2.5 - Compensation Point

Definition of Compensation Point

• The compensation point is the specific light intensity at which the rate of photosynthesis is exactly equal to the rate of respiration in a plant.
• At this point, the net gaseous exchange of the plant is zero:
  • The amount of carbon dioxide (${\text{CO}}_2$) absorbed for photosynthesis equals the amount of carbon dioxide released during respiration.
  • The amount of oxygen (${\text{O}}_2$) absorbed for respiration equals the amount of oxygen released during photosynthesis.

Relationship and Implications on Plant Growth

1. Light Intensity Below the Compensation Point

• Respiration rate is higher than photosynthesis rate.

• Glucose is consumed faster than it is produced.

• Result: The plant will deplete its stored food reserves, fail to grow, and will eventually die.

2. At the Compensation Point

• Photosynthesis rate equals respiration rate.

• All organic matter (glucose) produced by photosynthesis is fully utilized for respiration.

• Result: No net gain or loss of biomass. Plant growth is stagnant.

3. Light Intensity Above the Compensation Point

• Photosynthesis rate is higher than respiration rate.

• More glucose is produced than is consumed.

• Result: Excess glucose is stored as starch, and the plant has enough energy and organic materials for growth, development, tissue repair, and reproduction (flowering, seeding, and fruiting).