Biology 9700 · AS & A Level · Control and coordination in plants

Control and coordination in plants — practice question

Gibberellin is a plant growth hormone with a part to play in germination and stem elongation.
(a)[2]

Outline the way gibberellin is involved in activating genes for stem elongation.

(b)[4]

Outline the role played by gibberellin in the germination of wheat seeds.

(c)[4]

Stem length in pea plants is controlled by a single gene. Pea plants can be either tall or short. A study was done to investigate the effect of applying gibberellin to short pea plants. Two groups of short pea seedlings were used, group P and group Q. Group P consisted of 20 seedlings that had a paste containing gibberellin applied two days after germination. Group Q consisted of 20 seedlings that had a paste without gibberellin applied two days after germination. The stem length of the pea plants was measured at intervals over 20 days. With reference to Fig. 8.1, describe the results of the investigation and compare the growth rate of plants in group P and group Q.

(d)[3]

Explain the function of the gene that controls stem length in pea plants.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: DELLA proteins stop gene activation

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