Plant hormones

Question 1

What is the name given to plant response to light?

Answer 1

phototropism

Question 2

What is the name given to a plants response to gravity.

Answer 2

geotropism or gravitropism

Question 3

What is the name of the hormone that controls growth in plants?

Answer 3

The hormone auxin controls growth in plants.

Question 4

Explain how auxin controls phototropism in plants.

Answer 4

Auxin is broken down by sunlight and so concentrates in the unlit side of the shoot. The cells on the unlit side of the shoot elongate and grow causing the shoot to bend towards the light.

Question 5

Explain how auxin controls gravitropism in shoots and roots.

Answer 5

Auxin makes shoot cells grow but inhibits growth in root cells.

So auxin causes unequal growth of cells = the lower side now grows more slowly than the upper side

this causes the shoots and roots to grow towards the force of gravity

Question 6

What is the role of gibberellins in plants.

Answer 6

Gibberellins are important in initiating seed germination.

Question 7

What is the role of ethene in plants?

Answer 7

Ethene controls cell division and ripening of fruits.

Question 8

Describe how auxins can be used in agriculture and horticulture.

Answer 8

Auxins are used:
• as weed killers
• as rooting powders
• for promoting growth in tissue culture.

Question 9

Describe how ethene can be used in agriculture and horticulture.

Answer 9

Ethene is used in the food industry to control ripening of fruit during storage and transport.

Question 10

Describe how gibberellins can be used in agriculture and horticulture.

Answer 10

Gibberellins can be used to:
• end seed dormancy
• promote flowering
• increase fruit size.

Question 11

Plant growth pracitcal

Answer 11

1) Put cotton wool into three petri dishes, and add the same volume of water to each dish.
2) Add ten seeds to each dish and place them in a warm place where they won’t be disturbed.
3) Allow the seeds to germinate, and add more water if the cotton wool dries out.
4) Once the seeds have germinated, ensure the petri dishes each contain the same number of seeds, and remove any extra seeds if necessary.
5) One petri dish will sit in full light on a windowsill, the second will be in a dark cupboard, and the final dish will be placed in partial light.
6) Every day for one week, measure the height of each seedling and record the results in a table. You must record the height of the individual seedlings on each day.
7) Calculate the mean of the seedlings each day, and compare the mean heights in the three different locations.

Question 12

What are the control variables in this experiement (5)

Answer 12

same temperature / water / soil type/ same seedling type & number

Question 13

How do you measure bent plants?

Answer 13

using a thread

then measure thread

Question 14

describe natural selection

Answer 14

• Individual organisms within a particular species show a wide range of variation for a characteristic.
• Individuals with characteristics most suited to the environment would be more successful competitors and are more likely to survive to breed successfully.
• The characteristics that have enabled these individuals to survive are then passed on to the next generation.
• overtime beneficial characteristics become more common in the population and the species changes - it evolves