The Venus flytrap is indigenous to the swampy regions of Carolina in the USA. It lives in nutrient-poor soil and depends on capturing insects to make up for the deficiency of certain elements in its habitat.

The plant has an elaborate system to trap and digest insects, which other plants – apart from the aquatic waterwheel plant – just don’t have. Normally, man and animals eat plants for nutrition. In this case the plant eats animals!

Puzzles to Solve

Over the years, researchers have begun to explore the science behind the plant. First there was the puzzle of how the plant can snap its clamshell leaves around an insect in less than a second. It was discovered that their leaves snap from convex to concave in the same way that a contact lens can flip inside out. Like most lenses, Venus flytrap leaves are doubly curved, that is, curved in two directions, which allows the leaves to store elastic energy.

With a contact lens, the two directions are perpendicular to one another. With a Venus flytrap leaf, they are not. That property creates an especially rapid elasticity that causes the leaf to snap even more quickly from convex to concave.

Bending and stretching are inseparable for doubly curved objects. If you think of a cut-open tennis ball and you try to bend it, you end up stretching it as well and then it flips direction. This is how the leaves work. Their large, highly curved leaves snap more rapidly than smaller, weakly curved leaves and the prey has no chance of escaping.

Then came the puzzle as to how the trap is sprung. It was later discovered that each side of the trap has three to four sensor hairs, each no longer than 0.5cm. An insect must trip a hair twice, or two hairs, within 20 seconds for the trap to respond; this allows it to avoid snapping shut on raindrops or other false alarms.

The first time a hair is triggered, it creates an electrical signal that travels along the surface of the trap, much like the electrical signal that travels through an animal’s nerve cell. The energy of that first signal is stored. When the second touch occurs, it also generates an electrical signal. Together, the energy from these two signals passes the threshold required for the trap to respond.

The travelling electrical signals result from the movement of charged atoms, called ions, across the membranes of cells within the trap lobes. During the second signal, cells in the centre of each lobe lose water, along with the ions. This causes the cells to lose turgor – the water pressure that keeps a plant rigid. As a result, the lobes snap together.

Digestion

After the trap has snapped shut, the plant leaves turn into an external stomach, sealing the trap so no air gets in or out. Glands produce enzymes that digest the insect—first the exoskeleton made of chitin, then the nitrogen-rich blood, which is called hemolyph.

The digestion takes several days depending on the size of the insect, and then the leaf re-opens. By that time, the insect is a ‘shadow skeleton’ that is easily blown away by the wind.

In examining the digestive process, a number of questions arose. Firstly, what was the signal that started digestion; how does digestion take place; and lastly, how does the plant remove the excess salt from its prey?

Researchers discovered that the trigger hairs, as well as closing the trap, also generated electrical impulses that somehow stimulated glands in the trap to produce jasmonic acid. In non-carnivorous plants this acid is a defence mechanism against predators, but in the Venus flytrap it is the opposite. Tens of thousands of its tiny glands make and secrete hydrolases which eat the predator.

Furthermore, they discovered that specialised sodium transporters removed excess salt by depositing it into ‘capture organs’ so it wouldn’t interfere with the plant’s metabolism.

The production of jasmonic acid triggers the glands to secrete an acidic cocktail with more than 20 ingredients, including chitinases to dissolve the saccharides of the exoskeleton, proteases to dissolve the proteins, nucleases to dissolve the nucleic acids, lipases to dissolve the fats, and phosphatases to isolate the phosphates. These proteins are hydrolysed into their constituent amino acids – and the marvel is, that these only digest the prey and not the leaf itself!

The ammonium transporter increases uptake of nitrogen from the prey into the plant cells.

Photosynthesis supplies the energy to begin the digestive process, but in order to maintain this process it produces additional energy by oxidising amino acids that it extracts from its prey, thereby gaining access to yet another energy source.

Another team of researchers found that the plant does not consume an insect that has pollen on it from another plant of its own species. What they discovered was that because the plant’s flowers typically are located 20cm above its traps on a long, bare stalk, the insects that carried pollen were attracted to the flowers not the traps. These pollen-carrying insects could fly above the danger-zone, in contrast to most of the prey animals that found their way into the traps by walking into them.

Evolutionary suggestions

Two scientists, Waller and Gibson, mapped out the probable steps that would have been required to evolve from a sticky trap ancestor into a carnivorous snap-trap. First the ancestral plant must have adapted tentacles which were modified into trigger hairs and marginal ‘teeth’. Next it sped up how quickly it detected prey and tried to respond. Then the plant would had to have found a way to become selective, so it only tried to trap live prey (excluding insects that carried its own pollen) and not any detritus that landed upon it.

Finally, it must have evolved its tentacles into sensory hairs and teeth that detect and wrap around prey, respectively, while also losing its sticky glands and growing new digestive glands capable of digesting the victim’s corpse.

This reads like science fiction. To change tentacles into a unique combination of hair trigger counts, to transform leaf shape to form convex traps, to manufacture complex enzymes and salt-removing traps within an ordinary leaf, is too much to swallow. Once again, all these properties had to be working at the same time for the flower to survive.

The construction of the whole system also required foresight to know that an insect would be able to provide the additional energy for the plant and would have the appropriate properties to provide that extra energy.That foresight could have only come from the Creator of all things.