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Crassulacean acid metabolism

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An elaborate carbon fixation pathway in which the stomata are open in cooler and more humid night-time hours, permitting the uptake of CO2 to be fixed and stored as a four-carbon acid (i.e. malate) so that during the hotter and drier day-time hours the CO2 is released providing the enzyme rubisco with high concentration of CO2 while the stomata are closed to reduce water loss through evapotranspiration.


The pathway renders plants able to thrive and adapt in arid environments. CAM was first observed by the botanists, Ranson and Thomas, in the Crassulaceae family of succulents.

Word origin: from the Crassulaceae family of succulent plants where it was first observed.

Abbreviation: CAM.

Compare: C3 carbon fixation pathway, C4 carbon fixation pathway.
See also: CAM plant.