Nonrandom Bioelectrical Signals in Plant Tissue

Abstract

The results of investigations on nonevoked bioelectrical activity in the India-rubber tree (Ficus elastica) are presented. Metal electrodes inserted into the plant issue were used as the ionic-to-electronic conduction converting elements. Nonevoked pulse bursts were observed with amplitudes in the 10 to 200 microvolts range. An upper limit value of the cell refractory period has been estimated from the maximum pulse frequency observed.The existence of evoked action potentials in plants due to a stimulation of the cell depolarization-repolarization process is well established. The concept of stimulation covers a broad range of interactions between the cell and its environment. In some cases the act of observation might be considered a stimulation in itself because of the interaction present during the observation. The general bioelectrical measurement situation is influenced by the not negligible interaction between the measurement apparatus and the object under investigation.In the present work, measurements have been made of nonevoked bioelectrical signals in the tissue of the India-rubber tree (Ficus elastica). Nonevoked in this case means that no stimulus was applied to the plant except for the presence of the electrodes in the petioles and the bias current of the amplifiers which is less than 10" amp. Bursts of pulses with well defined and rather constant amplitudes have been found to be produced by bioelectrical generators located in the plant tissue. Pulse burst lengths ranging from 30 sec to 25 min have been observed. The frequency of occurrence of the pulses within the burst is in the 0.5 to 200 pulses per minute range. Great effort was made to ensure that pulses generated by sources external to the plant were not mistaken for signals generated in the plant. Because of the electrode arrangement used, the pulses observed are assumed to represent the cellular action potential produced by groups of cells, analogous to the extracellular action potential as defined in medical electrophysiology (3). This assumption is substantiated by the fact that, while the single plant cell polarization-depolarization action potential has an amplitude of about 70 mv (6,14), the potentials measured in the course of the present work were all in the 10 to 200 /tv range. A difference in amplitude of the same order of magnitude between the intra-and extra-cellular action potentials is also found in medical electrophysiology (1 1).As in animal tissue, the electrical activity in plant tissue is based on ion transport mechanisms (8). Due to this circumstance, it is necessary to make a conversion from the ionic conduction present in the tissue to the electronic conduction which occurs in the measuring circuit, in order to measure electrical effects in the plant tissue. This conversion is accomplished at the tissue-electrode interface. The electrodes should preferably perform this conversion without disturbing the ionic concentrations or permanently damaging the plant tissue. In the present work, metal electrodes made of stai...

Propagated fluctuations of the electric potential in the apoplasm of Lepidium sativum L. roots

“…The experiments with killed roots, with anoxia and ether strongly support the interpretation that the fluctuations are of biological origin. Other support comes from reports indicating that the occurrence of EEP fluctuations in organs of different plants is a biological phenomenon (Karlsson 1972;Pickard 1972Pickard , 1974Glebicki et al 1986Glebicki et al , 1989. Pickard (1972Pickard ( , 1974 classified the fluctuations into three categories: repetitive spiking, solitary fluctuations, and general activity.…”

“…Pickard (1972) could detect a general activity of low amplitude in roots of intact plants, but not in isolated roots. Karlsson (1972) Ficus elastica) which fell into two types: one was similar to the "repetitive spiking", the second resembled the "general activity". The latter activity was very similar to the fluctuations in the Lepidium root apex both in shape and amplitude.…”

“…Several reports indicate the occurrence of spontaneous low-amplitude fluctuations of the electric potential in the apoplasm of various plant organs (Karlsson 1972;Pickard 1972Pickard , 1974Glebicki et al 1986). Local illumination of leaves induced temporal patterns of the extracellular * To whom correspondence should be addressed Abbreviations: AC = alternating current; AP = action potential ; ACF=autocorrelation function; CCF=cross-correlation function; DC = direct current; EEP = extracellular electric potential potential (EEP) on electrodes located outside the illuminated region (Glebicki et al 1989).…”

The natural history of consciousness, and the question of whether plants are conscious, in relation to the Hameroff-Penrose quantum-physical ‘Orch OR’ theory of universal consciousness

“…From various zones of a small tree of Ficus elastica, the highest electrical impulse rate, recorded during a period of many weeks, was 3.3 Hz. 224 Unfortunately, the exact locations of the recording zones were not specified and, moreover, the frequencies varied from minute to minute: one zone had a frequency of 0.8 Hz, another of 1.7 Hz, while a third zone showed 1.7 Hz one minute and then 0. Hz.…”

Dynamic protoneural networks in plants

“…As other few contemporaneous studies devoted to the same approach in the seventies, [10][11][12] particularly those of Pickard (1972Pickard ( , 1973 who classified these recordings as spontaneous activity and putative APs reflecting endocellular activities, the physiological role of these potentials was attributed to a possible control of absolute refractory period from 20 to 60 times longer than in neurons. 16 The rapid motricity of Mimosa pudica was then demonstrated by Sibaoka and Stoeckel as due to parenchymatous excitable cells where propagated APs precede cell deturgescence and the motor phenomenon itself.…”