الفهرس 
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Abstract
SUMMARY
The work in the thesis aimed to study the effect of drought in various intervals of irrigation (30, 50, 70 days of cultivation) on the growth, some related metabolic activities and productivity of wheat plant. Also, the study shed light on the effect of spraying plants with silica nanoparticles with the concentrations (zero, 50 and 100 mg L-1) to track the role that the study could play, and the consequences of plant growth under different levels of drought.
Two field experiments were carried out during winter seasons 2020/21 and 2021/22 at Moshtohor region, Kalubia Governorate, Egypt. The treatments were designed in a split-plot design with three replications. Three water regimes were sorted at random in the master plots while, three silica nanoparticles spraying occupied the sub-plots. Growth characters were measured, and the necessary chemical analyzes were conducted to find out the effect of these treatments on the metabolic processes in wheat leaves plant. In addition, some measurements of the productivity of the wheat plant under study were estimated.
The main experimental results can be briefly summarized in the following points:
1- That all the characteristics of growth (No. days to 50% heading, shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, flag leaf area and No. leaves plant-1) There was a significant decrease in it with the increase in different levels of drought, and this was more evident when the plant was starved for 70 days at different stages of growth. The treatment of plants with silica nanoparticles led to a significant increase in all previous growth characteristics of wheat plants under different drought levels.
2- Increasing the different levels of dehydration showed a clear decrease in the degree of stability of the membranes and a clear increase in the degree of membrane leakage of ions and the peroxidation of fats through increasing the content of malondaldehyde in the tissue of the wheat plant during the vegetative growth stage. When plants were treated with nano-silica, it led to treatment of membrane damage resulting from drought and a decrease in the degree of membrane permeability and lipid peroxidation from (malonaldehyde) in wheat plants. The results also showed that the treatment with silica nanoparticles was more effective at a concentration of 100 mg/L.
3- The increase in the different levels of drought caused a significant decrease in the content of photosynthetic pigments (chlorophyll A, chlorophyll B, carotenoids, and total pigments) in the wheat plant under study when compared with plants not treated with drought (control) during the different stages of growth. It was possible to address the devastating effect of drought on the content of these pigments in wheat plants by spraying the plants with a nano-silica solution during the growth stages compared to plants exposed to drought only or not treated (control).
4- The study showed that the content of soluble, insoluble and total sugars decreased with increasing levels of drought when compared to untreated plants (control) during different stages of growth. The treatment with silica nanoparticles also caused a significant increase in the content of these sugars in plants treated with dehydration, compared to plants treated with dehydration without nanosilica.
5- Increasing the different levels of dehydration showed a clear accumulation in the proline content and a significant decrease in the total protein and total phenol in the wheat plant, especially in the high level of dehydration. The treatment of plants under different levels of dehydration and nano-silica led to a significant decrease in the level of proline and a significant increase in the total protein and total phenol in the wheat plant.
6- The results showed a significant decrease in the activity of the enzyme phenylalanine ammonialase as a result of the dehydration treatment in the grain filling stage of wheat plants. This was accompanied by a significant decrease in the total phenols content. The treatment with silica nanoparticles resulted in a significant increase in the activity of the enzyme phenylalanine ammonialase, with a significant decrease in total phenols in wheat plants compared to plants treated with drought only.
7- Drought stress caused a significant increase in the activities of the enzymes catalase, ascorbate peroxidase, guaiacol peroxidase, and glutathione S-transferase with an increase in drought levels, when compared to plants not exposed to drought in wheat plant, and when treated with nano-silica under drought stress, this led to a significant increase in the activities of each of the enzymes Catalase, ascorbate peroxidase, and guaiacol peroxidase, as well as a significant increase in the activities of the enzyme glutathione S-transferase, when compared to untreated plants in wheat during the growth stage, while the activity of the enzyme glutathione S-transferase decreased by treatment with nanosilica only compared to the control.
8- It was also observed that drought stress of wheat plants caused a significant increase in the activity of the enzyme carbonic anhydrase and nitrite reductase when compared to plants not treated with dehydration, while the treatment of wheat plant under drought conditions with silica nanoparticles led to an accumulation and a significant increase in the activity of enzyme carbonic anhydrase and nitrite reductase when compared to plants treated with drought.
9- Increasing the drought levels caused a decrease in the yield characteristics of the wheat plant (No. spike m-2, spike length, spike weight, seed index and grain yield fed-1) compared with other treatments, and it was found that the treatment with nano-silica at concentration 100 mg L-1 led to an increase in significant in each of No. spike m-2, spike length, spike weight, seed index and grain yield fed-1 compared to other treatments.
10- Increasing drought levels also led to a significant decrease in production components in wheat yield, and when treated with silica nanoparticles, it caused a significant increase in the values of production components compared to plants treated with dehydration.
11- The obtained results were discussed in the light of those recorded by other investigators.