B5: PLANT HORMONES

Question 1

What does auxin do?

Answer 1

controls growth near tips of roots and shoots in response to stimuli

Question 2

How does auxin cause plants to grow in response to a stimulus?

Answer 2

-unequal distribution of auxin = unequal growth rates
-so the plant grows in a specific direction (towards the stimulus)

Question 3

What is phototropism?

Answer 3

plant growth in response to light

Question 4

What is geotropism?

Answer 4

plant growth in response to gravity

Question 5

What does auxin do in shoots?

Answer 5

-auxin stimulates cell elongation
-stimulates growth towards light and against the direction of gravity

Question 6

What does auxin do in roots?

Answer 6

-auxin inhibits growth
-less cell elongation in root where auxin is concentrated
-stimulates growth in the direction of gravity

Question 7

What would happen if the tip of a shoot was removed?

Answer 7

there would be no auxin so no growth

Question 8

What would happen if the tip of a shoot was completely covered?

Answer 8

plant would grow straight regardless of light (no light reaches auxin so there is an equal distribution of auxin)

Question 9

What would happento the growth of shoots if the plant pot was turned on its side?

Answer 9

shoots bend up towards light and away from gravity

Question 10

RP- phototropism: method

Answer 10

-put cotton wool into 3 petri dishes, and add the same volume of water to each dish
-add 10 seeds to each dish and place them in a warm place where they won’t be disturbed
-allow the seeds to germinate, and add more water if the cotton wool dries out
-once the seeds have germinated, ensure the petri dishes each contain the same number of seeds, and remove any extra seeds if necessary
-put 1 petri dish on the windowsill in full light, 1 in darkness and 1 in partial light
-every day for 1 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
-calculate the mean of the seedlings each day, and compare the mean heights in the three different locations

Question 11

RP- phototropism: variables

Answer 11

IV - different exposure to light
DV - change in height of seedlings
CVs - volume of water, type of seedling, temp

Question 12

How could you investigate the effect of gravity on plant growth?

Answer 12

-place 4 seedlings on damp cotton wool in a petri dish each with their roots pointing in different directions
-store petri dish vertically in the dark
-roots of each seedling should grow downwards

Question 13

What does gibberellins do?

Answer 13

initiates seed germination

Question 14

What does ethene do?

Answer 14

controls cell division and ripening of fruits by stimulating enzymes

Question 15

What are the uses of auxin?

Answer 15

-weed killers
-rooting powders
-promoting growth in tissue culture

Question 16

What are the uses of gibberellins?

Answer 16

-ending seed dormancy
-promoting flowering
-increasing fruit size

Question 17

How is ethene used?

Answer 17

used for controlling ripening of fruits (during storage/transport)