Tropisms Flashcards
What is a nastic response?
Growth response to non-directional stimuli. eg. mimosa, venus fly trap
What is a tropic response?
Directional growth response to directional stimuli. eg. gravitropism, phototropism, thigmotropism.
What is the phototropic signal pathway?
Directional light percieved by photoreceptor, ana-symetric growth response towards light
What light triggers phototropism?
Blue light
What is the phototropic response of cry mutants in directional light?
Cry mutants are blind to blue light from above but not from the side.
What is the phototrophic response of nph mutants in directional light?
Nph mutants respond normally to blue light from above but are blind to blue light from the side.
How is auxin transported?
Auxin is transported basipetally by active transport.
Give an example of gravitropic response altering through plant development:
Peanut:
Gynophores are negatively gravitropic to allow pollination
Once fertilised, positively gravitropic to bury the peanut seed
Where is gravity sensed in the roots?
In the columella
What happens to root growth and gravitropism if the root cap is removed?
Accelerated growth but not gravitropism.
What happens to root growth and gravitropism if half the root cap is removed?
Root bends in absence of a gravity stimulus.
What cells sense gravity?
Statocytes
Containing starch granules (statoliths)
What evidence is there that statoliths sense gravity?
- Found in gravity sensing parts of plant
- Arabidopsis with less starch have less statoliths and have a reduced response
- Moving statoliths can create a response
What auxin transport protein is found in the plasma membrane of root caps?
AtPIN3
What regulates chloroplast movement in response to bright light?
Phototropin 2 - chloroplasts avoid bright light.
