[Specks13]

Can someone in simple terms please explain the difference between C3 and C4 plants? Thanks

[protozoan]

The difference is between enzymes which accept CO2 from the air. C3 plants use enzym ribulosodiphosphatcarboxylase while C4 and CAM plants use phosphoenolpyruvatcarboxylase to accept CO2 from the air. Also the primary product of photosynthesis of C3 plants is phosphoglycerat while in C4 plants it is oxalacetate The differences are also between structure of the photosynthetic apparat. I hope this helps, also hope you know what enzymes are.

[MrMistery]

The difference occurs in photosynthesis. From the point of view of the first subsance created, there are 3 types of plants: C3, C4 and CAM
As protozoan pointed out C3 plants use RuDP carboxylase to fix CO2 and the first organic molecule created is phosphoglycerat(this thing has 3 C atoms=> the name C3)
C4 plants use PEP carboxylase to fix CO2 and the first organic molecule is oxalacetic acid(4 C atoms, from which comes the name). At the C4 plants photosynthesis is 6 times faster than C3 plants
There is a third kind, the CAM plants. Would you like me to explaint those to u to?

[Specks13]

what would be an example of each type of plant? Is it as simple as saying a C4 plant requires less water than a C3 plant?

[Poison]

examples:
C3—–>wheat, barley, potatoes and sugar beet. (most of the plants are C3)
C4—–>fourwing saltbush, corn ,many of summer annual plants.
CAM—> cactuses,some orchids and bromeliads

[MrMistery]

From what i know, NO. None of my books states this
However, every serious book on the subject will tell you that CAM plants require less water. This is why they populate deserts and other such hostile environment. You can recognise a CAM plant because it has water in it’s leaves and stem(like aloe vera)
Regards,
Andrew

[thank.darwin]

Check out these sites…

http://www.biology.arizona.edu/biochemi … sis_2.html

http://www.bios.niu.edu/sims/metabolism … lism20.htm

Hope they clear things up 😀

[Poison]

CAM plants require less water. Not C3 or C4.
C4 plants use a reaction way called C4 way. This reaction is followed by C3 way. C4 way provides more CO2 to the C3 way.
C3 plants do not have C4 way.
CAM plants also use C3 and C4 ways. the difference is that the stomas of CAM plants are opened during night and CO2 is stored.

Hope this helped. 🙂

[MrMistery]

If i didn’t know the process Poison, i wouldn’t have understood a thing from what you said 😀 😀

[Poison]

But you know the process. So this is not a problem 4 u. Is it? 😆

[MrMistery]

Quite well, if i do say so myself 🙂 🙂

[Inuyasha]

C4 plants are like crabgrass the ones that grow when it tends to be hotter. C3 is like bluegrass. The differene depedns on their intake of CO2. C4 bypass the need to use CO2 therefore they do not have to open their stromatas to let in CO2 for photosyntheseis.

[2810712]

I’m a bit confused here, how do theC4s need less CO2 as to carry out equal no. of photosynth reactions, CO2 required should be the same. Also, the require ment is given in ‘ppm’ units [ parts per million] The above q arises if this ppm quantity corrosponds to the conc. of CO2 in plasma of cell, but if it is about the conc. of CO2 in air, the above q will not arise. I think the more % CO2 stored in C4 is used in photosynthesis, so they need less CO2 conc. in air.
Also, how do CAMs save water in photosynthesis ? ? ?
Please help, i’m really confused. 😳 😥

hrushikesh

[MrMistery]

Ok, i see you are really confused so i’ll try to clear up things for me: hope i can
Both C3 and C4 plants need the same amount of co2 to produce glucose: all processes bow down to the laws of chemistry. But in c3 plants, under higher temperatures, occurs a process called fotorespiration. RuDP-carboxylase(the enzime that fixes CO2 in c3 plants) has a hish afinity for oxygen. Under high intensity of heat and light, c3 plants close their stomates, therefore reducing the quantity of water. when there is no water, there is no energy to enable fixing CO2, therefore oxigen is fixed on that enzime. Through this process photosynthesis in c3 plants drops dramatically, by aprox 50%. The enzime that fixes co2 in c4 and cam plants does not have an afinity for o2, therefore it does not have this problem.
Because C4 plants do not have this problem, photosynthesis is 6 times more efficient in their case. That is why they need less co2.
How do CAM plants save water? Good question. CAM plants live in places with less water, that is true. THEY DO NOT SAVE WATER IN PHOTOSYNTHESIS. They save it by reducing transpiration. CAM plants keep their stomas open during the night when it is colder so transpiration is reduced greatly, almost 0. They take CO2 from the air then and transform it into malic or aspartic acid, which filles the vacuoles of the plant. During the day the plant turns these acids into glucose, so the stomas are closed.

Hope i made it clear for you.
Regards,
Andrew

[mashimaro]

I got a question…
Our teacher tell us that c3 is same with CAM. It’s true? We all got a bit confuse about that….

[mith]

nope, depends on which part, some part are the same.but they’re not identical

[mashimaro]

In which part it is same? According our teacher explaination, c3 plant undergoes Crussulacean Acid Metabolism while c4 plant undergoes Hatch- Slack Pathway…i rily confused wif it…can u explain to me? 😥

[MrMistery]

Your teacher is wrong.
All plant assimilation types(C3, C4 and CAM) undergo the Calvin cycle.
C4 and CAM plants have an additional cycle witch fixes CO2 into malic acid(usually) first and then "gives" it to Rubisco and runs the Calvin cycle. The two types of plan ts differ in 2 main ways:
1. C4 plants have certain anatomical adaptations, while CAM plants do not
2. C4 plants separate the 2 cycles spatially(one occurs in the mesophil cells and the other in the bundle sheeth cells) while CAM plants separate them temporally(one occurs during the day and the other at night)

Hope i was as clear as possible…

[bio_is_my_best_friend]

I thought that C4 was use by the evil terrorists of the Middle East.

[Justazz]

Hi, I have 1 little question. How CAM plants prevent fotorespiration? or don’t they? I understand why in C4 plants fotorespiration doesn’t occures, but CAM is mystery for me.

[mith]

read mrmistery’s post above.

[MrMistery]

and don’t double post…

[tittu]

Bringing alive this old thread,
If you keep a c3 plant and a c4 plant under the same bell jar, adequate licght, then what happens to the co2 conc in the jar?
a. [co2] drops to co2 compensation point of c3 plant
b. [co2] drops to co2 compensation point of c4 plant
c. [co2] goes on decreasing.
d. [co2] drops below co2 compensation point of c4 plant

This came in Indian Biology Olympiad 2008. I just dont get the rationale.

[mith]

You basically find which C02 binding enzyme has greater affinity.

[MrMistery]

tittu, that’s one of the practice questions on the IBO website, if i remember correctly. A C4 plant can undergo photosynthesis at lower concentrations of CO2 than the C3 plant. Therefore, the CO2 will keep decreasing after the inferior limit of the C3 plant, until it reaches the C4 inferior limit. B

[angelyn1985]

Just a question, are maize and soybean both C4 plants??

[MrMistery]

maize yes. As for soybean, i don’t know

[Cat]

Soybean is C3.

[Cristgonz]

simplyfied is that C4 (weeds) are more effective on the production of drymatter than C3 (plants except cactaceae and another ones) and C3 makes the normal photosynthesis cicle (krebs)-C4 do it easier.
you’ll never see a C3 Plant growing up on the pavement but you can see some annual or perennial grasses everywhere (i have seen them on some celigins here in my country haha)

[Cristgonz]

quote angelyn1985:

Just a question, are maize and soybean both C4 plants??

corn = C4
soybean = C3
that’s why corn need less water to make more dry matter.

[MrMistery]

quote Cristgonz:

[…] C3 makes the normal photosynthesis cicle (krebs)-C4 do it easier.[…]

Calvin-Bensen!

[Cristgonz]

quote MrMistery:

quote Cristgonz:

[…] C3 makes the normal photosynthesis cicle (krebs)-C4 do it easier.[…]

Calvin-Bensen!

haha thanks
sorry!! i’m just a little bit oxidized ! i did it in my first year of my career hehe.
:)!!
but i guess u got my idea xD

[alextemplet]

Aren’t C3 plants mostly monocots and C4 plants mostly eudicots?

[MrMistery]

No.

[danni1708]

can someone either confirm or tell me im completely wrong..
do c3 plants undergo photosynthesis during the day using sunlight etc..
whilst c4 plants undergo photosynthesis at night? using some other method..
am i on the right track here or thinking of something completely different??

[MichaelXY]

quote danni1708:

can someone either confirm or tell me im completely wrong..
do c3 plants undergo photosynthesis during the day using sunlight etc..
whilst c4 plants undergo photosynthesis at night? using some other method..
am i on the right track here or thinking of something completely different??

Photosynthesis can not happen without light, hence the name. So no, C4 does not undergo photosynthesis at night. I suspect you are thinking of CAM plants which open their stomata at night to transpire, and close the stomata during the day.

[MichaelXY]

quote alextemplet:

Aren’t C3 plants mostly monocots and C4 plants mostly eudicots?

Some grasses and canes (Sugar cane) are C4. Cane and grasses are typically monocots.

[mamut]

Can you please tell me if there is any other plant which has C3 and C4 subspecies besides Alloteropsis semialata thanks!

[Misteryunveiled]

Nice information sharing!!

Well to tell you that whether C4 plants save water more than C3 plants, then the answer may be YES!

and After Stomata closure, exchange of CO2 is stopped (not the water conc decreases). It is the reduced level of CO2 which become rate limiting than water in case of high temperature, (MrMistery man). Also the closing of stomata is triggered to stop excessive water transpiration, that means water would be more inside the cell when stomata is closed.
and I think there is no more subspecies reported in other plant which has C3 and C4 pathway than Alloteropsis semialata.
or
I may be wrong….

Time to find out 😆

[Author]

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