5.5.5 Gibberellins

Question 1

What do gibberellins do?

Answer 1

• Stimulate seed germination
• Stimulate elongation of stem (stimulate cell division in stem)

Question 2

Experimental evidence for role of gibberellin in stem elongation

Answer 2

• Dwarf plants have low levels of gibberellin
• Treating dwarf plants with gibberellins makes them grow to the same height as normal plants
• So some farmers apply gibberellin to short plants to stimulate growth

Question 3

Experimental Evidence for the role of gibberellin in seed germination

Answer 3

• Mutant seeds that don’t produce gibberellin don’t germinate, but do when gibberellin is applied
• Seeds of some lettuce that requires light to germinate can be made to germinate in the dark if gibberellin is applied