الفهرس 
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Abstract
Salinity is a major abiotic factor that limit plant development and productivity world wide. Under salinity, multiple adverse injuries occur, which affect plant growth and development at the physiological and biochemical dimensions. Therefore, many trails and approaches have been attempted to reduce the negative effects of salinity on plant growth and production. The objectives of this study were to synthesize and characterize the physical and chemical properties of Nitrogen, Phosphorus, Potassium nanofertilizers and Silicon nanoparticles, evaluate the impact of the Nano priming of NPK nanofertilizers and silicon nanoparticles on seed germination, and the effect of soil and foliar application of NPK nanofertilizers, soil application of silicon nanoparticles, and salinity on physiological parameters such as, chlorophyll content, enzyme activity such as catalase and peroxidase, nutrients concentration ,soluble protein , proline ,and sugar content in cucumber plants . To achieve these objectives, these experiments were conducted as follows: Seed germination experiment: Cucumber seeds (Cucumis sativus cv. Madaen F1) were soaked in various solutions that represent T0: control (priming in fresh water) , T1 : NPK bulk-fertilizers (bFs), T2: 50% of the NPK bulk-fertilizers dose as a nanofertilizers(nFs), T3: 25% of the NPK bulk-fertilizers dose as a nanofertilizers and T4 : 12.50 % of the NPK bulkfertilizers dose as a nanofertilizers at 25°C for 24 h. The Nano-primed seeds were rinsed with NPK nanofertilizers solution as the first priming experiment. The second priming experiment was seed soaking in different concentrations of silicon nanoparticles (1500, 3000, and 4500 ppm) in addition to seed soaking in distilled water as control. Five seeds were placed on each Petri dish; there were three replicate dishes for each treatment, and then germinated on moist filter paper in Petri dishes at 25oC. Five concentrations of 0 (control), 2.5, 5, 7.5 and 10 dSm-1 sea water were applied to each treatment for 7 days. After 7 days, germination percentage and seedling growth were measured. 1- Increasing salinity levels significantly reduced germination percentage of all priming treatments. This reduction in germination percentage (%) was significantly lower for seeds primed in NPK nanofertilizers compared to ones primed in bulk fertilizers and ones primed in Distilled water and the best treatment was 50% NPK nanofertilizers. The reduction in germination percentage occurred at high salinity levels was due to the harmful effect of salinity on physiological processes which are effective on seed germination. Also, seed priming in silicon nanoparticles solutions significantly decreased the reduction in germination percentage (%) compared to ones primed in distilled water and the best treatment was 4500 ppm of SiNps. 2- Increasing salt concentration reduced the radicle length, plumule length, radicle surface area, radicle reduction /increase (%), seedling fresh and dry weights, however priming in NPK nanofertilizers significantly increased the radicle length, plumule length, radicle surface area, seedling fresh and dry weights compared to seeds primed in NPK bulk fertilizers and ones primed in distilled water. Also, seed priming in silicon nanoparticles solutions significantly decreased the reduction in all growth parameters compared to ones primed in distilled water. 3- Nano priming of cucumber seeds at different salinity levels significantly improved vigor index, salt tolerance index especially at 50% NPK nanofertilizers and silicon nanoparticles (4500 ppm) priming treatment exposed to salinity stress.