stomatal movement in succulents 1. introduction 2.shrunken stomata 3.cam in succulents 4.overview of cam cycle

1. STOMATAL MOVEMENT IN
SUCCULENTS

2. SUCCULENTS
• Latin word- sucus,
means juice or sap
• Found in water
arid climates
or soil conditions
• absent, reduced, or
cylindrical-to-spherical
leaves
• reduction in the number
of stomata

3. • stems as the main site
of photosynthesis, rather than
leaves
• compact, reduced, cushion-like,
columnar, or spherical growth
form
• ribs enabling rapid increases in
plant volume and decreasing
surface area exposed to the sun
• waxy, hairy, or spiny outer surface
to create a humid micro-habitat
around the plant, which reduces
air movement near the surface of
the plant, and thereby reduces
water loss and creates shade

4. • roots very near the surface
of the soil, so they are able
to take up moisture from
very small showers or even
from heavy dew
• ability to remain plump and
full of water even with high
internal temperatures (e.g.,
52 °C or 126 °F)
• very impervious
outer cuticle (skin)
• mucilaginous substances,
which retain water
abundantly

5. Sunken stomata in succulents

6. Crassulacean Acid Metabolism
(CAM) in succulents
• Observed by Botanists Rason and Thomas in
late 1940s
• Its name refers to acid metabolism in
Crassulaceae not the Crassulacean acid.

7. What is crassulacean Acid
Metabolism?
• It is a carbon pathway
• Also known as CAM photosynthesis
• These plants fix carbon dioxide (CO2) during the
night, storing it as the four carbon acid malate
• The CO2 is released during the day, where it is
concentrated around the enzyme RuBisCO,
increasing the efficiency of photosynthesis.
• The CAM pathway allows stomata to remain shut
during the day, reducing evapotranspiration;
therefore it is espicially common in plants
adapted to arid conditions.

8. • CAM plants is subset of C4 plants
• The fixation now occurs in mesophyll cells so that
they will be more exposed to the air & in order to
take in more CO2.
• The malate, which is the product of the fixation
process is pumped deeper in the leaf so that it
won’t be exposed to air and to oxygen.
• This is to avoid photorespiration and the wasteful
process since RuBisCo is used in the Calvin cycle
• The process is a lot like the C4 pathway.

9. Overview of CAM
A two part cycle

10. During night
• CAM plant’s stomata are open ,allowing CO2
to enter and be fixated as organic acids that are
stored in vacuoles.
• The carbon dioxide is fixed in the mesophyll
cell’s cytoplasm by PEP reaction
• PEP- Phosphoenolpyruvic acid

12. During day
• During the day the stomata are closed and the
carbon is released to the Calvin cycle so that
photosynthesis may take place.
• The carbon is the organic acids is freed from
the mesophyll cell’s vacuoles and enters the
chloroplast’s stoma and into Calvin cycle .

14. Comparison chart
Plant characters C3 pathway C4 pathway CAM pathway
Photorespiration
rate
High Low/ negligible Very low/ negligible
Leaf anatomy Typical Kranz Xeromorphic
Typical
environment
All Tropical, elevated
daytime
temperature,
drought
Dry, arid
Stoma open during
the day?
Yes Yes No
No. of steps in
pathway
1 2 2
First molecule
produced in
pathway
3-phosphoglyceric
acid
Malic acid or
aspartic acid
Malate
Uses the Calvin
cycle
yes yes Yes