Plant Hormones

Question 1

Why do plants produce hormones and respond to external stimuli?

Answer 1

They grow towards sources of water and light which is needed in order to survive

Question 2

What is positive tropism?

Answer 2

The plant grows towards the stimulus

Question 3

What is negative tropism?

Answer 3

The plant grows away from the stimulus

Question 4

What is photo-tropism?

Answer 4

A tropism where the stimulus is light

Question 5

What is geotropism (also known as gravitropism)

Answer 5

A tropism where gravity is the stimlus

Question 6

How does the shoot respond to photo-tropism and geotropism?

Answer 6

Photo-tropism: Grows towards the light (positive tropism)

Geo-tropism: Grows against the force of gravity (negative tropism)

Question 7

How does the root respond to photo-tropism and geotropism?

Answer 7

Photo-tropism: Grows away from the light (negative tropism)

Geo-tropism: Grows in the direction of the force of gravity (positive tropism)

Question 8

How can plant hormones be used by farmers?

Answer 8

1. Weed killers

2. Rooting hormones

Question 9

What are auxins?

Answer 9

A family of hormones that controls growth in the tips of shoots and roots.

Question 10

What do auxins do?

Answer 10

• It is produced in the tips and moves backwards to stimulate cell elongation (enlargement)
• Promotes growth in the shoots of the plants
• Inhibits growth in the roots of the plants

Question 11

How do auxins promote growth in a plant’s shoots?

Answer 11

• When the tip of a shoot is exposed to light, more auxin gathers on the side that is shaded than the side that is in the light.
• This makes the cells grow faster on the shaded side of the shoot and causes the shoot to bend towards the light.

Question 12

How do auxins inhibit growth in a plant’s roots that grow towards gravity?

Answer 12

• A root growing sideways will have more auxin on the lower side of the root because of gravity.
• Extra auxin in the roots inhibit growth which means that the top of the root will elongate faster, causing the root to grow downwards

Question 13

How do auxins inhibit growth in a plant’s roots that grow towards moisture?

Answer 13

• An uneven amount of moisture either side of the root causes more auxin to gather on the side with more moisture.
• This inhibits growth on that side and the plant will bend in that direction, towards the moisture.

Question 14

If the tips of the shoots or roots have been removed what will happen?

Answer 14

There will be no growth because auxin is not produced.