The magnetic field (MF) is considered as a biophysical treatment to change the growth and development parameters. Current research was carried out to evaluate the effect of different intensities of MF (0, 45, 60, 70 and 75 mT) on seed germination and some morphologic and physiologic parameters of Rudbeckia hirta L. in dry and humid conditions for 30 min. Results showed that the MF treatment increased germination percentage of dry seeds more than humid seeds and control. The intensity of 70 mT induced the maximum content of germination of dry seeds (94.5%). The MF decreased the seeds germination rate in both dry and humid conditions, as the control seeds showed the highest germination rate (3.5 days). Investigation of all morphologic traits like plantlet length and vigor index and physiologic (humid and dry weights of plantlet) revealed that the MF caused more induction of growth in these traits than the control. Totally, the use of 70 mT MF on dry seeds for optimum growth and development in Rudbeckia hirta L. is recommended. پرونده مقاله