Plant response to stimulus Flashcards
What are some functions that hormones control in plants?
Division, elongation, and differentiation of cells.
What does auxin do?
Stimulates cell elongation, regulates branching and organ bending.
What do cytokinins do?
Stimulate plant cell division, promote later bud growth, slow organ death
What do gibberelins do?
Promote stem elongation, help seeds break dormancy and use stored reserves
What do brassinosteroids do?
Chemically similar to the sex hormones of animals, induce cell elongation and division
What does abscisic acid do?
Promotes stomatal closure in response to drought, promotes seed dormancy
What does ethylene do?
Mediates fruit ripening
What do blue-light photoreceptors do?
They control hypocotyl elongation, stomatal opening and phototropism (the orientation of a plant or other organism in response to light).
What do phytochromes do?
They act like molecular on-off switches. Red light turns phytochromes ‘on’, and far-red light turns it ‘off’. They regulate shade avoidance and germination.
Describe the role of circadian rhythms in plants
They control many functions in plants on a 24 hour time clock, which also interacts with the effects of dawn and dusk.
Where does information about the photoperiod come from in the plant?
Phytochrome conversion, flowering is often dictated by the photoperiod.
Describe the difference between short and long day plants
Short day plants require a night longer than a critical length to flower, long day plants need a night length shorter than a critical period to flower.
What is gravitropism?
The bending of an organ in response to gravity. Roots show positive gravitropism, stems show negative.
How do plant roots detect gravity?
Statoliths: starch-filled plastids
What is thigmotropism?
A growth response to touch.
