Complete Exam Guide Subject-wise practice platform
0 XP
Photosynthesis in Higher Plants

Photosynthetic Adaptations Practice Questions

20 free Photosynthetic Adaptations practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

Practice in Quiz Mode

Question 1 of 20 Medium

Which photosynthetic adaptation helps desert plants reduce water loss during carbon fixation?

  1. A Opening stomata during the day
  2. B Fixing CO2 at night into organic acids
  3. C Increasing photorespiration rate
  4. D Using RuBisCO with higher oxygen affinity

Correct answer: Fixing CO2 at night into organic acids

CAM plants (e.g., desert succulents) open stomata at night to fix CO2 into organic acids such as malic acid, reducing water loss by keeping stomata closed during the hot day. The stored CO2 is then released internally for the Calvin cycle during the day.

Question 2 of 20 Medium

In C4 plants, the initial fixation of CO2 occurs in which cell type?

  1. A Bundle sheath cells
  2. B Mesophyll cells
  3. C Guard cells
  4. D Companion cells

Correct answer: Mesophyll cells

In C4 plants, CO2 is initially fixed in mesophyll cells by PEP carboxylase, forming a four-carbon compound (oxaloacetate). This compound is then transported to bundle sheath cells where the Calvin cycle occurs.

Question 3 of 20 Medium

Which enzyme allows C4 plants to efficiently fix CO2 even at low concentrations?

  1. A RuBisCO enzyme
  2. B Thylakoid ATP synthase
  3. C PEP carboxylase
  4. D Ferredoxin NADP reductase

Correct answer: PEP carboxylase

PEP carboxylase has a very high affinity for CO2 and does not bind oxygen, unlike RuBisCO. This allows C4 plants to fix carbon efficiently even at low CO2 concentrations, minimizing photorespiration.

Question 4 of 20 Medium

CAM plants differ from C4 plants mainly in terms of:

  1. A Type of chlorophyll used in each cell type
  2. B Separation of steps in time rather than space
  3. C Complete absence of Calvin cycle from leaves
  4. D Higher rate of transpiration per unit leaf area

Correct answer: Separation of steps in time rather than space

CAM plants separate CO2 fixation (at night) and the Calvin cycle (during the day) temporally within the same cells. In contrast, C4 plants achieve spatial separation by using distinct cell types (mesophyll and bundle sheath).

Question 5 of 20 Medium

Which habitat most commonly favors the evolution of C4 photosynthesis?

  1. A Cold and wet alpine regions
  2. B Low-light shaded forest understory
  3. C Hot and dry tropical grasslands
  4. D Temperate freshwater aquatic habitats

Correct answer: Hot and dry tropical grasslands

C4 photosynthesis is advantageous in hot, dry, and high-light environments such as tropical grasslands. It reduces photorespiration and increases photosynthetic efficiency under such conditions.

Question 6 of 20 Medium

Kranz anatomy is a characteristic feature of which type of plants?

  1. A C3 plants
  2. B CAM plants
  3. C C4 plants
  4. D Hydrophytes

Correct answer: C4 plants

Kranz anatomy refers to the arrangement of bundle sheath cells surrounded by mesophyll cells, which is typical of C4 plants. This structure facilitates efficient CO2 concentration around RuBisCO.

Question 7 of 20 Medium

Which photosynthetic adaptation helps aquatic plants utilize dissolved carbon efficiently?

  1. A Thick, waxy cuticle layer
  2. B Deeply sunken stomatal pores
  3. C Reduced intercellular air spaces
  4. D Ability to use bicarbonate ions

Correct answer: Ability to use bicarbonate ions

Many aquatic plants can utilize bicarbonate ions as a carbon source when dissolved CO2 is scarce. This adaptation helps them overcome low availability of free CO2 in water.

Question 8 of 20 Medium

Why is photorespiration minimal in C4 plants?

  1. A RuBisCO enzyme is entirely absent from bundle sheath
  2. B Oxygen concentration is reduced around RuBisCO
  3. C Light reactions do not occur in bundle sheath cells
  4. D Stomata in bundle sheath remain permanently closed

Correct answer: Oxygen concentration is reduced around RuBisCO

C4 plants concentrate CO2 around RuBisCO in bundle sheath cells, which lowers the relative oxygen concentration. This suppresses the oxygenase activity of RuBisCO and minimizes photorespiration.

Question 9 of 20 Medium

Which plant is a classic example of CAM photosynthesis?

  1. A Wheat
  2. B Maize
  3. C Opuntia
  4. D Sugarcane

Correct answer: Opuntia

Opuntia (prickly pear cactus) is a classic CAM plant that conserves water in arid environments. It opens stomata at night to fix CO2 as malic acid, which is decarboxylated during the day for photosynthesis.

Question 10 of 20 Medium

In CAM plants, malic acid accumulates mainly in:

  1. A Chloroplasts
  2. B Mitochondria
  3. C Vacuoles
  4. D Cytosol

Correct answer: Vacuoles

During the night, CO2 is fixed into malic acid and stored in vacuoles. During the day, malic acid is broken down to release CO2 for photosynthesis.

Question 11 of 20 Medium

Which factor primarily drives the evolution of photosynthetic adaptations in plants?

  1. A Nitrogen and phosphorus soil availability
  2. B Wind speed, direction, and duration
  3. C Light, temperature, and water availability
  4. D Soil texture and mineral content alone

Correct answer: Light, temperature, and water availability

Photosynthetic adaptations are mainly driven by environmental factors such as light intensity, temperature, and water availability. These factors determine the efficiency of CO2 uptake and enzyme activity.

Question 12 of 20 Medium

C3 plants show higher photorespiration under which condition?

  1. A Low temperature and high CO2
  2. B High temperature and low CO2
  3. C Low light intensity
  4. D High humidity

Correct answer: High temperature and low CO2

High temperature and low CO2 levels increase the oxygenase activity of RuBisCO in C3 plants. This leads to increased photorespiration.

Question 13 of 20 Medium

Which structural feature reduces water loss in desert plants performing photosynthesis?

  1. A Large leaf surface area
  2. B Thin cuticle
  3. C Reduced leaves or spines
  4. D Numerous stomata on upper surface

Correct answer: Reduced leaves or spines

Desert plants often have reduced leaves or spines to minimize surface area. This structural adaptation reduces transpiration and water loss.

Question 14 of 20 Medium

Which type of photosynthesis is most energy efficient under high light and temperature?

  1. A C3 photosynthesis
  2. B C4 photosynthesis
  3. C CAM photosynthesis
  4. D Anoxygenic photosynthesis

Correct answer: C4 photosynthesis

C4 photosynthesis is highly efficient under high light and temperature conditions. It minimizes photorespiration by concentrating CO2 around RuBisCO.

Question 15 of 20 Medium

In aquatic plants, stomata are generally:

  1. A Absent or non-functional
  2. B Present only on upper surface
  3. C Present only on lower surface
  4. D Highly sunken

Correct answer: Absent or non-functional

Submerged aquatic plants often lack functional stomata because gas exchange occurs directly through the plant surface. This is an adaptation to an aquatic habitat.

Question 16 of 20 Medium

Which compound is the first stable product of CO2 fixation in C4 plants?

  1. A Higher number of chloroplasts per cell
  2. B Thick cuticle and spine-like leaf structures
  3. C Reduced chlorophyll and accessory pigment content
  4. D Exclusive reliance on the CAM pathway

Correct answer: Higher number of chloroplasts per cell

Shade-adapted plants often have a higher number of chloroplasts and greater chlorophyll content per cell. This maximizes light capture under low-light conditions in the forest understory.

Question 17 of 20 Medium

Why are CAM plants generally slow-growing compared to C4 plants?

  1. A They lack chlorophyll
  2. B CO2 uptake is limited to nighttime
  3. C They perform photorespiration extensively
  4. D They cannot use ATP efficiently

Correct answer: CO2 uptake is limited to nighttime

CAM plants fix CO2 only at night, which limits the total amount of carbon fixed. This results in slower growth compared to C4 plants.

Question 18 of 20 Medium

Which habitat adaptation is seen in shade-loving plants regarding photosynthesis?

  1. A Higher number of chloroplasts per cell
  2. B Thick cuticle and spines
  3. C Reduced chlorophyll content
  4. D Exclusive CAM pathway

Correct answer: Higher number of chloroplasts per cell

Shade plants often have a higher number of chloroplasts and increased chlorophyll content. This allows them to efficiently capture limited light.

Question 19 of 20 Medium

Which statement correctly compares C3 and C4 plants?

  1. A C3 plants have Kranz anatomy, C4 plants do not
  2. B C4 plants show negligible photorespiration
  3. C C3 plants fix CO2 using PEP carboxylase
  4. D C4 plants are confined to cold climates

Correct answer: C4 plants show negligible photorespiration

C4 plants have a mechanism to concentrate CO2, resulting in negligible photorespiration. C3 plants lack this adaptation and show higher photorespiration.

Question 20 of 20 Medium

The primary advantage of CAM photosynthesis is:

  1. A Higher ATP yield
  2. B Complete absence of Calvin cycle
  3. C Maximum water conservation
  4. D Faster growth rate

Correct answer: Maximum water conservation

CAM photosynthesis is an adaptation for extreme water conservation. By opening stomata at night, plants significantly reduce water loss in arid environments.

0 / 20 answered