Leila Chaari

Bio: Leila Chaari is an academic researcher from University of Sfax. The author has contributed to research in topics: Adsorption & Organic matter. The author has an hindex of 6, co-authored 13 publications receiving 139 citations.

Effect of phosphogypsum on growth, physiology, and the antioxidative defense system in sunflower seedlings

Abstract: Phosphogypsum (PG) is the solid waste product of phosphate fertilizer production and is characterized by high concentrations of salts, heavy metals, and certain natural radionuclides. The work reported in this paper examined the influence of PG amendment on soil physicochemical proprieties, along with its potential impact on several physiological traits of sunflower seedlings grown under controlled conditions. Sunflower seedlings were grown on agricultural soil substrates amended with PG at rates of 0, 2.5, and 5 %. The pH of the soil decreased but electrical conductivity and organic matter, calcium, phosphorus, sodium, and heavy metal contents increased in proportion to PG concentration. In contrast, no variations were observed in magnesium content and small increases were recorded in potassium content. The effects of PG on sunflower growth, leaf chlorophyll content, nutritional status, osmotic regulator content, heavy metal accumulation, and antioxidative enzymes were investigated. Concentrations of trace elements in sunflower seedlings grown in PG-amended soil were considerably lower than ranges considered phytotoxic for vascular plants. The 5 % PG dose inhibited shoot extension and accumulation of biomass and caused a decline in total protein content. However, chlorophyll, lipid peroxidation, proline and sugar contents, and activities of antioxidant enzymes such as superoxide dismutase and catalase increased. Collectively, these results strongly support the hypothesis that enzymatic antioxidation capacity is an important mechanism in tolerance of PG salinity in sunflower seedlings.

Changes in Soil Macronutrients after a Long-Term Application of Olive Mill Wastewater

Abstract: The land spreading of olive mill wastewater (OMW) derived from olive oil production can represent a suitable option to enrich and maintain agriculture soils under south Mediterranean climates. Therefore, OMW spreading field may represent a low cost contribution to crop fertilization and soil amendment. The main objective of this study was to investigate the long-term effects of raw OMW application on soil macronutrients and phenolic compounds dynamics. The results showed that regular application of three doses: 50, 100 and 200 m3·ha-1 of OMW for nine successive years increased the soil electrical conductivity significantly (p ≤ 0.05%) with the increase of OMW rates at the depth 0 - 20 cm. The pH variations were not detected after ten months of the spreading date. Furthermore, soil sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) values were substantially affected by OMW salinity. The soil organic matter (SOM) increased from 0.068% observed for the control sample to 0.2%, 0.34% and 0.48%, respectively, with the increase of OMW rate in the top layer (0 - 20 cm). The potassium, phosphorus and nitrogen increased gradually with the OMW application dose. The Ca2+ contents on soil decreased with the spreading of OMW rate, as referred to control. In addition, the phenolic compounds variations were not proportional to doses applied and its levels remained high as compared with the control essentially on top layers (0 - 40 cm). This practice should be beneficial to organic farming and is an alternative solution to direct spreading of raw OMW on soil.

Ecophysiological responses of almond ( Prunus dulcis ) seedlings to cadmium stress

Abstract: Almond (Prunus dulcis L.) seedlings were exposed to 0, 25, 50, 100 and 150 μM of CdCl2 in a solution culture under controlled conditions. The effects of cadmium (Cd) exposure on almond seedlings growth, stomatal architecture, gas exchange and physiological parameters were investigated. Under cadmium stress conditions, significant decrease in fresh and dry weight, length of shoot and chlorophyll content were observed. Stomatal conductance, transpiration and net photosynthetic rates were generally depressed by Cd stress, despite stomatal frequency values and stomatal pore size remained unchanged. Exposure to Cd severely restricted the starch content and increased soluble sugars.

Effects of cadmium on lipids of almond seedlings (Prunus dulcis)

Abstract: Background: Cadmium uptake and distribution, as well as its effects on lipid composition was investigated in almond seedlings (Prunus dulcis) grown in culture solution supplied with two concentrations of Cd (50 and 150 μM). Results: The accumulation of Cd increased with external metal concentrations, and was considerably higher in roots than in leaves. Fourteen days after Cd treatment, the membrane lipids were extracted and separated on silica-gel thin layer chromatography (TLC). Fatty acid methyl esters were analyzed by FID-GC on a capillary column. Our results showed that Cd stress decreased the quantities of all lipids classes (phospholipids, galactolipids and neutral lipids). Galactolipid, phospholipid and neutral lipid concentrations decreased more in roots than in leaves by Cd-treatment. In almost all lipid classes the proportion of palmitic acid (16:0), linoleic (18: 2) and that of linolenic (18: 3) acid decreased, suggesting that heavy metal treatment induced an alteration in the fatty acid synthesis processes. Conclusions: In conclusion, our results show that the changes found in total fatty acids, in the quantities of all lipids classes, and in the in the profiles of individual polar lipids suggest that membrane structure and function might be altered by Cd stress.

Evolution of several soil properties following amendment with olive mill wastewater

Abstract: Olive mill wastewater (OMW) is the main waste product of the olive oil industry and is characterized by high salinity and high organic matter content. Until today, in several olive oil-producing countries, untreated OMW is pumped into agricultural land with potential adverse effects on soil properties. The main objective of this study was to investigate the effects of OMW application on soil physicochemical proprieties. Three OMW levels (50, 100 and 200 m3 ha−1 year−1) were applied over eight successive years. Electrical conductivity, pH, total phosphorus and total nitrogen were studied at different soil depths. Results showed that OMW infiltration caused a modification of soil physicochemical characteristics. The most important effects on soil composition included a significant increase in P and N availability, which enhanced soil fertility in the OMW-treated soil.