Sowing Seeds in a Magnetic Field

Starch grains are not magnetic in the usual sense - if you held one against your refrigerator it wouldn't stick. But the grains are "diamagnetic," which means they develop a weak magnetic field when other magnets are nearby. The diamagnet's field will naturally oppose that of the nearby magnet - hence the prefix "dia" - so the starch grains will be repelled. Although the effect is weak, this diamagnetic response allows researchers to use magnets to move the starch grains.

"By changing only the internal displacement of the starch grains, we can put one of these two arguments to rest," explains Hasenstein, a professor at the University of Louisiana at Lafayette. "If the starch grains are the gravity-sensing trigger, we should see the flax-seed roots curve along the magnetic gradient. And if the pressure on the cell walls triggers the curvature, we should see no response."

Image courtesy University of Wisconsin-Madison. This plant originally sprouted with the pot upright and was later turned on its side. The new stem growth curved to re-align with gravity.

Infrared cameras will automatically photograph the germinating roots. Regular cameras can't be used because the chamber will be kept completely dark. The darkness allows scientists to know that the seeds are responding to the magnetic fields, not just growing toward a light source.

Don't bother trying this experiment at home with ordinary refrigerator magnets. Only special "high-gradient" magnetic fields will do. Hasenstein's experiment uses magnets about 50 times more powerful than a typical refrigerator magnet. The magnets have ferromagnetic wedges attached to them, which focus a strong magnetic field into a small area. Around that area, the strength of the field tapers off quickly, creating the "gradient" of field strength that moves the starch grains.

High-gradient magnetic fields will be used in two chambers of the experiment, while a third chamber will use a homogeneous magnetic field as a "control."

The lessons learned won't only apply to flax seeds (which were chosen for their small size and their quick, reliable germination). All normal plants have these starch grains, so the results of this experiment will add to our basic understanding of plants in general.

Starch grains or protoplasm? No matter which proves correct, researchers will have lingering questions. For example: "how does the mechanical trigger (e.g., starch grains drifting downward) produce a biochemical response?" BioTube/MFA won't provide all the answers right away, but it is an important first step - one that will teach us something fundamental about the leafy-green life all around us.