Question

What are the advantage and disadvantage of CAM metabolism for plants?

Answer 1

Crassulacean Acid Metabolism (CAM) has the advantage of essentially eliminating evapotranspiration through a plants stomata (water loss through gas exchange) during the day, allowing CAM plants to survive in inhospitable climates where water loss is a major limiting factor to plant growth.

Explanation:

The advantage CAM plants observe involves the ability to grow and reproduce in regions where competition from C3 and C4 plants is minimal. By closing stomata during the day, gas exchange (CO2 in and O2/H2O out) does not occur.
This advantage (wrt water loss) also limits the total amount of photosynthesis the plant is capable of during sunlight hours, since at night (during dew-point water loss due to evapotranspiration is limited/negligible and stomates open) CO2 is stockpiled in the form of crassulaic acid and when that acid is completely consumed during the following day, no additional photosynthesis can be performed, regardless of available water or sunlight.

It is worth noting that the tissues are much more complex and growth occurs at a reduced rate, meaning they have a hard time competing for habitat in most climates where C3 plants dominate.