Electrical Communication in the Venus Flytrap (CIE A Level Biology)

• Some plants possess communication systems that enable them to coordinate the different parts of their bodies
• The Venus flytrap (Dionaea muscipula) is a carnivorous plant that gets its supply of nitrogen compounds by trapping and digesting small animals (mainly insects)

David J. Stang via Wikimedia Commons

The Venus flytrap (Dionaea muscipula)

• The specialised leaf is divided into two lobes on either side of a midrib
• The inside of the lobes is red and has nectar-secreting glands on the edges to attract insects
• Each lobe has three stiff sensory hairs that respond to being touched
• If an insect (e.g. a fly) touches one of these hairs with enough force, action potentials are stimulated, which then travel very fast across the leaf
• These action potentials cause the two lobes to fold together along the midrib, capturing the insect

Venus flytrap diagram

The Venus flytrap has specialised features that enable it to catch and digest insects

How the closure of the trap is achieved

• If one of the sensory hairs is touched with enough force, calcium ion channels in cells at the base of the hair are activated
• When these channels open, calcium ions flow in and generate a receptor potential
• If two of the sensory hairs are stimulated within a period of about 30 seconds, or one hair is stimulated twice within this period, action potentials will travel across the trap and cause it to close
  • When the trap is open, the lobes of the leaf are convex in shape but when the trap is triggered, the lobes quickly become concave, bending downwards and causing the trap to shut
  • This is thought to occurs as a result of a release of elastic tension in the cell walls

• Sealing the trap requires ongoing activation of the sensory hairs – the prey trapped inside provides this ongoing stimulation, generating further action potentials
• Further stimulation of the sensory hairs causes calcium ions to enter gland cells where they stimulate the exocytosis of vesicles containing digestive enzymes
• The trap then stays closed for up to a week to allow the prey to be digested and the nutrients from it to be absorbed by the plant