2.81: Describe the Geotropic Responses to Stimuli

GEOTROPIC RESPONSE: Growth in Response to the Direction of Gravity

AUXINS: Plant Hormone Produced in the Stem Tips and Roots, which Controls the Direction of Growth

• Auxin is Produced at the Tip of Stems and Roots and Changes the Elasticity of Cells (More Elastic will Absorb More Water and therefore Grow Longer, Causing Bending in the Stem or Root)
• Factors such as Gravity can Interfere the Transport of Auxin Causing it to be Unevenly Distributed, Causing a Geotropic Response

GEOTROPIC RESPONSES OF PLANTS:

ROOTS	STEM
Diagram Showing Positive Geotropism caused by Auxins in the Roots	Diagram Showing Negative Geotropism caused by Auxins in the Stem
*Auxins Stops Growth in Root Cells When Roots Grow Sideways, Auxins Produced at the Tip of the Roots will Accumulate on the Underside (Bottom) due to Gravity Auxins Inhibits the Growth of Root Cells so will cause the Underside to Stop Growing Upper Side (Opposite Side) Will continue to Grow Longer and Elongate Roots will Grow Downwards Towards the Direction of Gravity, Allowing Positive Geotropism	*Auxins Increases Growth in Stem Cells When Stems Grow Sideways, Auxins Produced at the Tip of the Stem will Accumulate on the Underside (Bottom) due to Gravity Auxins Stimulates the Growth of Stem Cells so will cause the Underside to Grow Longer and Elongate Underside will Grow Upwards Against the Direction of Gravity, Allowing Negative Geotropism