Are Plants Conscious?

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Immobilized Plants

After an hour of exposure to the anesthetic diethyl ether, the leaf traps of Venus flytraps ( Dionaea muscipula Ellis ) no longer close upon stimulation. Although humans have used anesthetics for more than 150 years, scientists are still not quite sure, physiologically speaking, exactly how such a diverse group of compounds manages to immobilize the nervous systems of humans and animals. One popular theory contends that anesthetics might act on specific nervous system receptors. Further complicating this mystery is the fact that anesthetics also work on plants, even though plants lack nerve cells. A new study has found that anesthetics affect plant movements by disrupting the ability of plant cells to transmit electrical signals and communicate with each other across neighboring cell membranes. Plant biologist František Baluška at the University of Bonn, Germany, and an international team of researchers applied a range of anesthetics—diethyl ether gas, lidocaine, ethyl vinyl ether, and xenon gas—to a range of moving plants, including fly-snapping Venus flytraps; peas, whose tendrils reach out to climb; and the sensitive plant, Mimosa pudica , which has leaves that fold inward when disturbed. Anesthetics, the team confirmed, immobilize plants much like they immobilize animals and humans. For example, when prodded under anesthesia, Venus flytraps failed to close, and the electrical signals that coincided with their shutting traps—similar to those between activated muscle or brain cells—ceased. When exposed to diethyl ether gas, pea tendrils stayed curled tight rather than vining. And when lidocaine was applied to Mimosa roots, its freezing effect reached the plants’ touch-sensitive leaves. In addition, anesthetics interfered with seed germination and the build-up of chlorophyll in garden cress. The researchers also anesthetized maize seedlings and Arabidopsis thaliana , model organisms analogous to the lab rats of the plant world, in order to investigate the effects of anesthetics at the microscopic level. Both plants showed a disruption in key processes related to cell-to-cell communication across the membranes of their root cells, which appear to function similarly to the synapses between communicating brain cells. Baluška and the team believe that their work in plants demonstrates alternative avenues for studying the mechanisms of anesthetics. Instead of searching for specific cell receptors affected by anesthetics, synapse-like cell membranes may hold the secret to anesthetics’ effects on plant and animal life alike. That means, the team suggests, that plants could serve as potential study subjects in tests of these essential medical compounds. ( Annals of Botany )