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Question

The table below shows photosynthetic type, temperature and sunlight intensity levels.

Photosynthetic TypeTemperatureSunlight Intensity
A. C3 Planti HighP. High
B. C4 plantii ModerateQ. Moderate
iii LowR Low

Which of the following correctly matches the plant photosynthetic type with the temperature and sunlight conditions in which photosynthetic rate per unit leaf area is maximum for that plant?

The correct answer is A - ii - Q; B - i - P

Photosynthetic Plant Types and Conditions

Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose. Different types of plants have adapted different photosynthetic pathways to thrive in specific environmental conditions, primarily related to temperature and light intensity. The two main types discussed here are C3 plants and C4 plants.

C3 Photosynthesis Efficiency

C3 plants are the most common type, including crops like wheat, rice, and soybeans. Their photosynthetic pathway, known as the Calvin cycle, directly fixes carbon dioxide into a three-carbon compound. C3 photosynthesis is generally more efficient under moderate temperature and moderate light intensity. At high temperatures, C3 plants experience a process called photorespiration, which reduces their photosynthetic efficiency. Their photosynthetic rate typically saturates at lower light intensities compared to C4 plants.

C4 Photosynthesis Efficiency

C4 plants, such as maize, sugarcane, and millet, have evolved a mechanism that minimizes photorespiration and increases water use efficiency, especially in hot and dry environments. They first fix carbon dioxide into a four-carbon compound in mesophyll cells, which is then transported to bundle sheath cells where CO2 is released and enters the Calvin cycle. This CO2 concentration mechanism allows C4 plants to maintain high photosynthetic rates even at high temperatures and high light intensities, conditions where C3 plants become less efficient.

Matching Photosynthetic Types to Optimal Conditions

Based on the characteristics of C3 and C4 plants:

  • For C3 plants (A), the maximum photosynthetic rate per unit leaf area is typically observed under moderate temperature (ii) and moderate sunlight intensity (Q).
  • For C4 plants (B), the maximum photosynthetic rate per unit leaf area is typically observed under high temperature (i) and high sunlight intensity (P).

Let's look at the given table and options:

Photosynthetic Type Temperature Sunlight Intensity
A. C3 Plant i High P. High
B. C4 plant ii Moderate Q. Moderate
iii Low R Low

Matching the plant type with its optimal conditions from the table:

  • C3 Plant (A) matches with moderate temperature (ii) and moderate sunlight intensity (Q). This gives the combination A - ii - Q.
  • C4 plant (B) matches with high temperature (i) and high sunlight intensity (P). This gives the combination B - i - P.

Therefore, the correct matching is A - ii - Q; B - i - P.

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Important Questions from Photosynthesis

  1. Kranz anatomy is found in _____ plant.

  2. Which plant pigment is present in tomatoes?

  3. Which one of the following reactions takes place during the reduction phase of the Calvin - Benson cycle?

  4. The following statements were made with the assumption that the concentration of 3- phosphoglycerate is high inside chloroplasts of an actively photosynthesizing leaf.

    A. There will be high concentration of triose phosphate in the chloroplast.

    B. The activity of ADP-glucose pyrophosphorylase will be inhibited.

    C. The carbon flow will be diverted from sucrose to starch.

    D. Starch synthesis will be inhibited and carbon flow will be more towards sucrose synthesis.

    Which one of the following combinations of above statements is correct?

  5. Which one of the following are the correct encoding sites of large and small subunits of Rubisco enzyme in red and brown algae?

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