Practise Use of plant hormones. 13 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Plant hormones are used in agriculture and horticulture. Give two uses of gibberellins.
To end seed dormancy; to promote flowering; to increase fruit size
Suggest one advantage to a flower grower of using gibberellins to promote flowering.
The flowers can be made ready for a particular date or market
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Plant hormones are used in agriculture and horticulture.
(a) Which plant hormone is used in rooting powders? Tick (✓) one box.[1]
Auxin
Ethene
Gibberellin
Testosterone
(b) Which plant hormone is used to control the ripening of fruit during storage and transport? Tick (✓) one box.[1]
Auxin
Ethene
Gibberellin
Insulin
(c) Give two uses of gibberellins.[2]
(d) Auxins are used as weedkillers. Give one other use of auxins.[1]
Show the answer and mark scheme
(a)Answer: Auxin
(b)Answer: Ethene
(c)Answer: To end seed dormancy; to promote flowering; to increase fruit size
to end seed dormancy / make seeds germinate
to promote flowering
to increase fruit size
(d)Answer: Rooting powders / promoting growth in tissue culture
rooting powder / to make cuttings grow roots / promoting growth in tissue culture
Question 2Medium6 marks
A farmer sprays a field of wheat with a weedkiller that contains a synthetic auxin. The weedkiller kills broad-leaved weeds, such as dandelions, but it does not kill the wheat.
(a) Explain how the auxin weedkiller kills the weeds.[2]
(b) Explain why killing the weeds increases the yield of wheat.[2]
(c) Suggest one reason why the weedkiller kills dandelions but not wheat.[1]
(d) Give one advantage of using a selective weedkiller rather than removing weeds by hand.[1]
Show the answer and mark scheme
(a)Answer: The weeds absorb the auxin, which makes them grow very rapidly and uncontrollably, so they die
the auxin causes (very) rapid / uncontrolled growth
which the weed cannot sustain, so it dies
(b)Answer: There is less competition for light, water and mineral ions, so the wheat grows better
less competition (between weeds and wheat)
for light / water / mineral ions / space
(c)Answer: Broad leaves absorb more weedkiller than the narrow leaves of wheat
broad leaves absorb more (weedkiller) / wheat has narrow leaves so absorbs less / wheat is less sensitive to auxin
(d)Answer: It is quicker and cheaper for a large field
quicker / cheaper / needs fewer workers
Question 3Hard4 marks
A farmer is deciding how to control weeds in a cereal field: using a selective auxin-based weedkiller, or using a machine that uproots weeds mechanically between the rows of crop plants.
Evaluate the use of the selective weedkiller compared with mechanical weeding for this farmer.[4]
Show the answer and mark scheme
Answer: The weedkiller reaches weeds growing close to crop plants and is usually quicker and cheaper over a large field, but it has a cost, repeated use risks weeds evolving resistance, and it could affect non-target plants; mechanical weeding uses no chemicals but is slower and may miss weeds close to the crop; a justified conclusion
(for weedkiller) it can kill weeds growing very close to crop plants that a machine might damage the crop while trying to reach
(for weedkiller) it is usually quicker to apply, and cheaper than a machine and driver, over a large field
(against weedkiller) it has a cost, and repeated use could lead to weeds evolving resistance, or could affect non-target plants if it drifts
(for mechanical) it uses no chemicals, so it may suit organic farming and there is no risk of weeds evolving resistance
(against mechanical) it is slower, may not remove weeds very close to the crop stems, and could damage crop roots
a justified conclusion, e.g. the weedkiller is the better choice for a large field, as long as it is not used too often