Question

Tropic movement occur as a result of
A. Unidirectional effect of environmental factors on plant organs
B. Bidirectional effect of environmental factors on plant organs
C. Multidirectional effect of environmental factors on plant organs
D. No effect of environmental factors on plant organs

Answer 1

Hint: Tropism is the directional response of an organism towards stimulus. Plants or plant parts can either show movement towards the stimulus (positive tropism) or away from the stimulus (negative trophim). The response is in terms of growth.

Complete Answer:
Trophic movement is the movement of plants in terms of growth towards the stimulus. The stimulus here is environmental factors like sunlight, gravity etc. Few types of trophic movement exhibited by plants are-
1. Phototropism- It is the directional movement in response to light either towards the light or away from the light.
2. Chemotropism- It is due to the reaction to chemical stimuli.
3. Geotropism- It is the plant movement in response to gravity.
4. Hydrotropism- It is the movement of plants to the presence or absence of water.
5. Thermotropism- It is the response of the plants towards the change in temperature.

The correct answer is (A). Tropic movement occurs as a result of unidirectional effect of environmental factors on plant organs.

Note: Nastic movement may or may not be a growth movement. It differs from the tropic movement because it is independent of the direction of stimulus. Example is curling the leaves of touch me not plant in response to touch.