Plant Hormones Flashcards
What is the definition of a plant hormone?
A low molecular weight substance that acts specifically at low concentrations, and binds to specific receptors to trigger a response.
Which hormones promote growth?
Auxin, brassinosteroid, cytokinin, gibberellin, karrikins, polyamine and strigolactone
Which hormones inhibit growth or promote death?
Abscisic acid, ethylene, oligosaccharide
Which hormones provide defence?
Jasmonic acid, nitric oxide, oligosaccharide, salicylic acid and systemin
what is phototropism?
Movement towards light.
Where is light signal perceived by the plant to help it bend to light.
At the tips of plants.
What do we know about auxin?
- The chemical structure
- Auxin promotes root formation and inhibits bud outgrowth
- Auxin moves through the shoot from tip to base
- Different tissues have different sensitivities to auxin
- Auxin affects growth in a concentration and tissue specific way
What is a gibberellin (GA)?
It inhibits growth inhibitors, rather than promoting growth in and of itself.
It can break seed dormancy.
Induces starch in grains.
Helps the transition from juvenile to adult.
Can initiate flowering or promote the transitition to fruiting in some species,
What is a cytokinin?
- Promotes plant cell division
- Acts antagonistically to auxin
- Delays leaf death
- Moves up the plant from the roots
- Promotes lateral bud growth when apical dominance is removed by chopping off meristem
What is ethylene?
- Promotes fruit ripening
- Induces senescence (leaf components are broken down and transported back into plant before detaching)
- Induces flowering in bromeliads but inhibits in most other species
- Breaks seed and bud dormancy in some species
What is abscisic acid?
- Induces ethylene production
- Places buds into winter dormancy
- Promotes root and shoot growth when under water stress (lack of water)
- Stress responses
What are strigolactones?
- Regulate shoot and root branching to nutrient responses/deficiencies
- promotes symbiosis with fungi
What are brassinosteroids?
Contribute to:
- Growth
- cell division, elongation and differentiation
- Stress tolerance
- Reproductive development
- it is not very abundant in plant tissues like other hormones
What is jasmonic acid?
- involved in stress response to pathogens or damage
What are plant growth regulators (PGRs)?
The collective term for natural and synthetic plant hormones.
