Plant responses
Plant responses
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
Method
- Students collect their equipment and label the sides of 3 petri dishes with their initials.
- Into the petri dishes, they should place a layer of cotton wool. Using the pipette, they add a fixed amount of water to each of the petri dishes.
- Ten seeds are then added to each of the dishes, using forceps if required, ensuring the seeds are spaced out.
- The three petri dishes should be placed on the side in the laboratory or prep room (somewhere they are not likely to be disturbed or knocked o) for a couple of days to allow germination to start.
- The seeds should be watered daily, adding the same fixed amount of water to each petri dish until the seeds begin to germinate.
- After a couple of days, any ungerminated seedlings should be removed and students should make sure the total number of germinated seeds to be investigated in each of the three petri dishes is the same.
- Measure and record the starting height of each of the seedlings in mm. Students will need a results table for the starting heights and each of the environmental conditions being tested: darkness, sun light and partial light.
- One of their petri dishes should be placed onto a windowsill (sun light) for a few days, another petri dish should be placed into a cupboard (darkness) for a few days, and the third needs to be placed in partial light (so these petri dishes need to be alternated between a day on the windowsill and a day in the dark cupboard – this may need to be done by the technician or teacher).
- Students must measure the height of the seedlings for at least 5 consecutive days and record the values in the results tables.
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.
