Effect of Split Time of Nitrogen Fertilizer and Selenium on Activity Antioxidant Enzymes and Flavor Precursors of Edible Onion (Allium cepa L.)

Selenium is an essential element for humans and animals. However, its effects on plants are less well known. In the present study, the effect of different levels of selenium and nitrogen split on activity antioxidant enzymes and flavor precursors of Isfahan yellow iandraces onion was studied.In this experiment, the factors involved the management of nitrogen use in 3 levels including control, total fertilization at the time of transplantation and one-third fertilization recommended at the time of transplantation+ one-third fertilization at the time of bulb initiation+ one-third fertilization at the time of bulb growth, and the second factor is the selenium in 3 levels: 0, 10 and 50 mgL-1 sodium selenate. The results showed that peroxidase activity increased with increasing selenium concentration. Foliar application of selenium with nitrogen split in three steps had a positive effect on the activity of catalase. At all three levels of selenium, total nitrogen, total sulfur and amino acids (serine, cysteine, methionine and glutathione) increased with increasing nitrogen concentration. As the concentration of selenium increased, the total sulfur content decreased, which resulted in a decrease in the amount of amino acids and flavor precursors. The results showed that the combined use of selenium and nitrogen had a positive effect on the amount of antioxidant enzymes, amino acids and onion flavor precursors.