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IGCSE · Practice questions · Fertilisation and germination

Tube, nucleus, seed.

Six original Cambridge-style questions on fertilisation in plants, the pollen tube (Extended), and planning and interpreting germination experiments.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Pollinate, grow, fuse, germinate.

01
Recall
[2 marks]

State what is meant by fertilisation in a flowering plant and name the structure that develops into a seed.

  • Fertilisation: a pollen nucleus (male gamete) fuses with a nucleus in an ovule (female gamete). ✓
  • The (fertilised) ovule develops into a seed. ✓
02
Explain
[4 marks]

Extended. Describe what happens after a pollen grain lands on the stigma, up to and including fertilisation.

  • A pollen tube grows out of the pollen grain. ✓
  • It grows down through the style to the ovary, towards an ovule, carrying the pollen nucleus. ✓
  • It enters the ovule through the micropyle. ✓
  • The pollen nucleus fuses with the female nucleus in the ovule (fertilisation), forming a zygote. ✓
03
Analysis
[4 marks]

Plan an experiment to show that seeds need oxygen to germinate. Include a control and how you would remove oxygen.

  • Set up two tubes, each with the same number and type of seeds on damp cotton wool, at the same temperature (e.g. 20 °C). ✓
  • Remove oxygen from one tube, for example by using boiled (cooled) water covered with oil, or by sealing it with a chemical that absorbs oxygen. ✓
  • The control tube has air (oxygen); keep water and temperature the same. ✓
  • Leave for several days and count how many seeds germinate in each tube. ✓
04
Data
[3 marks]

Seeds were kept on damp cotton wool at different temperatures for 5 days.

Temperature / °C515253545
Seeds germinated (out of 20)0920130

Describe and explain the results.

  • Germination increases from 5 to 25 °C (maximum, all 20) and then decreases, with none at 45 °C. ✓
  • At low temperature the enzymes in the seed work slowly (molecules have less kinetic energy), so few or no seeds germinate in 5 days. ✓
  • At high temperature the enzymes are denatured, so seeds cannot break down their food store and do not germinate. ✓
05
Explain
[3 marks]

Explain why a seed needs water to germinate.

  • Water is absorbed so the seed swells and the seed coat splits. ✓
  • Water activates enzymes, which break down stored food (e.g. starch to sugar). ✓
  • The soluble products are transported to the growing embryo, which uses them for respiration and growth. ✓
06
Explain
[2 marks]

A student says that seeds need light to germinate. Describe how you could test this claim and the result you would expect.

  • Put seeds on damp cotton wool at the same suitable temperature, one tube in the light and one in a dark cupboard. ✓
  • Expected: seeds in both tubes germinate, showing light is not needed (the seed uses its food store, not photosynthesis). ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.