Measurements of the bioelectrical potential of a Japanese oak (Quercus crispula Blume) sapling: Effect of the radial distribution of inorganic ingredients within a tree stem on the diurnal change in resting potential

Abstract

This study investigated the relation between the resting potential of a 2-year-old Japanese oak (Quercus crispula Blume) sapling and its physiology, especially the radial transport of water containing inorganic ingredients in the stem using the scanning electron microscope-energy dispersive X-ray microanalyzer (SEM-EDXA) method. The resting potential of a sapling could be monitored continuously with our measuring apparatus. Changes in resting potential were due to the light. The hyperpolarization and depolarization peaks of the resting potential, whose absolute voltage was about 10mV, occurred right after lights-off and lights-on, respectively. The resting potential was found to show periodic responses for each day unit. At night (lights-off), the resting potential tended to depolarize with an increase in tangential strain. On the other hand, during the daytime (lights-on) the resting potential tended to hyperpolarize, depolarize, or show a nearly constant value for the tangential strain. The water containing inorganic ingredients was transported, via transpiration, in both directions between the mature xylem zone and the phloem zone through differentiating xylem cells. This water transport within a tree stem had a significant effect on the diurnal changes in resting potential.