The compensation point is the amount of light intensity on the light curve

Light curve

In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...

 where the rate of photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 exactly matches the rate of respiration

Cellular respiration

Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...

. At this point, the uptake of CO₂

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 through photosynthetic pathways is exactly matched to the respiratory release of carbon dioxide, and the uptake of O₂ by respiration is exactly matched to the photosynthetic release of oxygen.

In assimilation terms, at compensation point, the net carbon dioxide assimilation is zero. Leaves release CO₂ by photo respiration

Photorespiration

Photorespiration, or "'photo-respiration'", is a process in plant metabolism by which RuBP has oxygen added to it by the enzyme , instead of carbon dioxide during normal photosynthesis. This is the beginning step of the Calvin-Benson cycle...

 and day respiration but CO₂ is also converted into carbohydrate by photosynthesis.Assimilation is then the difference in the rate of these processes. At normal partial pressure of CO₂(338microbar in 1980),there is an irradiation at which the net assimilation of CO₂ is zero.For instance,early morning and late evenings,compensation point may be reached as photosynthetic activity decreases and respiration increases. Therefore, partial pressure of CO₂ at compensation point(gamma) is a function of irradiation. Irradiation dependence of compensation point is explained by RuBP

Ribulose-1,5-bisphosphate

Ribulose-1,5-bisphosphate is an organic substance that is involved in photosynthesis. The anion is a double phosphate ester of the ketose called ribulose. Salts of this species can be isolated, but its crucial biological function involves this colourless anion in solution...

 (ribulose-1,5-bisphosphate) concentration. When the acceptor RuBP

Ribulose-1,5-bisphosphate

Ribulose-1,5-bisphosphate is an organic substance that is involved in photosynthesis. The anion is a double phosphate ester of the ketose called ribulose. Salts of this species can be isolated, but its crucial biological function involves this colourless anion in solution...

 is in saturated concentration, gamma is independent of irradiation. But at low irradiation, only a small fraction of the sites on RuBP carboxylase-oxygenase enzyme(Rubisco

RuBisCO

Ribulose-1,5-bisphosphate carboxylase oxygenase, commonly known by the shorter name RuBisCO, is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants to energy-rich molecules such as glucose. RuBisCo is an abbreviation...

) have the electron acceptor RuBP. This decreases the photosynthetic activity and therefore affects gamma. Intracellular Concentration of CO₂ affects the rates photosynthesis and photo respiration

Photorespiration

Photorespiration, or "'photo-respiration'", is a process in plant metabolism by which RuBP has oxygen added to it by the enzyme , instead of carbon dioxide during normal photosynthesis. This is the beginning step of the Calvin-Benson cycle...

. At higher carbon dioxide concentrations, photosynthesis rate is higher while at low CO₂ concentrations, photo respiration is higher.

Timing

This point is reached during early mornings and late evenings. Respiration is relatively constant whereas photosynthesis depends on the amount of sunlight.
When the rate of photosynthesis equals the rate of respiration, compensation point occurs.

Rate

At the compensation point, the rate of photosynthesis is balanced to the rate of respiration. Products of photosynthesis are used up in respiration so that the plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

is neither consuming nor building biomass.

Depth

For aquatic plants where the level of light at any given depth is roughly constant for most of the day, the compensation point is the depth at which light penetrating the water creates the same balanced effect.