3.3 Phytohormones Flashcards
How are phytohormones transported through a plant?
Active transport, diffusion and mass flow in phloem sap and/or xylem vessels.
What are Auxins (IAA) responsible for?
Phototropism and cell elongation
How does phototropism occur?
Auxins congregate on the dark side of the plant which causes the plant to bend in the opposite direction.
What is Abscisic Acid (ABA) responsible for?
Inhibition of bud growth
What is the adaptive advantage of Abscisic Acid?
The plant uses less energy growing buds and seeds during the winter as they would be killed by the low temperatures, or to focus more energy on growing.
What are Cytokinins responsible for?
Stimulation of cell division (cytokinesis). Balances with auxin levels so roots and shoots are proportional. Delays leaf senescence.
What is Gibberellin (GA) responsible for?
Encouraging germination and stem elongation; breaks seed and bud dormancy. Delays senescence in citrus fruits.
What is the process of breaking bud dormancy?
- Seed absorbs water
- Gibberellin produced
- Gibberellin presence initiates starch reserve breakdown.
- Energy from starch reserve breakdown is used for germination.
What is Ethylene responsible for?
Stimulation of fruit ripening/initiating abscission
What part of the plant increases when cytokinin levels increase and auxin levels decrease?
Shoots and buds
What part of the plant increases when cytokinin levels decrease and auxin levels increase?
Roots
