Biology Second Paper Archives | Page 488 of 1022

What are C4 Plants?

Plants that produce four-carbon oxaloacetic acid as the first stable compound during carbon assimilation in photosynthesis are called C4 plants. There are more than 900 species of C4 plants in 19 genera of cryptic flora. Several C4 plants exist in the Poaceae and Cyparaceae families.

Importance of hatch-slack or C4 cycle

1. Production of pyruvic acid: Pyruvic acid is produced in the C4 cycle. The pyruvic acid produced is stored in the plant body.
2. Plant Food: Food production is high in the C4 cycle. This food fulfills the needs of plants. If the cycle does not occur, the plant body will lack nutrients.
3. Animal Food: Food produced in the C4 cycle is stored in plant bodies. Animals consume plants as food and fulfill their nutritional needs.
4. Keeping photosynthesis going: Without the C4 cycle, the process of photosynthesis would have stopped. Hence the C4 cycle plays an important role in photosynthesis.
5. Organic acid production: Oxaloacetic acid and malic acid are produced in this cycle. These organic acids complete the biological functions of plants.
6. Essential components: Oxaloacetic acid, malic acid, pyruvic acid, phospho-enol pyruvic etc. are produced in C4 cycle. These elements are essential for plants.
7. Metabolism: Different types of acids or substances produced in this cycle cause metabolism in the plant body.
8. ATP production: ATP is produced in the C4 cycle. ATP provides energy to the plant body.
9. NAD malic pathway: NAD malic enzyme C4 pathway is functional in plants like China, Kaun, Millet etc.
These plants produce food through this cycle.
10. NADP malic pathway: NADP malic enzyme C4 pathway is functional in plants like Bhutra, Eksu, Sargam, Crab grass etc. These plants produce food through this cycle.
11. Phospho-enol pyruvate pathway: Phospho-enol pyruvate carboxykinase C4 pathway is functional in guinea grass.
1. Production of pyruvic acid: Pyruvic acid is produced in the C4 cycle. The pyruvic acid produced is stored in the plant body.
2. Plant Food: Food production is high in the C4 cycle. This food fulfills the needs of plants. If the cycle does not occur, the plant body will lack nutrients.
3. Animal Food: Food produced in the C4 cycle is stored in plant bodies. Animals consume plants as food and fulfill their nutritional needs.
4. Keeping photosynthesis going: Without the C4 cycle, the process of photosynthesis would have stopped. Hence the C4 cycle plays an important role in photosynthesis.
5. Organic acid production: Oxaloacetic acid and malic acid are produced in this cycle. These organic acids complete the biological functions of plants.
6. Essential components: Oxaloacetic acid, malic acid, pyruvic acid, phospho-enol pyruvic etc. are produced in C4 cycle. These elements are essential for plants.
7. Metabolism: Different types of acids or substances produced in this cycle cause metabolism in the plant body.
8. ATP production: ATP is produced in the C4 cycle. ATP provides energy to the plant body.
9. NAD malic pathway: NAD malic enzyme C4 pathway is functional in plants like China, Kaun, Millet etc.
These plants produce food through this cycle.
10. NADP malic pathway: NADP malic enzyme C4 pathway is functional in plants like Bhutra, Eksu, Sargam, Crab grass etc. These plants produce food through this cycle.
11. Phospho-enol pyruvate pathway: Phospho-enol pyruvate carboxykinase C4 pathway is functional in guinea grass.

Significance of C4 pathway

1. Physical Growth: Most plants in the C4 cycle have high physical growth.
2. Crop Production: C4 cycle plants have higher crop production rates.
3. Carbohydrate production capacity: C4 cycle plants have higher sugar production capacity than E3 plants.
4. Photosynthesis Rate: The CO2 consumer in the C4 cycle is PEP, so the potential for photosynthesis is low.
5. Organic acid production: C4 plants have more organic acid production capacity.
6. Effect of CO2: Because of the high specificity of carboxylase for CO2, carbon assimilation in plants is not disrupted even at very low CO2 concentrations.

Where does C4 cycle occur?

The C4 cycle occurs in monocots and some dicots in summer. The C4 cycle occurs in Gramini and Cyperaceae and in 16 dicotyledonous genera. Currently, the C4 pathway in plants such as sugarcane (Saccharum officinarum), bhutra (Zea mays), mutha grass (Cyperus rotundus), Panicum maximum, Amaranthus cruentus, Chloris gayana, crown of thorns (Euphorbia milii), Triticum etc. can be observed.

Stages of C4 cycle

1. Reaction of mesophyll cells
(i) Under the action of carboxylase enzyme, phospho-enol pyruvic acid reacts with atmospheric CO2 to produce oxaloacetic acid.
(ii) Oxaloacetic acid is converted to malic acid (aspartic acid) with the help of malic dehydrogenase enzyme. At this time NADPH+H+ takes part in the reaction to produce NADP.
2. Reaction of bundlesheath cells
(iii) Pyruvic acid is produced from malic acid (aspartic acid) under the action of decarboxylase enzyme.
(iv) Phospho-enol pyruvic acid is produced from pyruvic acid under the action of pyruvic acid kinase enzyme. At this time, ATP takes part in the reaction and produces ADP.
Phospho-enol pyruvic acid then re-enters the Hatch-Slack cycle and keeps the cycle going.

Stages of Hatch-Slack cycle

Characteristics of the hatch-slack or C4 cycle

(i) CO2 acceptor in C4 cycle is phosphoenol pyruvic acid.
(ii) The first stable compound in the C4 cycle is oxaloacetic acid.
(iii) A cycle occurs at low concentrations of CO2 (0.1-1.0 ppm).
(iv) This cycle occurs at high temperature (32-450C).
(v) The cycle occurs in mesophyll and bundlesheath chloroplasts.
(vi) It occurs in high light.
(vii) It occurs mainly in plants of tropical countries.
(viii) C4 cycle C4 occurs in plants.
(ix) The CO2 fixing enzyme in this cycle is carboxylase.
(x) Plants in cycle A have higher rate of photosynthesis.

Where does C4 cycle occur?

Hatch and Slack or C4 cycle definition

In 1966 Australian scientists M. D. Hatch and C. R. Slack described the pathway of carbon assimilation in the light neutral phase of photosynthesis called the Hatch-Slack cycle. They proved that the first stable compound produced in photosynthesis was four-carbon oxaloacetic acid (OAA). Hence it is called C4 cycle. This cycle is also known as dicarboxylic cycle. In 1970, it was recognized as Hatch-Slack cycle. In 1965, Hugo Kortschak, Hart and George Burr first observed that oxaloacetic acid was the first stable substance produced during CO2 oxidation in sugarcane leaves. The cycle is also called the HSK pathway because scientists Hatch, Slack and Kortschak discovered the series of reactions in the C4 pathway. Currently, this pathway has been discovered in many plants of 16 genera.

Example of C3 plants

All plants except C4 plants are C3 plants. E.g.- Paddy, Wheat, Barley/Sorghum, Mango, Yam, Jackfruit, Litchi, Banana, Jute, Algae, Bryophyta, Pteridophyta, Gymnosperms etc.