Effects of drought-induced holm oak dieback on BVOCs emissions in a Mediterranean forest.

Climate change is impairing tree physiology and growth, causing an increase in tree dieback in many Mediterranean forests. These desiccation phenomena are leading to changes in land cover and plant community composition. Mediterranean plants are capable to emit large amount of Biogenic Volatile Organic Compounds (BVOCs), whose emission and biosynthesis is strongly affected by environmental conditions. This study evaluates the seasonal changes in understory species composition in two forest stands in Southern Tuscany characterized by different levels of Quercus ilex L. crown defoliation (low and high defoliation, LD and HD) and the relationship with BVOCs emissions over three years. We found significant changes in the understory plant community following Q. ilex crown defoliation and mortality, observing an increment in the number of shrubs both in HD and LD stands. The environmental sampling of BVOCs fully reflected the changes in vegetation cover and composition, with a reduction in the amount of monoterpene emissions due to the increasing rates of defoliation and mortality of Q. ilex trees. Our results suggest that terpene emissions from Mediterranean forests would be modified by an increase of Q. ilex dieback, with important consequences for functioning of this forest ecosystem and its atmospheric chemistry.

Interactions and competition processes among tree species in young experimental mixed forests, assessed with chlorophyll fluorescence and leaf morphology.

Chlorophyll a fluorescence (ChlF) and leaf morphology were assessed in two sites in Europe (Kaltenborn, Germany, and Satakunta, Finland) within a forest diversity experiment. Trees at Satakunta, planted in 1999, form a stratified canopy, while in Kaltenborn the trees are 7 years old, with no apparent canopy connection among broadleaf species. The following ChlF parameters from measured OJIP transient curves were examined: F(V)/F(M) (a proxy for maximum quantum yield); ΨEo (a proxy for efficiency in transferring an electron from reduced QA to the electron transport chain); I-P phase (a proxy for efficiency of reducing final acceptors beyond PSI); and PItot (total performance index for potential energy conservation from photons absorbed by PSII to reduction of PSI end acceptors). At Satakunta F(V)/F(M) and ΨEo in Betula pendula were higher in monocultures and lower in mixed plots, perhaps due to increasing light availability in mixed plots, which can induce photoinhibition. The opposite trend was observed in Picea abies, which was shaded in mixed plots. At Kaltenborn F(V)/F(M) decreased in Fagus sylvatica and P. abies in mixed plots due to competition both above- and belowground. At Satakunta LMA increased in B. pendula leaves with increasing species richness. Leaf area of ten leaves was reduced in F. sylvatica in mixed plots at Kaltenborn. By up-scaling the overall fluorescence response to plot level (PItot_plot ), a significant positive correlation with tree diversity was found at Kaltenborn, but not at Satakunta. This could suggest that competition/facilitation processes in mixed stands play a significant role in the early stages of forest establishment, but then tend to be compensated in more mature stands.

Bacterial mutagenic evaluation of Luxabendazole, a new broad spectrum anthelmintic, with the Salmonella typhimurium His- and the Escherichia coli Tryp- reversion tests.

Luxabendazole is a new benzimidazole carbamate chemotherapeutic agent, which has proved to be effective against adult and immature stages of the major gastrointestinal nematodes, trematodes and cestodes. The mutagenic properties of Luxabendazole were investigated in the in vitro Ames Salmonella and E. coli tests. The product was tested at concentrations of 0.5, 5, 50, 500, 1250 and 2500 micrograms/plate in the TA1535, TA1538, TA98 and TA100 strains of Salmonella typhimurium, and 0.5, 5, 50 and 500 micrograms/plate in the WP2, WP2uvrA- and its pKM 101-containing derivative CM891 (WP2 uvrA- pKM101) strains of Escherichia coli, with and without S9 microsomal activation (post-mitochondrial liver fraction from Wistar rats pretreated with Aroclor(R)). Positive and negative controls were included in each experiment. From the present study it can be concluded that Luxabendazole, over a dose range of 0.5-2500 micrograms/plate, is unlikely to present a mutagenic hazard, as demonstrated by the Ames test.

[Genotoxic study of commercial dyes with tartrazine base in S. typhimurium his- and E. coli trp-]. / Estudio genotóxico de colorantes comerciales con base Tartracina en S. typhimurium his- y E. coli trp-.

We study the genotoxic character of 21 food dyes samples with tartrazine in different trade-marks. Two homologated assays "in vitro" of reverse mutation in S. typhimurium and E. coli are used, with metabolic activation. There is no evidence of mutagenic character in any sample.