c4 and cam plants
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C4 AND CAM PLANTS
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EVOLUTION OF C4 AND CAM PLANTS
At the beginning of the sixties it was
observed by Hawaiian Sugar Planter's
Association
The Australian plant physiologist M. D.HATCH and his English colleague C. R.
SLACK confirmed this result
The cycle is also known as the HATCH-
SLACK-cycle or the C4 cycle. Plants with
this cycle are called C4-plants (and CAM
plants, respectively)
http://www.biologie.uni-hamburg.de/b-online/e24/24b.htmhttp://www.biologie.uni-hamburg.de/b-online/e24/24b.htmhttp://www.biologie.uni-hamburg.de/b-online/e24/24b.htmhttp://www.biologie.uni-hamburg.de/b-online/e24/24b.htmhttp://www.biologie.uni-hamburg.de/b-online/e24/24b.htm -
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TYPESOF PHOTOSYNTHESIS
C3
C4
CAM
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CONCEPTS: PHOTOSYNTHESIS
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CONCEPTS STOMATA
Photosynthesis: CO2 + Water --> Sugar +O2
Photosynthesis is the production of sugar
(stored energy) and oxygen using energy fromthe sun to combine carbon dioxide and water.
CO2 is brought into plants and O2 is released
from plants through pores (stomata) in their
leaves and other tissues.
RUBISCO is the enzyme plants use to
undergo photosynthesis.
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CONCEPTS
Respiration: Sugar + O2 --> CO2 + Water +E Respiration is the burning of sugar in the
presence of oxygen to release energy stored
in the sugar and produces carbon dioxideand water as by-products.
Photorespiration: Occurs under highlight/heat when RUBISCO tends to react with
O2 (undergoing respiration) rather than CO2
(undergoing photosynthesis). This slows rates
of photosynthesis under high light/heat (this is
not what the plant wants to happen).
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THE C4 PATHWAY
1. CO2 is fixed to a three-carbon compound
called phosphoenolpyruvate to produce the
four-carbon compound oxaloacetate. The
enzyme catalyzing this reaction, PEPcarboxylase, fixes CO2 very efficiently so the
C4 plants don't need to have their stomata
open as much. The oxaloacetate is then
converted to another four-carbon compoundcalled malate in a step requiring the
reducing power of NADPH.
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THE C4 PATHWAY
2. The malate then exits the mesophyll cells and
enters the chloroplasts of specialized cells called
bundle sheath cells. Here the four-carbon malate is
decarboxylated to produce CO2, a three-carbon
compound called pyruvate, and NADPH. The CO2combines with ribulose bisphosphate and goes
through the Calvin cycle.
3. The pyruvate re-enters the mesophyll cells,
reacts with ATP, and is converted back tophosphoenolpyruvate, the starting compound of the
C4 cycle.
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C4 LEAF ANATOMY
The C4 plants possess a characteristic leaf
anatomy. Their vascular bundles are surrounded by
two rings of cells. The inner ring, called bundle
sheath cells, contain starch-rich chloroplasts
lacking grana which differ from those in mesophyllcells present as the outer ring. Hence, the
chloroplasts are called dimorphic. This peculiar
anatomy is called kranz anatomy (kranz, German
for "wreath").
http://en.wikipedia.org/wiki/Leafhttp://en.wikipedia.org/wiki/Starchhttp://en.wikipedia.org/wiki/Chloroplasthttp://en.wikipedia.org/wiki/Mesophyllhttp://en.wikipedia.org/wiki/Mesophyllhttp://en.wikipedia.org/wiki/Chloroplasthttp://en.wikipedia.org/wiki/Starchhttp://en.wikipedia.org/wiki/Leaf -
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C4 LEAF ANATOMY
The primary function of kranz anatomy is to provide
a site in which carbon dioxide can be concentrated
around RuBisCO, thereby reducing
photorespiration. In order to facilitate the
maintenance of a significantly higher carbon dioxideconcentration in the bundle sheath compared to the
mesophyll, the boundary layer of the kranz has a
low conductance to carbon dioxide, a property
which may be enhanced by the presence ofsuberin.
http://en.wikipedia.org/wiki/Photorespirationhttp://en.wikipedia.org/wiki/Suberinhttp://en.wikipedia.org/wiki/Suberinhttp://en.wikipedia.org/wiki/Photorespiration -
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EXAMPLES OF PLANTS THAT USE C4
CARBON FIXATION
Many grass (Poaceae) species including:
Miscanthus
Maize
Sugar cane Sorghum
Millet
Corn
many other tropical grasses.
http://en.wikipedia.org/wiki/Poaceaehttp://en.wikipedia.org/wiki/Miscanthushttp://en.wikipedia.org/wiki/Zea_mayshttp://en.wikipedia.org/wiki/Sugar_canehttp://en.wikipedia.org/wiki/Sorghumhttp://en.wikipedia.org/wiki/Millethttp://en.wikipedia.org/wiki/Millethttp://en.wikipedia.org/wiki/Sorghumhttp://en.wikipedia.org/wiki/Sugar_canehttp://en.wikipedia.org/wiki/Zea_mayshttp://en.wikipedia.org/wiki/Miscanthushttp://en.wikipedia.org/wiki/Poaceae -
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ADVANTAGES OF THE C4 PATHWAY
C4
plants have a competitive advantage over plants
possessing the more common C3 carbon fixation
pathway under conditions ofdrought, high temperatures
and nitrogen orcarbon dioxide limitation
97% of the water taken up by C3 plants is lost through
transpiration, compared to a much lower proportion in C4plants, demonstrating their advantage in a dry
environment.
C4 metabolism originated in open habitats, where the
high sunlight gave it an advantage over the C3 pathway.
Drought was not necessary for its innovation - rather,the increased resistance to water stress was a by-
product of the pathway and allowed C4 plants to more
readily colonies arid environments.
http://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/Droughthttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Droughthttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixationhttp://en.wikipedia.org/wiki/C3_carbon_fixation -
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ADVANTAGES OF THE C4 PATHWAY
Today, C4 plants represent about 5% of Earth's
plant biomass and 1% of its known plant species.Despite this scarcity, they account for around 30%
of terrestrial carbon fixation. Increasing the
proportion of C4 plants on earth could assist
biosequestration of CO2 and represent an importantclimate change strategy
Present-day C4 plants are concentrated in the
tropics (below latitudes of 45)
http://en.wikipedia.org/wiki/Biosequestrationhttp://en.wikipedia.org/wiki/Climate_changehttp://en.wikipedia.org/wiki/Climate_changehttp://en.wikipedia.org/wiki/Climate_changehttp://en.wikipedia.org/wiki/Climate_changehttp://en.wikipedia.org/wiki/Biosequestration -
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CAM PLANTS
The first recognition of the nocturnal
acidification process(CAM) can be traced to
the Romans, who noted that certain
succulent plants taste more bitter in themorning than in the evening.
(Rowley,1978)
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CAM PLANTS
CAM ("crassulacean acid metabolism") plants are
also C4 plants but instead of segregating the C4 and
C3 pathways in different parts of the leaf, they
separate them in time instead. (CAM stands for
crassulacean acid metabolism because it was firststudied in members of the plant family
Crassulaceae.)
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CAM PLANTS
At night,
CAM plants take in CO2 through their open stomata
(they tend to have reduced numbers of them).
The CO2 joins with PEP to form the 4-carbon
oxaloacetic acid. This is converted to 4-carbon malic acid that
accumulates during the night in the central vacuole of
the cells.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/J/Junctions.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/J/Junctions.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/J/Junctions.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/J/Junctions.html -
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CAM PLANTS
These adaptations also enable their owners to
thrive in conditions of
high daytime temperatures
intense sunlight
low soil moisture.
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SOMEEXAMPLESOF CAM PLANTS:
Cacti
Bryophyllum
the pineapple and all epiphytic bromeliads
sedums the "ice plant" that grows in sandy parts of the scrub
forest biome
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.html -
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BRYOPHYLLUM
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SEDUMS (STONE CROPS)
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ICE PLANT
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GEOLOGICAL DISTRIBUTION OF C4
AND CAM PLANTS
C4 PLANTS
o dominates
tropical savannahs
grasslands
Southern Great US plains, Argentina, Bolivia,
Pakistan, Nepal and Kenya
o Accounts for 30% global terrestrial carbon fixation
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o Dominance of tropical environment achieved in
past 10 Myr
Important aspect
variability on an interannual and seasonal
basis thrive in arid and semi-arid regions
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CAM PLANTS
o Best known for desert succulents
o Reverse stomatal behavior
Terrestrial CAM Stem succulents
Small woody spp. With succulent leaves
Can be found in all terrestrial growth forms
Euphorbia forbesii(Euphordiaceae), Haloxylon(Chenopodiaceae), Calligonum
(Polygonaceae)
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Aquatic CAM
Found worldwide in palustrine
Laustrine
Isoetes (Lycophyta, Isoetaceae) Crassula (Crassulaceae)
CAM Epiphytes
Tropical lowland forests epiphytes
Bromeliaceae, Orchideaceae
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CONCLUSION
C4 photosynthesis
Uses PEP carboxylase to collectCO2 during day.
Delivers CO2 directly to RUBISCOto eliminate photorespiration and isfaster at pulling in CO2.
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CONCLUSION
CAM photosynthesis
Uses PEP carboxylase to collectCO2 during night.
Stores CO2 in form of acid. Allowsidling.
Delivers CO2 directly to RUBISCOto eliminate photorespiration and is
faster at pulling in CO2.
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