1 Flowering plants often produce fruit.
State one hormone that promotes the ripening of fruit.
[1]
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, 2 A student setting up an experiment to investigate the effect of light on cress plant seedlings accidentally shone
the bright light onto one side of the face of another student. He noticed that the student immediately responded
by raising her hand to shield her eye from the light.
The response of the cress seedlings to light shining from one direction was slower, but after 24 hours the cress
seedlings had grown towards the light.
Describe the mechanisms that produced the responses to light in the cress seedlings and in the human.
cress seedlings
human
[7]
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, 3 Plants have evolved response mechanisms to a variety of abiotic and biotic stimuli.
Flowering plants respond to changes in the length of day. The advantage of this response is that these plants
begin to flower only when environmental conditions are favourable.
Karl Hamner studied the effect of exposure to light and darkness on flowering in cocklebur plants. He placed
cocklebur plants in darkness for different periods of time. Some of his results are shown in Table 6.1.
Period of darkness (h) Flash of light during the period of Flower production
darkness?
8.5 No Yes
6.5 No No
12.5 Red light after 6 hours No
12.5 Red light after 6 hours, followed by Yes
a flash of far red light
6.5 Several flashes of far red light Yes
Table 6.1
Suggest what conclusions can be drawn from the results in Table 6.1 about the effect of exposure to light and
darkness on flowering in cockleburs.
[3]
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, 4 Herbicides work in a number of different ways.
(i) Some herbicides, known as phenoxy herbicides, mimic the action of the auxin, indoleacetic acid (IAA).
What is the normal action of IAA in plant cells?
[1]
(ii) The herbicide atrazine works by disabling plastoquinone, one of the proton pumps in photosystem II.
Explain how atrazine would kill a susceptible plant.
[5]
© OCR 2023. You may photocopy this page. 4 of 31 Created in ExamBuilder
State one hormone that promotes the ripening of fruit.
[1]
© OCR 2023. You may photocopy this page. 1 of 31 Created in ExamBuilder
, 2 A student setting up an experiment to investigate the effect of light on cress plant seedlings accidentally shone
the bright light onto one side of the face of another student. He noticed that the student immediately responded
by raising her hand to shield her eye from the light.
The response of the cress seedlings to light shining from one direction was slower, but after 24 hours the cress
seedlings had grown towards the light.
Describe the mechanisms that produced the responses to light in the cress seedlings and in the human.
cress seedlings
human
[7]
© OCR 2023. You may photocopy this page. 2 of 31 Created in ExamBuilder
, 3 Plants have evolved response mechanisms to a variety of abiotic and biotic stimuli.
Flowering plants respond to changes in the length of day. The advantage of this response is that these plants
begin to flower only when environmental conditions are favourable.
Karl Hamner studied the effect of exposure to light and darkness on flowering in cocklebur plants. He placed
cocklebur plants in darkness for different periods of time. Some of his results are shown in Table 6.1.
Period of darkness (h) Flash of light during the period of Flower production
darkness?
8.5 No Yes
6.5 No No
12.5 Red light after 6 hours No
12.5 Red light after 6 hours, followed by Yes
a flash of far red light
6.5 Several flashes of far red light Yes
Table 6.1
Suggest what conclusions can be drawn from the results in Table 6.1 about the effect of exposure to light and
darkness on flowering in cockleburs.
[3]
© OCR 2023. You may photocopy this page. 3 of 31 Created in ExamBuilder
, 4 Herbicides work in a number of different ways.
(i) Some herbicides, known as phenoxy herbicides, mimic the action of the auxin, indoleacetic acid (IAA).
What is the normal action of IAA in plant cells?
[1]
(ii) The herbicide atrazine works by disabling plastoquinone, one of the proton pumps in photosystem II.
Explain how atrazine would kill a susceptible plant.
[5]
© OCR 2023. You may photocopy this page. 4 of 31 Created in ExamBuilder
