Houcine Sebei

Allelopathic effect of Schinus molle essential oils on wheat germination

Gas chromatography-flame ionisation detection (GC-FID) and gas chromatography–mass spectrometry (GC–MS) analyses of the essential oils of leaves and fruits of the ornamental Shinus molle L. were reported and their allelopathic effect on wheat (Triticum aestivum L.) was evaluated. Qualitative and quantitative differences between fruit and leaf oils were observed. Both oils were rich in monoterpene hydrocarbons and the major constituents were limonene and β-phellendrene (35.9–65.4%), α-phellendrene (24.3–20.1%), myrcene (12.8–7.7%) and α-pinene (5.9–1.7%) for fruits and leaves, respectively. Both essential oils showed a dose-dependent allelopathic activity on wheat germination and radicle elongation with leaf oil being the more phytotoxic.

Volatile oil constituents of Rosa canina L.: Differences related to developmental stages and floral organs

Abstract The evolution of the volatile oils during three developmental stages of Rosa canina L. flowers and the repartition of the constituents of the oils among different floral parts were examined using high-resolution gas chromatography and gas chromatography–mass spectrometry. Numerous components belonging to different chemical classes suggesting the occurrence of different metabolic pathways were identified. The main component in all oil samples was 2-phenylethanol, and its content increased gradually during the floral development process. Irrespective of flowers developmental stage, hydrocarbons were found to be the main group components. A great qualitative and quantitative change of the essential oil composition among different floral parts was also revealed. The volatile oil compositions are discussed in relation to their defensive and pollinators attraction roles.

Responses of Nigella sativa L. to Zinc Excess: Focus on Germination, Growth, Yield and Yield Components, Lipid and Terpene Metabolism, and Total Phenolics and Antioxidant Activities

A comprehensive analysis of the responses of Nigella sativa L. to elevated zinc concentrations was assessed in pot experiments. Zn excess supply did not affect the germination but drastically reduced radicle elongation. A concentration-dependent reduction in all growth parameters, yield, and yield components was observed. With the increasing Zn concentrations, total lipid contents decreased and changes in fatty composition toward the production of saturated ones were underscored. Despite the reduction in the seeds essential oil yield, a redirection of the terpene metabolism toward the synthesis of oxygenated compounds has been evidenced. A significant increase in the total phenols and flavonoids contents concomitant with improved antioxidant activities has also been found. Collectively, these results highlight the possible use of N. sativa L. in phytoremediation applications, on the one hand, and that Zn excess could represent an excellent alternative to improve the nutritional attributes of this important species, on the other hand.

Volatile Oil Constituents of Rosa canina L.: Quality As Affected by the Distillation Method

The volatile oils of R. canina flowers were isolated by hydrodistillation (HD) and traditional dry distillation (DD) and analyzed by HRGC-FID and GC-MS. Compared to HD, DD at 50°C leads to the isolation of high quality oil which contains the highest content of oxygenated compounds (83%). The main components are the 2-phenethyl alcohol and eugenol. The percentage of the 2-phenethyl alcohol, a highly desirable component in rose oil, was significantly higher (58.4%) in DD extract when compared to that of HD one (13.6%). As temperature increased (100°C) during DD, the oil quality decreased. The most significant changes were observed in 2-phenethyl alcohol percentage (4.5%). Moreover, an increase of alkanes/alkenes and the production of furan derivatives were observed. So, DD at moderate temperature (50°C) seemed more suitable to improve the volatile oil quality and hence, to make more value of R. canina.

Taxonomic notes and distribution of taxa of Orobanche gr. minor (Orobanchaceae) from Tunisia

Abstract New records for the flora of Tunisia and, in part, for North Africa of taxa of Orobanche sect. Orobanche subsect. Minores (Beck) Teryokhin, are reported. These records come from field research carried out between 2010 and 2014 in the Kroumiria region in northwestern Tunisia and herbarium studies. Infraspecific taxa and chorological data about the identified taxa (Orobanche amethystea Thuill., Orobanche canescens C. Presl, Orobanche hederae Duby, Orobanche litorea Guss., Orobanche minor Sm. and Orobanche pubescens d’Urv.) are reported. Literature data on host and distribution are also revised. Orobanche litorea is new to North Africa, and O. canescens has been confirmed for North Africa more than 100 years after the only known collection. Orobanche hederae and O. pubescens are new to Tunisia.