NCERT Solutions for Class 11 Biology Chapter – 13 Photosynthesis in Higher Plants includes all the important topics with detailed explanation that aims to help students to understand the concepts better. Students who are preparing for their Class 11 Biology exams must go through NCERT Solutions for Class 11 Chapter -13 Photosynthesis in Higher Plants. NCERT Solutions will make you understand the topics in most simple manner and grasp it easily to perform better.
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Exercises
1. By looking at a plant externally can you tell whether a plant is C3 or C4? Why and how?
Answer
We can’t tell whether a plant is C3 or C4 by looking at a plant externally. However, plants which which are adapted to dry climates follow the C4 pathway. Unlike C3 plants, the leaves of C4 plants have a special anatomy but this difference can only be observed at the cellular level.
2. By looking at which internal structure of a plant can you tell whether a plant is C3 or C4? Explain.
2. By looking at which internal structure of a plant can you tell whether a plant is C3 or C4? Explain.
Answer
As leaves of C4 plants have a special anatomy called Kranz anatomy. This makes them different from C3 plants. Special cells, known as bundle-sheath cells, surround the vascular bundles. These cells have a large number of chloroplasts. They are thick-walled and have no intercellular spaces. Therefore, we can tell whether a plant is C3 or C4 through internal structure.
Answer
In C4 plants photorespiration does not occur because they have a mechanism that increases the concentration of CO2 at the enzyme site. This takes place when the C4 acid from the mesophyll is broken down in the bundle sheath cells to release CO2 that results in increasing the intracellular concentration of CO2. In turn, this ensures that the RuBisCO functions as a carboxylase minimising the oxygenase activity. Thus, the photosynthesis rate increases and make C4 plants more productive.
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Answer
5. Suppose there were plants that had a high concentration of Chlorophyll b, but lacked chlorophyll a, would it carry out photosynthesis? Then why do plants have chlorophyll b and other accessory pigments?
Answer
Answer
Answer
The plants placed in light will have darker leaves as compared to leaves of a plant placed in shade. As leaves in shade get lesser light for photosynthesis so they perform lesser photosynthesis as compared to the leaves or plants kept in sunlight. To increase the rate of photosynthesis, the leaves present in shade have more chlorophyll pigments. This increase in chlorophyll content increases the amount of light absorbed by the leaves, which in turn increases the rate of photosynthesis which makes the leaves or plants in shade greener than the leaves or plants kept in the sun.
(b) What could be the limiting factor/s in region A?
(c) What do C and D represent on the curve?
(a) At point A
9. Give comparison between the following:
(a) C3 and C4 pathways
(b) Cyclic and non-cyclic photophosphorylation
(c) Anatomy of leaf in C3 and C4 plants
(b) Cyclic and non-cyclic photophosphorylation
(c) Anatomy of leaf in C3 and C4 plants
8. Figure 13.10 shows the effect of light on the rate of photosynthesis. Based on the graph, answer the following questions:
(a) At which point/s (A, B or C) in the curve is light a limiting factor?(b) What could be the limiting factor/s in region A?
(c) What do C and D represent on the curve?
Answer
(b) Light is a limiting factor also, water, temperature, and the concentration of carbon dioxide could also be limiting factors in the region A.
(c) C represents the stage beyond which light is not a limiting factor. D represents the stage beyond which intensity of light has no effect on the rate of photosynthesis.(a) C3 and C4 pathways
(b) Cyclic and non-cyclic photophosphorylation
(c) Anatomy of leaf in C3 and C4 plants
Answer
(a) C3 and C4 pathways
C3 pathways | C4 pathways |
| The primary acceptor of CO2 is RUBP – a five-carbon compound. | The primary acceptor of CO2 is phosphoenol pyruvate – a three-carbon compound. |
| The first stable product is 3 phosphoglycerate. | The first stable product is oxaloacetic acid. |
| It occurs only in the mesophyll cells of the leaves. | It occurs in the mesophyll and bundle-sheath cells of the leaves. |
| It is a slower process of carbon fixation and photo-respiratory losses are high. | It is a faster process of carbon fixation and photo-respiratory losses are low. |
(b) Cyclic and non-cyclic photophosphorylation
Cyclic photophosphorylation | Non-cyclic photophosphorylation |
| It occurs only in photosystem I. | It occurs both in photosystems I and II. |
| It involves only the synthesis of ATP. | It involves the synthesis of ATP and NADPH2. |
| In this process, photolysis of water does not occur. Therefore, oxygen is not produced. | In this process, photolysis of water takes place and oxygen is liberated. |
| In this process, electrons move in a closed circle. | In this process, electrons do not move in a closed circle. |
(c) Anatomy of leaf in C3 and C4 plants
Anatomy of leaf in C3 | Anatomy of leaf in C4 |
| Bundle-sheath cells are absent | Bundle-sheath cells are present |
| RuBisCo is present in the mesophyll cells | RuBisCo is present in the bundle-sheath cells. |
| The first stable compound produced is 3-phosphoglycerate – a three-carbon compound. | The first stable compound produced is oxaloacetic acid – a four-carbon compound. |
| Photorespiration occurs | Photorespiration does not occur |
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