In this work, the direct influence of magnetic fields on plants is discussed via the ion cyclotron resonance (ICR) theory, the mechanism for the biological action of magnetic fields in the low-frequency region. Wheat seeds (Triticum aestivum) were exposed to a combination of the local geomagnetic field (BDC=20.9 μT) and a sinusoidal (AC) extremely low-frequency magnetic field (BAC=0.1 or 0.3 mT) at one of the three different frequencies, one of which was a resonance frequency for the Ca2+ ions. The persistent exposure to combined static geomagnetic and alternating magnetic fields did not alter the germination of wheat seeds, although under the specified conditions of exposure significant differences in the growth of seedlings were observed. The application of the AC field tuned to the ICR frequency for Ca2+ ions (fAC=16 Hz) did not affect the germination process of wheat seeds but there was an effect on the growth process of the exposed seedlings. The number of emergent seedlings was significantly modified only for BAC=0.3 mT field (increase of 43%), while the fresh weight of 10-day-old seedlings was increased for both treatments (increase of 85% and 80% for 0.1 mT and 0.3 mT fields, respectively). After the exposure to fAC=11 Hz field, exposed seeds produced seedlings with significantly decreased fresh weight (decrease of 27% and 38% for 0.1 mT and 0.3 mT fields, respectively). Wheat seeds failed to respond to fAC=21 Hz fields in any of the seedling emergence parameters measured.