Ayda Khadhri

Responses of leaf growth and gas exchanges to salt stress during reproductive stage in wild wheat relative Aegilops geniculata Roth. and wheat (Triticum durum Desf.)

In order to investigate the effect of salinity on the growth and photosynthesis of the wild wheat and wheat, three accessions of Aegilops geniculata from Ain Zana, Zaghouan and Sbitla and one variety of durum wheat (Triticum durum) were grown in the INRAT greenhouse and treated with different salinity levels. The growth of leaves, water status and gas exchange parameters have been measured at the reproductive stage. The flag leaf length, total leaf dry weight, water status, CO2 assimilation rate, stomatal conductance, intercellular CO2 and transpiration for the three Ae. geniculata accessions and wheat variety significantly decreased with increasing salt. The decline in photosynthesis measured in response to salt stress was proportionally greater than the declines in transpiration, resulting in a reduction of water-use efficiency, at both the leaf and whole-plant levels. Among the factors inhibiting photosynthetic activity, those of a stomatal nature had a greater effect. This study has shown a high degree of variation of these characters mainly related to geographical origin. It was observed also that Sbitla accession was less affected by the imposed salt stress than all the others while Ain Zana was the most affected one.

Barks Essential Oil, Secondary Metabolites and Biological Activities of Four Organs of Tunisian Calligonum azel Maire

This study is the first to investigate the chemical composition of barks essential oil (EO), secondary metabolites and biological activities of the MeOH and infusions extracts of seeds, leaves, barks and roots of Calligonum azel Maire (Polygonaceae) harvested from Tunisian desert. The gas chromatography/mass spectrometry (GC/MS) results showed the presence of fifty‐four compounds in barks EO. The major components were: viridiflorol (14.6%), α‐eudesmol (8.65%), trans‐caryophyllene (6.72%), elemol (6.63%), β‐eudesmol (6.21%). The obtained results showed that C. azel is a very rich plant in secondary metabolites. High contents in polyphenols, flavonoids and tannins were observed in both extracts of all studied organs. Significant differences were found between both extracts of the four organs. Thus, polyphenols and tannins were more abundant in leaves infusion extract, while, flavonoids showed a high level in barks extract. The antioxidant activity data demonstrated that all extracts showed strong antioxidant and radical scavenging activities. The MeOH extracts presented potential for antibacterial and antifungal activities against all tested microorganisms. The inhibition zones diameters and minimal inhibitrice concentration values were in the range of 9 – 15 mm and 2.5 – 20 μg/ml, respectively. This study demonstrated that C. azel can be regarded as an excellent plant source for natural antimicrobial agents.

Germination responses of Cymbopogon schoenanthus to salinity

Germination studies of Cymbopogon schoenanthus (Poaceae) distributed along southern Tunisia were carried out to assess the effects of salinity. A preliminary experiment showed 30°C as the optimum germination temperature for seeds of this species. After that, seed germination was studied at different salinity levels. Our results revealed a decrease in germination percentage with increasing salinity. Germination rate, however, was maintained up to 200xa0mM NaCl and drastically declined at 300xa0mM NaCl.

Evaluation of Calligonum azel Maire, a North African desert plant, for its nutritional potential as a sustainable food and feed

This study is the first to evaluate the potential of Calligonum azel Maire as a food ingredient. The plant materials flowers, leaves, stems and roots were analyzed by wet-chemical and instrumental methods for major and minor composition. The highest protein and sugar contents were recorded in the flowers (17.8% and 1.6% respectively), while the fat content was most abundant in the leaves (2.9%). Hexane extracts screened by gas chromatography (GC) for fatty acid composition showed 14 major compounds such as oleic acid, linoleic acid and palmitic acid, but also ω3 and ω6 unsaturated fatty acids. The essential oils extracted by hydrodistillation were screened by GC/MS and 31 compounds were identified including estragole, naphthalene, anethole, phytol and curcumene. The HPLC-DAD screening revealed that the methanolic extracts do not contain any pharmacologically active compound with adverse properties, but quercetin, hordenine and vanillin were abundant in the flowers, leaves and roots. Proton nuclear magnetic resonance (1H NMR) spectroscopy showed that glucose, sucrose and fructose were abundant in acetone and methanol extracts, while urea and glycerol were abundant in the aqueous extracts. A sensory evaluation of the aqueous infusions showed properties of the flowers reminiscent of other herbal teas. In conclusion, our results corroborate the suitability of the traditionally described use of Calligonum azel Maire as food and feed. The further study of this plant as a sustainable nutritional ingredient appears to be worthwhile.

Phenolic profiling and antioxidant capacity of Calligonum azel Maire, a Tunisian desert plant

The comprehensive phenolic fingerprint of Calligonum azel Maire plant fractions, collected from the Tunisian Desert, have been assessed for the first time as a source of natural antioxidants. Total phenolic content (TPC), Trolox Equivalent Antioxidant Capacity (TEAC) in scavenging DPPH, ABTS+ and Ferric Reducing Antioxidant Power (FRAP) were determined. C. azel Maire showed a relevant content in phenolic compounds, which are related to the antioxidant activity. The flowers presented the highest antioxidant capacity against DPPH free radicals, while the leaves showed the highest scavenging capacity against ABTS. As for the FRAP assay, results showed that the roots had the highest ferric reducing antioxidant power. Methanol extracts of the four organs were screened by ultra high performance liquid chromatography coupled to quadruple time of flight mass spectrometry and the identified phenolics were further quantified. Flavones and flavanols were the most abundant phenolic compounds identified, and were quantitatively measured as luteolin and catechin equivalents. Although the phenolic profile was diverse between the four organs, the obtained results showed that Calligonum azel Maire is an excellent source of various natural antioxidants with high radical scavenging capacities, which could be used in food preservation. Further studies on the isolation of such compounds appear to be of high interest.

Responses of Cymbopogon schoenanthus to salt stress

Cymbopogon schoenanthus is an aromatic and medicinal plant rich in essential oil. The physiological behavior of this species, related with growth production, the photosynthetic pigments, the nutritional status and the osmotic adjustment were studied. Saline treatments varied from 0 to 150 mM NaCl. The results show that the growth of C. schoenanthus was affected by the salinity and the effect increased with more stress at 100 mM of NaCl. Besides the response of C. schoenanthus to the salt stress, this study has allowed us to conclude that this plant is excluder glycophyte and less tolerant to salt stress. Key words: Cymbopogon schoenanthus , NaCl, growth, mineral nutrition, osmotic adjustment.