الفهرس 
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Abstract
Biotic and abiotic stress in crops are a major hurdle in attaining potential yield worldwide. Salinity and Fusarium Wilt are among the most important abiotic and biotic stress effect the crops specially rice and wheat. In the present study, we aimed to assess the effects of exogenous Si ions (NaSiO3) or silica nanoparticles (extracted from rice straw) application on rice and wheat plants and their calli growth under saline conditions and Fusarium wilt infection conditions. The results showed: Decreease in pigments and soluble carbohydrate in rice and wheat plants under stress, this decrease was significant in the non treated plants and Nanosilica treated plants but non significant in silica ions treated plants. Increase in Plasma membrane permeability, lipid peroxidation, free amino acids, Na+ , shikimic acid H2O2 and Abscisic acid in the samples under stress, this increase was in high ratio in the non treated samples (rice and wheat plants and calli) and Nanosilica treated samples but in low ratio in silica ions treated samples and decreased with time. Increase in antioxidant enzymes (Super oxide dismutase, catalase, poly phenol oxidase, soluble and cell wall bound peroxidase) activity, non enzymatic antioxidant content (Phenols (soluble and cell wall bound) and proline), protein, jasmonic acid, Ca+2 , Cl- , K+ and Si+4 content of the samples under stress, this increase was in the non treated samples and Nanosilica treated samples in low ratio and decreased with the increase in the time exposed to stress but in silica ions treated samples was in high ratio and increased with the time. Appearance new protein bands appeared in rice and wheat plants and calli. Relative expression of the two genes in rice (Oryza sativa)OsLsi1 and OsLsi2and in wheat (Triticum aestivum)TaLsi1 and TaLsi2 in the roots affected by the silicon treatment as the expression of the two genes decreased, while in case of the Nanosilica treatment nearly no change occurs in the expression of the two genes compared to the control. In case of salt stress or in case of the Fusarium infection the silicon treated plants showed the higher expression rate of the two genes followed by the Nanosilica, while incase of the non treated plants the expression of the two genes was so low.