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Seed Germination Investigation

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Seed Germination Investigation

A football tournament is coming up, and the organisers want to establish which conditions help seeds germinate reliably before planting a field-edge shelter belt. Use the evidence and investigation plan below to analyse germination. Germination means the seed embryo resumes growth; count a seed as germinated when its radicle is at least 2 mm long.

Build the science

A seed contains an embryo and a food store. During germination, water uptake (imbibition) softens the seed coat and activates metabolism. The embryo respires, using oxygen to release energy from stored food. The radicle usually emerges first, followed by the shoot. Most seeds need water, oxygen and a suitable temperature to germinate; light is not essential for every species. Soil is not essential if these conditions are provided by another suitable medium.

1.Which statement best explains why soil is not listed as an essential condition for germination?

Seeds can take in water and oxygen and use stored food without soil.
Soil provides all the light a seed needs.
Seeds germinate only when they are buried in soil.
Soil stops the embryo respiring.

2.Explain how water uptake helps a dry seed begin growing. Include one physical change and one biological change.

3.Which structure normally emerges first, and what is its main early role?

Mei and Ngaio plan a fair test

The tournament grounds team tests whether temperature affects germination in radish seeds. They use four labelled dishes, each containing 20 seeds on the same type and amount of moist paper. Each dish receives 10 mL of water at the start and is checked at the same time each day. The dishes are kept in darkness. The only planned difference is temperature: 5°C, 15°C, 25°C or 35°C. A seed is counted as germinated when its radicle reaches 2 mm. The paper must stay moist, not submerged.

4.Identify the independent variable and the dependent variable in this investigation.

5.Name two control variables and explain briefly how controlling them makes the temperature comparison fair.

6.Write a testable hypothesis for the temperature investigation. Predict a pattern across the four temperatures and give a scientific reason.

Read the evidence

These are the tournament team’s results. Percentage germinated is calculated as (number germinated ÷ 20) × 100. All dishes were checked on day 5.

Temperature

Seeds germinated (out of 20)

Germination percentage

Mean radicle length (mm)

5°C

20%

15°C

70%

25°C

90%

35°C

45%

7.Use the results to identify the temperature with the highest germination percentage. State the percentage and number of seeds germinated.

8.Compare the results at 5°C and 25°C. What do the numbers suggest about temperature and the rate of early seedling growth?

9.The team concludes that 25°C is the best temperature for every seed species. Is this conclusion justified by the results? Explain one limitation and suggest one improvement.

10.A dish at 35°C was found with paper that had dried out. How would this affect the test, and what should the team do with that result?

11.Why should the team keep the dishes moist but not submerged? Link your answer to water and oxygen.