Tropisms ‘mouth’ region are hairs that detect

Tropisms are natural responses of organisms to external stimuli. Thigmotropism is a response that’s often seen in plants in response to touch or contact. In this lesson, you’ll learn about thigmotropism and its functions in plants.

Senses and Tropisms

Senses are physiological characteristics in organisms that respond to changes in the environment. In humans, the five basic senses are sight, sound, taste, hearing, and touch.

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Whenever these senses are stimulated, they can generate a response. The responses, particularly when plant movement is involved, are known as tropisms. In this lesson, we’ll discuss a tropism related to the sense of touch, known as thigmotropism.

What Is Thigmotropism?

Thigmotropism is a movement or response that is generated when an organism is stimulated by touch. This type of stimulus is known as contact stimulus and is important for the growth and development of many organisms.

Specifically, this response is typically seen in plants, and can affect the arrangement and orientation of a plant during its growth.

How Does Thigmotropism Work?

Plants use thigmotropism in many ways. These include growth and nutrition. Let’s look at each of these uses more closely.

Have you ever seen a vine of ivy or garden plants that grow along fences? Maybe you’ve seen a trellis with flowers and plants growing along the sides of buildings. Those plants are exhibiting thigmotropism, and it’s helping them to grow in a particular pattern.Plants use hormones to grow in response to a contact stimulus. For example, in climbing plants, such as those found on a trellis or along a fence, the cells of the plant that are in contact with the surface of a stimulus will produce auxin, a hormone that stimulates growth. Specifically, the auxin will stimulate non-contacted cells to grow faster, which will result in the plant curving around the contact surface. Another hormone, called ethylene, may also be used to assist with stem and tissue growth as the plant grows around the object.

Some plants use thigmotropism to capture food. One of the most notable examples is the Venus flytrap. The Venus flytrap is a plant that feeds on insects in its environment with leaves that are connected on one side that resemble an open mouth. In this ‘mouth’ region are hairs that detect fine touch. When an insect lands on the connected leaves, the hairs are able to detect its presence. If an insect happens to touch any of these hairs twice, the leaves will close around the insect, and the plant has captured its prey! In this example, thigmotropism is used for capturing food, rather than directing the growth process as seen in climbing plants.

Lesson Summary

Thigmotropism is a movement or response that is generated when an organism is stimulated by touch. This basic sense, or contact stimulus, is important for the growth and development of many organisms. In climbing plants, thigmotropism helps them direct the pattern of growth around an object that is in contact with the plant; the hormones auxin and ethylene are used to facilitate this growth process. In other plants, such as the Venus flytrap, thigmotropic responses are used to capture food and provide nutrients for survival.


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