what do you mean by tropism ? ☆ Also named that.
Answers
★A growth movement of a plant part in response to an external stimuli in which the direction of stimuli determines the direction of response is called Tropism.
★If the growth movement is towards stimuli, then it is positive tropism
★If the growth movement is away from
stimuli then it is negative tropism.
☆Phototropism :- Light
☆Geotropism :- earth gravity
☆Hydrotropism :- Water
☆Thigmotropism :- Touch
☆Chemotropism :- Chemical
Tropism
The growth movements of plants in response to a directional stimulus is called tropism.
Types of Tropism
Positive Tropism: The growth movements of plants that are in the same direction as the stimulus.
Negative Tropism: The growth movements of plants that are in the opposite direction to the stimulus.
Examples of Tropism
❊ Phototropism
⇒The growth movements of plants in response to the directional stimulus of light is called phototropism. The roots of the plants are negatively phototropic while the stems are positively phototropic. The growth of auxins on the darker region causes this movement.
❊ Geotropism
⇒The growth movements of plants in response to the directional stimulus of gravity of earth is called geotropism. The roots are positively geotropic while the stems are negatively geotropic when a plant is placed horizontally on a ground.
❊ Hydrotropism
⇒The growth movements of plants in response to the directional stimulus of water is called hydrotropism. The roots of the plants are hydrotropic in nature.
❊ Thigmotropism
⇒The growth movements of plants in response to the directional stimulus of touch is called thigmotropism. Tendrils and twiners show these movements.
❊ Chemotropism
⇒ The growth movements of plants in response to the directional stimulus of chemicals is called chemotropism. For example; pollen grains extend pollen tubes to reach the ovule.
