Plant Responses to Stimuli

Rucete ✏ Biology In a Nutshell

1. Phototropism

• Plant shoots grow toward light
• This response helps maximize exposure to sunlight for photosynthesis
• Controlled primarily by the hormone auxin

2. Gravitropism (Geotropism)

• Roots grow downward, and shoots grow upward in response to gravity
• Ensures proper orientation of plant parts
• Auxin redistributes in the plant to promote root and shoot direction

3. Thigmotropism

• Plant growth in response to touch
• Example: climbing plants coil around supports or fences
• Allows plants to stabilize and reach sunlight or other resources