When a Venus flytrap (Dionaea muscipula) attacks prey by closing it’s leaf, it undergoes the fastest movement of any plant. The rate at which it closes is approximately 100ms. Trigger hairs stimulate the leaf to close on the prey. While other studies have studied the hairs and their responses to stimuli, this study focuses on the actual mechanics of the leaf’s closure.
To study the closing of the leafs high speed video, microscopy, and modeling showed how the quick closing of the leaf is attributed to a “snap-buckling instability,” that is controlled by the plant itself (Forterre 421).
Until recently the belief was that movement to disperse seeds, pollen, and perform other functions in plants was the result of an “acid-induced wall loosing, and a rapid loss of pressure in turgid pressure in motor cell” ( Forterre 422). However, the tissue involved in this motion would only be able to be used once, and would not allow for the fast closing action of the flytrap. With these theories being looked at more skeptically focus has moved toward the theory that elastic deformations may be the root of the mechanism.
To study how the closing of the leaf occurs one must first understand what the leaf looks like as it closes. By painting ultraviolet dots on the leaves and taping the closing action the scientist were able to quantify the movement of the leaf as it closed. Using this data the scientists were able to determine that the close had three states. The first state which is described as a “slow initial phase,” in which 20 percent of the motion occurs in 1/3 of a second, a “rapid intermediate phase,” in which 60 percent of the motion occurs in 1/10 of a second, and a “second slow phase,” in which 20 percent of the motion occurs in 1/3 of a second. During this time the leaf changes from a convex to concave shape. Figure one as seen through the links section shows that the closure of the leaf is the result of a buildup of elastic energy that is then released at a high rate to capture prey. The stresses on the leafs were also studied and it was found through cutting the leafs in differing directions that the horizontal axis is responsible for most of the elastic buildup. This was determined by seeing which fibers responded to the cutting in differing manner, as well as looking at the cell shape and size. Cell shape on the x-axis was more elongated vertically meaning that those cells were designed for the elastic buildup and could contribute more to the elastic potential energy of the leaf, than those cells oriented in the y direction.
The writers attribute the closure of the leaf solely to the geometry of the leaf. The leaf can stretch itself without very much cost slowly and then release all the stored up energy in one giant swoop.
The size of the leaf’s also mattered greatly. The larger the leaf the more energy is required the stretch the leaf and buildup potential kinetic energy, however more energy is then released when the leaf closes. This energy allows for the leaf to close at a faster rate allowing for a more efficient prey capture. The closure was observed to be made as quickly as possible with little regard to have smooth the closure was. This makes sense because the plant is attempting to catch food that is moving quickly and the faster the trap shuts the more likely the plant is to capture prey.
In summary of the summary, the elastic potential energy of the plant is the reason for the snapping that occurs. The process begins with a small chemical component, but is for the most part solidly the resulted of the leaf’s cells and design. The leaf has evolved to allow for the building up of elastic potential energy and is also designed for the energy to be released at the proper time due to hair stimulus. Once again physics pervades all aspect of our lives and all of the lives of all organisms on earth, as it should because the goal of physics is to help understand and explain the world we live in. These scientists have opened a new small world of understanding that who knows could lead to much, much more. The cells and plant structures could be used to make mechanical devices that slowly build up energy for a great burst of activity, hmm kind of like a capacitor I suppose.

Hosted by www.Geocities.ws