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Les effets du changement climatique induisent dans la région méditerranéenne la recrudescence d’évènements extrêmes comme la sécheresse accentuant la dégradation des écosystèmes forestiers de Quercus suber L. Des jeunes plants de 3 provenances tunisiennes de Q. suber (El Feija (EF), Ben Metir (BM) et Oued Zen (OZ)) ont été évalués pour leur tolérance au manque d’eau en les soumettant durant 90 jours à 3 régimes hydriques (S0, irrigation à 100 % de la capacité au champ (CC); S1, 50 % CC; S2, 25 % CC). De nombreuses variables ont été mesurées (croissance des tiges, surface foliaire, densité et dimension des trichomes et des stomates, échanges gazeux et concentration en chlorophylles). Le déficit hydrique a occasionné une réduction des variables écophysiologiques et une augmentation de la densité des stomates et des trichomes. Une variabilité intraspécifique a été enregistrée. Les plants EF et BM ont montré un indice de plasticité phénotypique supérieur à celui des plants OZ. La meilleure flexibilité vis-à-vis du stress hydrique s’est traduite chez les plants EF par une augmentation de l’efficience de l’utilisation de l’eau intrinsèque (EUEi) convertie en une croissance plus soutenue des tiges. Dans un contexte global de réchauffement climatique et de fragilité des forêts méditerranéennes, la réussite des nouveaux boisements de Q. suber exige le choix de provenances les plus adaptées à la faible disponibilité en eau à l’instar de la provenance EF.

Biodiversity has been confronted with anthropogenic threats and several natural threats such as biological invasions. The success of these invasions involves phytotoxic products released by invasive plants that can exhibit allelopathic effects on target species. Thus, aqueous extracts from different parts of the Mediterranean yellow star-thistle [Centaurea solstitialis subsp. schouwii (DC.) Gugler], were tested for their allelopathic effects on seed germination and seedling growth of Sulla coronaria (L.). Bioassays were conducted in vitro to test the effects of the aqueous extracts of shoot, basal and root parts of C. solstitialis subsp. schouwii at two different concentrations (50 g·L−1 and 10 g·L−1). The concentrations of total polyphenols, flavonoids, and tannins of the extracts were also evaluated. Our results showed inhibitory effects on the germination and seedling growth of S. coronaria seedlings, particularly with the extract form the basal part, reaching 84%. This study confirms the linear relationships between the allelopathic effects of C. solstitialis subsp. schouwii and the polyphenol and flavonoid contents. However, further experiments are needed under field conditions to confirm the results obtained under laboratory conditions.

Dans les regions arides et semi-arides, la productivite des sols salinises ne cesse de diminuer causant d’importants dommages socio-economiques et environnementaux. L’utilisation du genre Salix don...

The pollution of soils by heavy metals resulting from mining activities is one of the major environmental problems in North Africa. Mycorrhizoremediation using mycorrhizal fungi and adapted plant species is emerging as one of the most innovative methods to remediate heavy metal pollution. This study aims to assess the growth and the nutritional status of ectomycorrhizal Pinus halepensis seedlings subjected to high concentrations of Pb, Zn, and Cd for possible integration in the restoration of heavy metals contaminated sites. Ectomycorrhizal and non-ectomycorrhizal P. halepensis seedlings were grown in uncontaminated (control) and contaminated soils for 12 months. Growth, mineral nutrition, and heavy metal content were assessed. Results showed that ectomycorrhizae significantly improved shoot and roots dry masses of P. halepensis seedlings, as well as nitrogen shoot content. The absorption of Pb, Zn, and Cd was much higher in the roots than in the shoots, and significantly more pronounced in ectomycorrhizal seedlings&mdash, especially for Zn and Cd. The presence of ectomycorrhizae significantly reduced the translocation factor of Zn and Cd and bioaccumulation factor of Pb and Cd, which enhanced the phytostabilizing potential of P. halepensis seedlings. These results support the use of ectomycorrhizal P. halepensis in the remediation of heavy metal contaminated sites.

L’usage des pesticides a base de sels de zinc (Zn) en agriculture intensive engendre son accumulation continue dans le sol. Le recours a l’utilisation du genre Salix constitue une solution viable a long terme pour extraire le Zn en exces. Trois clones de Salix sp., originaires de la zone mediterraneenne sud, ont ete evalues quant a leur degre de tolerance a quatre differentes concentrations de ZnSO4·7H2O (0,4, 250, 500 et 750 μmol·L−1) pendant 45 jours. A la fin de cette periode, plusieurs variables ecophysiologiques ont ete evaluees. Les traitements appliques ont montre des differences genotypiques relatives a la sensibilite au stress cause par le Zn. Cette variabilite clonale tres prononcee s’est manifestee par l’apparition de symptomes de toxicite et des perturbations physiologiques, ainsi que par une reduction de croissance. Nos resultats laissent presager les possibilites de l’utilisation des clones de Salix comme modele agroforestier pour lutter contre l’accumulation du zinc dans les sols agricoles ...

We sought to identify risk factors and neonatal outcomes associated with the failure of the INSURE method ( INtubation- SURfactant- Extubation) during nasal continuous positive airway pressure for preterm infants with respiratory distress syndrome. We used a retrospective analysis of the prenatal histories, clinical courses, and laboratory data of all inborn infants with gestational age 27 to 34 weeks and respiratory distress syndrome treated with INSURE method. Infants were categorized into two groups: INSURE failure group and INSURE success group. One hundred nine infants were eligible to the study. INSURE failure was registered in 35 infants (32.1%). After control for confounding variables, INSURE failure was significantly associated with arterial partial pressure of carbon dioxide (adjusted odds ratio [OR] = 1.82; 95% confidence interval [CI] = 1.76 to 90.56), mean arterial-to-alveolar oxygen tension ratio (adjusted OR = 1.13; 95% CI = 1.06 to 85.34) and severe radiological grade (adjusted OR = 1.31; 95% CI = 1.15 to 70.16). Positive predictive values of these variables were 70, 75, and 55%, respectively. Patent ductus arteriosus and mortality rates were significantly higher in INSURE failure group. Arterial partial pressure of carbon dioxide, arterial-to-alveolar oxygen tension ratio, and severe radiological grade are predictors of the failure of INSURE method in preterm infants with respiratory distress syndrome. However, a prospective randomized controlled trial is needed to determine whether or not infants at risk for INSURE failure are better off being treated with mechanical ventilation.