Similarities and Difference between C3 and C3 Plants
(C3 plants vs C4 plants – A Comparison Table)
Green plants are unique to possess the ability to fix light energy from sunlight through a process called photosynthesis. The photosynthesis essential involves the synthesis of carbohydrates with atmospheric carbon dioxide, water and energy obtained from the sunlight. The process of photosynthesis in plants is completed in two broad steps, a light dependent ‘Light Reaction’ and a light independent ‘Dark Reaction”.
In the light reaction, the chlorophyll molecules in the plants absorb energy from sunlight and synthesize energy rich chemical molecules such as ATP and reduced coenzymes (NADPHH+). In the dark reaction, these energy rich molecules are used up for the synthesis of carbohydrates with carbon dioxide. There are essentially three different types of dark reaction pathways are operated in different plants on earth and they are named on the basis of the components of these pathways. They are C3 plants, C4 plants and CAM plants.
The present post describes the similarities and differences between C3 plants and C4 Plants.
C3 Plants: Plants which uses C3 cycle (Calvin cycle) of dark reaction of photosynthesis. C3 cycle is the first described dark reaction pathway. Majority of the plants (~95%) on earth are C3 type. The first stable product formed in C3 cycle is a three carbon (3C) compound, hence the name. The photosynthetic efficiency of C3 plants is comparatively less due the high rate or photorespiration. For a considerable period of time, the C3 cycle was thought to be the only dark reaction pathway in plants.
C4 Plants: These plants in addition to C3 cycle, uses an additional dark reaction pathway called C4 cycle. Very few plants (~5%) on earth are C4 type. The first stable product formed in C4 cycle is a four carbon (4C) compound, hence the name. The photosynthetic efficiency of C4 plants is very high due to the absence of photorespiration.
Similarities between C3 and C4 Plants
@. Both C3 and C4 are types of dark reactions of photosynthesis.
@. Both C3 and C4 plants fix energy from sunlight.
@. Both C3 and C4 plants synthesize carbohydrates.
@. The general equation of photosynthesis (6CO2 + 12H2O → 6C6H12O6 + 6O2 + 6H2O) is similar in both C3 and C4 plants.
@. Both C3 and C4 plants require 6 molecules of CO2 and 12 molecules of water to synthesis one molecule of glucose.
@. The carbohydrate product of both C3 and C4 cycle is a three-carbon sugar phosphate molecules called Glyceraldehyde 3 phosphate (G3P).
@. Both C3 and C4 plants requires chloroplasts for doing photosynthesis.
@. The light reaction of photosynthesis is similar in both C3 and C4 plants.
@. RuBP can accept CO2 in both C3 and C4 plants.
Difference between C3 and C4 Plants
C3 Plants C4 Plants
1 C3 plants uses C3 cycle or Calvin cycle for dark reaction of photosynthesis. C4 plants uses C4 cycle or Hatch-Slack Pathway for the dark reaction of photosynthesis.
2 Examples of C3 plants: Wheat, Rye, Oats, Rice, Cotton, Sunflower, Chlorella. Examples of C4 plants: Maize, Sugarcane, Sorghum, Amaranthus.
3 First stable product in C3 cycle is a 3 carbon (3C) compound – Phosphoglyceric Acid (PGA). First stable product in C4 cycle is a 4 carbon (4C) compound – Oxaloacetic Acid (OAA).
4 C3 plants are cool season plants, commonly seen in cool and wet areas. C4 plants are warm season plants, commonly seen in dry areas.
5 Majority of plants on earth are C3 plants (~95% of total green plants). C4 plants are less in number (about ~5%).
6 C3 plants are abundant in temperate conditions. C4 plants are abundant in tropical conditions.
7 Leaves of C3 plants do not have Kranz anatomy. Leaves of C4 plants show Kranz Anatomy.
8 In C3 plants, the bundle sheath cells do not contain chloroplasts. In C4 plants, the bundle sheath cells contain chloroplasts.
9 In C3 plants, the carbon dioxide fixation takes place only at one place. In C4 plants, the carbon dioxide fixation takes places twice (one in mesophyll cells, second in bundle sheath cells).
10 C3 plants possess only one CO2 acceptor. C4 plants possess two CO2 acceptors (primary acceptor and secondary acceptor).
11 The atmospheric CO2 acceptor in C3 plants is RuBP (Ribulose-1,5-bisphosphate). The first CO2 acceptor (primary acceptor or atmospheric CO2 acceptor) in C4 plants is PEP (phosphoenolpyruvate)
12 No secondary CO2 acceptor in C3 plants. The secondary acceptor of CO2 (metabolic CO2 acceptor) in C4 plants is RuBP.
13 In C3 plants, the complete steps of dark reaction takes place in the mesophyll cells only. In C4 plants, the mesophyll cells will only do the initial steps of C4 cycle. Subsequent steps are carried out in bundle sheath cells.
14 Chloroplasts monomorphic (single type) in C3 plants (usual granal type). Chloroplasts dimorphic: Those in the bundle sheath are large agranal and those in mesophyll are small and granal.
15 Chloroplasts do not contain peripheral reticulum. Chloroplasts do have peripheral reticulum.
16 C3 plants can perform photosynthesis only when the stomata are open. C4 plants can do photosynthesis even in the closed condition of stomata.
17 The optimum temperature for photosynthesis in C3 plants is very low. The optimum temperature for photosynthesis in C4 plants is high.
18 C3 plants are less efficient in Photosynthetic energy fixation. C4 plants are more efficient in photosynthesis.
19 Photorespiration rate is very high in C3 plants. Photorespiration is altogether absent in C4 plants (if present very little).
20 The carbon dioxide compensation point is high (about 50 ppm) in C3 plants. The carbon dioxide compensation point is low in C4 plants (2 to 5 or even 0 ppm).
21 C3 plants require an optimum temperature range of 18 – 24oC. C4 plants require an optimum temperature range of 32 – 55oC.
22 Growth of C3 plants begins when soil temperature reach 4 – 7oC. Growth of C4 plants begins when the soil temperature reach 16 – 21oC.
23 C3 plants are less efficient when the temperature increases. C4 plants are more efficient when the temperature increases.
24 C3 plants produce higher percentage of crude proteins than C4 plants. C4 plants produce fewer amounts of crude proteins than C3 plants.
25 The CO2 fixation is slow in C3 plants. The CO2 fixation is comparatively faster in C4 plants.
26 The rate of translocation of the end-products of photosynthesis very low in C3 plants. The rate of translocation of end-products of photosynthesis is very high in C4 plants.
27 The optimum temperature for growth is low to high in C3 plants. The optimum temperature of growth is high in C4 plants.
28 C3 cycle is evolved about 2.5 billion years ago. C4 cycle is comparatively recent in origin. Originated about 12 million years ago.