Venus Flytrap

Biology: Cambridge International A Level, topic 15.2.1

Venus Fly Trap

Venus flytraps rapidly close in response to tactile stimulation. This is useful as it allows them to capture insects for food.

The modified leaves of Venus flytraps are covered with hundreds of minute hairs.
When an insect lands on the hairs, it causes the leaves to close.
The insect becomes trapped and the flytrap can digest the insect as food.
The plant attracts insects through the red inner lobes of the leaves and a flora scent.

The tactile stimulation of the hairs causes an increase in Ca²⁺ ion concentration.
If this depolarisation reaches the threshold potential, an action potential is triggered. The action potential causes the leaves to close.
To reach the threshold, several hairs have to be stimulated. This helps limit the plant closing in response to smaller stimuli, such as the wind.
Repeated stimulation causes the leaves to seal. Digestive enzymes can then be released to digest the fly.

The tactile stimulation of the hairs on the leaves of Venus flytraps causes an increase in the concentration of which ion?