Diamagnetic Susceptibility and Root Growth Responses to Magnetic Fields in<i>Lens culinaris, Glycine soja</i>, and<i>Triticum aestivum</i>

We studied the response of root growth to different magnetic fields and forces. We submitted the seeds of three plant species, Lens culinaris L., Glycine soja Siebold & Zucc., and Triticum aestivum L., which differ in concentrations of paramagnetic (e.g., Fe or Co) and diamagnetic materials (e.g., starchy amyloplasts), to different static magnetic fields and forces. A magnetic field of 176 G reduced root growth of L. culinaris, G. soja, and T. aestivum, 37, 31, and 15%, respectively. A weaker magnetic field of 21 G reduced root growth of L. culinaris and G. soja only 13 and 21%, respectively, whereas it had no significant effect on the cereal T. aestivum. The germinating seeds of L. culinaris and G. soja were less diamagnetic than T. aestivum, and the latter had a smaller paramagnetic component. Since at room temperature, the paramagnetic component was much smaller than the diamagnetic one, the magnetic inhibition of root growth may be linked to the diamagnetic susceptibility, the inhibition being greater for the less diamagnetic materials and for the stronger magnetic forces. These results provide new examples of possible species-specific effects of moderate magnetic fields on plant growth, especially when growth is rapid, such as root growth after germination. We propose a simple hypothesis to relate root growth inhibition with magnetic fields and with the different responses found among species, seasons, and physiological and environmental conditions reported here and in the literature. It is based on a reduced magnetic force acting on the cell biological substances and on the cellular organelles such as amyloplasts, rather than on the cytoplasmic matrix where they are immersed as a consequence of their lower diamagnetic susceptibility. As a result, a nonuniform magnetic field exerts a ponderomotive force on the biological components in the opposite direction to the growing tip. This can result in intracellular magnetophoresis, and can account for inhibition of the root growth rate downwards. This inhibition would be stronger the lower the diamagnetic susceptibility.