How do venus fly traps work?

Biologist and eLife features editor Sarah Shailes snapped up this question from David...

Sarah - If you look at the inside of venus fly trap there are actually really tiny, short, stiff hairs on the inside of the leaves. When an insect lands on the trap and they wander around on the surface of the leaf, they actually touch the hairs and this can cause the hairs to bend. If the insect touches two hairs in quick succession, or the same hair twice immediately after the other, then it triggers an electrical signal that runs through the leaf, and it actually causes the leaf to snap shut.

Chris - Where’s it get the electricity from?

Sarah - It’s quite similar to how electrical signals work in the brain. So you get ions moving across the membranes surrounding the cells carrying the electrical signal. The difference with plants is that they don’t have neurons but there are connections between the cells that allow the electrical signals to just go straight through, so that’s how it travels along.

Chris - Andrew…

Andrew - So given there’s sort of clearly a connection to the type of brain activity that we have, have those mechanisms evolved independently or are they actually related in terms of their genetic basis as well?

Sarah - That’s a really interesting question. They will have evolved independently but the channels in the membrane that allow the ions to move through, there can be similarities between them and they can work in quite similar ways. But they’re genetically different usually, plant ion channels.

Chris - So given that venus fly traps are green, and they’re therefore gathering energy from the Sun because they’re photosynthesising, why do they need to fish around in the air for flies to eat when they can just make their food from the Sun?

Sarah - The parts of the world that venus fly traps live in, although they do get some energy from sunlight, they are often in very nutrient poor areas. So by digesting the insects, they get a whole load of nutrients that they wouldn’t get from sunlight.