Résumé
This investigation was carried out to study the effect of some fertilizers and growth regulators separately and the interaction between them, on growth, alkaloidal concentration and yield of Catharanthus roseus plant. All the fertilization levels increased plant height, number of leaves and branches per plant, dry weight of leaves and roots per plant as well as alkaloidal concentration. The growth regulators used were gibberellin, cycocel and ethrel. Gibberellin at 100 ppm markedly increased the vegetative growth characters, alkaloidal concentration and yield in the different plant organs. Significant increase in these characters resulted from the combined treatment between the high fertilization level [N300 P150 K75 kg/feddan] and the different concentration of gibberellin and cycocel. On the other hand, reduction in these characters was observed with the combined treatments between ethrel concentrations and different fertilization levels