ARMA forecasts). Moreover, this approach is also more realistic and comprehensive than the standard normal distribution-based VaR model that is commonly used. Results reveal that there is significant two-way risk spillover effect between WTI and Brent markets. Supplementary study indicates that at the 99% confidence level, when negative market news arises that brings about a slump in oil price return, historical information on risk in the WTI market helps to forecast the Brent market. Conversely, it is not the case when positive news occurs and returns rise. Historical information on risk in the two markets can facilitate forecasts of future extreme market risks for each other. These results are valuable for anyone who needs evaluation and forecasts of the risk situation in international crude oil markets.