Magnetic detection of injury-induced ionic currents in bean plants

A superconducting quantum interference device (SQUID) multichannel magnetom eter was used to measure the temporal and spatial evolution of the magnetic field accompanying stimulation by burning and/or cutting of Vicia faba pla nts. These magnetic fields are caused by ionic currents that appear after i njury in different parts of the plant. All measured V. faba plants responde d to the burning stimulation with detectable quasi-d.c. magnetic signals. I n order to measure these signals, a suitable modulation had to be used. The covariance method was applied to analyse the measured data. The results de monstrate a dipolar-like magnetic signal, exponentially decreasing in time, above the cutting type of injury. After the burning stimulation, the magne tically detected activity was concentrated predominantly above the leaves/p etioles and less above the stem. Possible mechanisms for this behaviour are suggested. A comparison with previously known electrical measurements of p lant injury is given.