Document Type : Original Article
The growth of medicinal plants and biosynthesis of secondary metabolites is influenced by plant growth regulators. In this study we investigated influence offour levels (0, 500, 1000, and 1500 mg l-1) of2-chloroethyltrimethylammonium chloride (Cycocel), a plant growth retardant, on growth parameters and some biochemical parameters of cannabis plants. Cycocel only at 500 mg l-1 decreased shoot length of male plants. The fresh weight of leaves in female plants decreased with 1500 mg l-1Cycocel. The other Cycocel treatments increased the fresh weight of leaves in female and male plants. Root and stem fresh weight of male and female plants showed an increase in most treatments (except for 1500 mg l-1Cycocel). Cycocel at 1000 mg l-1 had enhancing effect on the fresh weight of male and female flowers. Also, the plants treated with Cycocel had a higher content of soluble carbohydrates and protein. Malondialdehyde content was decreased in male and female plants by 500 mg l-1Cycocel treatment. Tetrahydrocannabinol (THC) content increased in male plant leaves under 1000 and 1500 mg l-1Cycocel treatment, but in female plants only 500 mg l-1Cycocel caused an increase in THC content in leaves. While Cycocel decreased cannabidiol (CBD) content in male leaves, in female leaves it increased CBD concentration. In fact, only 500 mg l-1Cycocelled to more CBD content in female flowers while the other treatments declined CBD content in female flowers. The findings showed that the response to Cycocel depended on the sex in cannabis plants. Ineffectiveness of Cycocel in reducing shoot length suggests that cannabis is insensitive to Cycocel as an inhibitor of gibberellin biosynthesis and its application at specific concentrations can be used to improve growth.