Plant Responses GCSE Biology Practical
Investigate the effect of light or gravity on the growth of newly germinated seedlings
Students are required to investigate the effects of light or gravity on the growth of newly germinated seedlings. They will need to calculate and plot the mean height values on a graph of seedlings which have been germinated in different light conditions.
Equipment (per pair of participants)
• Seeds
• 3 x petri dishes
• Cotton wool
• A ruler
• Water
• Pipette
• Fine point forceps
• Access to a windowsill and a dark cupboard
Investigating Seedling Growth Under Different Light Conditions
Method
Preparation
- Collect Equipment
- Gather 3 petri dishes, a pipette, cotton wool, forceps, a ruler, and 30 seeds.
- Label the sides of the 3 petri dishes with your students initials for identification.
- Set Up Petri Dishes
- Place a layer of cotton wool inside each petri dish.
- Using the pipette, add a fixed amount of water to each dish to moisten the cotton wool.
- Position Seeds
- Using forceps if necessary, place 10 seeds evenly spaced on the cotton wool in each petri dish.
- Initial Germination Period
- Place the petri dishes in a safe location where they won’t be disturbed (e.g., the prep room or a quiet area of the laboratory).
- Water daily with the same fixed amount of water in each petri dish until the seeds begin to germinate (approximately 2–3 days).
- Prepare for Testing
- Remove any ungerminated seeds so that each petri dish contains the same number of germinated seedlings.
- Measure and record the starting height of each seedling (in millimeters) in a results table.
Experimental Conditions
- Assign Light Conditions
- Sunlight: Place one petri dish on a windowsill with full exposure to sunlight.
- Darkness: Place another petri dish in a dark cupboard.
- Partial Light: Alternate the third petri dish daily between the windowsill (day) and the cupboard (night).
Note: Ensure consistent placement and alternation; teachers or technicians may assist with moving the dishes.
- Daily Monitoring
- Measure and record the height of the seedlings in each petri dish daily for 5 consecutive days.
- Add these measurements to your results table, keeping track of the environmental condition for each dish.
Technician tips
Advance preparation
- Suitable seeds include cress, white mustard, or brassica rapa. The experiment should be performed in advance to test how long it takes for the seeds to germinate. The fixed amount of water added to the cotton wool should also be trialled and determined for the students.
- Some seeds are quite small. They could be divided into small containers for counting out by each student group. The technician or teacher may need to rotate the partial light petri dishes between the windowsill and the cupboard if it is not feasible for students to access the laboratory daily.
To do this practical you will need
Need some Biology inspiration and help?
Investigate the effect of light or gravity on the growth of newly germinated seedlings. The experiment involves students calculating the height value on a graph of seedling to generate different light conditions. To do this practical students will need brassica rapa seeds, petri dishes, rulers, cotton wools, cress seeds, fine point forceps and disposable pipettes. At Philip Harris, we provide essential biology equipment you need to carry out experiments safely and efficiently in your school or science lab. Shop our biology equipment today.
