B11.9 Plant hormones and the responses Flashcards
What are plant roots sensitive to?
Gravity and light
Shoots will grow towards light and against the force of gravity
This means that whichever way up the seed lands - plant always grows the right way up
What is tropisms/tropic responses?
The responses of plant roots and shoots to light and gravity
What is phototropism?
The response of a plant to light
What is gravitropism/geotropism?
The response of a plant to gravity
What is the role of auxin?
Controlling the responses of plants to light and gravity
What happens when a shoot responds to light from one side only?
Shoot will bend towards the light - auxin moves from the side of the shoot where the light is falling to the unlit side of the shoot
Once the light falls evenly on the shoot - levels of auxin will be equal on all side so the shoot grows straight again
What are the problems with high levels of auxin?
Inhibit growth of root cells
How does gravitropism work?
Plant is laid on its side in the dark - auxin is equally spread through the tissues
In the root more auxin gathers on the lower side
In the shoot - more auxin gathers on the lower side
Root grows more on the side with the least auxin make it bend and grow down
Shoot grows more on the side with the most auxin
When it has grown up - auxin makes it evenly spread out again
Why is tropic responses so important of shoots and roots?
Plants need to respond to surroundings
so that roots grow down into soil when a seed germinates and shoots grow up towards light for photosynthesis.
Shoots need to be able to grow into light if something shades them, whilst roots need to be able to grow towards water.
Trophic responses enable plants to respond to light and gravity
In which direction do shoots grown?
Towards light against the force of gravity
In which direction does roots grow?
In the direction of the force of gravity
