Chapter 16 - Plant Responses Flashcards
What is abiotic stress?
Non-living environmental factor that could harm a plant (e.g. mineral deficiency, drought, etc.)
what are auxins responsible for?
tropsims, leaf fall (abscission) prevention, stimulating ethene production, cell elongation, and maintaining apical dominance.
what do giberrellins do?
- Cause food stores to become mobile during germination
- stem elongation
- causes pollen tube growth for fertilisation
what does ethene do?
- ripens fruits
- promotes leaf fall (abscission)
What does ABA (abscisic acid) do?
- maintains seed dormancy
- stimulates stomatal closure
- initiates protective responses against cold (antifreeze)
What is geotropism?
the tropism response to gravity - shoots are negative, roots are positive
What is phototropism?
the tropism response to unilateral light - shoots are positive, roots are negative
What is thigmotropism?
the tropsim response to pressure
What is hydrotropism?
the tropism response to water
What are the commercial uses of giberellins?
delay ripening of fruit
What are the commercial uses of auxins?
- producing seedless fruit
- weedkiller
What are the commercial uses of ethene?
ripening fruit quickly
What are the commercial uses of cytokines?
prevent the ageing of ripened fruit
What is Abscission?
leaf drop, as a result of ethene responding to an abscission zone, which uses enzymes to weaken the cell walls - caused by long periods of darkness.
How do plants prevent themselves from freezing?
- Certain chemicals (
What is a tropism?
A directional growth response of plants
Why do shoots so positive phototropism?
- auxin diffuses to the shaded side of the shoot tip
- as it does this, it stimulates H+ ions to move into cell wall via active transport
- Disruption to H-bonds makes cell more permeable
- Cells on shaded side elongate due to higher turgor pressure
- shoot elongates on shaded side, causing plant to bend towards the light.
How do hormones stimulate stomata to close?
- ABA binds to comp. receptors on guard cell membrane, causing Ca2+ ion channels on tonoplast to open - Ca2+ ions diffuse from vacuole.
- positive feedback causes other channels to open
- solute gradient increases, so water potential outside of cell decreases
- water diffuses out by osmosis
- guard cells get flaccid and close.
What is apical dominance?
Occurs during growth of apical shoot, where lateral shoots do not grow (caused by action of auxins, ABA and cytokinins.
