C3 plants are defined as the plants that exhibit the C3 pathway. These plants use the Calvin cycle in the dark reaction of photosynthesis. The leaves of C3 plants do not show kranz anatomy. Here the photosynthesis process takes place only when the stomata are open. Approximately 95% of the shrubs, trees, and plants are C3 plants.
On the other hand, C4 plants are defined as the plants that use the C4 pathway or Hatch-slack pathway during the dark reaction. The leaves possess kranz anatomy, and the chloroplasts of these plants are dimorphic. About 5% of plants on earth are C4 plants.
Let us have a detailed look at the important difference between C3 and C4 plants.
Also Read: Kranz Anatomy
C3 vs C4 Plants
Following are the difference between C3 and C4 plants:
|The first stable intermediate product is 3- carbon acid:- phosphoglyceric acid.||The first stable intermediate product is a 4 carbon acid:- oxaloacetate (which is then reduced to malate)|
|Photosynthetic functions occur only in mesophyll cells – on the surface of the leaves||Photosynthetic functions occur in mesophyll and bundle sheath cells.|
|C3 requires cool and wet environments.||C4 requires tropical and dry environments.|
|95% of the green plants are C3 plants.||5% of the green plants are C4 plants.|
|Examples include rice, wheat, oats, barley, cotton, peanuts, tobacco, sugar beets, soybeans and spinach||Examples include Maize, Sugarcane, pearl millet, sorghum.|
|Leaves of these plants DO NOT show Kranz anatomy.||Leaves of these plants show Kranz anatomy.|
|C3 Plants are common in temperate climates.||C4 plants are common in tropical climates.|
|C3 plants exhibit only granal type of chloroplast||C4 plants exhibit granal as well as agranal type of chloroplast|
|Carbon dioxide fixation occurs only once.||Carbon dioxide fixation occurs twice.|
|All the steps of dark reaction take place in mesophyll cells.||The initial steps are carried out in mesophyll cells and the subsequent steps are carried out in bundle-sheath cells.|
|The optimum temperature for photosynthesis is comparatively lower than that of C4 plants||The optimum temperature for photosynthesis is comparatively higher than C3 plants|
|C3 photosynthesis is the oldest and the most common||C4 photosynthesis is a recent phenomenon, emerging after C3 photosynthesis|
|Photorespiration is not suppressed||Photorespiration is suppressed|
|Carbon dioxide fixation is slow.||Carbon dioxide fixation is faster.|
|Photosynthesis occurs when stomata are open||Photosynthesis occurs even when stomata are closed.|
C3 plants are those where the initial product is 3-phosphoglycerate with 3 carbon atoms. These plants also known as temperate plants. These plants reduce into carbon dioxide directly in the chloroplast.
These plants can be annual perennial. They are highly rich in proteins. Wheat, oats, rye, orchardgrass are some of the examples of C3 plants.
These plants carry out the C3 cycle to fix carbon from carbon dioxide into 3 carbon sugars. It is a cycle of chemical reactions where plants, over a period of time, can transform the 3 carbon compounds into nucleotides, amino acids and complex sugars(starches).
Most of the organic matter is created due to the process of carbon fixation. The sugars produced in the C3 or the Calvin cycle is also used up by the plants for storage of energy for a longer period of time.
The C3 cycle is often referred to as a light-independent reaction to the process of photosynthesis. This is because the C3 cycle is not supplied directly by the photons from the ultimate source of light – the Sun. The C3 cycle instead is fueled by ATP and NADPH that are generated by utilizing the energy derived from photons in the light-dependent reactions.
Calvin cycle is effective in converting carbon dioxide present in the atmosphere into carbon which can be utilized by living entities to produce proteins, sugars, lipids, and nucleotides. It efficiently eliminates greenhouse gas from the atmosphere – carbon dioxide.
The C3 cycle collects energy derived from sunlight for long-term storage of sugars that can further be used by plants and consumed by animals which forms the foundation for the food chain.
C4 plants are plants which cycle carbon dioxide to 4-carbon sugar compounds in order to enter the C3 or the Calvin cycle. The C4 plants are very productive in climatic conditions that are hot and dry and produce a lot of energy. Some of the plants that we usually consume are C4 plants such as pineapple, corn, sugar cane, etc.
Photorespiration decreases in hot conditions that exceed the ATP required to move CO2 from the mesophyll cells to bundle-sheath cells.
The C4 pathway is used by only 3% of the vascular plants. The plants are so-called because of the 4 carbon compound oxaloacetate produced during the pathway.
Similarities between C3 and C4 Plants
There are also a few similarities between the C3 and C4 plants:
- Both the plants fix energy from sunlight.
- Both synthesize carbohydrates.
- They are the type of dark reactions of photosynthesis.
- The site of photosynthesis is chloroplast in both types of plants.
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