The plasmodium of Physarum polycephalum reacts to direct current by migration toward the cathode. Cathodal migration was obtained upon a variety of substrata such as baked clay, paper, cellophane, and agar with a current density in the substratum of 1.0 µa./mm.2 Injury was produced by current densities of 8.0 to 12.0 µa./mm.2 The negative galvanotactic response was not due to electrode products. Attempts to demonstrate that the response was due to gradients or orientation in the substratum, pH changes in the mold, cataphoresis, electroosmosis, or endosmosis were not successful. The addition of salts (CaCl2, LiCl, NaCl, Na2SO4, NaHCO3, KCl, MgSO4, sodium citrate, and sea water) to agar indicated that change of cations had more effect than anions upon galvanotaxis and that the effect was upon threshold values. K ion (0.01 M KCl) increased the lower threshold value to 8.0 µa./mm.2 and the upper threshold value to 32.0 µa./mm.2, whereas the Li ion (0.01 M LiCl) increased the lower threshold to only 4.0 µa./mm.2 and the upper threshold to only 16.0 µa./mm.2 The passage of electric current produced no increase in the rate of cathodal migration; neither was there a decrease until injurious current densities were reached. With increase of subthreshold current densities there was a progressive decrease in rate of migration toward the anode until complete anodal inhibition occurred. There was orientation at right angles to the electrodes in alternating current (60 cycle) with current density of 4.0 µa./mm.2 and in direct current of 5.0 µa./mm.2 when polarity of current was reversed every minute. It is concluded that the negative galvanotactic response of P. polycephalum is due to inhibition of migration on the anodal side of the plasmodium and that this inhibition results in the limitation of the normal migration of the mold to a cathodal direction. The mechanism of the anodal inhibition has not been elucidated.
[1]
A. Cohen.
Nutrition of the Myxomycetes. I. Pure Culture and Two-Membered Culture of Myxomycete Plasmodia
,
1939,
Botanical Gazette.
[2]
L. V. Heilbrunn,et al.
The Electric Charge of Protoplasmic Colloids
,
1939,
Physiological Zoology.
[3]
F. Howard.
THE LIFE HISTORY OF PHYSARUM POLYCEPHALUM
,
1931
.
[4]
F. W. Bancroft.
On the influence of the relative concentration of calcium ions on the reversal of the polar effects of the galvanic current in paramecium
,
2009,
The Journal of physiology.
[5]
W Seifriz.
A theory of protoplasmic streaming
,
1937,
Protoplasma.
[6]
J. Tobias,et al.
Electrically induced polar changes in viscosity in the hyaline protoplasm of elodea with observations on streaming and plastid charge
,
1950
.
[7]
A. Watanabe,et al.
^|^Uuml;ber die negative Galvanotaxis der Myxomyceten-Plasmodien
,
1938
.
[8]
P WEISS,et al.
Experiments on cell and axon orientation in vitro; the role of colloidal exudates in tissue organization.
,
1945,
The Journal of experimental zoology.
[9]
P. de Bruyn.
Theories of Amoeboid Movement
,
1947,
The Quarterly review of biology.
[10]
W. Camp.
The Structure and Activities of Myxomycete plasmodia
,
1937
.
[11]
W. F. Hahnert.
A Quantitative Study of Reactions to Electricity in Amoeba proteus
,
1932,
Physiological Zoology.
[12]
I. Lorch,et al.
Folding and Unfolding of Protein Molecules in Relation to Cytoplasmic Streaming, Amœboid Movement and Osmotic Work
,
1950,
Nature.