ve seasons, 2012 and 2013 in a private orchard in Barshom vallage located at El-Kalubia Governorate Egypt. Washington Navel Orange trees (Citrus Sinensis) budded on sour orange rootstock (Citrus aurantium, L.) were 7- years- old and planted at 5 x 5 meters under basin irrigation system. This investigation aimed to study the effect of selenium (Se) levels (0, 20, 40, 80 and 160 ppm)  as foliar spray on growth, yield, fruit quality, leaf mineral content and enzymes activity of Washington Navel orange trees. The obtained data showed that, selenium had a significant promotive effect on growth, yield, fruit quality, leaf mineral content and enzymes activity of Washington Navel orange trees. Results indicated that treatment of Se at 40 ppm gave the highest significant results, whereas, treatment 160 ppm gave the highest fruit selenium content.

Se, Selenium; ROS, Reactive oxygen species; APX, Ascorbate peroxidase; CAT, Catalase; PAL, Phenylalanine ammonia-lyase; EDTA, Ethylenediamine tetra acetic acid; MDA, Malondialdehyde; POD, Peroxidase; PVP, Polyvinylpyrrolidone; SOD, Superoxide dismutase; TBA, Thiobarbituric acid; TCA, Trichloroacetic acid; NBT, Nitroblue tetrazolium; P5CR, ∆1-Pyrroline-5-carboxylate reductase; P5CS, ∆1-Pyrroline-5-carboxylate synthetase. OAT, Ornithine-δ-aminotransferase; P5CDH, ∆1-Pyrroline-5-carboxylate dehydrogenase and PDH, Proline dehydrogenase; Poly acrylamide gel electrophoresis (PAGE)   ABSTRACT   Selenium (Se) is not an essential nutrient for higher plants. Although, it is able to induce stress tolerance in many plant species. The present study was carried out to investigate the ability of Se to promote the tolerance of cucumber seedlings to salinity stress and to identify some biochemical parameter associated with Se–induced resistance in cucumber seedlings. Plants were irrigated with 2000 ppm NaCl after treatment with 1ppm Se for two weeks and samples collected after 7 days from started salt-treatment. The biochemical changes due to treatment with Se and /or NaCl were monitored by determination of lipid peroxidation (LPO), proline, phenolic compounds and percentage of electrolyte leakage (EL) from plant tissues. Moreover, the activities of peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD) and phenylalanine ammonialyase (PAL) were determined. The treatment of cucumber seedling with salinity (2000 ppm NaCl) in the presence or absence of selenium caused a remarkable elevation in free proline concentration and the level of phenolic compounds. Salinity stress caused a high level of lipid peroxidation which led to increase the percentage of electrolyte leakage from plant tissues. Se treatment caused a significant reduction in electrolyte leakage and malondialdehyde concentration of cucumber seedlings. The specific activities of antioxidant enzymes (POD, SOD, and APX) and PAL were significantly increased by the treatment with NaCl. Also, Se caused a significant elevation in the specific activities of POD, CAT, SOD, APX and PAL in cucumber seedlings grown under salt stress condition. On the other hand, Se caused a significant decrease in SOD activity in cucumber seedlings grown in non-salty condition. The isoenzymes pattern of POD demonstrated that peroxidase was up-regulated by Se either in control or NaCl-treated seedlings. The results concluded that Se induce six POD isoenzymes in cucumber seedlings. Se reduces and overcomes the oxidative injury caused by salinity stress. Moreover, the protective effect of Se against salinity stress may be carried out through a mechanism included activation of PAL which is responsible for phenolic compounds biosynthesis. The accumulation of these phenolic compounds in Se-treated seedling leads to a high activities of antioxidant defensive enzymes and increase the tolerance level towards salinity stress.

Selenium is a trace element essential in animal nutrition and exerts multiple actions related to enhance animal production, fertility, immune response and antioxidant defense system of chickens. The aim of the present study is investigating the benefit effects of selenium nanoparticles (SEN) in-ovo injection on productive performance, express stimulate antioxidant defense system and immune response of hatched chicks.  A total of 210 broiler breeder eggs ( Habbard Star-Bro) were divided into three in-ovo injection treatment groups,( 0, 5 and 10 ppm SEN) and incubated. Hatchability traits , productive performance,  biochemical profile, antioxidant status and immune response of hatched chicks were estimated. Results indicated significant increase in HDLcholesterol, T3, GSR, GSH, IGA, IGM and IGG as affected by in-ovo inoculated SEN levels. However feed conversion ratio, triglycerides and MDA significantly decreased by in-ovo treatments. No significant alternations were recorded in hatched chicks weight, feed intake, body weight, body weight gain, carcass characteristics, and serum levels of protein fractions, cholesterol, LDL- cholesterol, ALT, AST, ALP, uric acid, creatinine and glucose in in-ovo treated groups compared with the control one. It is summarized that, in-ovo inoculation of different levels of SEN can improve feed conversion ratio, lipid profile, antioxidants status and immunity of  broiler hatched chicks.