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.
2. Identify the type of movement: Mimosa pudica leaflets close rapidly when touched, indicating a quick, non-directional response to a stimulus.
3. Match the movement to the correct term: Since the movement is rapid and not related to growth direction, it aligns with 'thigmonastic movements'.
4. 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.
5. Evaluate the benefit: This response may protect the plant from herbivores or physical damage by making the leaves less accessible or less appealing.

Key Concepts

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.

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.

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.