8.1: Auxins (handout]

Question 1

What are auxins?

Answer 1

Hormones that plants produce

Question 2

What are auxin efflux pumps?

Answer 2

Move auxin from cytoplasm to cell wall

Question 3

How do auxin efflux pumps work? (2)

Answer 3

1. Different light intensities cause auxin efflux pumps to move
2. They set up the concentration gradient of auxin
   - lower if the lighter side, higher on the darker side

Question 4

After the auxin efflux pumps set up the concentration gradient of auxin, what happens next? (6)

Answer 4

1. Auxin binds to auxin receptor
2. This promotes the transcription of certain genes
3. This changes pattern of gene expression
4. Hydrogen ions are secreted into cell walls
5. This loosens the connection of cellulose fibers
6. Cell expands (elongation)

Question 5

Auxin is a ___ ____ that controls ____?

Answer 5

• growth promoter

- phototropism

Question 6

What is tropism?

Answer 6

Directional growth responses to directional stimuli

Question 7

Shoots are positively phototropic, meaning?

Answer 7

They grow towards the brightest source of light

- negatively phototropic means away

Question 8

Aside: the more auxin, the more?

Answer 8

The more auxin, it will promote gene expression

Question 9

Where is hydrogen ion concentration the highest?

Answer 9

ASK: hydrogen ion concentration is highest in Shady side to break down cellulose to be bendable
and elongate towards the Sun