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Thapsia garganica phytotoxicity was studied on Lactuca sativa L. and associated weeds, by pulverization of its aqueous extracts (at 10, 20, and 30 %), in pot experiments. To comprehend its mode of action on lettuce, seedlings were grown hydroponically in Hoagland nutrient solution for two months, then the T. garganica leaves aqueous extract was added to the medium for three days. After the harvest, a number of physiological and biochemical parameters had been determined. The antioxidant activity for DPPH (2,2-diphenyl-1-picrylhydrazyl radical) and FRAP (Ferric reducing antioxidant power), and secondary metabolite production were assessed by employing QUENCHER approach. The pulverization treatment was beneficial for lettuce growth, whose length of different organs has been improved at all concentrations. However, it has been very harmful to weeds and in a more important way to monocotyledons, which were totally burned at 30 %, compared to dicotyledons weeds. To allelopathic stress, lettuce developed a defense strategy manifested by a decrease of electrolyte leakage and malondialdehyde content (MDA), an increase in proline content and in polyphenols, flavonoids, flavanols, proanthocyanidins, condensed tannins and carotenoids production. Similarly, a stimulation of the antioxidant activity was recorded, by increasing DPPH free radical-scavenging activity and ferric reducing antioxidant power. For lyase type enzymes (the phenylalanine ammonia-lyase (PAL) and the tyrosine ammonia-lyase (TAL)) activities, an improvement of 25.00 % for the PAL and 38.00 % for the TAL were registered in roots and leaves, respectively. Chlorophyll contents were similarly affected, however the respiration decreased. T. garganica is a species rich in allelochemicals compounds, according to its allelopathic potential. The possibility of using its aqueous extract by spraying shows that it could be an ecofriendly approach to exploit its valuable allelochemicals.

Esparto ( Stipa tenacissima ) is a highly fibrous herbaceous plant. In addition, the fiber properties (suppleness, thinness, and cellulose content) make this plant a valuable raw material for papermaking in terms of both quality and quantity. In Tunisia, esparto is the only source of raw material for papermaking. In this paper, the chemical characteristics (cellulose, hemicelluloses, lignin, extractives, and ashes) of esparto leaves are analyzed in relation to growing conditions and plant biology. Four localized sites in the Kasserine region (central Tunisia) are examined. The chemical properties of esparto fibers vary significantly with site and season. In fall, esparto leaves contain more cellulose (46.4%) than in other seasons. In winter, esparto leaves have lower cellulose content (43.3%) and higher extractive content. The pulp properties across seasons indicate that pulp yield and strength properties are superior when leaves are harvested in fall.

a b s t r a c t Esparto fibers are cellulose-based fibers extracted from esparto (Stipa tenacissima) leaves. Morphologi- cal characteristics (length, width, and coarseness) of esparto fibers are analyzed in relation to growing conditions and plant biology. Seven localized sites in Kasserine in central western Tunisia are examined. The analysis of variance showed that all investigated characteristics vary significantly with site, season, and leaf level. Leaves reach minimum level in winter and maximum level in fall. Fiber differentiation is closely related to the vegetative cycle. Fibers are short and wide at the leaf base (basal level) and grow longer and thinner above the leaf. Results on the raw material (esparto leaves) were confirmed by results on esparto pulp.

The chemical composition of the essential oils from leaves and stems of Psidium guajava, grown in Tunisia were determined by gas chromatography coupled to mass spectrometry GC–MS. Twenty-one compounds were determined. The major compounds identified in the oil of the stems were α-humulene (10.93%), Germacrene D (16.79%) and Valerenol (10.62%), whereas leaf oil was dominated by Veridiflorol (36.4%) and Trans-caryophyllene (5.9%). The yield of the oil was 0.66% (v/w).