CAM (Crassulacean acid metabolism) is a carbon fixation pathway that was discovered in 1804 and further studied in 1840. It allows plants to concentrate carbon dioxide at night through malic acid and release it during the day to undergo photosynthesis more efficiently. CAM occurs in succulent plants and can be identified by diurnal fluctuations in organic acids and high phosphoenolpyruvate carboxylase activity. It provides advantages for plants in dry environments by improving water use efficiency.

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2.  CAM stands for --------------
 Discovered by Heyne (1804) and later by
Aubert (1815).
 Term coined by Ranson and Thomas (1940)
 Mechanism for concentrating CO2
 CAM is not restricted to the family
Crassulaceae
 Enables plants to improve H2O Efficiency
 CAM plants have advantage in dry
environment
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CAM can be defined according to
the following criteria
Succulents plants
Diurnal fluctuation of organic acid
High activities of PEP carboxylase
Stomata opening
Tropical origin and xeric
CAM permits much flexibility and permits
survival

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CAM PLANTS

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CO
MALIC ACID
OAA
K* MALATE MALATE
PYRUVIC ACID
CO2
C3 CYCLE
PYRUVATE
STARCHSTARCH
PEP

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• Do photosynthesis in the day time
• Indeed slow growing but they are very
competitive
• Advantage in water saving
• Can use Calvin cycle alone
• CAM plants are facultative

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• Requires PEPc
and
decarboxylase
• To avoid futile
cycle :
carboxylase at
night and
decarboxylase
during day
• Conversion
achieved by ------

9. C4 vs CAM Summary
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C4 plants
separate 2
steps of C
fixation
anatomically
in 2 different
cells
CAM plants
separate 2
steps of C
fixation
temporally
at
2 different
times
It’s all in
the timing!

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• PHOTOSYNTHETIC SYSTEMS BY
SUSAN M. DANKS,
E.HILARY EVANS
PETER A. WHITTAKER
• CAM BY
IRWIN. P. TING
MARTIN GIBBS
• PLANT PHYSIOLOGY BY
TEIZ AND ZEIGER

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