Question

Even though a very few cells in a C₄ plant carry out the biosynthetic — Calvin pathway, yet they are highly productive. Can you discuss why?

Answer 1

The productivity of a plant is measured by the rate at which it photosynthesises. The amount of carbon dioxide present in a plant is directly proportional to the rate of photosynthesis. C4 plants have a mechanism for increasing the concentration of carbon dioxide. In C4 plants, the Calvin cycle occurs in the bundle-sheath cells. The C4 compound (malic acid) from the mesophyll cells is broken down in the bundle-sheath cells. As a result, CO2 is released. The increase in CO2 ensures that the enzyme RuBisCo does not act as an oxygenase, but as a carboxylase. This prevents photorespiration and increases the rate of photosynthesis. Thus, C4 plants are highly productive.

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Answer 2

Answer:

Plant productivity can be estimated by the rate at which photosynthesis takes place. The amount of carbon dioxide in a plant is directly proportional to the rate of photosynthesis. In C4 plants, very few of the cells carry out the biosynthetic pathway yet they are highly productive for the following reasons.

• They have a mechanism that increases the CO2 concentration at the site of enzyme.

• Mesophyll cells are broken down in the bundle sheath cells that results in CO2 release which inturn increases the intracellular CO2 concentration .

• Rubisco functions as a carboxylase minimizing the oxygenase activity.

• Increase in photosynthesis make C4 plants more productive.