Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Agricultural Botany

The present study was conducted to investigate the effect of foliar application of 24-epibrassinolide (EBL) and spermine (Spm) on growth, yield, chemical constituents and the activity of antioxidant enzymes in wheat plants subjected to drought stress conditions. Wheat plants of cv. Giza 168 were subjected to well-watered conditions and drought stress conditions (75% and 50% of field capacity) with and without (0.5 oM EBL+100 oM Spm) foliar application at 45 and 75 days after sowing during two successive seasons 2013/2014 and 2014/2015. Drought stress significantly reduced relative water content (RWC), membrane stability index, concentration of total chlorophylls, total crude protein, growth, and yield of wheat plants, particularly under 50% of field capacity. However, foliar application (0.5 oM EBL+100 oM Spm) significantly improved the above parameters in drought stressed wheat plants. Moreover, drought stress significantly increased lipid peroxidation, electrolyte leakage, concentration of total sugars, total free amino acids, glycinebetaine and proline in wheat plants. However, lipid peroxidation and electrolyte leakage were significantly decreased in stressed plants treated with foliar application, meanwhile, concentration of total sugars, total free amino acids, glycinebetaine and proline were significantly increased. The activity of antioxidant enzymes; superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase, were slightly increased in response to drought treatments, while they significantly increased in response to foliar application in drought stressed wheat plants

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