CAIE IGCSE Biology 14.5.5 Auxin Control of Shoot Growth

Practise tracing auxin from the shoot tip to unequal distributions that cause differential elongation and bending.

Exam points

state that auxin is made in the shoot tip and diffuses through the plant
identify the shaded or lower side of a shoot as having the greater auxin concentration
link greater auxin concentration to faster cell elongation and bending of the shoot

[Maximum number: 1]

Fig. 6.1 shows some cells from the shoot tip of an onion, Allium cepa.

Fig. 6.1

Cells just behind a shoot tip absorb water and grow in length. A plant hormone stimulates cell elongation and controls the response of stems to gravity.

State the name of the plant hormone that stimulates cell elongation in stems.

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14.5.5—Role of auxin in controlling shoot question 1