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Articles by Ali Tekitek
Total Records ( 6 ) for Ali Tekitek
  Radhouane Chaffai , Ali Tekitek and Ezzedine El Ferjani
  Thin layer chromatography analysis of organic acids from maize plants supplied with Al or Zn (500 and 1000 μM) is reported here to elucidate the role of organic acids in heavy metal sequestration. Organic acids detection reveals three spots in root extracts, corresponding to malonic (Rf 0.25), fumaric (Rf 0.33) and salicylic acid (Rf 0.78). Moreover, this analysis indicate the spots in shoot extracts corresponding to tartaric (Rf 0.17), malonic (Rf 0.26), malic (Rf 0.33), succinic (Rf 0.44) and salicylic acid (Rf 0.75). Al or Zn treatments generated very intense spot (Rf 0.75) that increased in intensity in root and shoot extracts, as the concentration of Al or Zn increased. TLC analysis revealed differences in spot intensities between the Al and Zn-treated plants. In roots, malonic acid accumulates more with Zn than with Al, in contrast to the shoots. In shoots Zn treatment at 500 μM caused a more increase in intensity of spot corresponding to malate, whereas, salicylic acid accumulation was much higher in the Zn-treated extracts at 1000 μM. Together, we hypothesize that organic acids may be involved in Al or Zn sequestration. The observations that Al generally produced more increase than Zn in the spot intensity in root and shoot extracts, suggest that organic acids are more involved in Al than in Zn detoxification.
  Radhouane Chaffai , Ali Tekitek and Ezzedine El Ferjani
  This study focuses on the comparative effects of copper and cadmium on the organic acid content and exudation in maize (Zea mays L.). We have also discussed the role of organic acids in copper and cadmium tolerance. The maize seedlings were grown in hydroponics for 8 days and then treated with 100 μM copper or cadmium for 4 days. The copper reduced more than cadmium root fresh wt and shoot dry wt, while Cd had more decreasing effect on root dry wt. Analysis of organic acids in root exudates showed that citrate exudation was not affected by both metals, suggesting that root exudation was not involved in copper or cadmium tolerance in maize. This prompted us to investigate the role of organic acids in internal tolerance mechanism. Total organic acids were decreased in roots but remained unchanged in shoots of Cu and Cd-treated plants. However, malate content decreased substantially in roots by 68 and 53%, respectively with Cu and Cd. The marked increase in the content of citrate with both metals in roots, as well as in those of malate with Cu and citrate with Cd in shoots, underlined the main role of these organic acids in Cu and Cd tolerance in maize.
  Radhouane Chaffai , Mohamed Anis Elhammadi , Tini Nouhou Seybou , Ali Tekitek , Brahim Marzouk and Ezzedine El Ferjani
  The fatty acid composition and the polar lipid profiles are examined in maize (Zea mays L., cv. Alistrong) treated with 100 μM Cd. In roots, analysis of fatty acid composition reveals a general pattern of increase in the unsaturation level of most polar lipid classes, as indicated by the Double Bond Index (DBI). The results also include no alteration of total fatty acid, phospholipid (PL) and Steryl Lipid (SL) contents, but glycolipids (GL) were substantially increased. In shoots, the double bond indices of phosphatidylcholine (PC) and phosphatidylglycerol (PG) were decreased, whereas those obtained from MGDG, DGDG and SQDG showed an opposite response. The PG and MGDG content in shoots were markedly decreased by about 78 and 65%, respectively, indicating that the Cd toxicity caused severe damage to the structure and function of photosynthetic membranes. The increase of the malondialdehyde (MDA) content in roots indicates an oxidative stress, which can be involved in mediating compositional membrane alterations.
  Radhouane Chaffai , Ali Tekitek and Ezzedine El Ferjani
  Maize seedlings were grown in hydroponic nutrient solutions containing 0, 20, 50, 100, 250, 500 and 1000 μM Al(NO3)3.9H2O. The effect of aluminum on growth parameters and lipid composition of maize organs are studied. The results showed that Al inhibited dramatically root growth. Morphological symptoms characteristic of Al toxicity were observed in roots. The Al reduced significantly the fresh and dry matter production. Analyze of the lipid content showed a decrease in phospholipids in roots and shoots particularly at 1000 μM. Moreover, Al affected glycolipids in roots without any changes in shoots. The steryl lipids did not undergo variations. The increase of SL/PL ratio in roots and shoots point out elevated lipid membrane fluidity under Al stress. All the changes in lipid content were essential to restore optimal membrane properties for continuous growth under Al stress.
  Mohamed Anis Elhammadi , Radhouane Chaffai , Ali Tekitek and Ezzedine El Ferjani
  Fifteen-old sunflower (Helianthus annuus L.) plants on hydroponic culture were treated with 75 μM Cd. After 3 days of Cd exposure, a decrease in growth parameters (root and stem length and leaf area) was observed. In extracts of Cd-treated roots, gel-filtration chromatography detected one Cd-binding peptide designated PC-Cd complex, with an apparent Mr of 17.8 kDa. In response to Cd, the roots exhibited a higher accumulation of non protein thiols (NPTs) compared with control plants. Moreover, phytochelatin (PC) levels, estimated from the difference between total NPTs and glutathione (GSH), increased significantly, raising the possibility that PCs play a significant role in heavy metal detoxification. The higher PC concentrations were accompanied by lower GSH concentrations.
  Radhouane Chaffai , Ali Tekitek and Ezzedine El Ferjani
  Maize seedlings were grown in hydroponic nutrient solutions and treated for four days with 100 μM CuSO4 or Cd(NO3)2. The effects of copper and cadmium on growth parameters and lipid composition of maize organs were studied. The results showed that copper reduced more significantly than cadmium the fresh and dry matter production at the aerial part of the plant. The two metals were found to be localized in major part in roots. We focus on the soluble and cell wall fractions of these metals. Hence, the soluble fraction of Cd was greater than that of copper. By contrast, the cell wall fraction of Cu was more significant than that of Cd. Results showed that glycolipids were more affected than phospholipids and steryl lipids. Thus, copper reduced more significantly the glycolipids content in roots and shoots. Moreover, we have suggested that the increase in MDA content in roots by copper could be the result of membrane lipoperoxidation.
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