The Bioelectric Potentials of Plants and Their Functional Significance: V. Some Daily and Seasonal Changes in the Electrical Potential and Resistance of Living Trees

Continuous records of bioelectric stem potentials have been made throughout a season for three kinds of tree: Ulmus americana L., Pinus resinosa Ait., and Acer saccharum Marsh. Daily measurements of potential and resistance for a 15-month period have also been made on a maple and some direct measurements of current are also given. A yearly rhythm was clearly visible, also daily cycles, and during the growing season cycles of 5-minute frequency. The yearly and daily rhythms have been interpreted in terms of electro-osmosis or streaming potential and seem to be correlated with the transport within the tree. The 5-minute oscillations have been related to cambial growth.