Plant growth regulators/Hormones

Question 1

What are the 2 categories of plant hormone

Answer 1

1. Growth promoters (shoot, floral and root growth)
2. Growth inhibitors (Dormancy and ripening)

Question 2

Name 4 growth promoter hormones

Answer 2

Auxin
Cytokinin
Gibberellin
ethylene

Question 3

Name a growth inhibitor

Answer 3

Abscisic acid

Question 4

How do plant hormones work

Answer 4

They act as messengers by emitting signals (they do not act independently) throughout the plant - They act in v low concentrations - they respond to different biotic and abiotic factors/ needs

Question 5

What is the mechanism of a hormone creating a response

Answer 5

1. Hormone binds to a protein
2. Hormone+receptor change the proteins’ conformation to trigger a chain of events
3. changes in the proteins shape stimulates the production of relay molecules that trigger responses.

Question 6

Why are plant hormones important in a vine

Answer 6

Influence the growth rate of a vine
Influence the fruitfulness of a vine

Question 7

Describe Auxin and its functions

Answer 7

Stimulates cell elongation and cell division
Stimulates differentiation of phloem and xylem
mediates/controls phototropism and gravitropism
contributes to apical dominance - supresses lateral buds
Delays fruit ripening and leaf senescence

Question 7

Describe gibberellins + functions

Answer 7

1. Encourages stem elongation - stimulates cell division and elongation
2. Stimulates flowering
3. Breaks dormancy
4. Promotes fruit set
5. Used to Increase the size of seedless grapes
   High application of exogenous gibs can lead to poor budburst, increased rot,poor colour development

Question 8

Describe cytokinins + functions

Answer 8

1. Stimulates cell division
2. inhibits elongation of stems
3. stimulates lateral budburst
4. delays ripening

exogenous cytokinins are not widely used - expensive bad for health but if applied near fruit set + increased berry size Auxin and cytokinins have to work together to be effective

Question 9

Describe Ethylene + functions

Answer 9

Gaseous hormone
1.Stimulates release of dormancy
2. Stimulates root and shoot growth
3. Stimulates fruit ripening
4. Production increases during stress - drought and heat

Used for fruit maturation + promotes fruit ripening

Question 10

Describe abscisic acid + functions

Answer 10

• Counteracts action of gibberellins
• Inhibits growth during times of environmental stress by stimulating the closure of stomata.
• Promotes dormancy by Inhibiting shoot growth + stem elongation

applications increase a vines cold hardiness