Najoua Karray-Bouraoui

Phenolic composition of Cynara cardunculus L. organs, and their biological activities

Polyphenols are bioactive molecules exhibiting a lot of scientific attention due to their multiple biological activities. This study compared phenolic contents and antioxidant activity in Cynara cardunculus L. organs and focus on leaf phenolic compounds identification by RP-HPLC and their antibacterial activity. The analyzed organs exhibited different total polyphenol contents (7-14.8 mg GAE g(-1) DW). Leaf and seed phenolic contents were similar and two times higher than those in flowers. The same tendency was observed for the amount of flavonoids and tannins. However, seed extracts displayed the highest DPPH. scavenging ability with the lowest IC50 value (23 microg ml(-1)), followed by leaves and flowers (over 50 microg ml(-1)). In contrast, leaves showed the highest capacity to quench superoxide (IC50: 1 microg ml(-1)) as compared to seeds (6 microg ml(-1)). In addition, cardoon leaves were efficient to inhibit growth of pathogenic bacteria mainly against Staphylococcus aureus and Escherichia coli. The identification of phenolic compounds from leaves revealed that syringic and trans-cinnamic acids were the major molecules.

Nutrient uptake and management under saline conditions in the xerohalophyte: Tecticornia indica (Willd.) subsp. indica

In the present investigation, we studied uptake and management of the major cations in the xerohalophyte, Tecticornia indica (Willd.) subsp. indica as subjected to salinity. Plants were grown under greenhouse conditions at various salinity levels (0, 100, 200 and 400 mM NaCl) over 110 days. At harvest, they were separated into shoots and roots then analyzed for water contents, dry weights (DW), and Na+, K+, Ca²+, and Mg²+ contents. Plants showed a growth optimum at 200 mM NaCl and much better tissue hydration under saline than non-saline conditions. At this salt concentration (200 mM NaCl), shoot Na+ content reached its highest value (7.9 mmol · g-⁻¹ DW). In spite of such stressful conditions, salt-treated plants maintained adequate K+, Ca²+, and Mg²+ status even under severe saline conditions. This was mainly due to their aptitude to selectively acquire these essential cations and efficiently use them for biomass production.

Phenolic content, antioxidant and anti-inflammatory activities of Tunisian Diplotaxis simplex (Brassicaceae)

This study investigates the polyphenol content of Diplotaxis simplex extract and the biological activities of the main organ. The analysed extracts showed that polyphenol contents varied considerably as a function of organs. Furthermore, novel biological activities of this species were assessed. Flower extracts exhibit a potent in vitro antioxidant capacity using oxygen radical absorbance capacity and displayed a strong anti-inflammatory activity, inhibiting nitric oxide release, by 79.3% at 160 μg/mL. Our findings suggested that the Diplotaxis flower is a valuable source of antioxidants and anti-inflammatory agents.

Physiological responses of Arabidopsis thaliana to the interaction of iron deficiency and nitrogen form.

Physiological responses of Arabidopsis thaliana to the interaction of iron deficiency and nitrogen form were studied using plants grown in hydroponics. Thirty-three-day-old seedlings were submitted to four treatments for 7 days: NO 3 + 5 microM Fe; NO 3 + 0.1 microM Fe; NH 4 + 5 microM Fe and NH 4 + 0.1 microM Fe. Leaf growth and chlorophyll content were highest in NO 3 -fed, Fe sufficient plants, but were strongly diminished by Fe deficiency under nitric nutrition, and by ammoniacal nutrition independently of Fe regime. However, the leaves of NH 4 -fed plants presented a higher Fe content than those of Fe sufficient, NO 3 -fed plants. Thus, leaf chlorosis of NH 4 -fed in plant did not depend on Fe availability, and seemed to be due to another factor. Root acidification capacity and Fe-chelate reductase (FCR) activity were also dependent on N form. The medium was acidified under ammoniacal regime and alkalinized under nitric regime regardless of Fe level. FCR activity stimulation in response to Fe deficiency was observed only in NO 3- fed plants. In addition, both N form and Fe level induced antioxidant responses in rosette leaves. Ammoniacal regime increased both peroxidase expression and anthocyanin accumulation, whereas Fe deficiency enhanced superoxide dismutase expression.

The interaction between foliar GA3 application and arbuscular mycorrhizal fungi inoculation improves growth in salinized tomato (Solanum lycopersicum L.) plants by modifying the hormonal balance

The agriculture industry is frequently affected by various abiotic stresses limiting plant productivity. To decrease the negative effect of salinity and improve growth performance, some strategies have been used, such as exogenous application of plant growth regulators (i.e. gibberellic acid, GA3), or arbuscular mycorrhizal fungi (AMF) inoculation. To gain insights about the cross-talk effect of exogenous GA3 application and AMF inoculation on growth under salinity conditions, tomato plants (Solanum lycopersicum, cv. TT-115) were inoculated or not with the AMF Rhizophagus irregularis and exposed to different treatments during two weeks: 0M GA3+0mM NaCl, 10-6M GA3+0mM NaCl, 0M GA3+100mM NaCl and 10-6M GA3+100mM NaCl. Results have revealed that AMF inoculation or GA3 application alone, but especially their interaction, resulted in growth improvement under salinity conditions. The growth improvement observed in AMF-inoculated tomato plants under salinity conditions was mainly associated to ionic factors (higherK concentration and K/Na ratio) while the alleviating effect of GA3 application and its interaction with AMF appear to be due to changes in the hormonal balance. Foliar GA3 application was found to increase the active gibberellins (GAs), resulting in a positive correlation between GA3 and the growth-related parameters. Furthermore, cytokinins, indoleacetic acid and abscisic acid concentrations increased in AMF inoculated or GA3 treated plants but, notably, in AMF plants treated with GA3, which showed improved growth under salinity conditions. This suggests that there is an interactive positive effect between GAs and AMF which alleviates growth impairment under salinity conditions by modifying the hormonal balance of the plant.

Salt effects on shoot growth and essential oil yield and composition in safflower (Carthamus tinctorius L.)

Salinity effects on growth and essential oil composition of Tunisian safflower (Carthamus tinctorius) shoots grown in hydroponic medium were investigated. Plants treated with 25 mM NaCl showed remarkable morphological modifications and decrease in shoot dry matter. Under 50 and 75 mM NaCl, plants showed a withering and a drastic reduction in dry matter (50% and 70%, respectively). Under NaCl 25 mM, essential oil yield increased significantly (p<0.05) up to 70% and 27% respectively in plants from Tazarka and Kairouan provenances compared with the control. The major compound in Tazarka essential oil was found to be 1,8-cineole (23.5%) followed by methyl eugenol (18.0%), 1-pentadecene (9.1%) and camphene (9.0%). In plants from Kairouan provenance, the major compounds were 1-pentadecene (22.9%), methyl-eugenol (11.8%), linalool (8.1%) and camphene (7.9%). Whatever the origin, the application of 25 mM resulted in remarkable changes in the content and the percentage of the main oil components with the effect being more pronounced in plants from Tazarka.