Biology – Control and coordination in plants | e-Consult

The Venus flytrap exhibits a remarkably rapid response to mechanical stimulation, primarily through the triggering of sensory hairs on its lobes. Each lobe contains three sensitive trigger hairs. When a hair is stimulated repeatedly within a short time frame (typically 20 seconds), the trap closes. This rapid response is mediated by a complex interplay of electrical and hormonal signals.

Electrical Signals: Stimulation of a trigger hair causes a change in the ion permeability of the epidermal cells surrounding the hair. This leads to an influx of potassium ions (K+) and a subsequent depolarization of the cell membrane. This depolarization generates an action potential, a rapid change in membrane potential. This action potential propagates through the sensory cells and then spreads to adjacent motor cells. The propagation of these electrical signals is crucial for initiating the closing mechanism.

Auxin's Role: While the initial trigger is electrical, the closing of the trap is significantly influenced by the plant hormone auxin. When a hair is stimulated, the motor cells surrounding the lobes become activated. This activation leads to an increase in the concentration of auxin in the cell walls of these motor cells. The increased auxin concentration causes a change in cell wall properties, making the cells less elastic and more prone to taking up water. This increased turgor pressure within the motor cells contributes to the rapid and forceful closure of the trap. Auxin also plays a role in coordinating the closure of the lobes, ensuring a synchronized and effective capture.

The rapid electrical signal triggers a cascade of events, ultimately leading to the coordinated movement of the lobes and the capture of the prey. The sensitivity to repeated stimulation prevents the trap from closing unnecessarily, conserving energy.