Hormones in Plants

Question 1

What is Auxin? What does it control?

Answer 1

Auxin is a plant hormonethat controls growth near thetips of shoots and roots

Question 2

What does Auxin control the growth of a plant in response to?

Answer 2

Light (photosynthesis)

Gravity (gravitropism or geotropism)

Moisture

Question 3

Where is Auxin produced?

Answer 3

In the tips

Question 4

Where does Auxin go after being produced?

Answer 4

It is produced in the tips and then moves backwards to stimulate the cell elongation (enlargement) process which occurs in the cells just behind the tips

Question 5

What happens if the tip of a plants shoot is removed?

Answer 5

No auxin is avaliable and the shoot may stop growing

Question 6

Do shoots grow towards or away from light?

Answer 6

Towards

Question 7

Explain why shoots grow towards light

Answer 7

When a shoot tip is exposed to light, more auxin accumulates on the side that’s in the shade than the side that’s in the light

This makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light

Question 8

Do shoots grow towards or away from gravity?

Answer 8

Away from

Question 9

Explain why shoots grow away from gravity

Answer 9

When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side

This causes the lower side to grow faster, bending the shoot upwards

Question 10

Which ways to roots grow to gravity?

Answer 10

Towards gravity

Question 11

Explain why roots grow towards gravity

Answer 11

A root growing sideways will also have more auxin on its lower side

But in a root the extra auxin inhibits growth. This means the cells on top elongate faser, and the root bends downwards

Question 12

Do roots grow towards or away from moisture?

Answer 12

Towards

Question 13

Explain why roots grow towards moisture?

Answer 13

An uneven amount of moisture either side of a root produces more auxin on the side with more moisture

This inhibits growth on that side, causing the root to bend in that direction, towards the moisture

Question 14

Are weeds in crop fields broad-leaved or narrow-leaved?

Answer 14

Broad-leaved

Question 15

Are cereals and grasses broad-leaved or narrow-leaved?

Answer 15

Narrow-leaved

Question 16

What are selective weed killers made of? What sort of plants do they effect? How do they effect the plant?

Answer 16

They are made of plant growth hormones

They effect broad-leaved plants

They disrupt their normal growth patterms, which soon kills them, but leave the crops untouched (as crops are narrow leaved but this only effects broad leaved)

Question 17

Explain why adding rooting powder to plant cuttings make them grow?

How is this useful?

Answer 17

Plant cuttings won’t always grow in soil. If you add rooting powder (which contains auxin) they’ll produce roots rapidly and start growing new plants

This helps growers produce lots of clones of a really good plant very quickly