Re: plant growth-strong magnetic fields vs diamagnetism/paramagetism

Andrew:

40 Gauss, 4 millitesla (mT) in scientific terms, is a strong static magnetic field compared to the Earth's field (about 0.05 mT), but it is low compared to the fields needed to affect plant growth.

A number of workers have reported that static fields in the 50-500 milliT range affect plant growth, but I don't know of any reports of effects below about 50 mT. Interestingly, many reports suggest that it is the gradient (change in field strength with distance, T/m) that matters, not the field strength itself.

Most of this work is old (from the 1960's) and published in journals that are very hard to find. Two reviews that you might be able to find are:
- RP Mericle et al, Plant growth responses. In: Biological Effects of Magnetic Fields (edited by MR Barnothy), Plenum Press, NY, pp 183-195, 1964.
- NJ Simon, Biological Effects of Static Magnetic Fields, International Cryogenic Materials Commission, Boulder, CO, 1992.

John Moulder
Radiation Biologist
Medical College of Wisconsin