Question

Non-directional movement of a plant part with respect to stimulus is a

• A. Tropic movement
• B. Nastic
• C. Both A and B
• D. None of the above

Answer 1

The correct option is B Nastic

Plants exhibit two types of induced movements of curvature. These are namely tropic and nastic movements. The directional growth movements in which direction of growth is determined by the direction of stimulus are known as tropic movements. Examples: thigmotropism, phototropism, chemotropism, gravitropism etc. This makes option A incorrect. The non-directive growth movements of plants, wherein the direction of stimulus is not the determinant of the direction of movement, are known as nastic movements. These movements always occur in one direction. Examples: Seismonasty, photonasty, thermonasty etc. This makes option B correct. Thus, the correct answer is B.