The movement of plant in response to external stimulus of no particular direction is
taxism
tropism
hyptotropic movement
nastic movement
phototropism
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Plant stimuli refer to the changes or reactions in a plant's environment that cause it to respond in specific ways. Plants are sensitive to various environmental factors and can react to stimuli through growth or movement. This phenomenon is called tropism or nastic movement, depending on the type of response.
Types of Plant Stimuli:
1. Light (Phototropism):
Phototropism is the plant’s response to light. Plants tend to grow towards light sources.
Example: A sunflower bending towards the sun is an example of positive phototropism.
2. Gravitation (Gravitropism or Geotropism):
Gravitropism refers to a plant's growth in response to gravity. Roots typically grow downward (positive gravitropism), while stems grow upward (negative gravitropism).
Example: The growth of roots towards the soil and stems towards the sky.
3. Touch (Thigmotropism):
Thigmotropism is the plant's response to touch or physical contact. Plants like vines often grow around structures they touch.
Example: Creeping vines twining around a trellis.
4. Water (Hydrotropism):
Hydrotropism is the plant's growth response to moisture. Roots tend to grow towards areas with higher water content.
Example: Roots of a plant growing towards a wet area in the soil.
5. Temperature (Thermotropism):
Thermotropism is a plant’s response to temperature changes.
Example: Some plants may drop their leaves or close their flowers to protect themselves from extreme heat.
6. Chemicals (Chemotropism):
Chemotropism is the movement of plants in response to chemicals in their environment.
Example: Pollen tubes grow towards the ovule in response to chemical signals during fertilization.
Types of Movements in Plants:
1. Tropisms:
Directional movements (positive or negative) in response to stimuli like light, gravity, or touch.
2. Nastic Movements:
Non-directional movements that occur regardless of the direction of the stimulus.
Example: The closing of mimosa leaves when touched (seismonasty).
Why is This Important?
Survival: Stimuli responses like phototropism allow plants to maximize their exposure to sunlight for photosynthesis.
Reproduction: Stimuli like chemotropism help in processes like pollination.
Protection: Thigmotropism allows plants to cling to support structures, preventing damage.
Answer is D- Nastic movement
Nastic movements are plant movements that occur in response to environmental stimuli but unlike tropic movements, the direction of the response is not dependent on the direction of the stimulus.
