Question

The closure of lid of pitcher in pitcher plant, is due to

• A. A paratonic movement
• B. An autonomous movement
• C. A turgor movement
• D. A tropic movement.

Answer 1

The Correct Option is A

To address the question regarding the mechanism behind the closure of the lid in a pitcher plant, let's explore the different types of plant movements and their definitions:

1. Paratonic Movement: This type of movement is induced by external stimuli. It is not inherent to the plant but occurs as a response to an external factor, such as light, temperature, or touch. Paratonic movements, also known as nastic movements, do not depend on the direction of the stimulus.
2. Autonomous Movement: Autonomous movements are internal, spontaneous, and occur without any external stimulus. These movements are inherent to the plant's cells and tissues.
3. Turgor Movement: This movement results from changes in the turgor pressure within plant cells. It involves the gain or loss of water, causing cells to swell or shrink. It is common in sensitive plants such as Mimosa pudica.
4. Tropic Movement: Tropic movements occur in response to a stimulus, and the direction is dependent on the direction of the stimulus. Examples include phototropism (response to light) and gravitropism (response to gravity).

Now, focusing specifically on the pitcher plant, the closure of the lid is a response to the capture of prey (usually insects). This response is based on external stimuli such as the prey touching the plant's sensitive hairs. Therefore, this movement is categorized as a paratonic movement, as it is induced by the external stimulus of the prey.

Hence, the correct answer to the question is:

A paratonic movement

This reasoned explanation clarifies that the closure of the lid of the pitcher plant is due to an external trigger, fitting the definition of a paratonic movement. This selection rules out the other options as they do not align with the nature of the movement observed in pitcher plants.