spontaneous electrical activity in coprinus

Biology Department, Washington University, Saint Louis, Mo. 63130, U.s.A.

Spontaneous Electrical Activity in Coprinus

FRANCIS B. FULLER and BARBARA G. PICKARD

With 1 figure

Received January 29, 1972

Summary

Extracellular recordings from the stipes of the mushroom Coprinus curtis showed spon­taneous electrical fluctuations which resembled fluctuations reported in Phycomyces and in higher plants. The amplitudes of these fluctuations ranged to over a millivolt, rise times (10010-90610) were 0.1-0.2 s, and the half times for decay varied from about 0.25 to 2.5 s. The fluctuations were shown to be of biological origin.

Spontaneous electrical fluctuations have been reported in Phycomyces (PICKARD, 1971) and in three higher plants (PICKARD, 1972). The purpose of this paper is to report the finding of similar electrical fluctuations in a basidiomycete, Coprinus curtis.

Materials and Methods

Mushrooms were grown at 25° C on Emerson Yp Ss agar (Difco Labs., Detroit, Mich.). Light was provided 15 h per day at an intensity of 8 flW mm-2 from a bank of fluorescent tubes.

The equipment and the method employed to record the fluctuations was described by PICKARD (1972). Salt bridges contained 0.1 M KCl. Wi<lis of the reference pipettes were plunged into the nutrient agar in which the mushrooms were growing, and wicks of the recording pipettes were placed on the stipes of the 8-11 day old, 10-15 mm tall mushrooms. Except for preliminary experiments, recording was carried out in the radio frequency­shielded room.

Results and Discussion

As shown in Fig. 1, electrical fluctuations could be recorded from the stipe of Coprinus curtis. The regularly shaped fluctuations, which could be either positive­going or negative-going in the extracellular recordings, ranged from barely detectable signals to signals of 1 mV amplitude. The rise time (10~/o-90%) was characteristically 0.1-0.2 s. The time required for the return of the voltage half way to the baseline ranged from 0.25 to 2.5 s. Periods of activity alternated erratically with long periods during which no signals could be observed.

That the fluctuations were of biological origin is indicated by the complete absence of activity in 20 min checks of the recording system immediately before and after recording from the stipe; for these checks, both recording and reference pipettes were plunged into 0.1 M KCI. Checks were also made by recording with all pipette wicks

z. Pflanzenphysiol. Bd. 67. S. 291-292. 1972.

292 F. B. FULLER and B. G. PICKARD

contacting the surface of the medium in which the fungus was growing. Moreover, recordings from two adjacent mushrooms were always carried out simultaneously and with respect to the same reference electrode: individual signals were never coincident for the two mushrooms, and periods of activity for the two were not correlated.

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Fig. 1. Photograph of 4 excerpts from an oscillographic recording from the stipe of Coprinus curtis, showing typical voltage fluctuations. In the 2nd excerpt small but distinct signals of about 100-200 /lV amplitude can be seen in addition to the conspicuous large signals. The low-level background fluctuations of the 2nd and 3rd excerpts may well be due to numerous (capacitatively distorted) signals originating some distance from the recording wick.

The fluctuations detected in Coprinus are closely similar to those seen in both extracellular and intracellular recordings from Phycomyces (PICKARD, 1971, and unpublished data). The shapes and time-courses of the fluctuations are also similar to those of many of the solitary fluctuations reported for shoots of Ipomoea, Pisum, and Xanthium (PICKARD, 1972). It seems possible that these similar fluctuations have a common origin.

This research was supported by N.S.F. Grant No. GB-8262 to B.G.P. We thank Dr. LAURA BRADFORD of the Biology Department, Washington University, for providing fungus cultures and advice.

References

PICKARD, B. G.: Putative action potentials in Phycomyces, Ipomoea, and Xanthium. Plant Physiol. 47 suppl., 26 (1971).

- Spontaneous electrical activity in shoots of Ipomoea, Pisum, and Xanthium. Planta (Berl.) 102,91-114 (1972).

FRANCIS B. FULLER and BARBARA G. PICKARD, Biology Department, Washington University Saint Louis, Mo. 63130, USA.

Z. Pjlanzenphysiol. Rd. 67. S. 291-292. 1972.