Plant Hormones

Question 1

Auxin

Answer 1

Plant hormone which controls growth near tips of shoots and roots

Responds to phototropism, gravitropism and geotropism

Question 2

Why do shoots grow towards light?

Answer 2

More auxin accumulates on side in shade

Makes cells elongate faster on shaded side

So shoot bends towards light

Question 3

Why do shoots grow away from gravity?

Answer 3

Gravity produces unequal distribution of auxin in tip with more on lower side

Lower side grows faster

So shoot bends upwards

Question 4

Why do roots grow towards gravity?

Answer 4

Root growing sideways with have more auxin on lower side

But on a root, extra auxin inhibits growth

Cells on top elongate faster

So root bends downwards

Question 5

What method to investigate plant growth responses?

Answer 5

Using cress seeds under lamp

Question 6

Control variables of this experiment

Answer 6

Same number of seeds in each dish

Use seeds that have all come from same packet

Stable temperature

Same amount of water

Same light intensity

Question 7

Use of auxins commercially

Answer 7

Killing weeds

Growing from cuttings with rooting powder

Growing cells in tissue culture

Question 8

Gibberellin

Answer 8

Stimulates plant stems to grow

Question 9

Commercial uses of gibberellins

Answer 9

Controlling dormancy

Inducing flowering

Growing larger fruit

Question 10

Ethene

Answer 10

Stimulates ripening of fruits

Question 11

Commercial uses of ethene

Answer 11

Speed up ripening of fruit

Fruit can be picked whilst unripe and transported with ethene gas