112. Which one of the following plants exhibits both C3 and C4 pathways?
(1) Zea mays
(2) Oryzasativa
(3) Mesembryanthemumcrystallinum
(4) Arabidopsis thaliana
Detailed Explanation:
Question:
Which one of the following plants exhibits both C3 and C4 pathways?
✅ Correct Answer: (3) Mesembryanthemum crystallinum
Introduction to C3 and C4 Pathways:
The C3 and C4 pathways are two different methods plants use for carbon fixation during photosynthesis. These processes determine how plants capture and convert carbon dioxide (CO2) into organic compounds, ultimately contributing to their growth and energy production.
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C3 pathway is the most common form of photosynthesis and is used by many plants like wheat, rice, and soybean. It involves the enzyme RuBisCO to fix CO2 directly.
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C4 pathway, found in plants like corn (Zea mays) and sorghum, involves an additional step where CO2 is initially fixed into a four-carbon compound, which is later processed by RuBisCO. This pathway is more efficient in hot, dry conditions as it minimizes water loss.
Mesembryanthemum crystallinum – A Unique Plant:
Mesembryanthemum crystallinum, also known as the ice plant, is unique in that it can utilize both C3 and C4 pathways. This ability allows the plant to adapt to different environmental conditions, making it an ideal candidate for studying plant adaptability and carbon fixation mechanisms.
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Under normal conditions, the ice plant follows the C3 pathway.
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Under stress conditions such as drought or high salinity, the plant can shift to a C4-like pathway to enhance water-use efficiency and conserve resources. This ability is due to the plant’s facultative CAM (Crassulacean Acid Metabolism) system, which allows it to switch between different pathways based on the environmental stresses it experiences.
Other Plants Explained:
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(1) Zea mays (Corn): This is a typical C4 plant and does not exhibit the ability to switch between C3 and C4 pathways.
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(2) Oryza sativa (Rice): Rice follows the C3 pathway and does not exhibit the ability to utilize the C4 pathway.
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(4) Arabidopsis thaliana: This plant uses the C3 pathway and does not have the ability to use the C4 pathway.
Why is Mesembryanthemum crystallinum Special?
The ability of Mesembryanthemum crystallinum to switch between the C3 and C4 pathways is a remarkable adaptation that enables the plant to thrive in challenging environmental conditions. Researchers are interested in studying this plant because it could hold key insights into improving photosynthesis and drought resistance in crops.
Conclusion:
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Mesembryanthemum crystallinum stands out because of its ability to exhibit both C3 and C4 pathways, depending on environmental stress. This adaptability makes it a fascinating subject of research in the field of plant biology and photosynthesis.
✅ Correct Answer: (3) Mesembryanthemum crystallinum
