EN
Cultures of Penicillium claviforme were grown in a magnetic field (60-70 mT) for 12 days under constant light or constant darkness. In light, the magnetic field affected the length of the rhythm period, which was at first somewhat shortened and later prolonged (24 h —> 24 h —> 36 h —> 36 h). In darkness, activation of the biological clock was manifested in the rhythm of the formation of coremia rings. The period of induced rhythm was different from that induced in light, representing a multiple of the 24 h period (96 h —> 96 h —> 96 h). The magnetic field distinctly affected the morphology of the newly formed coremia, which were identical in light and in darkness. In the applied conditions the magnetic field replaced the inductive effect of light, activating the expression of the biological clock in darkness. This is the first time that a magnetic field has been used to replace the inductive effect of light.