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When the carbon dioxide concentration inside a leaf drops, photorespiration takes place. This takes place mostly on warm arid days when plants are compelled to shut their stomata to avert surplus water loss. The oxygen proportions of the leaf will automatically surge if the plants keep trying to fix carbon dioxide when their stomata are shut, all the carbon dioxide stored will be consumed and the oxygen proportions will surge when compared to carbon dioxide levels.

What is Photorespiration



Photorespiration is a process that occurs in Calvin Cycle during plant metabolism. In this process, the key enzyme RuBisCO that is responsible for The fixing of carbon dioxide reacts with oxygen rather than carbon dioxide. It occurs because of the conditions in which carbon dioxide concentration falls down and rubisco does not have enough carbon dioxide to fix and it starts fixing oxygen. Under suitable conditions, C3 plants have sufficient water, the supply of carbon dioxide is abundant and in such conditions, photorespiration is not a problem.

Photorespiration is influenced by high temperature as well as light intensity and accelerating the formation of glycolate and the flow through the photorespiratory pathway.

Photorespiration causes a light-reliant acceptance of O2 and discharge of CO2 and is related to the creation and metabolism of a minute particle named glycolate.

Photosynthesis and photorespiration are two biological processes (in flourishing plants) that can function simultaneously beside each other as photosynthesis gives off oxygen as its byproduct and photorespiration gives off carbon dioxide as its byproduct, and the said gases are the raw material for the said processes.

When the carbon dioxide levels inside the leaf dip to about 50 ppm, RuBisCO begins combining Oxygen with RuBP as an alternative to Carbon dioxide.

The final result of this is that as an alternative to manufacturing 2 molecules of 3C- PGA units, merely one unit of PGA is fashioned with a noxious 2C molecule termed phosphoglycolate.

To purge themselves of the phosphoglycolate the plant takes some steps. Primarily, it instantly purges itself from the phosphate cluster, transforming those units into glycolic acid. After that, this glycolic acid is transferred to the peroxisome and then transformed into glycine. The conversion of glycine into serine takes place in the mitochondria of the plant cell. The serine produced after that is used to create other organic units. This causes a loss of carbon dioxide from the flora as these reactions charge plant’s energy.

Also Read: Photosynthesis

To avert this procedure, two dedicated biochemical reactions were necessary to evolve in the flora of our world:

Photosynthesis in C4 plants

Plants that propagate in warm, arid climates similar to sugarcane and corn have developed a dissimilar system for carbon dioxide fixation. The structure of the leaves of these plants is dissimilar to that of a normal leaf. They are known to display Kranz anatomy. Dense-walled parenchyma cells termed as bundle sheath cells surround the phloem and xylem of these leaves where the maximum amount of photosynthesis happens.

Also Refer: The Plant Tissue System

CAM – Crassulacean Acid Metabolism

 This section of flora makes use of a procedure akin to the C4 section apart from the fact that they take carbon dioxide in nocturnal hours and convert it into malic or aspartic acid. The vacuoles of their photosynthetic cells provide a location to store them. As soon as the sun shines these plants shut their stomata and disintegrate the malic acid to keep the carbon dioxide ratio high enough to avert photorespiration. This permits the leaves to have their stomata shut with the intention of preventing withering. This section of flora doesn’t display Kranz anatomy.

Also Read: Stomata

For more information about the Photorespiration, its process and other related topics, visit us at  BYJU’S Biology.

Important Questions on Photorespiration

Q.1.What is Photorespiration?
Sol. Photorespiration can be defined as the evolution of carbon dioxide(CO2) during photosynthesis.

Q.2.What is Photosynthesis?

Sol. Photosynthesis is a biological process, which uses light energy (sunlight) to synthesise organic compounds.

Q.3.Which light range is most effective in photosynthesis?
Sol. Red light.

Q.4.What is the function of RuBisCO in photorespiration?

Sol. In photorespiration, RuBisCO catalyses the oxygenation of RuBP to one molecule of PGA and phosphoglycolate.

Q.5.What is the difference between photosynthesis and photorespiration?

Sol. Photosynthesis and photorespiration are different processes. In photosynthesis, carbon dioxide fixation takes place by the RuBisCO, whereas in the photorespiration RuBisCO reacts with oxygen and it competes with the Calvin cycle.

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