How carbon dioxide is fixed by the c4 plants in the bundle sheath

[In c4 plants] Atmospheric carbon dioxide is fixed in the mesophyll cells by  phosphoenol pyruvic acid (PEP) carboxylase into a 4-carbon compound oxaloacetic acid.

Oxaloacetate is then converted to malate/malic acid and transported into the bundle-sheath cells. This allows carbon dioxide to concentrate in ‘bundle of sheath’ cells around Rubisco, effectively removing its contact with oxygen thus preventing photorespiration

Inside the bundle sheath, malate breaks down, releasing a molecule of carbon dioxide which is then fixed by Rubisco and made into sugars via the Calvin cycle.

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Dr. Bbosa Science