Cam plants keep stomata closed in the daytime, thus reducing loss of water. they can do this because they use photosystem i and photosystem ii at night fix co2 into organic acids during the night fix co2 into pyruvate in the mesophyll cells fix co2 into sugars in the bundle-sheath cells

CAM plants keep stomata closed in the daytime, thus reducing the loss of water fix CO2 into organic acids during the night.
CAM plants are the plants which use the crassulacean acid metabolism. That means that these plants minimize losing water by separating steps of CO2 and the Calvin cycle in time, between night and day. During the night CO2 is fixed by PEP carboxylase into oxaloacetate and then converted to malate or another type of organic acid. Organic acids are broken down during the day and the released CO2 enters the Calvin cycle.

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