Question

Question 3 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?

Class XI Biology Chapter - Photosynthesis in Higher Plants Page 224

Answer 1

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(a) C3 cycle occurs in all the plants whether they are C3 or C4 plants.
(b) At high light intensities C3 and C4 plants show increase in the rate of photosynthesis.
(c) The availability of C02 levels is limiting to C3 plants. C3 plants respond to higher concentration of carbon dioxide.
(d) They have increased rate of photosynthesis. It leads to higher productivity in tomatoes and bell pepper.
(e) When these plants grow in C02 enriched
atmosphere, their yield increases

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.