There is yet another pathway taken by carbon in its flow from carbon dioxide to carbohydrate. It occurs in plants of the Crassulaceae family (mostly fleshy herbs) and in cacti. Such plants grow in regions of high light intensity (which is interesting given that the carbon pathway described following is not light dependent). The pathway is called CAM for crassulacean acid metabolism. Plants in which this pathway occurs accumulate malic and isocitric acids at night. These acids are converted back to carbon dioxide during the day. The stomates of CAM plants tend to close during the day, which prevents the entrance of carbon dioxide from the atmosphere. Plentiful carbon dioxide is available, however, from the reservoir of the malic and isocitric acids.
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