c4 and cam plants

8/22/2019 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.

c4 and cam plants

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