Mechanical Stimulation Of Trigger Hairs Research Articles

Anaesthesia with diethyl ether impairs jasmonate signalling in the carnivorous plant Venus flytrap (Dionaea muscipula).

General anaesthetics are compounds that induce loss of responsiveness to environmental stimuli in animals and humans. The primary site of action of general anaesthetics is the nervous system, where anaesthetics inhibit neuronal transmission. Although plants do not have neurons, they generate electrical signals in response to biotic and abiotic stresses. Here, we investigated the effect of the general volatile anaesthetic diethyl ether on the ability to sense potential prey or herbivore attacks in the carnivorous plant Venus flytrap (Dionaea muscipula). We monitored trap movement, electrical signalling, phytohormone accumulation and gene expression in response to the mechanical stimulation of trigger hairs and wounding under diethyl ether treatment. Diethyl ether completely inhibited the generation of action potentials and trap closing reactions, which were easily and rapidly restored when the anaesthetic was removed. Diethyl ether also inhibited the later response: jasmonic acid (JA) accumulation and expression of JA-responsive genes (cysteine protease dionain and type I chitinase). However, external application of JA bypassed the inhibited action potentials and restored gene expression under diethyl ether anaesthesia, indicating that downstream reactions from JA are not inhibited. The Venus flytrap cannot sense prey or a herbivore attack under diethyl ether treatment caused by inhibited action potentials, and the JA signalling pathway as a consequence.

Triggering a false alarm: wounding mimics prey capture in the carnivorous Venus flytrap (Dionaea muscipula).

In the carnivorous plant Venus flytrap (Dionaea muscipula), the sequence of events after prey capture resembles the well-known plant defence signalling pathway in response to pathogen or herbivore attack. Here, we used wounding to mimic prey capture to show the similarities and differences between botanical carnivory and plant defence mechanisms. We monitored movement, electrical signalling, jasmonate accumulation and digestive enzyme secretion in local and distal (systemic) traps in response to prey capture, the mechanical stimulation of trigger hairs and wounding. The Venus flytrap cannot discriminate between wounding and mechanical trigger hair stimulation. Both induced the same action potentials, rapid trap closure, hermetic trap sealing, the accumulation of jasmonic acid (JA) and its isoleucine conjugate (JA-Ile), and the secretion of proteases (aspartic and cysteine proteases), phosphatases and type I chitinase. The jasmonate accumulation and enzyme secretion were confined to the local traps, to which the stimulus was applied, which correlates with the propagation of electrical signals and the absence of a systemic response in the Venus flytrap. In contrast to plant defence mechanisms, the absence of a systemic response in carnivorous plant may represent a resource-saving strategy. During prey capture, it could be quite expensive to produce digestive enzymes in the traps on the plant without prey.

Abundance of cysteine endopeptidase dionain in digestive fluid of Venus flytrap (Dionaea muscipula Ellis) is regulated by different stimuli from prey through jasmonates.

The trap of the carnivorous plant Venus flytrap (Dionaea muscipula) catches prey by very rapid closure of its modified leaves. After the rapid closure secures the prey, repeated mechanical stimulation of trigger hairs by struggling prey and the generation of action potentials (APs) result in secretion of digestive fluid. Once the prey's movement stops, the secretion is maintained by chemical stimuli released from digested prey. We investigated the effect of mechanical and chemical stimulation (NH4Cl, KH2PO4, further N(Cl) and P(K) stimulation) on enzyme activities in digestive fluid. Activities of β-D-glucosidases and N-acetyl-β-D-glucosaminidases were not detected. Acid phosphatase activity was higher in N(Cl) stimulated traps while proteolytic activity was higher in both chemically induced traps in comparison to mechanical stimulation. This is in accordance with higher abundance of recently described enzyme cysteine endopeptidase dionain in digestive fluid of chemically induced traps. Mechanical stimulation induced high levels of cis-12-oxophytodienoic acid (cis-OPDA) but jasmonic acid (JA) and its isoleucine conjugate (JA-Ile) accumulated to higher level after chemical stimulation. The concentration of indole-3-acetic acid (IAA), salicylic acid (SA) and abscisic acid (ABA) did not change significantly. The external application of JA bypassed the mechanical and chemical stimulation and induced a high abundance of dionain and proteolytic activity in digestive fluid. These results document the role of jasmonates in regulation of proteolytic activity in response to different stimuli from captured prey. The double trigger mechanism in protein digestion is proposed.

Morphing structures of the Dionaea muscipula Ellis during the trap opening and closing

The Venus flytrap is a marvelous plant that has intrigued scientists since the times of Charles Darwin. This carnivorous plant is capable of very fast movements to catch a prey. We found that the maximal speed of the trap closing in the Dionaea muscipula Ellis is about 130 000 times faster than the maximal speed of the trap opening. The mechanism and kinetics of this movement was debated for a long time. Here, the most recent Hydroelastic Curvature Model is applied to the analysis of this movement during closing and opening of the trap with or without a prey. Equations describing the trap movement were derived and verified with experimental data. Chloroform and ether, both anesthetic agents, induce action potentials and close the trap without the mechanical stimulation of trigger hairs. We tested this by dropping 10 μL of ether on the midrib inside the trap without touching any of the mechanosensitive trigger hairs. The trap closed slowly in 10 s. This is at least 20 times slower than the closing of the trap mechanically or electrically. The similar effect can be induced by placing 10 μL of chloroform on the midrib inside the trap, however, the lobes closing time in this case is as fast as closing after mechanical stimulation of the trigger hairs.

Electrotonic and action potentials in the Venus flytrap

The electrical phenomena and morphing structures in the Venus flytrap have attracted researchers since the nineteenth century. We have observed that mechanical stimulation of trigger hairs on the lobes of the Venus flytrap induces electrotonic potentials in the lower leaf. Electrostimulation of electrical circuits in the Venus flytrap can induce electrotonic potentials propagating along the upper and lower leaves. The instantaneous increase or decrease in voltage of stimulating potential generates a nonlinear electrical response in plant tissues. Any electrostimulation that is not instantaneous, such as sinusoidal or triangular functions, results in linear responses in the form of small electrotonic potentials. The amplitude and sign of electrotonic potentials depend on the polarity and the amplitude of the applied voltage. Electrical stimulation of the lower leaf induces electrical signals, which resemble action potentials, in the trap between the lobes and the midrib. The trap closes if the stimulating voltage is above the threshold level of 4.4V. Electrical responses in the Venus flytrap were analyzed and reproduced in the discrete electrical circuit. The information gained from this study can be used to elucidate the coupling of intracellular and intercellular communications in the form of electrical signals within plants.

Chlorophyll a fluorescence induction (Kautsky curve) in a Venus flytrap (Dionaea muscipula) leaf after mechanical trigger hair irritation

This paper describes experiments on transient changes in chlorophyll a fluorescence in traps of the carnivorous plant Venus flytrap (Dionaea muscipula) that occur in association with mechanical stimulation of trigger hairs and propagation of action potentials (APs). The experiments show the following reproducible effects of APs on the fluorescence induction (Kautsky-, or OJIPSMT curve) in a 100s low intensity light pulse (i) no change in the OJ phase attributed to release of photochemical quenching, (ii) a small enhancement, if at all of increase in the thermal JIP phase, (iii) a two- to threefold deceleration of the fluorescence decline (quenching) during the PSMT phase in the 2–100s time range, and (iv) a transient 15–50% increase in variable fluorescence within ∼20s under steady state light condition with, after ∼80s, a 10% undershoot that reverses in several tens of seconds to the original steady state. The results are discussed in terms of a hypothesis that the fluorescence decline during the SMT phase of the Kautsky induction curve, attributed to NPQ, is caused by the ΔμH+-driven increase in proton conductance of the CFo channel of the ATPase during its activation. A signal-transducing role of Ca2+ is suggested.

Energetics and forces of the Dionaea muscipula trap closing

The Venus flytrap is the most famous carnivorous plant. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3 s without mechanical stimulation of trigger hairs. Here we present results for direct measurements of the closing force of the trap of Dionaea muscipula Ellis after mechanical or electrical stimulation of the trap using the piezoelectric thin film or Fuji Prescale indicating sensor film. The closing force was 0.14 N and the corresponding pressure between rims of two lobes was 38 kPa. We evaluated theoretically using the Hydroelastic Curvature Model and compared with experimental data velocity, acceleration and kinetic energy from the time dependencies of distance between rims of lobes during the trap closing. The Charge Stimulation Method was used for trap electrostimulation between the midrib and lobes. From the dependence of voltage between two Ag/AgCl electrodes in the midrib and one of the lobes, we estimated electrical charge, current, resistance, electrical energy and electrical power dependencies on time during electrostimulation of the trap.

Mechanical model of the ultrafast underwater trap ofUtricularia

The underwater traps of the carnivorous plants of the Utricularia species catch their prey through the repetition of an "active slow deflation followed by passive fast suction" sequence. In this paper, we propose a mechanical model that describes both phases and strongly supports the hypothesis that the trap door acts as a flexible valve that buckles under the combined effects of pressure forces and the mechanical stimulation of trigger hairs, and not as a panel articulated on hinges. This model combines two different approaches, namely (i) the description of thin membranes as triangle meshes with strain and curvature energy, and (ii) the molecular dynamics approach, which consists of computing the time evolution of the position of each vertex of the mesh according to Langevin equations. The only free parameter in the expression of the elastic energy is the Young's modulus E of the membranes. The values for this parameter are unequivocally obtained by requiring that the trap model fires, like real traps, when the pressure difference between the outside and the inside of the trap reaches about 15 kPa. Among other results, our simulations show that, for a pressure difference slightly larger than the critical one, the door buckles, slides on the threshold, and finally swings wide open, in excellent agreement with the sequence observed in high-speed videos.

On the mechanism underlying photosynthetic limitation upon trigger hair irritation in the carnivorous plant Venus flytrap (Dionaea muscipula Ellis).

Mechanical stimulation of trigger hairs on the adaxial surface of the trap of Dionaea muscipula leads to the generation of action potentials and to rapid leaf movement. After rapid closure secures the prey, the struggle against the trigger hairs results in generation of further action potentials which inhibit photosynthesis. A detailed analysis of chlorophyll a fluorescence kinetics and gas exchange measurements in response to generation of action potentials in irritated D. muscipula traps was used to determine the ‘site effect’ of the electrical signal-induced inhibition of photosynthesis. Irritation of trigger hairs and subsequent generation of action potentials resulted in a decrease in the effective photochemical quantum yield of photosystem II (ΦPSII) and the rate of net photosynthesis (AN). During the first seconds of irritation, increased excitation pressure in photosystem II (PSII) was the major contributor to the decreased ΦPSII. Within ∼1 min, non-photochemical quenching (NPQ) released the excitation pressure at PSII. Measurements of the fast chlorophyll a fluorescence transient (O-J-I-P) revealed a direct impact of action potentials on the charge separation–recombination reactions in PSII, although the effect seems to be small rather than substantial. All the data presented here indicate that the main primary target of the electrical signal-induced inhibition of photosynthesis is the dark reaction, whereas the inhibition of electron transport is only a consequence of reduced carboxylation efficiency. In addition, the study also provides valuable data confirming the hypothesis that chlorophyll a fluorescence is under electrochemical control.

Biologically Closed Electrical Circuits in Plants

The Venus flytrap is a marvel of plant bioelectrochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. Thigmonastic movements in the Venus flytrap, associated with fast responses to environmental stimuli, appear to be regulated through electrical signal transductions. The thigmonastic responses of the Venus flytrap can be considered in three stages: stimulus perception, electrical signal transmission, and induction of mechanical, hydrodynamical and biochemical responses. The hydroelastic curvature mechanism closely describes the kinetics of leaf movements. The electrical properties of the Venus flytrap were investigated and an equivalent electrical circuit was proposed that explains the experimental data.

Biologically Closed Electrical Circuits and Voltage Gated Ion Channels in Plants

The Venus flytrap is a marvel of plant electrical, mechanical and biochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. The Venus flytrap can accumulate small subthreshold charges, and when the threshold value is reached, the trap closes. Thigmonastic movements in the sensitive plant Mimosa pudica L., associated with fast responses to environmental stimuli, appear to be regulated through electrical and chemical signal transductions. The thigmonastic responses of Mimosa pudica can be considered in three stages: stimulus perception, electrical signal transmission, and induction of mechanical, hydrodynamical and biochemical responses. We investigated the mechanical movements of the pinnae and petioles in Mimosa pudica induced by the electrical stimulation of a pulvinus, petiole, secondary pulvinus, or pinna by low electrical voltage and charge. Both voltage and electrical charge are responsible for the electro stimulated closing of a leaf. The mechanism behind closing the leaf in Mimosa pudica is discussed. The hydroelastic curvature mechanism closely describes the kinetics of Mimosa pudica leaf movements.

Electrical memory in Venus flytrap

Electrical signaling, memory and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since the XIX century. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3 s without mechanical stimulation of trigger hairs. Here we developed a new method for direct measurements of the exact electrical charge utilized by the D. muscipula Ellis to facilitate the trap closing and investigated electrical short memory in the Venus flytrap. As soon as the 8 µC charge for a small trap or a 9 µC charge for a large trap is transmitted between a lobe and midrib from the external capacitor, the trap starts to close at room temperature. At temperatures 28–36 °C a smaller electrical charge of 4.1 µC is required to close the trap of the D. muscipula. The cumulative character of electrical stimuli points to the existence of short-term electrical memory in the Venus flytrap. We also found sensory memory in the Venus flytrap. When one sustained mechanical stimulus was applied to only one trigger hair, the trap closed in a few seconds.

Biologically Closed Electrical Circuits in Venus Flytrap

The Venus flytrap (Dionaea muscipula Ellis) is a marvel of plant electrical, mechanical, and biochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. The Venus flytrap can accumulate small subthreshold charges and, when the threshold value is reached, the trap closes. Here, we investigated the electrical properties of the upper leaf of the Venus flytrap and proposed the equivalent electrical circuit in agreement with the experimental data.

Plant electrical memory

Electrical signaling, short-term memory and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since the XIX century. We found that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. The closing time of Venus flytrap by electrical stimulation is the same as mechanically induced closing. Transmission of a single electrical charge between a lobe and the midrib causes closure of the trap and induces an electrical signal propagating between both lobes and midrib. The Venus flytrap can accumulate small subthreshold charges, and when the threshold value is reached, the trap closes. Repeated application of smaller charges demonstrates the summation of stimuli. The cumulative character of electrical stimuli points to the existence of short-term electrical memory in the Venus flytrap.

Charge induced closing of Dionaea muscipula Ellis trap

In terms of bioelectrochemistry, Venus flytrap responses can be considered in three stages: stimulus perception, electrical signal transmission, and induction of mechanical and biochemical responses. When an insect touches the trigger hairs, these mechanosensors generate receptor potentials, which induce solitary waves activating the motor cells. We found that the electrical charge injected between a midrib and a lobe closes the Venus flytrap leaf by activating motor cells without mechanical stimulation of trigger hairs. The mean electrical charge required for the closure of the Venus flytrap leaf is 13.6 μC. To close the trap, electrical charge can be submitted as a single charge or applied cumulatively by small portions during a short period of time. Ion channel blocker such as Zn2+ as well as an uncoupler CCCP, dramatically decreases the speed of the trap closing a few hours after treatment of the soil. This effect is reversible. After soil washing by distilled water, the closing time of Venus flytrap treated by CCCP or ZnCl2 decreases back from 2–5 s to 0.3 s, but higher electrical charge is needed for trap closure. The mechanism behind closing the upper leaf of Venus flytrap is discussed.

Closing of Venus Flytrap by Electrical Stimulation of Motor Cells

Electrical signaling and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since XIX century, but the exact mechanism of Venus flytrap closure is still unknown. We found that the electrical stimulus between a midrib and a lobe closes the Venus flytrap leaf by activating motor cells without mechanical stimulation of trigger hairs. The closing time of Venus flytrap by electrical stimulation of motor cells is 0.3 s, the same as mechanically induced closing. The mean electrical charge required for the closure of the Venus flytrap leaf is 13.6 μC. Ion channel blockers such as Ba2+, TEACl as well as uncouplers such as FCCP, 2,4-dinitrophenol and pentachlorophenol dramatically decrease the speed of the trap closing. Using an ultra-fast data acquisition system with measurements in real time, we found that the action potential in the Venus flytrap has a s a duration time of about 1.5 ms. Our results demonstrate that electrical stimulation can be used to study mechanisms of fast activity in motor cells of the plant kingdom.

How the Venus flytrap snaps

The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100 ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as "one of the most wonderful in the world". The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of the trigger hairs to stimuli and quantified the propagation of action potentials in the leaves. Here we complement these studies by considering the post-stimulation mechanical aspects of Venus flytrap closure. Using high-speed video imaging, non-invasive microscopy techniques and a simple theoretical model, we show that the fast closure of the trap results from a snap-buckling instability, the onset of which is controlled actively by the plant. Our study identifies an ingenious solution to scaling up movements in non-muscular engines and provides a general framework for understanding nastic motion in plants.