Plant hormones Flashcards
define tropism
A plants movement/growth towards or away from the stimulus (light and water)
name the three types of tropisms
gravitropism - gravity
phototropism - light
hydrotropism - water
what type of tropism does roots have?
negative phototropism (-VE)
positive gravitropism and hydrotropism (+ VE)
what type of tropism does a stem have?
negative gravitropism and hydrotropism (-VE)
positive phototropism (+VE)
What is the hormone which controls tropism?
Auxin
What are the plant hormones?
Ethene
Auxin
Gibberellins
What does the plant hormone ethene do?
- controls fruit ripening
- allows stored fruit ripen quickly
What is auxin?
A plant hormone which produces at the tip of plant roots and shoots
What does the plant hormone Gibberellin do?
- causes germination which causes flowering
- prevents seeds forming which increases the size of fruits
What does the plant hormone Auxin do?
- controls plant growth by making plant cells grow longer and divide more.
- a weed killer which attack some plants but not others.
What happens when light if fallen directly above the shoots?
If light falls on the plant directly from above the auxin diffuses evenly down the stem causing plant cells to all elongate at the same rate. The plant grows upwards
What happens when light if fallen to one side of the shoots?
The auxin will diffuse unevenly to the shady side of the cell making the shady side of the cell elongate at a faster rate than those on the sunny side. Over time this will cause the plant to bend itself towards the light source so it can absorb more of the light.
