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Question Video: Recalling the Term Used to Describe the Response of a Plant to a Touch Stimulus Biology

What is the response of plants to a touch stimulus known as?


Video Transcript

What is the response of plants to a touch stimulus known as? (A) Hydrotropism, (B) thigmotropism/haptotropism, (C) chemotropism, (D) geotropism, or (E) traumatotropism.

Let’s start by defining a few key terms that are important in understanding this question. The directional growth movements of an organism like a plant in response to certain stimuli are called tropisms. Remember, a stimulus is a detectable change in an organism’s internal or external environment that may trigger a response in that organism.

There are many different stimuli that plants are able to respond to, and this question concerns one particular stimulus: touch. Have you ever seen a vine wrapped around a tree, or perhaps ivy climbing up the walls of a building? Even pea plants have small tendrils that twist around objects like sticks to keep themselves upright. These are just a few examples of how plants may respond by growing in response to touching another solid object.

Let’s take a closer look at this process in the pea plant example. When a part of the climbing plant, like a tendril, comes into contact with a solid object, this triggers the release of plant hormones and proteins. This results in the cells that are directly in contact with the object to grow slowly. In contrast, the cells on the opposite side are stimulated to grow rapidly. This causes the tendril to coil or twine closely around the object. This process is called thigmotropism or sometimes haptotropism. The prefix thigmo- means touch, so it refers to the stimulus itself. The prefix hapto- means to fasten, descriptively illustrating the action that the plant takes in wrapping around and fastening itself to another object.

With this information, we can answer this question correctly. This question asks us to identify the response of plants to a touch stimulus. And we now know that this phenomenon is (B), thigmotropism/haptotropism.

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