A student wanted to investigate the conditions required for the germination of mustard seeds.

She set up 5 boiling tubes each containing 8 mustard seeds on cotton wool, sealed with rubber bungs:

• Tube A contained dry cotton wool and was placed at room temperature in the light.
• Tube B contained moist cotton wool and was placed at room temperature in the light.
• Tube C contained moist cotton wool and was placed in a fridge (at 4°C) in the dark.
• Tube D contained moist cotton wool and was placed at room temperature in the dark.
• Tube E contained moist cotton wool and was placed at room temperature in the light and contained an oxygen-absorbing chemical.

The student left the tubes for 4 days and then returned to observe the results. She measured the length of the shoots and recorded how many had germinated.

Some of her results are shown below:

• Tube A: no seeds germinated.
• Tube B: 6 seeds germinated with the following shoot lengths: 1.5 cm, 2.2 cm, 1.8 cm, 1.6 cm, 2.1 cm, and 1.6 cm.
• Tube C: 2 seeds germinated with shoot lengths of 0.2 cm and 0.4 cm.

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