Over at his new Photonist blog, physicist-turned-journalist David Harris has a fascinating breakdown of a recent study that attempted to measure biomagnetism in plants. How crazy is that? Not as crazy as you might guess. Humans and animals have small magnetic fields, after all. There's good reason to suspect that plants would have them, too. The study is even more interesting because it involves the corpse flower—a favorite of plant of random-fact purveyors everywhere, thanks to its Hollywood set-design looks, rotting-flesh smell, and infrequent blooming habits.
How small are these fields? The average magnetic field at the surface of the Earth is about 1 gauss. That is the field that makes your compass swing about to align with north. Magnetic fields from activity in the human heart have been measured at about 1 microgauss, one millionth of the Earth's field. Human brain activity has been measured at about 1 nanogauss, 1000 times smaller again.
Are all plants the same? Not at all. But the physicists decided to use something quite exotic to enhance their chances of measuring the field. They decided to look at Amorphophallus titanum, the Titan Arum. It's a tuberous plant native to Indonesia and has the unusual characteristics of only flowering every few years, the flowering lasting for about 12 hours, and the the odor emitted upon flowering is described by the physicists as "cadaverine and putrescine." Indonesians call it the bunga bangkai, or corpse-flower. The reason why the Titan Arum seems potentially interesting is that it has this very rapid activity when it flowers, and there happened to be one in Berkeley about to flower when the scientists were looking at doing the study. So much is going on inside the plant that there should be lots of movement of ions, thereby increasing the magnetic fields generated. A model of the ionic motion suggested fields of up to 30 microgauss.
So just tell us, what did they measure?! The physicists found that the magnetic fields coming from the plant were less than 0.6 microgauss while their model suggested fields of up to 30 microgauss. Clearly the model doesn't work well but it is also a remarkably small field. It could be signficantly smaller than that limit but there was too much magnetic noise around to know for certain.
If you're feeling let down, here, don't. Science is still interesting, even when it doesn't yield the predicted results. Either way, we've learned something important about the world. Better yet, this single study opens up whole new avenues of research. As Harris points out in his write-up, the next step isn't admitting defeat—it's seeing what kind of magnetic fields can be detected around much smaller active plants, such as the sensitive plant, which folds up its leaves when touched. And there's also another question begged here: If plants really don't have very strong magnetic fields, relative to animals and humans, why is that the case? How do we benefit from our magnetic fields, and why don't those benefits extend to plants?
Thanks to Phil Marshall!
