Compensation Point

Compensation point is a term used to describe the condition when the rate of photosynthesis is equal to the rate of respiration in a plant or an aquatic ecosystem. It can be measured by the light intensity or the carbon dioxide concentration at which this balance occurs.

Light Compensation Point

The light compensation point (Ic) is the light intensity on the light curve where the rate of photosynthesis exactly matches the rate of cellular respiration. At this point, the uptake of CO2 through photosynthetic pathways is equal to the respiratory release of carbon dioxide, and the uptake of O2 by respiration is equal to the photosynthetic release of oxygen.

The light compensation point depends on the plant species, meteorological conditions, and stress due to drought, diseases, or pests. It can be reached during early mornings and late evenings when the light intensity is low. For aquatic plants, the light compensation point is the depth at which light penetrating the water creates the same balanced effect.

CO2 Compensation Point

The CO2 compensation point (Γ) is the CO2 concentration at which the rate of photosynthesis exactly matches the rate of respiration. There is a significant difference in Γ between C3 plants and C4 plants: on land, the typical value for Γ in a C3 plant ranges from 40–100 μmol/mol, while in C4 plants the values are lower at 3–10 μmol/mol. Plants with a weaker CCM, such as C2 photosynthesis, may display an intermediate value at 25 μmol/mol.

The CO2 compensation point reflects the competition between oxygen and CO2 during photosynthesis. Higher CO2 concentrations favor photosynthesis whereas low CO2 concentrations favor photorespiration, producing a CO2 compensation point Γ for a given irradiation.

Significance of Compensation Point

Compensation point is an important concept for understanding the factors that affect plant growth and productivity. It indicates the minimum light intensity or CO2 concentration required for a plant to survive and grow. It also determines the distribution and adaptation of plants in different environments. For example, C4 plants have lower CO2 compensation points than C3 plants, which gives them an advantage in hot and dry conditions where CO2 is limiting¹. Similarly, aquatic plants with low light compensation points can grow deeper in the water than those with high light compensation points.

Source:

(1) Compensation point - Wikipedia. https://en.wikipedia.org/wiki/Compensation_point Accessed 07/06/2023.

(2) What is compensation point - BYJU'S. https://byjus.com/question-answer/what-is-compensation-point/ Accessed 07/06/2023.

(3) Compensation point is | Biology Questions - Toppr. https://www.toppr.com/ask/question/compensation-point-is/ Accessed 07/06/2023.