2.79 plants respond to stimuli

• Stimuli are changes in the environment. e.g temperature changes or light changes.

• The plant has receptors that detect the stimuli and then turn those into a response.

• The responses often take the form of growth. this type of response to a stimulus is called a tropism.

• Tropisms that involve: light are called phototropism. involve gravity are called geotropism.

• The connection between the receptor and the response usually takes the form of plant hormones sometimes called plant growth regulators.  e.g. Auxin