Photosynthesis & Plant Physiology – NDA Biology PYQs

NDA 2024-I

Q. 1. Leaves of most plants appear green because the chlorophyll present in it:

(a) absorbs red and blue light while reflecting green light.

(b) absorbs green light only.

(c) absorbs green light while reflecting red and blue light.

(d) reflects red light and absorbs blue and green light.

Answer: (a) absorbs red and blue light while reflecting green light.

Explanation: Chlorophyll absorbs light energy primarily in the red (around 660–700 nm) and blue (around 430–450 nm) regions of the visible spectrum. It reflects and transmits green light (around 500–560 nm), which is why leaves appear green to our eyes. The absorbed red and blue light are used to drive the light-dependent reactions of photosynthesis. Concept Tested: Chlorophyll absorbs red and blue light; reflects green light → leaves appear green

★ JOVIK Exam Insight NDA tests the optical properties of chlorophyll. Chlorophyll absorbs: RED + BLUE. Reflects: GREEN. This is why plants look green. Carotenoids (accessory pigments) absorb blue-green and reflect yellow-orange, giving autumn leaves their colour.

NDA 2023-II

Q. 2. Which one of the following is NOT a requirement for photosynthesis?

(a) Chlorophyll

(b) CO₂

(c) Water

(d) O₂

Answer: (d) O₂

Explanation: Photosynthesis requires: light energy, chlorophyll (the light-absorbing pigment), carbon dioxide (CO₂, the carbon source), and water (H₂O, the electron donor). Oxygen (O₂) is a PRODUCT of photosynthesis, not a requirement. During the light reactions, water is split by photolysis, releasing O₂ as a by-product. The oxygen produced diffuses out of the leaf through stomata. Concept Tested: O₂ is a product of photosynthesis, not a raw material; CO₂, water, and chlorophyll are required

NDA 2023-I

Q. 3. Organisms capable of using CO₂ as principal carbon source are called:

(a) Autotrophs

(b) Heterotrophs

(c) Parasites

(d) Decomposers

Answer: (a) Autotrophs

Explanation: Autotrophs are organisms that can synthesise their own food using inorganic substances. Plants use CO₂ as their principal carbon source during photosynthesis, fixing it into organic compounds (glucose). Chemosynthetic bacteria also use CO₂ as a carbon source. Heterotrophs (including animals, fungi, and most bacteria) cannot fix CO₂: they depend on organic matter produced by other organisms. Parasites are a type of heterotroph that lives on or in a host. Concept Tested: Autotrophs use CO₂ as principal carbon source (photosynthesis or chemosynthesis)

Q. 4. During a laboratory experiment, a student immerses epidermal leaf peel in a hypertonic solution. After some time, the student examined the cells under a microscope and observed that:

(a) the cells swelled.

(b) the cells were plasmolysed.

(c) the cells built up turgor pressure.

(d) the cells size was unaffected.

Answer: (b) the cells were plasmolysed.

Explanation: A hypertonic solution has a higher solute concentration (lower water potential) than the cell contents. By osmosis, water moves OUT of the cell into the surrounding solution. In plant cells, this causes the cell membrane and cytoplasm to shrink and pull away from the rigid cell wall: a process called plasmolysis. The cell becomes flaccid. Swelling and turgor pressure occur when cells are placed in a hypotonic (more dilute) solution. Concept Tested: Plasmolysis: plant cells placed in hypertonic solution lose water → cytoplasm shrinks away from cell wall

NDA 2021-II

Q. 5. Shoots of plant show upward movement and it can be designated to be

(a) Negatively phototropic

(b) Positively chemotropic

(c) Positively hydrotropic

(d) Negatively geotropic

Answer: (d) Negatively geotropic

Explanation: Plant shoots grow upward, away from the pull of gravity. Growth responses to gravity are called geotropism. Shoots grow against the direction of gravitational pull: this is negative geotropism. Roots show positive geotropism (grow downward, towards gravity). Phototropism is growth towards or away from light. Hydrotropic responses relate to water. The shoot’s upward growth is best described as negatively geotropic. Concept Tested: Plant shoot upward growth – negatively geotropic (grows against gravity’s direction)

Q. 6. Which one of the following statements about the process of photosynthesis is correct?

(a) Chemical energy is converted into light energy.

(b) Carbon dioxide is oxidised to form carbohydrate.

(c) Water molecule splits into hydrogen and oxygen.

(d) Light energy is directly used to split water.

Answer: (c) Water molecule splits into hydrogen and oxygen.

Explanation: In the light reactions of photosynthesis, water molecules are split (photolysis) into hydrogen ions (H⁺) and oxygen (O₂). This process requires light energy but is carried out by the water-splitting enzyme (OEC: Oxygen Evolving Complex) rather than light acting directly on water. Option (d) is incorrect because light does not directly split water. Option (a) is reversed. Option (b) is wrong because CO₂ is REDUCED (not oxidised) to form carbohydrate. Concept Tested: Photolysis: water molecules split into H⁺ and O₂ during light reactions; CO₂ is reduced (not oxidised) to form glucose

★ JOVIK Exam Insight Two common NDA errors about photosynthesis: (1) CO₂ is REDUCED to glucose: it gains hydrogen atoms. It is not oxidised. (2) The O₂ released comes from WATER (photolysis), not from CO₂. These two facts appear in multiple NDA papers.

NDA 2021-I

Q. 7. The gaseous product of a process in plants is a requirement for another vital process that releases energy. Given below are four combinations of the process and product. Identify the correct answer.

(a) Respiration and Nitric oxide

(b) Transpiration and Water vapour

(c) Photosynthesis and Oxygen

(d) Germination and Carbon dioxide

Answer: (c) Photosynthesis and Oxygen

Explanation: Photosynthesis produces oxygen (O₂) as a gaseous by-product. This oxygen is required for aerobic respiration: the vital process that releases energy in cells. The cycle is complete: photosynthesis produces O₂, and respiration consumes it. Transpiration releases water vapour, which is not a requirement for respiration. Germination releases CO₂, not O₂. Concept Tested: Photosynthesis produces O₂ → O₂ is required for aerobic respiration (energy release)

Q. 8. In a dicot pot herb, vaseline/vegetable oil was applied on the upper surface of one leaf (Experimental leaf 1) and on the lower surface of another leaf (Experimental leaf 2). Vaseline/Vegetable oil was not applied on the control leaf. The plant was deliberately not watered for several days. Which leaf will dry up last?

(a) Experimental leaf 1

(b) Experimental leaf 2

(c) Control leaf

(d) All the leaves will dry up simultaneously

Answer: (b) Experimental leaf 2

Explanation: In dicotyledonous plants, the majority of stomata are located on the lower (abaxial) surface of leaves. Stomata are the primary route for water loss by transpiration. Applying vaseline to the lower surface (Experimental leaf 2) blocks most of the stomata, greatly reducing transpiration. Without water loss, this leaf retains moisture the longest and will dry up last. Blocking the upper surface (Experimental leaf 1) has less effect because fewer stomata are present there. The control leaf loses water freely through all its stomata. Concept Tested: Most stomata in dicot leaves are on the lower surface; blocking lower surface minimises transpiration and delays drying

★ JOVIK Exam Insight Stomata location is a tested NDA concept: dicots → most stomata on lower (abaxial) surface. Floating leaves (e.g., lotus) → stomata only on upper surface. Grasses (monocots) → stomata on both surfaces equally. This question tests applied knowledge of stomata distribution.

NDA 2018-II

Q. 9. The oxygen evolved during photosynthesis comes from splitting of

(a) water

(b) carbon dioxide

(c) oxygen

(d) light

Answer: (a) water

Explanation: The oxygen released during photosynthesis comes entirely from water (H₂O), not from CO₂. This was conclusively demonstrated by experiments using heavy oxygen isotopes (¹⁸O). During the light reactions, the enzyme OEC (Oxygen Evolving Complex) splits water molecules: 2H₂O → 4H⁺ + 4e⁻ + O₂. The O₂ released is the by-product of this water-splitting (photolysis). The carbon in CO₂ is used to make glucose, not to produce oxygen. Concept Tested: Oxygen released in photosynthesis comes from photolysis of water, not from CO₂

NDA 2016-II

Q. 10. Consider the following statements about cactus:

1. The leaves are reduced to spines.

2. The stem does the photosynthesis.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Both statements are correct. In cacti (xerophytes adapted to desert conditions), the leaves are modified into spines (thorns) to minimise water loss: spines have a very small surface area and reduce transpiration. The green fleshy stem takes over the function of photosynthesis: it is the primary photosynthetic organ. The stem also stores water. This dual adaptation (reduced leaves + photosynthetic stem) is a key xerophytic feature of cacti. Concept Tested: Cactus adaptations: leaves → spines (reduce water loss); green stem → site of photosynthesis

Q. 11. A plant having yellow leaves with dead spots has the deficiency of

(a) Potassium

(b) Magnesium

(c) Nitrate

(d) Phosphate

Answer: (b) Magnesium

Explanation: Magnesium is the central metal atom in the chlorophyll molecule. Without sufficient magnesium, the plant cannot synthesise adequate chlorophyll, leading to yellowing of leaves (chlorosis). The yellow appearance with dead spots is characteristic of magnesium deficiency. Older leaves are affected first. Potassium deficiency causes scorching at leaf margins. Nitrate deficiency causes uniform yellowing (from older leaves). Phosphate deficiency causes purplish discolouration. Concept Tested: Magnesium deficiency: yellow leaves with dead spots (chlorosis) because Mg is the metal in chlorophyll

NDA 2015-II

Q. 12. Carbon and energy requirements of autotrophic organisms are fulfilled by:

(a) Photosynthesis

(b) Gluconeogenesis

(c) Glycogenesis

(d) External sources

Answer: (a) Photosynthesis

Explanation: Autotrophs fulfil both their carbon and energy requirements through photosynthesis. In photosynthesis, light energy is captured and used to fix CO₂ (carbon source) into organic molecules (glucose), which also stores chemical energy. Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors (found in animals/bacteria). Glycogenesis is the synthesis of glycogen. External sources are used by heterotrophs, not autotrophs. Concept Tested: Photosynthesis fulfils both the carbon and energy requirements of autotrophs

NDA 2015-I

Q. 13. Statement I: Growth of plants is smooth with a complete fertilizer.

Statement II: A complete fertilizer always contains N, P, K.

(a) Both the statements are individually true and Statement II is the correct explanation of Statement I

(b) Both the statements are individually true but Statement II is not the correct explanation of Statement I

(c) Statement I is true but Statement II is false

(d) Statement I is false but Statement II is true

Answer: (a) Both the statements are individually true and Statement II is the correct explanation of Statement I

Explanation: Statement I is correct: plants grow optimally when given a balanced (complete) fertilizer that provides all essential macronutrients. Statement II is also correct: a complete fertilizer always contains the three primary macronutrients: Nitrogen (N), Phosphorus (P), and Potassium (K): often written as NPK. Statement II explains Statement I because N, P, K are the most essential nutrients for plant growth, and a fertiliser containing all three supports healthy overall growth. Concept Tested: Complete fertilizer contains N, P, K: the three primary macronutrients essential for plant growth

Q. 14. In plants, which one of the following gases is released during Photosynthesis?

(a) Carbon dioxide

(b) Oxygen

(c) Hydrogen

(d) Methane

Answer: (b) Oxygen

Explanation: Oxygen (O₂) is the gaseous product released by plants during photosynthesis. It is produced when water molecules are split during the light reactions (photolysis). This released oxygen diffuses out of the leaf through the stomata into the atmosphere. Carbon dioxide is a raw material for photosynthesis, not a product. Hydrogen and methane are not produced during photosynthesis. Concept Tested: Oxygen is the gas released during photosynthesis (from photolysis of water)

NDA 2014-II

Q. 15. Which one among the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(c) Gibberellin

(d) Estrogen

Answer: (c) Gibberellin

Explanation: Gibberellin is a plant hormone (phytohormone) that promotes stem elongation, seed germination, flowering, and fruit development. It is produced in young leaves, seeds, and root tips. Insulin is a hormone produced by the pancreas in animals (regulates blood glucose). Thyroxin is produced by the thyroid gland in animals. Estrogen is an animal sex hormone produced by the ovaries. Only gibberellin is a plant hormone. Concept Tested: Gibberellin is a plant hormone; insulin, thyroxin, and estrogen are animal hormones

NDA 2013-I

Q. 16. Which one among the following hormones stimulates the plant cells to grow in a manner such that the plant appears to be bent towards light?

(a) Cytokinin

(b) Auxin

(c) Gibberellin

(d) Abscisic acid

Answer: (b) Auxin

Explanation: Phototropism (bending towards light) is controlled by auxin (Indole-3-acetic acid, IAA). When light strikes one side of a shoot, auxin migrates to the shaded side. Higher auxin concentration on the shaded side causes those cells to elongate more than the cells on the lit side. This unequal growth bends the shoot towards the light source. Cytokinin promotes cell division. Gibberellin promotes elongation. Abscisic acid promotes dormancy and stomatal closure. Concept Tested: Auxin causes phototropism: migrates to shaded side → unequal cell elongation → shoot bends towards light

★ JOVIK Exam Insight Plant hormone functions for NDA: Auxin → phototropism, apical dominance. Gibberellin → stem elongation, germination. Cytokinin → cell division, delay senescence. Abscisic acid → dormancy, stomatal closure (stress hormone). Ethylene → fruit ripening, leaf fall.

NDA 2012-I

Q. 17. Which one among the following nutrients is a structural component of the cell wall of plants?

(a) Manganese

(b) Potassium

(c) Phosphorus

(d) Calcium

Answer: (d) Calcium

Explanation: Calcium is a structural component of the plant cell wall. Calcium ions (Ca²⁺) form cross-links with pectin in the middle lamella: the layer between adjacent cell walls: providing structural rigidity and stability. Calcium also plays a role in cell signalling. Potassium is involved in stomatal regulation and enzyme activation. Phosphorus is in nucleic acids, ATP, and membranes. Manganese is a micronutrient involved in photosynthesis. Concept Tested: Calcium is a structural component of plant cell walls (cross-links with pectin in the middle lamella)

Q. 18. Which of the following is not a micronutrient for a plant?

(a) Iron

(b) Magnesium

(c) Molybdenum

(d) Manganese

Answer: (b) Magnesium

Explanation: Plant nutrients are classified as macronutrients (needed in large amounts) and micronutrients (needed in trace amounts). Magnesium is a macronutrient: it is required in relatively large amounts as the central atom of chlorophyll and as an enzyme activator. Iron, molybdenum, and manganese are all micronutrients required in trace amounts. Other macronutrients include N, P, K, Ca, S, and Mg. Concept Tested: Magnesium is a macronutrient (central atom of chlorophyll); iron, molybdenum, and manganese are micronutrients

NDA 2011-II

Q. 19. The metal constituent of chlorophyll is

(a) Iron

(b) Potassium

(c) Manganese

(d) Magnesium

Answer: (d) Magnesium

Explanation: Chlorophyll is the primary photosynthetic pigment. Its central metal atom is magnesium (Mg²⁺), which is held within a porphyrin ring structure. The magnesium is coordinated by four nitrogen atoms of the porphyrin. This magnesium-centred porphyrin structure is essential for absorbing light energy. Iron is the central metal in haemoglobin (in blood) and in cytochromes. Manganese is involved in the water-splitting reaction in photosynthesis but is not part of chlorophyll. Concept Tested: Magnesium is the central metal atom of the chlorophyll molecule

NDA 2011-I

Q. 20. Sandalwood tree is considered a:

(a) total root parasite.

(b) total stem parasite.

(c) stem parasite.

(d) partial root parasite.

Answer: (d) partial root parasite.

Explanation: Sandalwood (Santalum album) is a hemiparasite: it is green (partially photosynthetic) and derives only some of its nutrients, especially water and minerals, from the roots of neighbouring host plants. It attaches to host roots using haustoria. Since it taps the host roots and is not fully parasitic (it can photosynthesise), it is classified as a partial root parasite. Cuscuta (dodder) is an example of a total stem parasite. Concept Tested: Sandalwood (Santalum album) is a partial root parasite (hemiparasite): partially photosynthetic, taps host roots

Q. 21. Which one among the following Indian scientists proposed a theory for long distance transport of water in plants?

(a) J.C. Bose

(b) Birbal Sahni

(c) P. Maheshwari

(d) N.S. Parihar

Answer: (a) J.C. Bose

Explanation: Jagadish Chandra Bose (J.C. Bose) was a pioneering Indian scientist who made fundamental contributions to plant physiology. He proposed the theory of electrical signalling in plants and also contributed to understanding water transport in plant stems. The cohesion-tension theory of water transport is associated with Dixon and Joly, but J.C. Bose contributed to understanding long-distance transport in plant stems and developed instruments to study plant responses. Among the options, J.C. Bose is the correct answer. Concept Tested: J.C. Bose contributed to theories of long-distance water transport in plants

NDA 2010-II

Q. 22. Statement I: Autotroph plants contain the pigment chlorophyll for meeting their requirement of carbon and energy.

Statement II: Photosynthesis is the process of converting water into food using sunlight and oxygen.

(a) Both the statements are individually true and statement II is the correct explanation of statement I

(b) Both the statements are individually true but statement II is not the correct explanation of statement I

(c) Statement I is true but statement II is false

(d) Statement I is false but statement II is true

Answer: (c) Statement I is true but statement II is false

Explanation: Statement I is correct: autotrophic plants use chlorophyll to absorb light energy and carry out photosynthesis, which meets their carbon (CO₂ fixation) and energy (ATP production) requirements. Statement II is incorrect: photosynthesis is not “converting water into food using oxygen.” Photosynthesis uses sunlight, water, and CO₂ to produce glucose and oxygen. Oxygen is a PRODUCT of photosynthesis, not a raw material. Concept Tested: Photosynthesis uses CO₂ + H₂O + light → glucose + O₂; oxygen is a product, not a raw material

NDA 2010-I

Q. 23. Xerophytes thrive in

(a) hot and arid condition

(b) cool and wet condition

(c) hot and wet condition

(d) cool and arid condition

Answer: (a) hot and arid condition

Explanation: Xerophytes are plants specially adapted to survive in extremely dry (arid) and often hot environments with very little water. Examples include cacti, succulents, and date palms. Their adaptations include reduced leaves (spines), thick waxy cuticle, sunken stomata, water storage in stems, and deep root systems. Hydrophytes grow in aquatic/wet conditions. Mesophytes grow in moderate conditions. Concept Tested: Xerophytes are adapted to hot and arid (dry) conditions: desert plants

---