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Ch. 37 - Plant Sensory Systems, Signals, and Responses
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 37 - Plant Sensory Systems, Signals, and ResponsesProblem 12b
Chapter 37, Problem 12b

Leaflets of Mimosa pudica (common names: sensitive plant, touch-me-not) have a remarkable ability to close up in response to being touched or physically moved.
How fast can the leaflets close?
How does this occur?
And more importantly, what benefit could this unusual response provide to the plant?
Which of the following terms best describes the leaflet movement?
a. Thigmonastic movements
b. Thigmotropism
c. Thigmomorphogenesis
d. Apical dominance

Verified step by step guidance
1
Understand the terms: Each option describes a different type of plant response to stimuli. 'Thigmonastic movements' are rapid movements in response to touch, 'thigmotropism' is growth in response to touch, 'thigmomorphogenesis' is a change in growth pattern due to mechanical stress, and 'apical dominance' is the suppression of lateral bud growth by the apical bud.
Identify the type of movement: Mimosa pudica leaflets close rapidly when touched, indicating a quick, non-directional response to a stimulus.
Match the movement to the correct term: Since the movement is rapid and not related to growth direction, it aligns with 'thigmonastic movements'.
Consider the mechanism: The closing of leaflets is due to changes in turgor pressure within the cells at the base of the leaflets, causing them to fold.
Evaluate the benefit: This response may protect the plant from herbivores or physical damage by making the leaves less accessible or less appealing.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Thigmonastic Movements

Thigmonastic movements are non-directional responses to touch or physical stimuli, where the movement is independent of the direction of the stimulus. In Mimosa pudica, the rapid closure of leaflets upon touch is a classic example of thigmonastic movement, which is a defense mechanism to deter herbivores or prevent damage.
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Plant Defense Mechanisms

Plants have evolved various defense mechanisms to protect themselves from herbivores and environmental stress. The rapid closure of Mimosa pudica's leaflets can deter herbivores by making the plant appear less appealing or by startling them, thus reducing the likelihood of being eaten or damaged.
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Mechanism of Leaflet Closure

The closure of Mimosa pudica's leaflets is facilitated by changes in turgor pressure within the pulvini, specialized cells at the base of the leaflets. When stimulated, these cells lose water rapidly, causing the leaflets to fold. This process is reversible, allowing the plant to reopen its leaves once the stimulus is removed.
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Related Practice
Textbook Question

In general, small seeds that have few food reserves must be exposed to red light before they will germinate. (Lettuce is an example.) In contrast, large seeds that have substantial food reserves typically do not depend on red light as a stimulus to trigger germination. State a hypothesis to explain these observations.

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Textbook Question

In many species native to tropical wet forests, seeds do not undergo a period of dormancy. Instead, they germinate immediately. Predict the role of ABA in these seeds. How would you test your prediction?

725
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Textbook Question

Leaflets of Mimosa pudica (common names: sensitive plant, touch-me-not) have a remarkable ability to close up in response to being touched or physically moved.

How fast can the leaflets close?

How does this occur?

And more importantly, what benefit could this unusual response provide to the plant?

Researchers studied the rate of closing and reopening of leaflets by measuring changes in the distance between opposing leaflets after being touched. Their results are shown in the accompanying graph (d/dmax is actual leaflet distance relative to maximal leaflet distance).

How long does it take for leaflets to close?

How long to reopen?

727
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Textbook Question

Leaflets of Mimosa pudica (common names: sensitive plant, touch-me-not) have a remarkable ability to close up in response to being touched or physically moved.

How fast can the leaflets close? How does this occur?

And more importantly, what benefit could this unusual response provide to the plant?

The mechanism of leaflet closure is similar to what happens during the shrinking of guard cells and closing of stomata (see Figure 37.22). When in the open position, special cells on the upper surface of Mimosa leaflets are filled with water and are under pressure.

Explain how osmosis and flow of ions into and out of these special cells may be involved in leaflet closure and reopening.

839
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Textbook Question

Leaflets of Mimosa pudica (common names: sensitive plant, touch-me-not) have a remarkable ability to close up in response to being touched or physically moved.

How fast can the leaflets close?

How does this occur?

And more importantly, what benefit could this unusual response provide to the plant?

If just the leaflets located toward the end of a leaf are touched, the adjacent leaflets close in fairly rapid succession until all leaflets on a leaf close up.

Explain how electrical signaling may be involved in this response.

794
views
Textbook Question

Leaflets of Mimosa pudica (common names: sensitive plant, touch-me-not) have a remarkable ability to close up in response to being touched or physically moved.

How fast can the leaflets close? How does this occur?

And more importantly, what benefit could this unusual response provide to the plant? Researchers have hypothesized that rapid leaf movements in Mimosa serve as a defense mechanism (e.g., closing leaflets may deter plant-eating insects).

Propose an experiment to test this hypothesis.

644
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