Stimulus and Response

Stimulus and Response

• A stimulus is anything that causes a response in an organism.
• A response is the activity of the cell, organism, or part of an organism as a result of a stimulus.
• The growth of a plant is affected by;
  • External factors (e.g., light, temperature) and
  • Internal factors (e.g., growth regulators).
• Growth regulators control the growth of plants and can stimulate growth or inhibit growth.

Plant Tropisms

• A tropism is the growth response of a plant to a stimulus.
• A positive tropism occurs when a plant grows towards the stimulus.
• A negative tropism occurs when a plant grows away from the stimulus.

Plant tropisms include:

1. Phototropism
2. Geotropism
3. Thigmotropism
4. Hydrotropism
5. Chemotropism