PLANT PHYSIOLOGY , Vol 114, Issue 3 989-998, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Wound-Induced Changes of Membrane Voltage, Endogenous Currents, and Ion Fluxes in Primary Roots of Maize
A. J. Meyer and M. H. Weisenseel
Botanisches Institut I, Universitat Karlsruhe (TH), Kaiserstrasse 12, D-76128, Karlsruhe, Germany
The effects of mechanical wounding on membrane voltage, endogenous ion
currents, and ion fluxes were investigated in primary roots of maize (Zea
mays) using intracellular microelectrodes, a vibrating probe, and
ion-selective electrodes. After a wedge-shaped wound was cut into the
proximal elongation zone of the roots, a large inward current of
approximately 60 [mu]A cm-2 was measured, together with a change in the
current pattern along the root. The changes of the endogenous ion current
were accompanied by depolarization of the membrane voltage of cortex cells
up to 5 mm from the wound. Neither inhibitors of ion channels nor low
temperature affected the large, wound-induced inward current. The fluxes of
H+, K+, Ca2+, and Cl- contributed only about 7 [mu]A cm-2 to the
wound-induced ion current. This suggests the occurrence of a large mass
flow of negatively charged molecules, such as proteins, sulfated
polysaccharides, and galacturonic acids, from the wound. Natural wounding
of the root cortex by developing lateral roots caused an outwardly directed
current, which was clearly different in magnitude and direction from the
current induced by mechanical injury.
