Anatomy of Leaf in C3 and C4 plants: The plants which use C3 carbon fixation pathway and the first product of carbon dioxide fixation is a 3-carbon organic compound, 3-phosphoglycerate, are termed as C3 plants. The plants in which the first product of carbon dioxide fixation is a 4-carbon organic compound, oxaloacetate, are termed as C4 plants.
Anatomy of Leaf in C3 and C4 plants
The C4 plants have a peculiar type of leaf anatomy, called .Kranz anatomy.. The palisade mesophyll of a C3 plant forms a row of closely packed cells just beneath the upper epidermis of the leaf, whereas in a C4 plant these cells form a ring (Kranz) around the bundle sheath cells and veins of the leaves. The bundle sheath cells of C4 plants contain large number of chloroplasts and one can easily recognise C4 plants by their prominent dark green veins.
Similarities Between C3 And C4 Plants
- Both plants are types of dark reactions of photosynthesis.
- Plants of these fix energy from sunlight.
- Both plants synthesize carbohydrates.
- They require chloroplasts for photosynthesis.
- Both consist of the same light reactions.
- CO2 is accepted by RuBP in both C3 and C4 plants.
Difference Between C3 And C4 Plants
|C3 Plants||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.|
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