Role of Light in Photosynthesis

Essential Functions of Light

• Light is the primary energy source required to produce carbohydrates from $H_2O$ and $CO_2$.

• It is essential for the development of chlorophyll and triggers the opening of stomata to facilitate the entry of $CO_2$.

Spectral Efficiency and Wavelengths

• Photosynthesis functions most effectively in the Red, blue, orange, and purple portions of the visible spectrum compared to green and yellow.

• The process is generally carried out well at wavelengths between $400\,nm-480\,nm$ and at $680\,nm$.

Light Intensity and Utilization

• The rate of photosynthesis increases with light intensity up to a definite limit.

• Excessive light causes enzymes to disintegrate and reduces chlorophyll production, which decreases the rate of photosynthesis.

• Only a small proportion of the total light falling on the leaf is actually utilized for photosynthesis.