L12 Plant Physiology: Hormones Flashcards
(40 cards)
What are the main plant hormones responsible for growth promotion?
- Auxins
- Gibberellins (GAs)
- Cytokinins (CKs)
What are the main plant hormones responsible for growth inhibition?
- Abscisic Acid (ABA)
- Ethylene
What is the most common form of Auxin?
Indole Acetic Acid (IAA)
Where are Auxins produced in plants?
In the apical meristem at the tips of shoots
How do Auxins affect cell rigidity?
They raise pH around cells, making them less rigid
What processes do Auxins promote in plants?
- Elongation
- Root formation
- Bud growth
What factors can reduce Auxin levels?
- Shortening of days
- Drought
- Nutritional deficiency
Plant will only grow when conditions allow them to
What is apical dominance?
The tendency of plants to grow upwards rather than sideways
How do Auxins in the apical tip influence ethylene production?
They stimulate ethylene production, which inhibits axillary bud growth
What is the effect of distance from the apical tip on growth inhibition?
Inhibition diminishes in direct proportionality to distance from the apical tip
What is the commercial use of Auxins in agriculture?
- Promotes root growth
- Uniform flowering
- Sets fruit
- Prevents fruit drop
How are synthetic Auxins used in agriculture?
As herbicides to selectively kill broad-leaved weeds
What is a notable negative effect of synthetic Auxins on humans?
They have been shown to be toxic to humans
What were some consequences of using Agent Orange (weedkiller)?
- Caused cancer
- Caused birth defects in humans
What is a negative ecological impact of selective killing of weeds?
Negative impact on biodiversity
What are cytokinins?
Plant growth hormone
What processes are cytokinins involved in?
Cell growth, cell-division in roots and shoots, differentiation of tissues
How do cytokinins interact with auxins?
Antagonistic to auxins, they promote lateral bud growth
What effects do cytokinins have on nutrients and chlorophyll?
Attract nutrients to cells, delay the breakdown of chlorophyll
What are gibberellins named after?
Gibberella fujikuroi fungus
What is the primary function of gibberellins?
Causes cell elongation, cell division, lengthening of internodes, rapid stem growth
What type of growth do gibberellins emphasize?
Vegetative growth over fruiting
Why is vegetative growth emphasized by gibberellins?
Key to providing healthy, prolific leafy material for herbal use
How can gibberellins be modulated in plants?
Artificially to influence food characteristics
