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Olive tree cultivation in theMediterranean goes back to ancient times. Evensince the Roman Age, olive cultivation spreadto the entire Mediterranean basin. Thislongevous tree integrates and identifieseconomically, socially, and culturally theinhabitants of this basin and determines itsrural landscape. For the residents of theMediterranean, olive oil constituted the mainsource of nutritional fats, their most valuableexport product, and was identified with theirculture. Even now, olive cultivation has amultiple importance for the Mediterranean. Theolive groves, which grow mostly on inclined,shallow, and low fertility soils, and onhand-made stone terraces, have limited wateringrequirements and sustain the fragile naturalresources of the Mediterranean. Today,olive cultivation in the Mediterranean is anadditional income source and supports thepopulation in rural areas during the winterperiod, which profit from summer and seatourism activity. Although anagro-ecosystem, the olive grove resembles thenatural Mediterranean ecosystem and abandonmenttransforms them into natural Mediterranean typeforests. Their change of use from olivecultivation to pasture degrades the ecosystemand decreases the natural resources, because ofover-grazing. At this time, two major factorsthreaten the traditional olive cultivation (i)the competition of the intensive olive grovesin plain and irrigated areas and (ii) thecheaper seed-oils, which intensify theabandonment of traditional olive groves andchange them into pasture, resulting in thedeterioration of the ecosystem. Olivecultivation has left its mark on life in theMediterranean and has contributed to thesustainability of natural resources.Nevertheless, it succumbs under the pressure ofcurrent socioeconomic situations. Today, theconservation of olives in productionconstitutes a necessity for the fragileMediterranean ecosystems and a challenge foreverybody involved.
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Though halophytes are naturally adapted to salinity, their salt-tolerance limits are greatly influenced by their provenance and developmental stage. In the present study, physio-biochemical responses of two Tunisian ecotypes of the oilseed coastal halophyte Cakile maritima (Brassicaceae) to salinity (0–400 mM NaCl) were monitored during germination and vegetative growth stages. Tabarka and Jerba seeds were collected from humid or arid climatic areas, respectively. Plant response to salinity appeared to depend on the ecotype and salinity levels. Increasing salinity inhibited germination process. Jerba seeds were found to be more salt tolerant than the Tabarka ones. At the autotrophic stage of growth and under salt-free conditions, Jerba was less productive than Tabarka (in terms of dry matter accumulation), but plant biomass production and leaf expansion (area and number) of the former ecotype were progressively improved by 100 mM NaCl, as compared to the control. In contrast, at the same salt concentration, these parameters decreased under increasing salinity in Tabarka (salt sensitive). Leaf chlorophyll content was reduced at severe salinity, but this effect was more conspicuous in the sensitive Tabarka plants. Na+ contents in the Jerba and Tabarka leaves collected from the 400 mM NaCl-treated plants were 17- and 12-fold higher than in the respective controls. This effect was accompanied by a significant reduction in the leaf K+, Mg2+ and Ca2+ contents, especially in the salt-treated Tabarka. A significant accumulation of proline and soluble carbohydrates in leaves was found during the period of intensive leaf growth. These organic compounds likely play a role in leaf osmotic adjustment and in protection of membrane stability at severe salinity.
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The composition of the essential oil obtained by hydrodistillation from the aerial parts of several populations of Artemisia campestris L. (Asteraceae), collected from four areas of south-eastern of Tunisia (Bengardane, Benikhdache, Jerba and Tataouine), was analysed by GC–MS. Thirteen to fifteen components were identified in each sample, representing more than 95% of the total oil. All samples were dominated by the presence of β-pinene (24.2–27.9%), p-cymene (17.4–22.3%) and α-pinene (4.1–11.0%), representing more than 45% of the total oil. The distribution of other components in the different extracts was qualitatively and quantitatively irregular. The variability of the composition can be attributed to the climatic and geographical conditions among areas
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