Plant Movement

Question 1

What is Phototropism?

Answer 1

• Response to light
• Different tissues respond differently
– Shoots are positively phototropic
– Roots are negatively phototropic
• Auxin levels higher on “dark side” = more cell elongation on dark side = turn toward the light

Question 2

What is Geotropism?

Answer 2

• Again different tissues respond differently – Shoots are negatively geotropic
– Roots are positively geotropic
• Helpful in that you don’t have to sow seeds the right way up (rem. prac experiment with corms)

Question 3

Other tropisms?

Answer 3

• Roots of willows have been known to break concrete sewer pipe to gain water (hydrotropism)
• Roots will often grow toward high concentrations of nutrient (chemotropism)

Question 4

What are Multiple Stimuli?

Answer 4

Multiple Stimuli
• Shoots grow away from gravity but toward light
• What happens if light is not UP
• Light almost always wins

Question 5

What are Nastic movements?

Answer 5

Nastic movements
• These movements, unlike tropisms are not dependent on the direction of the stimulus
• E.g. caused by changes in temperature, humidity
• Examples include, closing of a venus fly trap, movments due to changes in turgor pressure
• Climbing vines, flowers opening and closing