Which of the following is NOT a growth movement in plants?

RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Non Nursing Subjects

Medium

Appeared in: RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Explanation

The movement of leaves in response to touch (e.g., in the Mimosa pudica plant) is a type of nastic movement called thigmonasty.
Nastic movements are rapid, reversible responses to a stimulus and are caused by changes in turgor pressure within specialized plant cells (pulvini), not by cell growth.
Because this movement is temporary and does not involve permanent cell division or elongation, it is not classified as a growth movement.

Option B: This is a growth movement. The downward growth of roots is a classic example of positive geotropism, where the plant part grows in the direction of the gravitational pull.
Option C: This is a growth movement. The growth of a pollen tube towards an ovule is an example of chemotropism, where growth is directed by a chemical stimulus.
Option D: This is a growth movement. The upward growth of shoots is an example of negative geotropism, where the plant part grows against the force of gravity.

Visual 1: Diagram: Comparison of Tropic vs. Nastic movements. The visual should show a plant stem bending towards a light source to illustrate directional, slow tropism, contrasted with a Mimosa leaf rapidly folding upon being touched to illustrate non-directional, fast nastic movement.
Visual 2: Animation: A short video showing the rapid folding and subsequent slow reopening of Mimosa pudica leaves. This demonstrates the reversible nature of turgor-driven movements.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Distinction between growth movements (tropism) and non-growth movements (nasty) in plants as background academic context rather than a clinical decision trigger.
While not a clinical topic, understanding fundamental biological principles like stimulus-response is a key part of the general science syllabus for many competitive examinations, including those for nursing.
The principle of a stimulus triggering a specific cellular response is universal in biology, from plant movements to human nerve impulses and muscle contractions.
What if the question asked for a movement that IS dependent on the direction of the stimulus? In that case, any of the growth movements (roots growing down, shoots growing up, or pollen tubes growing towards ovules) would be correct, as they are all directional tropic movements.

How to Approach the Question

First, identify the negative keyword 'NOT'. This signals that you must find the option that is an exception to the category mentioned.
Next, define the key concept: 'growth movement'. This refers to a permanent change in a plant's structure due to cell division and elongation, which is typically a slow process.
Evaluate each option against this definition.
Analyze Option A: The movement of leaves when touched is a fast, temporary, and reversible action. This does not fit the definition of permanent growth.
Analyze Options B, C, and D: Roots growing 'downwards', shoots growing 'upwards', and pollen tubes growing 'towards' ovules all describe permanent elongation in a specific direction. These are all clear examples of growth.
Conclude that the touch response of leaves is the only option that is not a growth movement, making it the correct answer.

Concept Tested & Keywords

Concept Tested: Distinction between growth movements (tropism) and non-growth movements (nasty) in plants.
Stem keywords: growth movement, plants
Lead-in keywords: NOT
Negative lead-in flag: The question uses the negative keyword 'NOT', asking to identify the option that is an exception.

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