Summary of Plant Hormones

Question 1

What are the 4 types of plant hormones?

Answer 1

auxins
gibbrellins
ethene
abscisic acid

Question 2

What are auxins?

Answer 2

• made by root tips, shoot tips, young leaves
• promotes growth in shoots by cell elongation
• inhibits growth in root tips and leaf loss
• can be used for roding powders and weed killers

Question 3

What are gibbrellins?

Answer 3

• made by seeds, and young leaves
• promotoes seed germination and flowering, and stem elongation
• also promote lateral shoot growth
• used in production of seedless grapes

seed germination in gibbrellins -

• starch is hydrolysed into glucose in seeds
• glucose is then respired to make ATP
• that energy is used so seed can germinate

Question 4

What is ethene?

Answer 4

• made by old leaves and ripening fruit
• control leaf loss/ drop
• control fruit ripening
• roots are picked and transported when unriped
• ripen on demand in supermarket

leaf loss in ethene -

• old leaves make ethene which causes layer of cells in staulk to expand and break
• therefore leaf falls which saves water and nutrients

Question 5

What is abscisic acid?

Answer 5

• cause the stomata to close
• inhibit gibberellins
• reduce drought stress

Question 6

What is stomatal closure in absisic acid?

Answer 6

• stomata close to save water lost from transpiration
• guard cells turgid = open
• ABA binds to receptor on guard cell membrane - opens potassium and calcium ions
• ions diffuse out of guard cell
• increase water potential of guard cell
• h2o will leave guard cell by osmosis - guard cell flaccid - stomata closes