It is commonly known that plants move to face the sun. Do these slow-moving plants have a brain? The answer, as any young student could tell you, is no. How about fast-moving plants, like the carnivorous Venus Fly Trap or the Mimosa pudica? The answer is still no; plants do not have a brain or neurons. Can plants, lacking neurons, be used to teach neuroscience?
Neuroscientist Greg Gage answers with a surprising yet resounding yes. To think that a topic as complex as neuroscience could be taught by examining mundane-seeming plant movement may seem like a stretch. As Greg Gage demonstrates however, neither is plant movement mundane, nor is neuroscience beyond the grasp of regular folks.
The human nervous system transmits signals quickly throughout the body using neurons. Neurons are cells that pass signals to other neurons, or muscle or gland cells. Neurons chain to form extensive neural networks. Neurons are electrically excitable, meaning that a pulse called an action potential is generated due to chemical imbalances. Action potentials travel down the neuron, eventually activating synaptic connections with the next cell in the network. You may be familiar with the electrocardiogram (EKG), which measures the firing of action potentials in the neurons in the heart.
As previously mentioned, plants do not have neurons. But they do have action potentials that transmit messages, and these messages may transmit in interesting ways. In one of the coolest science talks to grace the TED stage, Greg Gage introduces the Mimosa pudica and Venus Fly Trap. The leaves and branches of the Central and South American Mimosa pudica plant curl up upon being touched. The Venus Fly Trap is slightly more interesting.
The opening and closing of the Venus Fly Trap head is known to most. Less well-known is the mechanisms behind how the Venus Fly Trap traps flies. The Venus Fly Trap head has small hairs that trigger action potentials when touched. Touching a hair briefly is not enough to shut the flytrap head.
It takes the Venus Fly Trap a significant amount of energy, and between 24 and 48 hours to reopen a closed trap, if no fly is captured. For that reason, the plant wants to ensure a fly is present before springing the trap. It does this by counting the seconds between successive action potentials. If there are at least 20 seconds between the firing of action potentials, then the flytrap springs shut.
Greg Gage goes the extra mile by wiring together the Mimosa pudica and Venus Fly Trap to demonstrate how action potentials can pass between different plants. Gage touches the hairs of the Venus Fly Trap, triggering an action potential that travels down the plant and into connecting wires. These wires transmit the signal to the Mimosa pudica which in turn curls up its leaves.
Simple demonstrations like these may be used in classrooms to teach basic neurology to students. Due to their relative simplicity but shared electrophysiology, plants may be the key to better explaining more difficult physiological concepts in middle and high-schools.
Mahdi Al-Husseini is the volunteer organizer of TEDxDouglasville, a senior at Georgia Tech studying biomedical engineering and public policy, and a U.S. Army cadet.