GCSE Biology Required Practical: Tropic Effects on Seedling Growth

Key Stage 4

Meaning

Investigate the effects of light or gravity on the germination and growth of seedlings.

Method

Investigate the effects of light on the growth of seedlings.

• Independent Variable - Light intensity.
• Dependent Variable - Height of the seedlings.
• Control Variables - Orientation of the seeds (never turned upside down it tilted). Abundant water for all seedlings. Same temperature for all seedlings.

1. Place cotton wool lining the bottom of three petri dishes.
2. Add water to the petri dishes.
3. Place ten mustard seeds into each petridish allowing them to be spread apart from one another.
4. Allow the mustard seeds to germinate.
5. Once the seeds have germinated remove any seeds that have not germinated then make sure all petri dishes have the same number of germinated seeds.
6. Place 1 petri dish in direct sunlight, 1 in the shade and 1 in a dark cupboard, all in the same room.
7. Use a ruler to measure the height of seedlings every day for 7 days. Each day ensure there is sufficient water in the cotton wool for the seedlings to grow.

Investigate the effects of gravity on the growth of seedlings.

• Independent Variable - Orientation of the seedlings.
• Dependent Variable - Height of the seedlings.
• Control Variables - Light received by the seedlings (all kept in out of direct sunlight). Abundant water for all seedlings. Same temperature for all seedlings.

1. Place cotton wool lining the bottom of two petri dishes.
2. Add water to the petri dishes.
3. Place ten mustard seeds into each petridish allowing them to be spread apart from one another.
4. Allow the mustard seeds to germinate.
5. Once the seeds have germinated remove any seeds that have not germinated then make sure all petri dishes have the same number of germinated seeds.
6. Place both petri dishes carefully on their side, not allowing any seeds to fall out of position. Add an arrow to both pointing down.
7. Every day rotate one of the petri dishes to be upside down from the previous day.
8. Use a ruler to measure the height of seedlings every day for 7 days. Each day ensure there is sufficient water in the cotton wool for the seedlings to grow.