Title: Factors Affecting Photosynthesis - QforQuestions
Headings: Factors Affecting Photosynthesis
Factors Affecting Photosynthesis
Factors Affecting Photosynthesis
External factors:
Light
Temperature
Carbon dioxide
Oxygen
Water
Internal factors
Chlorophyll
Age of leaf:
Protoplasmic factor
Photosynthetic products
Internal structure of leaf
Blackman’s law of limiting factor:

Content: Suppose a leaf is subjected to a light intensity, sufficient for the assimilation of 5 mg carbon dioxide per hour. Under these conditions, if a plant is supplied with only one 1 mg of carbon dioxide, the rate of photosynthesis would be limited by carbon dioxide (because concentration of carbon dioxide is less than what can be assimilated in the available intensity of light). Now if the carbon dioxide concentration is gradually increased, the rate of photosynthesis will also increase correspondingly until the assimilation rate of 5 mg carbon dioxide per hour has been reached. However, further increase in carbon dioxide concentration, i.e., more than 5 mg per hour will not increase the rate of photosynthesis. This is because the light now becomes the limiting factor. Under these circumstances, any further increase in the rate of photosynthesis can be brought about only if there is an increase in the light intensity. The above experiment shows that of all the factors, the photosynthetic rate depends upon the factor which is present in relatively minimum concentration. This factor is known as “limiting factor.” All other factors present in optimum or maximum concentration will not be able to increase the rate of photosynthesis until the amount of limiting factor is increased correspondingly. Fig: