No Such Thing as a Free Lunch for Venus Flytraps
ScienceDaily (Aug. 3, 2010) — Charles Darwin described the Venus Flytrap as 'one of the most wonderful plants in the world.' It's also one of the fastest as many an unfortunate insect taking a stroll across a leaf has discovered. But what powers this speed? Dr Andrej Pavlovič of Comenius University, Slovakia, has been studying the plants with the help of some specialised equipment and a few unlucky insects.
Dead insect in the closed trap of a Venus flytrap. (Credit: iStockphoto/Don Bayley)
In the wild the Venus Flytrap grows in the bogs and savannahs of North and South Carolina. This is not a healthy environment for many plants as it is low in the nitrogen to needed to build proteins. The Venus Flytrap has overcome this problem by developing a taste for meat. It has convex bi-lobed leaves with three trigger hairs on each lobe. When something knocks these hairs twice an electrical signal flips the leaves into concave shapes. If the captured creature struggles to escape it continues to tickle the trigger hairs. This causes the plant's trap to close tighter and release enzymes to digest its prey.
Pavlovič looked at how the Flytraps snapped their leaves around their prey and thought that it might cost the plant energy to catch its food this way. To test his idea, he set up an infrared gas analyzer and a chlorophyll fluorescence imaging camera to watch the plants. He used a wire to make a trap snap and then simulated an insect struggling in the closed trap. Then he watched what happened as the plant caught its victim.
Pavlovič said: "When a trap was triggered, photosynthesis slowed down and then recovered over ten minutes after the traps stopped being stimulated. In addition, the gas analyser showed an increase in respiration from the traps. To power the trap, the Venus Flytraps converted sugars they had photosynthesized back into carbon dioxide and energy. It is like an animal which also increases breathing when it has an increased demand for energy. The measurements showed that the effects are linked not to whether or not the trap is open, but to the stimulation of the trigger hairs. The measurements are connected with electrical signals produced by trigger hair irritation. These signals are similar to the signals which spread through the animal neurons."
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Read more here/Leia mais aqui: Science Daily
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AOBPreview originally published online on November 3, 2009
Annals of Botany 2010 105(1):37-44; doi:10.1093/aob/mcp269
Trap closure and prey retention in Venus flytrap (Dionaea muscipula) temporarily reduces photosynthesis and stimulates respirationAndrej Pavlovi*, Viktor Demko and Ján Hudák
Trap closure and prey retention in Venus flytrap (Dionaea muscipula) temporarily reduces photosynthesis and stimulates respirationAndrej Pavlovi*, Viktor Demko and Ján Hudák
Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina B2, 842 15, Bratislava, Slovak Republic
* For correspondence. E-mail pavlovic@fns.uniba.sk
Received: 10 August 2009 Returned for revision: 11 September 2009 Accepted: 5 October 2009 Published electronically: 3 November 2009
Background and Aims: The carnivorous plant Venus flytrap (Dionaea muscipula) produces a rosette of leaves: each leaf is divided into a lower partcalled the lamina and an upper part, the trap, with sensory trigger hairs on the adaxial surface. The trap catches prey by very rapid closure, within a fraction of a second of the trigger hairs being touched twice. Generation of action potentialsplays an important role in closure. Because electrical signals are involved in reduction of the photosynthetic rate in different plant species, we hypothesized that trap closure and subsequent movement of prey in the trap will result in transient downregulation of photosynthesis, thus representing the energetic costs of carnivory associated with an active trapping mechanism, which has not been previously described.
Methods: Traps were enclosed in a gas exchange cuvette and the trigger hairs irritated with thin wire, thus simulating insect capture and retention. Respiration rate was measured in darkness (RD). In the light, net photosynthetic rate (AN), stomatal conductance (gs) and intercellular CO2 concentration (ci) were measured, combined with chlorophyll fluorescence imaging. Responses were monitored in the lamina and trap separately.
Key Results: Irritation of trigger hairs resulted in decreased AN and increased RD, not only immediately after trap closure but also during the subsequent period when prey retention was simulated in the closed trap. Stomatal conductance remained stable, indicating no stomatal limitation of AN, so ci increased. At the same time, the effective quantum yield of photosystem II (PSII) decreased transiently. The response was confined mainly to the digestive zone of the trap and was not observed in the lamina. Stopping mechanical irritation resulted in recovery of AN, RD and PSII.
Conclusions: We put forward the first experimental evidence for energetic demands and carbon costs during insect trapping and retention in carnivorous plants, providing a new insight into the cost/benefit model of carnivory.
Key words: Action potential, carnivorous plant, cost/benefit model, chlorophyll fluorescence imaging, Dionaea muscipula, photosynthetic rate, respiration rate, Venus flytrap
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