Salinity is one of the most important abiotic stresses, especially in arid regions. Such devastating constraint is converted mainly to oxidative burst. Thus, plants have to develop strategies to scavenge salt-related regenerated oxidant molecules. In the present work, fully aged plants derived from two Vitis vinifera L. cultivars, the Tunisian autochthonous tolerant genotype Razegui and the salt sensitive Syrah, were analyzed regarding their short term response to 100 mM NaCl, in hydroponic cultures.The ratio [ASA/ASA ? DHA] was calculated on the basis of the oxidation of ascorbic acid (ASA) into dehydroascorbic acid (DHA) in leaves. Results proved that oxidative stress was generated. This led to the accumulation of malondialdehyde which referred to a lipid peroxidation mainly in the sensitive Syrah. In order to cope with these oxidative disturbances, trans-resveratrol as well as its glucosides trans-piceid and cis-piceid have been de novo synthesized in the sensitive variety. Razegui stilbene concentrations were presented here for the first time and unexpectedly did not show a very important variation during the salt elicitation.
The aroma composition of the grape juice of Khamri, a native variety of Vitis vinifera grown in Tunisia, was investigated for the first time. A total of 27 free and 20 glycosidically bound compounds were identified by gas chromatography-mass spectrometry. According to the obtained results, the aroma compounds were C6 alcohols, benzene compounds, terpenes, acids and norisoprenoids. On the basis of gas chromatography-olfactometry, these compounds were grouped, according to volatiles exhibiting the identical odor quality, into 10 groups of the same character (aromatic series) as a way of establishing an aroma profile for the studied variety. The high glycosidically bound norisoprenoid concentrations and the absence of the bound form of the acids were a positive factor for the Khamri variety potential aroma.
PRACTICAL APPLICATIONSThis article aimed on the identification of the unknown Tunisian grapevine varieties that are very well adapted to the arid conditions and that could have a good quality. The discovery of unknown autochthonous grapevine varieties with good aroma and pomological characteristics could be of great 3 Corresponding
Struvite (MgNH4PO4·6H2O) can precipitate from wastewater thereby recovering both ammonium and phosphorus while simultaneously producing a valuable fertilizer. In the present work, the precipitation of struvite by CO2 repelling at initial constituent ions concentrations in the range between 123.89 and 800 mg L−1 and different airflow rates is investigated. Struvite precipitation is induced by an increase of the solution supersaturation occurring concurrently with the removal of the dissolved CO2 from the solution. The precipitates obtained are characterized by powder X‐ray diffraction and scanning electronic microscopy. For all experiments, struvite is the only phase observed. Whatever the airflow used, the precipitation pH decreases with increasing the initial phosphorus concentration. Struvite precipitates at supersaturations in the range 6–18 and pH in the range 6.5–8.5. High phosphorus removal efficiencies (>70%) are obtained at high struvite supersaturations. The increase in the airflow rate results in a significant decrease in the phosphorus removal efficiency. When the initial phosphorus concentration increases, the particle size distribution becomes monomodal covering a broad range of particle sizes up to 140 µm. This is of utmost importance since larger struvite crystals are easier to separate from the liquid phase and release ammonium and phosphorus from struvite faster, promoting the use of struvite as a fertilizer.
Phosphorus and ammonium can both be recovered in the presence of magnesium through struvite (MgNH4PO4·6H2O) crystallization. The present work aimed to optimize struvite crystallization at turbulent solution flow. Struvite was crystallized by magnetic stirring at different initial phosphorus concentrations between 200 and 800 mg·L−1 and high stirring rates between 100 and 700 rpm. The crystals obtained were analyzed by powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. For all experiments, the only phase detected was struvite. It was shown that for an initial phosphorus concentration of 200 mg·L−1, increasing the stirring rate to 500 rpm accelerated the precipitation of struvite, improved the phosphorus removal efficiency, and obtained larger struvite crystals. A decrease in the phosphorus removal efficiency and smaller struvite crystals were obtained at higher stirring rates. This was attributed to the solution turbulence. The limiting effect of turbulence could be overcome by enhancing the initial phosphorus concentration or by lowering the stirring rate. The highest phosphorus removal efficiency (~99%) through large struvite crystals (~400 μm in size) was obtained for an initial phosphorus concentration of 800 mg·L−1 and a stirring rate of 100 rpm.
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