A single touch can provide sufficient mechanical stimulation to trigger Venus flytrap closure

Abstract

The carnivorous Venus flytrap catches prey by an ingenious snapping mechanism. Based on work over nearly 200 years, it has become generally accepted that two touches of the trap's sensory hairs within 30 s, each one generating an action potential, are required to trigger closure of the trap. We developed an electromechanical model, which, however, suggests that under certain circumstances one touch is sufficient to generate two action potentials. Using a force-sensing microrobotic system, we precisely quantified the sensoryhair deflection parameters necessary to trigger trap closure and correlated them with the elicited action potentials in vivo. Our results confirm the model's predictions, suggesting that the Venus flytrap may be adapted to a wider range of prey movements than previously assumed.

Broadening the definition of a nervous system to better understand the evolution of plants and animals

“… 30 , 31 The Venus flytrap uses the distinct electrical states of its cells to process information, 29 and this mechanism could allow for reacting to a wide range of prey movements. 32 Also, it has been observed that the Venus flytrap has several interconnected electrical circuits. 28 Despite these interesting features, this plant is not an oddity.…”

Kinematics Governing Mechanotransduction in the Sensory Hair of the Venus flytrap

“…The different aspects of mechanotransduction in the Venus flytrap were investigated through various theoretical and experimental approaches. Previously, we introduced an electromechanical model [ 10 ] built on the concepts of plant electrical memory [ 4 ] to complement our force-deflection tests on sensory hairs. We found hair deflection thresholds for angular displacement and velocity which successfully elicit action potentials, thereby closing the trap.…”

“…Mechanical tests on sensory hairs were able to quantify the stimulus thresholds needed to elicit action potentials (APs) and, furthermore, a loss of sensitivity at high stimulation frequencies was reported [ 9 ]. Recently, with the help of an electromechanical model, it was shown that a charge-dependent rule can explain mechanotransduction in the flytrap’s sensory hair [ 10 ]. Subsequent experiments confirmed that the number of stimulations needed to close the trap depends on the stimulus parameters, namely the angular velocity and the angular displacement of the sensory hair.…”

“…Then, we simulated a single-touch stimulus by deflecting the sensory hair up to a predefined angular displacement ( ). We selected the range of such that a single stimulus can initiate trap closure as previously observed in our experiments [ 10 ]. As a result of the stimulus, we obtained the cell wall deformation as an output, from which we calculated the stretch produced on the cell wall.…”

Rapid movements in plants

“…When the lobes receive two or more successive stimuli within approximately 30 seconds, they suddenly snap shut and trap the prey inside (Brown and Sharp 1910 ). A recent study employing the fine displacement of the sensory hair showed that a single deflection with relatively slow angular velocity (0.03–4 radian per second) can induce multiple action potentials and thus trigger the trap closure (Burri et al 2020 ). Live-imaging analysis using transgenic D. muscipula has recently demonstrated that cytosolic Ca 2+ levels in the trap lobes cumulatively increase in response to individual stimuli, suggesting that Ca 2+ plays a role in this counting system (Suda et al 2020 ).…”