Response - Response to Stimuli: Plant Growth Factors Flashcards
What is a tropism?
The growth of a part of a plant in response to a directional stimulus.
What is IAA?
Indoleacetic Acid - an auxin which controls plant cell elongation.
Give an example of a plant growth factor.
IAA
Are plant growth factors produced in small or large quantities?
Small quantities.
What direction is IAA transported in?
Away from the the tip of the shoots or roots where it’s produced.
What does the acid growth hypothesis involve?
The active transport of hydrogen ions from the cytoplasm into spaces in the cell wall.
What can IAA do to young cell walls?
Increase their plasticity.
What does the acid growth hypothesis explain?
How IAA can increase the plasticity of young cell walls.
Give 2 types of tropisms that shoots show.
Positive phototropism
Negative geotropic
Give 3 types of tropism that roots show.
Negative phototropism
Positive geotropism
Positive hydrotropism
What does IAA do in roots?
Inhibits cell elongation.
What does IAA do in shoots?
Promotes cell elongation.
Describe how IAA causes shoots to be positively phototropic. (6 points)
Cells in tip produce IAA IAA transported evenly down shoot Light causes IAA to move to shaded side IAA causes cells to elongate Cells on shaded side elongate more Shoot bends towards light
Describe how IAA causes roots to be positively geotropic. (6 points)
Cells in tip produce IAA IAA transported to all sides of root Gravity causes IAA to move to lower side IAA inhibits cell elongation Cells on lower side elongate less Root bends towards gravity
