Cacti are among the most important and diverse plant families cultivated worldwide for various purposes, including food, medicine, cosmetic, and ornamental. To investigate the growth and physiological changes of Opuntia cylindrica under the treatment of auxin (IBA), cytokinin (Kin), and gibberellin (GA) hormones in concentrations of 250, 500, and 1000 mg/L, this study was conducted in a completely randomized design in the greenhouse of Islamic Azad University, Gorgan branch in 2020. The IBA treatment not only did not cause a significant change in the fresh weight (FW) and height, but also had no significant effect on the content of pigments, sugar, soluble protein, and phenolic compounds except flavonoids, the activity of phenylalanine ammonia-lyase (PAL) and superoxide dismutase (SOD) enzymes. But the treatment of cactus with Kin was caused a significant increase in FW, content of soluble protein, phenolic compounds, and increase the activity of PAL, SOD, and peroxidase (POD) enzymes. GA treatment caused a decrease in FW by 14 and 23%, a significant decrease in the content of pigments Chl. a by 31 and 70% and Chl. b by 37 and 68% and POD enzyme activity by 60 and 50% at 500 and 1000 mg/L, respectively. While the content of phenolic compounds and the activity of PAL and SOD enzymes were significantly enhanced. It seems that Kin at the concentrations of 500 and 1000 mg/L was the best treatment for reinforcement of the growth of O. cylindrica with high phenolic and antioxidant capacity. On the other hand, the decrease in FW and the content of chlorophylls in plant treated with GA, indicated the presence of stress in the plant, and the increase in the content of phenolic compounds and the activity of antioxidant enzymes specially at concentrations of 500 and 1000 mg/L probably moderated the stress.
