Propagated fluctuations of the electric potential in the apoplasm of Lepidium sativum L. roots.

The electric potential on the surface of the Lepidium sativum L. root apex was recorded by means of six non-polarizable electrodes. Nonevoked fluctuations of the potential with amplitudes below 0.1 mV were observed. The fluctuations could be reversibly inhibited either by ether vapor or by anoxia caused by N2. They did not occur in killed roots. Cross-correlation analysis of the fluctuations from six electrodes located one above another along the 3-mm apical region showed a pattern of time delay which indicates that the fluctuations may be the consequence of signals propagated in the root with a velocity of 3-9 mm · s(-1) in a basipetal direction from the root cap. We hypothesize that the fluctuations are due to signals of an unknown nature propagated along an intrasymplasmic continuous system, the "symreticulum", composed of the cortical ER of individual cells and desmotubules passing through the plasmodesmata.