Effect of Nitrogen and Salicylic Acid on Growth and Alkaloid Content in Catharanthus roseus L.

In order to evaluate effect of adding four different levels of nitrogen (0, 60, 120, and 180 kg N ha-1), and foliar spraying of salicylic acid at three different concentrations (0, 75, and 150 mg L-1) on the growth characteristics , leaf content of vinblastine and vincristine alkaloids of violet (Catharanthus roseus L.), a pot experiment was conducted using a completely randomized design with three replicates, during the 2024-2025 growing season in the wood canopy of the College of Agriculture, Al-Muthanna University, located in southern Iraq. Results showed that the plants treated with (180 kg N ha-1) were significantly superior, giving them the highest averages in the characteristics of plant height (61.99 cm), branches number (19.31 branch plant-1), number of leaves (228.1 leaf plant-1), dry weight of shoot (13.76 g plant-1), dry weight of roots (2.85 g plant-1), leaf content of total nitrogen (4.05% ), leaf content of vinblastine alkaloid (6.15 ppm) and of vincristine alkaloid (8.10 ppm), while the fertilizer level (120 kg N ha-1) had a significant effect on the treated plants in the two traits of leaf area and dry leaf weight, giving the highest values (328.5 dm2 plant-1 and 7.21 g plant-1), respectively. The results also showed that plants sprayed with salicylic acid at a concentration of 150 mg L-1 significantly outperformed all studied traits and gave the highest values in plant height. (59.99 cm), number of branches (17.21 branch plant-1), number of leaves (226.0 leaf plant-1), leaf area (325.0 dm2 plant-1), dry weight of leaves (6.94 g plant-1), dry weight of shoots (11.92 g plant-1), dry weight of roots (2.83 g plant-1) leaf content of total nitrogen (3.98 %), leaf content of vinblastine alkaloid (6.07 ppm) and vincristine alkaloid ( 8.02 ppm).