Rate of photosynthesis from experimental data: Class 11 practice
Rate of photosynthesis can be measured as gas (oxygen) released per unit time. Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Rates
- Graphs
The idea behind rate of photosynthesis from experimental data
Rate of photosynthesis can be measured as gas (oxygen) released per unit time. Limiting factors: when light is low, raising light increases rate; above saturation, another factor limits it.
Step-by-step method
- Find the gas released and the time.
- Rate = volume ÷ time.
- Compare rates to judge the limiting factor.
Worked example 1 (Basic)
An aquatic plant gives off 13 mL of oxygen in 2 minutes. Find the rate.
- 13 ÷ 2
- Answer: 6.5 mL/min
Worked example 2 (Standard)
A leaf disc releases 31 bubbles in 6 min at low light and 62 bubbles in 6 min when light is doubled. What does this show?
- Rate doubled from 5.17 to 10.33 per min
- Light was limiting
- Answer: Light intensity was the limiting factor
Worked example 3 (Challenge)
At 4 klux the rate is 1.4 mL/min and at 8 klux it is 1.4 mL/min. Is light limiting at 4 klux?
- Rate unchanged when light doubles
- Answer: No — light is saturating; another factor (CO₂ or temperature) is limiting
Common mistakes and misconceptions
- Dividing time by volume
- Comparing totals over different times
Practice questions
- (Basic) An aquatic plant gives off 11 mL of oxygen in 7 minutes. Find the rate.
- (Basic) An aquatic plant gives off 8.5 mL of oxygen in 8 minutes. Find the rate.
- (Standard) A leaf disc releases 29 bubbles in 2 min at low light and 58 bubbles in 2 min when light is doubled. What does this show?
- (Standard) A leaf disc releases 22 bubbles in 8 min at low light and 44 bubbles in 8 min when light is doubled. What does this show?
- (Challenge) At 4 klux the rate is 4.5 mL/min and at 8 klux it is 4.5 mL/min. Is light limiting at 4 klux?
- (Challenge) At 4 klux the rate is 3.5 mL/min and at 8 klux it is 3.5 mL/min. Is light limiting at 4 klux?
Answer key with full working
- Q1: 11 ÷ 7 → Answer: 1.57 mL/min
- Q2: 8.5 ÷ 8 → Answer: 1.06 mL/min
- Q3: Rate doubled from 14.5 to 29 per min → Light was limiting → Answer: Light intensity was the limiting factor
- Q4: Rate doubled from 2.75 to 5.5 per min → Light was limiting → Answer: Light intensity was the limiting factor
- Q5: Rate unchanged when light doubles → Answer: No — light is saturating; another factor (CO₂ or temperature) is limiting
- Q6: Rate unchanged when light doubles → Answer: No — light is saturating; another factor (CO₂ or temperature) is limiting
Syllabus note
This skill is listed under "Photosynthesis in Higher Plants" for Class 11 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.
Related practice and notes
Frequently asked questions
Which chapter is rate of photosynthesis from experimental data in?
"Photosynthesis in Higher Plants", Class 11 Biology (NCERT/CBSE). Other boards may place it differently.
How were the answers checked?
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.