Coleus forskohlii Briq., a medicinal plant from the Lamiaceae family, has been utilized worldwide to treat various disorders. The primary active compound in this plant is forskolin, a diterpene that ac cumulates in its rhizome. This study aims to assess the in vitro culture of C. forskohlii by investigat ing the effects of different concentrations of auxin hormone (1 and 2 mg L-1) and zinc oxide (ZnO) nanoparticles (10 and 20 ppm) as elicitors on biometrical traits related to rooting as well as forskolin content. Each treatment was replicated three times, and the results were analyzed using SPSS version 20. We observed that most traits examined decreased in samples treated with 1 mg L-1 of IAA hor mone. In contrast, samples treated with 2 mg L-1 of IAA exhibited the highest values compared to the control samples. However, the differences in the examined characteristics among the samples were not statistically significant. Notably, the number of adventitious roots and the forskolin content increased with each increment in IAA hormone concentration. In plants treated with 2 mg L-1 IAA hormone, all measured biometrical traits surpassed those of the control group as well as those of samples co-treated with IAA (2 mg L-1) and ZnO nanoparticles (10 and 20 ppm). The forskolin content followed a similar trend. However, the lowest values for these traits were observed in the plants treated with 2 mg L-1 IAA and 20 ppm ZnO nanoparticles. These findings indicate that 2 mg L-1 of IAA hormone significantly impacts both root morphology and phytochemical characteristics compared to 1 mg L-1. Furthermore ZnO nanoparticles at a concentration of 20 ppm exhibited an inhibitory effect on root morphology and forskolin content, which could not be mitigated by treatment with 2 mg L-1 IAA
