Nitraria retusa and Atriplex halimus (xero-halophytes) plants were grown in the range 0-800 mM NaCl while Medicago arborea (glycophyte) in 0-300 mM NaCl. Plants were harvested after 120 days of salt-treatment. The present study was designed to study the effect of salinity on root, stem and leaf anatomy, water relationship, and plant growth in greenhouse conditions. Salinity induced anatomical changes in the roots, stems and leaves. The cuticle and epidermis of N. retusa and A. halimus stems were unaffected by salinity. However, root anatomical parameters (root cross section area, cortex thickness and stele to root area ratio), and stem anatomical parameters (stem cross section area and cortex area) were promoted at 100-200 mM NaCl. Indicating that low to moderate salinity had a stimulating effect on root and stem growth of these xero-halophytic species. At higher salinities, root and stem structures were altered significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea, they were strongly altered as salinity rose. NaCl (100-300 mM) reduced leaf water content by 21.2-56.2% and specific leaf area by 51-88.1%, while increased leaf anatomical parameters in M. arborea (e.g. increased thickness of upper and lower epidermis, palisade and spongy mesophyll, entire lamina, and increased palisade to spongy mesophyll ratio). Similar results were evidenced in A. halimus leaves with salinity exceeding 100 mM NaCl. Leaves of N. retusa were thinner in salt-stressed plants while epidermis thickness and water content was unaffected by salinity. The size of xylem vessel was unchanged under salinity in the leaf's main vein of the three species while we have increased number in M. arborea leaf main vein in the range of 200-300 mM NaCl. A longer distance between leaf vascular bundle, a reduced size and increased number of xylem vessel especially in stem than in root vascular system was evidenced in M. arborea treated plants and only at (400-800 mM) in the xero-halophytic species. The effects of NaCl toxicity on leaf, stem and root ultrastructure are discussed in relation to the degree of salt resistance of these three species. Our results suggest that both N. retusa and A. halimus show high tolerance to salinity while M. arborea was considered as a salt tolerant species.

Cinq diagrammes polliniques sont commentés. Sur tous s'observe dans la seconde moitié de l’Holocène la substitution de chênaies sclérophylles essentiellement de Quercus suber, à des chênaies caducifoliées de Q.canariensis . Une séquence du Pleistocene récent est révélée pour la première fois en Afrique du Nord ; elle témoigne d’une période forestière de chênaies au sein de laquelle se manifestent trois phases d’aridité.

Nitraria retusa and Atriplex halimus (xerohalophytes) plants were grown in the range 0-800 mM NaCl while Medicago arborea (glycophyte) in 0-300 mM NaCl. Salt stress caused a marked decrease in osmotic potential and a significant accumulation of Na ? and Cl -in leaves of both species. Moderate salinity had a stimulating effect on growth rate, net CO 2 assimilation, transpiration and stomatal conductance for the xero-halophytic species. At higher salinities, these physiological parameters decreased significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea they decreased linearly with salinity. Nitraria retusa PSII photochemistry and carotenoid content were unaffected by salinity, but a reduction in chlorophyll content was observed at 800 mM NaCl. Similar results were found in A. halimus, but with a decrease in the efficiency of PSII (F 0 v/F 0 m) occurred at 800 mM. Conversely, in M. arborea plants we observed a significant reduction in pigment concentrations and chlorophyll fluorescence parameters. The marked toxic effect of Na ? and/or Clobserved in M. arborea indicates that salt damage effect could be attributed to ions' toxicity, and that the reduction in photosynthesis is most probably due to damages in the photosynthetic apparatus rather than factors affecting stomatal closure. For the two halophyte species, it appears that there is occurrence of co-limitation of photosynthesis by stomatal and non-stomatal factors. Our results suggest that both N. retusa and A. halimus show high tolerance to both high salinity and photoinhibition while M. arborea was considered as a slightly salt tolerant species.

Les relations pluie pollinique-végétation sont précsiées en Kroumirie montagneuse à partir due trois transects de surface réalisés dans des chênaies pures ou mixtes de Quercus suber et Quercus canariensis à sous-bois d’Erica arborea. Il est montré que Q.canariensis est un bien meilleur producteur pollinique que Q.suber et que son pollen pénètre dans tous les milieux.

No abstract