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Plant Physiology 44:1383-1392 (1969)
© 1969 American Society of Plant Biologists

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Articles

Effects of External Cations and Respiratory Inhibitors on Electrical Potential of the Xylem Exudate of Excised Corn Roots 1

Robert F. Davis2 and N. Higinbotham

a Department of Botany, Washington State University, Pullman, Washington 99163

Glass capillary microelectrodes were used to study the electrical potential difference (PD) between the xylem exudate of excised corn roots, Zea mays L. Golden Bantam hybrid, and the external solution. A survey of the effects of various ions on the PD was made. With 1 mM single salt solutions, the PD was between 25 and 50 mv, exudate negative. The PD responded to concentration differences in single salt solutions of K+, Na+, and Ca2+ in a manner suggestive of cation selectivity and cation diffusion potentials. With Ca2+ present, the PD was insensitive to concentration changes of other cations. Substitution of NO3– for Cl– in K+ solutions increased the PD by 2 to 5 mv, although in general the PD showed little response to anion concentration changes. The PD was partially abolished by cyanide. The remaining fraction of the PD was sensitive to concentration changes in external K+, and we postulate that the PD is the result of both a diffusion potential and an electrogenic pump.

2 Present address: Laboratory of Neurophysiology, Department of Neurology, College of Physicians and Surgeons of Columbia University, New York, New York.

1 This investigation was supported by NSF grants G9560 and GB5117X to Dr. N. Higinbotham.






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Copyright © 1969 by the American Society of Plant Biologists