Rate and Limiting Factors of Photosynthesis

Rate and Limiting Factors of Photosynthesis

Rate of Photosynthesis

• Photosynthesis is the process by which plants convert water, sunlight and carbon dioxide into glucose and oxygen.
• The rate at which this process occurs is known as the rate of photosynthesis.
• This rate can be measured by the volume of oxygen produced or the rate at which carbon dioxide is used up.
• Higher photosynthesis rates mean more food (glucose) created for the plant’s use.

Limiting Factors of Photosynthesis

• The rate of photosynthesis is influenced by three key limiting factors: light intensity, carbon dioxide concentration and temperature.
• A shortage in any of these factors can reduce the rate of photosynthesis, regardless of the levels of the other parameters.

Light Intensity and Photosynthesis

• Light intensity is crucial for photosynthesis as light energy from the sun is what excites the chlorophyll in green plant cells, initiating the process.
• As light intensity increases, so does the rate of photosynthesis - up to a certain point. Beyond this optimum level, the rate plateaus as the other factors become limiting.

Carbon Dioxide Concentration and Photosynthesis

• Carbon dioxide is one of the raw materials needed for photosynthesis.
• If there’s too little carbon dioxide, the rate of photosynthesis can be slow, even if there’s plenty of light.
• Once again, boosting the concentration of carbon dioxide increases the rate of photosynthesis to a point, after which it stabilises, assuming other resources remain unchanged.

Temperature and Photosynthesis

• Even though the photosynthesis process is not a chemical reaction, it’s still influenced by the temperature as it affects the enzymes that facilitate the process.
• When the temperature is too low, the rate of photosynthesis is slow because the enzymes are not as active.
• However, at high temperatures, the critical enzymes can denature leading to a drop in photosynthesis rate. For many plants, the optimum temperature is around 25-30°C.

Interplay of Factors in Photosynthesis

• The various limiting factors of photosynthesis interact. For example, at low light intensity, a rise in temperature or carbon dioxide concentration might not boost photosynthesis significantly.
• Plants in different conditions are adapted to optimise photosynthesis according to their specific circumstances. For instance, desert plants are adapted to photosynthesise at high light intensities and temperatures.