Transcript C4 and CAM Photosynthesis

C4 and CAM Photosynthesis
Adaptations to high
temperature
C4 Photosynthesis
• Some plants, adapted to hot, dry
environments, use a special process
called C4 photosynthesis.
• Some examples of C4 plants are: Corn,
Sugar Cane, CrabgrassAND Most
tropical grasses are C4 plants.
C3 Plants
Plants that use only the Calvin
cycle for light independent
reactions may be referred to as C-3
because during the cycle, the 6-C
sugar splits to two 3-carbon
sugars.
Specialized leaves of a C-4 plant
have tightly packed layers of cells.
They have bundle sheath cells and
mesophyll cells surrounding leaf
veins.
What occurs during C-4 photosynthesis?
Carbon Dioxide is first incorporated
into a C-4 (four carbon) acid in the
mesophyll cells.
Why is C-4 necessary?
When stomata close…
When this happens photosynthesis operates
at a much reduced rate, due to RuBP bonding
with Oxygen under low CO2 conditions.
Thus some of the enzyme is converted to
CO2, bypassing the Calvin cycle. When this
happens photosynthesis operates at a much
reduced rate. The rate of photorespiration
increases
C4 photosynthesis, therefore provides
the needed carbon dioxide when the
stomata close.
It is a specialization discovered in
desert plants such as cactus, and
pineapple. Other C4 plants are: Jade
plant and agave plant.
• C4 plants can function at maximum efficiency in
conditions of high temperature and high light
intensity while keeping their stomata closed
to avoid excessive water loss.
• CAM evolved in plants that grow in extreme
heat & little rain. (It is not very efficient, and
plants grow slowly.)
• By contrast, high temperature
may inhibit photosynthesis in
C3 plants by as much as 40%!
What Happens in CAM
Photosynthesis?