Factors Affecting Rate of Photosynthesis

 The process of photosynthesis is affected by two types of factors namely:

1. Internal factors
   1. Chlorophyll
   2. Leaf anatomy
   3. Accumulation of end products and
   4. Hormones
2. External factors
   1. Carbon dioxide
   2. Water
   3. Sunlight
   4. Oxygen and
   5. Temperature

Internal factors

1. Chlorophyll
The process of photosynthesis depends on the amount of chlorophyll present in the leaf. If chlorophyll is absent in a leaf, photosynthesis does not takes place.

2. Leaf anatomy
Leaf anatomy also influences the photosynthesis. The important anatomic structures which influence photosynthesis are size, shape, position and frequency of stomata.

3. Accumulation of end products
If the end products of photosynthesis are translocated at a slow rate, the rate of photosynthesis reduces.

4. Hormones
The rate of photosynthesis is also influenced by certain hormones present in a plant such as cytokinins, gibberellins and abscisic acid. Cytokinins and gibberellins increase the rate of photosynthesis, while the abscisic acid reduces it.

External factors

1.Carbon dioxide 
The amount of carbon dioxide in the atmosphere is 0.03%. If the amount of CO₂ increases up to 0.1%, the rate of photosynthesis also increases. But, the rate of photosynthesis decreases, if the amount of CO₂ increases beyond 0.1%.

2. Water
Water is a very important raw material for photosynthesis. A slight decrease in amount of water causes closing of stomata. This results in less absorption of CO₂ in leaves, hence the process of also slows down..

3. Sunlight
Photosynthesis does not take place in dark. If the intensity of sunlight is increased slowly, the rate of photosynthesis increases up to a certain point (called saturation point). If the intensity of sunlight increases beyond saturation point, then photosynthesis slows down.

4. Oxygen
It is observed that a small quantity of oxygen is essential for photosynthesis, whereas a high quantity of oxygen slow down the rate of photosynthesis.

5. Temperature
At low temperature the rate of photosynthesis is slow. As the temperature is increased, the rate of photosynthesis also increases up to a certain point. But a high increase in temperature slows down the rate of photosynthesis.

Test Your Understanding and Answer These Questions:

1. Explain the various factors which affect the rate of photosynthesis?