الفهرس 
MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
Three experiments in which 25dayold transplants of lettuce (Lactuca sativa var baladi) were planted in clayloamy soil (2:1 v/v) and fertilized with increasing concentrations of urea (as a foliar spray) either alone or in combination with low (3 mmhos), medium (5 mmhos) or high (7 mmhos) concentration of NaCl, were conducted. All experiments were designed to investigate further the possible effects of using different rates of urea fertilizer in the regulation of growth and development, as well as in the concurrent effects on the endogenous contents of carbohydrates, pigments, nitrogen constituents, proline and glycine amino acid contents, protein banding patterns, photosynthetic activity, nitrogenrelated enzyme activities including urease, nitrate reductase, glutamine synthetase and asparaginase and antioxidant enzyme activities including superoxide dismutase (SOD), ascorbate peroxidase (APO), catalase (CAT) and glutathione reductase (GR), in normal and in variously salinized lettuce plants, at vegetative and adult growth stages. It is of interest to mention that the calculated percent recoveries (improvement) in all growth parameters and in the associated metabolites in the variously salinized lettuce plants foliary sprayed with increasing concentrations of urea fertilizer showed, in general, significant positive values compared with those of control salinized lettuce plants alone. Thus, we can conclude that foliar application of urea to the salinized lettuce plants can partly alleviate the damage effects of salinity on growth and metabolism of lettuce plants. The present results are discussed in relation to the action of foliar spray of urea fertilizer to normal and salt stressed lettuce plants and in the meantime in relation to pervious published work concerned with different mechanisms of action of salinity and of urea fertilization.