Water deficit stress induces different monoterpene and sesquiterpene emission changes in Mediterranean species. Relationship between terpene emissions and plant water potential.

The effects of water deficit stress and plant water potential (psi) on monoterpene and sesquiterpene leaf emissions from Rosmarinus officinalis, Pinus halepensis, Cistus albidus and Quercus coccifera were studied over 11 days of water withholding (from t(1) to t(11)), after substrates had achieved their field capacity (control pots: t(0)). Volatile compounds were sampled from the same twig per plant all throughout the study, using a dynamic bag enclosure system. Volatiles, collected in Tenax TA, were studied by means of GC-FID and GC-MS. Monoterpene emissions of water stressed plants (t(1)-t(11)) were either similar to those of control seedlings (R. officinalis and Q. coccifera) or higher (P. halepensis and C. albidus). By contrast, sesquiterpene emissions were strongly reduced or inhibited after four days of water withholding, particularly for R. officinalis, thus altering terpene emission composition. Despite the positive effect of water stress on leaf monoterpene emissions of P. halepensis and C. albidus, the significant correlation between these emissions and psi showed a slow decrease of these emissions over long term water deficit periods. This contrasted with the rapid decline of sesquiterpene emissions of R. officinalis according to lower values of psi. These results provide an overall picture of the different responses of monoterpene and sesquiterpene emissions to progressive water loss. They also reveal the utility of using psi for estimating some emission rates of some species according to drought conditions.

Phenolic compounds content in Pinus halepensis Mill. needles: a bioindicator of air pollution.

Foliar phenol concentrations (total and simple phenols) were determined in Aleppo pine (Pinus halepensis Mill.) needles collected in June 2000, from 6 sites affected by various forms of atmospheric pollutants (NO, NO(2), NO(x), O(3) and SO(2)) monitored during two months. Results show an increase in total phenol content with exposure to sulphur dioxide and a reduction with exposure to nitrogen oxide pollution. p-Coumaric acid, syringic acid and 4-hydroxybenzoic acid concentrations increase with exposure to nitrogen oxide pollution, whereas gallic acid and vanillin decrease in the presence respectively of sulphur dioxide and ozone. This in situ work confirms the major interest of using total and simple phenolic compounds of P. halepensis as biological indicators of air quality.

Evaluation of the total peroxyl radical-scavenging capacity of flavonoids: structure-activity relationships.

The antioxidant activity of a series of flavonoids against peroxyl radicals generated from thermal homolysis of 2, 2'-azobis-amidinopropane was determined by the Total Oxyradical Scavenging Capacity (TOSC) assay. Seven flavonoids with hydroxy and/or methoxy substitution were analyzed and compared to the water-soluble vitamin E analogue Trolox. The most active compound was the flavonol quercetin, followed by its 3-glycoside derivative rutin; these were 7 and 5 times, respectively, better scavengers of peroxyl radical than Trolox. Among the flavones with both hydroxy and methoxy substitution, the most active against peroxyl radicals was the 5,6,4'-trihydroxy-7,8,3'-trimethoxyflavone (thymonin), with a TOSC value 1.5 times greater than that of Trolox. The activity of the remaining flavones was in the following relative order: 5, 4'-dihydroxy-6,7,8,3'-tetramethoxyflavone > 5-hydroxy-3,6,7,3', 4'-pentamethoxyflavone (artemetin) > 5,4'-dihydroxy-3,6, 7-trimethoxyflavone > 5,6,7,8,2',3',4',5'-octamethoxyflavone (agehoustin A). The data suggest a potential role for dietary intake of flavonoid-containing foods in lowering the risk of certain pathophysiologies that have been associated with free-radical-mediated events.

Potentialites autotoxiques et allelopathiques de Cistus albidus L.

This study focuses on how allelopathic mechanisms may be involved in the floristic composition and dynamics of Cistus albidus shrubbery. Allelopathic potential of essential oils was measured for Lactuca sativa (toxicity for other species) and Cistus albidus (self-toxicity). These oils have little effect on germination but significantly increase, even in low quantities, the number of unviable seedlings and inhibit normal seedling growth. These results explain, at least partially, the existence of monospecific stands over several years and the lack of natural regeneration of the Cistus albidus populations. Bioassays performed using natural aerial leachates of Cistus albidus revealed no significant effects on the above-mentioned parameters. Leaching does not seem to be an important means of allelochemicals release. Nevertheless, essential oils have been quantified in litter and soil, indicating a possible occurrence of allelopathy in such ecosystems.

Chimeric EWS-FLI1 transcript in a Ewing cell line with a complex t(11;22;14) translocation.

Peripheral neuroectodermal tumors include the differentiated neuroepithelioma and the undifferentiated Ewing's tumor. Despite clinical and pathological differences, both malignancies are characterized by a t(11;22)(q24;q12) translocation which is observed in > 90% of the cases. Molecularly, the translocation is underlaid by a rearrangement between the EWS and Fli-1 genes on chromosomes 22 and 11, respectively. Because of the difficulties in the differential diagnosis between various small round cell tumors of childhood, including Ewing's tumor, a molecular diagnostic assay would be desirable. A prerequisite for predicting the reliability of such a test resides in the molecular elucidation of the peripheral neuroectodermal tumor cases which do not exhibit the prototypical translocation. We have analyzed one such case of Ewing's tumor-derived cell line with a t(11;22;14)(q24;q12;q11) translocation. An EWS-Fli-1 fusion transcript was evidenced by polymerase chain reaction amplification of a reverse transcription product obtained from total RNA. Direct sequencing was performed to demonstrate that the molecular rearrangement in this particular Ewing sample resulted in a fusion transcript similar to those observed in tumors with the prototypical translocation.