Conditions affecting the rate of Photosynthesis

 

The rate at which photosynthesis occur depend on the following 3 factors:

The amount of  CARBON DIOXIDE - the more carbon dioxide that is available to the plant, the faster the rate of photosynthesis, because carbon dioxide is one of the raw-materials.

  

The amount of SUNLIGHT - the amount of light received by chlorophyll determines how quickly  photosynthesis occur.  The faster the light strikes the leaf, the quicker the rate of photosynthesis.  The type of light that hits the leaf is also important.  Most plants appear green because they reflect green light.  Therefore, green light does not take part in driving the process of photosynthesis.  Red and Blue light are absorbed, hence these two colours are the most important ones for photosynthesis.

The TEMPERATURE - photosynthesis is a chemical process, controlled by enzymes such as chlorophyll.  So it works best at warm temperatures, but not too hot.

From the graphs, it can be said that if Light, carbon dioxide and temperature are scarce, they will keep the rate of photosynthesis down. Therefore, they are called  LIMITING FACTORS.

For example, on a hot, sunny day when there is plenty of light and high temperature, the rate of photosynthesis depends on how much carbon dioxide there is.  Carbon dioxide is then said to be the limiting factor. 

Photosynthesis Experiments

 

🔬 Knowledge Check: Photosynthesis Rates

Test your understanding of the factors that limit how quickly plants make food.

1. What happens to the rate of photosynthesis as light intensity increases?

• The rate decreases.
• The rate increases up to a certain point.
• The rate stays exactly the same.

2. If a plant has plenty of light and heat but very little carbon dioxide, what is the 'limiting factor'?

• Light Intensity
• Temperature
• Carbon Dioxide concentration

3. Why does the rate of photosynthesis drop if the temperature gets too high?

• The enzymes are destroyed.
• There is too much light.
• The plant runs out of starch.

4. How can farmers use the science of limiting factors to grow crops faster in a greenhouse?

• By reducing the amount of water.
• By increasing the concentration of carbon dioxide.
• By keeping the greenhouse dark.

5. When a graph for light intensity levels off (becomes flat), what does this indicate?

• Photosynthesis has stopped completely.
• The plant is dead.
• Light is no longer the limiting factor; something else is.

Click to Reveal Answers

1. The rate increases up to a certain point (The speed goes up until another factor limits it).
2. Carbon Dioxide concentration (This is the factor in short supply).
3. The enzymes are destroyed (Enzymes are protein catalysts that cannot survive extreme heat).
4. Increasing the concentration of carbon dioxide (This removes it as a limiting factor).
5. Light is no longer the limiting factor (The plant is working as fast as it can with the heat or CO2 available).

Tags:Photosynthesis, Rate of photosynthesis, carbon dioxide