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Biology · May / June 2021 · Paper 41 · Question 4

0610

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Two identical potted plants were used to investigate plant responses. Plant A was placed on a clinostat that continually rotated. Plant B was not rotated. Both plants were then placed on their sides and kept in the dark. Fig. 4.1 shows the two plants at the start of the experiment and after seven days. plant A plant B at the start box to exclude light after seven days Fig. 4.1

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  • 4(a)[1]

    gravitropism ;

  • 4(b)[2]

    idea of negating the effect of gravitational pull / gravity, on one side of the plant (only) ;

    (used as a control) to compare with (the response of) plant B ;

  • 4(c)(i)[1]

    auxin ;

  • 4(c)(ii)[3]

    any three from:

    (auxin / hormone produced in the tip)

    moves / diffuses, away from tip / down the, stem or shoot or plant ; moves to / collects on, one / lower side (of stem / plant) ;

    stimulates cell elongation ;

    stem / plant, bends / grows / turns, upwards ;

    AVP ;

  • 4(d)[3]

    any three from:

    reach light for photosynthesis ;

    (reach air for) carbon dioxide for photosynthesis ;

    (reach air for) oxygen for respiration ;

    idea that they grow tall so that flowers are exposed for, (wind / insect) pollination ;

    AVPs e.g. roots grow downwards / towards (direction of) gravity ; to reach, water / ions or minerals ;

    to anchor plant in the soil ;

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