Khaled Mguis

Fatty acid and sterol oil composition of four Tunisian ecotypes of Ziziphus zizyphus (L.) H.Karst

Abstract Oils isolated from seeds of Ziziphus zizyphus (L.) H. Karst. were investigated by capillary gas chromatography. A comparison of four Tunisian ecotypes (Sfax, Choutrana, Mahres and Mahdia) shows that they differ only in the quantitative composition, while the qualitative profiles are similar. Ten fatty acids are identified from seed oils. The qualitative study shows that oleic acid is the major compound in Sfax and Mahdia ecotypes seed oils. The ecotype of Choutrana is rich in linoleic acid. Unsaturated fatty acids ranged from 40.4% to 44.4% of the total fatty acids for each ecotype. The ratio of the poly-unsaturated/saturated (P/S) varied from 9.6 to 10.1 in all ecotypes. Five major sterols have been identified. The β-sitosterol is the prominent component in all the ecotypes and the highest level is found in the Sfax ecotype. Stigmasterol is more abundant in Sfax and Choutrana ecotypes. Campesterol is important in Choutrana seeds.

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.

Phenotypic responses of the wild wheat relative Aegilops geniculata Roth and wheat ( Triticum durum Desf.) to experimentally imposed salt stress

In order to study the salt effect on the wild wheat and durum wheat, three accessions of Aegilops geniculata L. from Ain zana, Zaghouan, and Sbitla and one variety of wheat (Triticum durum L.) have been grown in the INRAT green house and treated with different salt concentrations. The morphological, phenological and yield characters have been measured for each plant and analyzed using SAS software. 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.

Morphogenetic responses of Populus alba L. under salt stress

The morphogenetic responses to salt stress of Tunisian Populus alba clones were studied in order to promote their plantation in damaged saline areas. One year-old plants of three P. alba clones (MA-104, MA-195 and OG) were subjected to progressive salt stress by irrigation during two consecutive years. The plants were grown in a nursery, inside plastic receptacles containing sandy soil and were irrigated with tap water (control) or 3–6 g/l NaCl solution. During this study, leaf epinasty, elongation rate, vigor, internode length, plant architecture, and number of buds were evaluated. Test clone response was highly dependent on the applied treatment and degree of accommodation. The most pronounced alterations were induced under 6g/l of NaCl treatment including leaf epinasty, leaf elongation rate delay, vigor decrease, internode length shortening, and morphogenetic modifications. These responses were less noticeable in the MA-104 clone with respect to the two other clones. The salt effect induced a delay in the leaf elongation rate on the MA-195 and OG clones leading to an early leaf maturity. The vigour and internode length of the MA-104 clone was less affected than the other clones. The OG clone was the most salt-sensitive thus, it developed shorter branches and more buds number than MA-195 and MA-104. The effect of long-term salt stress was to induce early flowering of the P. alba clones which suggests that mechanism of salt accommodation could be developed.

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.