Comparative study of the effect of some types of nitrogen fertilizers on growth, alkaloid content and some physiological traits of the ornamental-medicinal plant Agave Americana cv marginata under greenhouse cultivation

In the present study, the effect of three types of nitrogen fertilizers under potting and greenhouse cultivation on growth rate, total nitrogen content, protein, free amino acids and leaf and root alkaloids and leaf nitrate reductase activity in American agave cultivar Marginata was investigated.Fertilizers including urea (46%), NPK compound fertilizer of type 20 20 20, and Dr. Bio biofertilizer (containing Azotobacter) were applied in two concentrations each, and their effects were compared with the effects ofsoil without fertilizer as a control. Increasing fertilizer in all cases, and especially in the case of biofertilizer, reduced the nitrate reductase activity of the leaves and also changed the overall nitrogen content of the root in favor of increasing it in the leaves. Urea increased wet and dry weight, total protein content, free amino acids and leaf and root alkaloids. Biofertilizer significantly increased fresh and dry weight and leaf protein content, fresh weight and content of free amino acids and root protein. This fertilizer had no significant effect on the alkaloid content of leaves and roots. Increasing the NPK fertilizer also increased the fresh and dry weight and free amino acids of the leaves and the content of total proteins and alkaloids in the leaves and roots and decreased the fresh weight and free amino acids of the roots.