What Are C3 Plants?
C3 plants are plants which use only the Calvin cycle for fixing the carbon dioxide from the air. In the first step of the cycle, carbon dioxide reacts with RuBP to produce two 3-carbon molecules of 3-phosphoglyceric acid (3-PGA). Calvin Cycle is the means by which plants assimilate carbon dioxide from the atmosphere, ultimately into glucose.
The entire process from light energy capture to sugar production occurs within the chloroplast. The light energy is captured by the non-cyclic electron transport process which uses the thylakoid membranes the required electron transport.
Examples of C3 plants include:
What You Need To Know About C3 Plants
- C3 cycle evolved about 2.5 billion years ago
- C3 plants are abundant in temperate conditions
- In C3 plants, the complete steps of dark reaction takes place in the mesophyll cells only
- In C3 plants, chloroplasts do not contain peripheral reticulum
- In C3 plants, the carbon dioxide compensation point is higher (about 50 ppm) in C3 plants
- Photorespiration rate in C3 plants is very high
- C3 plants perform photosynthesis only when the stomata are open
- In C3 plants, the necessary optimum temperature for photosynthesis is very low (18 to 24 degrees Celsius)
- In C3 plants, the rate of translocation of the end-products of photosynthesis is very low
- Carbon dioxide fixation is relatively slow in C3
- Growth of C3 plants begins when soil temperature reach 4-7 degrees Celsius
- C3 plants produce fewer amounts of crude protein than C 4 plants
- Leaves of C3 plants do not possess kranz anatomy
- Majority of plants on earth are C3 plants (95% of total green plants)
- The first stable product in C3 cycle is a 3 carbon (3C) compound Phosphoglyceric Acid (PGA)
- C3 plants possess only one carbon dioxide acceptor
- The atmospheric carbon dioxide in C3 plants is RuBP (Ribulose-1,5-bisphosphate)
- In C3 plants, the carbon dioxide fixation takes place only at one place
- Examples of C3 plants include sunflower, beans, wheat, oats, rice, cotton, chlorella, spinach, rice, cotton etc
What are C4 Plants?
A C4 plant is a plant that cycles carbon dioxide into four-carbon sugar compounds to enter into the Calvin cycle. C4 plants utilize the C4 carbon fixation pathway whereby the carbon dioxide is first bound to a phosphoenolpyruvate in mesophyll cell resulting in the formation of a four-carbon compound (oxaloacetate) that is eventually taken to the bundle sheath cell where it will be decarboxylated to liberate the carbon dioxide to be used in the C3 Pathway.
C4 plants are very efficient in hot, dry climates and make a lot of energy. Examples of C4 Plants include: Sugarcane
What You Need To Know About C4 Plants
- The C4 cycle is relatively recent in origin, it is believed to have evolved about 12 million years ago
- C4 plants are abundant in tropical conditions
- In C4 plants, the mesophyll cells will only do the initial steps of C4 cycle. Subsequent steps are carried out in bundle sheath cells.
- In C3 plants, chloroplasts do have peripheral reticulum.
- The carbon dioxide compensation point is low in C4 plants (2 to 5 or even 0 ppm)
- In C4 plants, photorespiration is very church absent or if present is very little
- C4 plants can do photosynthesis even when the stomata are closed
- In C4 plants the optimum temperature for photosynthesis is high (32 to 55 degrees Celsius
- The rate of translocation of end-products of photosynthesis is very high in C4 plants
- Carbon dioxide fixation is relatively faster in C4 plants
- The growth of C4 plants begins when the soil temperature reaches 16- 21 degrees Celsius
- C4 plants produce more amounts of crude protein than C3 plants
- The leaves of C4 plants possess Kranz anatomy
- C4 plants are less in number (about 5%)
- The first stable product in C4 cycle is a 4 carbon (4C) compound- Oxaloacetic Acid (OAA)
- C4 plants possess two carbon dioxide acceptors (primary acceptor and secondary acceptor)
- The first carbon dioxide acceptor ( primary acceptor or atmospheric carbon dioxide acceptor) in C4 plants is PEP (phosphoenolpyruvate)
- In C4 plants, the carbon dioxide fixation takes place twice (one in the mesophyll cells, second in bundle sheath cells)
- Examples of C4 plants include sugarcane, Amaranthus, pineapple, sorghum, maize etc
Difference Between C3 And C4 Plants In Tabular Form
|ELEMENTS OF COMPARISON||C3 Plants||C4 Plants|
|Meaning||These are plants whose first product after carbon assimilation from sunlight is 3 carbon molecule or 3- phosphoglyceric acid for production of energy.||These are plants which convert sunlight energy into 4-carbon molecules or oxaloacetice acid.|
|Examples||Sunflower, Beans, wheat, Oats, Rice, Cotton, chlorella, Spinach, rice Cotton.||Sugarcane, Amaranthus Sorghum Maize|
|First stable Product||3-phosphoglycerate (3-PGA).||Oxaloacetate (OAA).|
|Optimum temperature for photosynthesis||15-25 Degrees Celsius.||30-40 degrees Celsius.|
|Pathway||C3 plants make use of C3 pathway.||C4 plants make use of C4 pathway.|
|Chloroplast||Chloroplast of C3 plants is monomorphic (existing in only one form).||Chloroplast of C4 plants is dimorphic.|
|Mesophyll cells||Mesophyll cells perfom full photosynthesis in C3 plants.||Mesophyll cells in C4 plants do not perform full photosynthesis but solely preliminary fixation.|
|Photosynthesis||C3 perform photosynthesis only when stomata are open.||C4 perform photosynthesis when stomata are closed.|
|Glucose Synthesis||C3 plants require 12NADPH and 18ATP for glucose synthesis.||C4 plants require 12NADPH and 30ATP.|
|Photorespiration||Have a higher rate of photorespiration.||Have a lower rate of photorespiration.|
|Population in %||Averagely 85% of total plants species are C3.||C4 plants are averagely 15% of total plant species.|
|Leaves||Leaves of C3 plants do not possess kranz anatomy.||The leaves of C4 plants possess Kranz anatomy.|
|CO2 Compensation Point (ppm)||Ppm in C3 is 30-70||Ppm in C4 plants is 6-10|
|Carboxylating Enzyme||Carboxylating Enzyme in C3 plants is RuBP carboxylase.||Carboxylating Enzyme in C4 plantsis PEP carboxylase.|
|Description||They can be described as cool season plants.||C4 plants can be described as warm season plants.|
What Are Some Of The Similarities Between C3 And C4 Plants?
- Both C3 and C4 plants synthesize carbohydrate.
- Both C4 and C4 plants requires chloroplasts carry out photosynthesis.
- RuBP can accept CO2 in both C3 and C4 plants.
- The carbohydrate product of both C3 and C4 cycle is a three-carbon sugar phosphate molecule known as Glyceraldehyde 3 phosphate (G3P).
- Both C3 and C4 plants require 6 molecules of CO2 and 12 molecules of water to synthesis one molecule of glucose.
- Both C3 and C4 plants fix energy from sunlight.
- The light reaction of photosynthesis is similar in both c3 and c4 plants
- Both C3 and C4 are types of dark reactions of photosynthesis.