CAM was first discovered in the late 1940s. It was
observed by the botanists Ranson and Thomas, in
the Crassulaceae family of succulents (which
includes jade plants and Sedum). Its name refers
to acid metabolism in Crassulaceae, not the
metabolism of Crassulacean acid.
Identifying a CAM plant
CAM can be considered an adaptation to arid
CAM plants often display other xerophytic
characters, such as thick, reduced leaves with a
low surface-area-to-volume ratio; thick cuticle;
and stomata sunken into pits. Some shed their
leaves during the dry season; others (the
succulents) store water in vacuoles.
CAM plants not only are good at retaining water
but also use nitrogen very efficiently.
CAM plants can also be recognized as plants
whose leaves have an increasing sour taste during
the night yet become sweeter-tasting during the
day. This is due to malic acid stored in the
vacuoles of the plants' cells during the night and
then used up during the day.
Crassulacean acid metabolism, also known
as CAM photosynthesis, is a carbon
fixation pathway that evolved in some plants as
an adaptation to arid conditions (drought).
the stomata in the leaves closed during the day to
reduce evapotranspiration and but open at night
to collect carbon dioxide (CO2).
The CO2 is stored as the four-carbon acid malate,
and then react with RuBisco, produce sugar
through photosynthesis at day.
Example: cactus, pine apple etc.
When the stomata open, the CO2 is absorb into the cell.
The PEP carboxylase, carbon dioxide in fixing-enzyme react
with CO2 to produce malate, the organic acid will stored in
vacuole of the cell in low concentration.
The malate will go trough Calvin cycle during the day
because the Calvin cycle cannot operate during the night
while it still need ATP and NADPH.
During day process, its prevent the loss of water vapour in the
plant, the stomata is closed.
Then, the malate is release from the vacuole because high
concentration inside and break down into CO2. The CO2
reacts with the RuBP( ribulose bisphosphate) and went trough
the standard Calvin cycle. The the sugar were produced
The benefits of CAM
The most important benefit to the plant is the
ability to leave most leaf stomata closed during
Being able to keep stomata closed during the
hottest and driest part of the day reduces the loss
of water through evapotranspiration, allowing
CAM plants to grow in environments that would
otherwise be far too dry.
o The C4 pathway bears resemblance to CAM; both act to
concentrate CO2 around RuBisCO, there by increasing its
o CAM concentrates it in time, providing CO2 during the
day, and not at night, when respiration is the dominant
o C4 plants, in contrast, concentrate CO2 spatiallly, with a
RuBisCO reaction centre in a "bundle sheath cell" being
inundated with CO2.