A verdant garden, softly draped with all manner of greenery, is a tranquil setting to most. But to scientists, it can be tranquilized further.

Just like humans, plants can succumb to the effects of general anesthetic drugs, researchers report this week in the Annals of Botany. The finding is striking for a variety of reasons—there’s the pesky fact that plants lack a central nervous system, for one thing. But, perhaps more noteworthy is that scientists still aren’t sure how general anesthetics work on humans—let alone plants. Despite that, doctors have been using the drugs daily for more than a century to knock people out and avert pain during surgeries and other medical procedures. Yet the drugs’ exact effects on our body’s cells and electrical signals remain elusive.

The authors of the new study, led by Italian and German plant biologists, suggest that plants could help us—once and for all—figure out the drugs’ mechanism of action. Moreover, the researchers are hopeful that after that’s sorted out, plants could be a useful tool to study and develop new anesthetic drugs. “As plants in general, and the model plant [Arabidopsis] thaliana in particular, are suitable to experimental manipulation (they do not run away) and allow easy electrical recordings, we propose them as ideal model objects to study anaesthesia and to serve as a suitable test system for human anaesthesia,” they conclude.

So how do you knock out a plant?

For the study, Stefano Mancuso of the University of Florence and František Baluška of the University of Bonn, along with colleagues, rounded up a variety of plants known for their movement. This includes the famous Venus flytrap (Dionaea muscipulaI) and the creeping herb Mimosa pudica (sometimes called a shy plant), whose leaves fold inward when touched. The researchers also gathered carnivorous sundew plants (Drosera capensis), which have vibrant, sticky tentacles that bend to ensnare prey. Last, the researchers looked at growing pea tendrils, which twirl around as they grow upward.

The researchers exposed the plants to a few different general anesthetics, in a few different ways. They enclosed some in chambers where they were surrounded by diethyl ether vapor or xenon gas. For some, the researchers washed their roots and exposed them to lidocaine.

In all cases, the anesthetics temporarily caused the plants to go still and unresponsive. The Venus flytrap's spikey trap didn’t slam shut when poked. The shy plant was no longer shy; it’s leaves stayed open when gently brushed. Similarly, the sundew plants didn’t bend to capture dead fruit flies and the pea plant’s tendrils drooped and curled up instead of whirling in normal upward fashion.

What could the drugs be doing?

While scientists still aren’t clear on how general anesthetics like diethyl ether work, there are a couple of leading hypotheses. These are generally that the drugs interact with specific receptors on nerve cells or alter the fats (lipids) within the membranes around our nerve cells. Both could disable gated ion channels embedded in the membranes that control electrical impulses in nerves. In any case, in humans the drugs cause reversible loss of consciousness and pain perception, along with immobility.

After finding that the drugs also caused immobility in plants, the researchers looked deeper to try to understand what was going on. After anesthetizing a Venus fly trap, the researchers looked at the action potentials—electrical pulses—on the traps’ surfaces using an electrode. Without an anesthetic, the scientists could measure pulses, but the pulses were lost following diethyl ether exposure. It took about 900 seconds for the action potential to recover. This suggests that the drugs knocked out the plants’ bioelectrical system, just like in humans.

Next, the researchers wanted to see if the drugs would interfere with the lipid membranes in plant cells. They turned to Arabidopsis, a weed in the mustard family that’s easy to work with in laboratories. (It’s basically the mouse of the plant science world.) The researchers looked at how Arabidopsis root cells were handling membrane-bound cargo inside the cell, which requires an elaborately maintained cell membrane to pull off properly. The researchers found that under anesthesia, the plant cells lost the ability to process and recycle that membrane-bound cargo.

This, the researchers argue, hints that the drugs are altering lipid membranes to cause their stunning outcomes. That said, plants do have and use similar receptor proteins to control ion channels in cells as humans do. Researchers will have to do much more work to fully knock out the mechanism.

Annals of Botany, 2017. DOI: 10.1093/aob/mcx155 (About DOIs).