B3.2.7 Uses of Plant Hormones

Question 1

Function of auxin

Answer 1

Stimulate growth by causing cell elongation
Also help to regulate fruit development
Without auxins fruit are often too small

Question 2

Function of ethene

Answer 2

Causes plant fruits to ripen by stimulating the conversion of starch into sugar
This is why a ripe fruit tastes sweeter than an unripe one
The only plant hormone that exists as a gas

Question 3

Gibberellins function

Answer 3

Promote growth, particularly stem elongation
End dormancy periods of seeds and buds
This leads to shoots and flowers opening

Question 4

How is auxin used as weed killer

Answer 4

Auxin weed killer makes the weeds grow too fast
This rapid uncontrolled growth kills the plant

Question 5

How do auxin promote root growth

Answer 5

Rooting powder contains auxin
Gardeners use auxin to produce identical plants from cuttings
They cut off a plant from a shoot, dip it into rooting powder and plant it
After a few days, rooots develop from the cut stem
The new roots anchor into the soil and take up water and minerals

Question 6

How does auxin delay ripening

Answer 6

Sprayed on fruit trees
Allows a harvest to all be collected at the same time
Can prevent fruit from dropping too early

Question 7

How is ethene used to ripen fruit

Answer 7

Sprayed onto fruit trees and plants so their fruits ripen quicker
Allows fruit to be ready earlier in the growing season

Question 8

How do auxins produce seedless fruit

Answer 8

Seeds are produced after a plant is pollinated by insects or the wind
If auxins are applied to unpollinated flowers, the plant produces seedless fruit

Question 9

How do gibberellins / auxins control dormancy

Answer 9

Seeds remain dormant until conditions are ideal for growth so they don’t germinate at the end of summer
Commercial growers trigger seed germination in winter by spraying them with g/a in the greenhouse