Every Plant Physiology question CSIR-NET Life Sciences has set in its last 11 papers, sorted by topic, with 16 of them solved step by step. Answers follow NTA’s final answer keys.
Unit 6 of the CSIR-NET Life Sciences syllabus, System Physiology – Plant, covers photosynthesis, respiration and photorespiration, nitrogen metabolism, plant hormones, sensory photobiology, solute transport, secondary metabolites and stress physiology. We went through all 11 papers from February 2022 to June 2025 and pulled out every question from this unit. In these 11 papers it carried more Part B and Part C questions than any other unit.
How much of the paper is Plant Physiology?
Across the 11 papers, 131 of the 1,375 Part B and Part C questions (9.5%) came from Unit 6. That ranks it first of the 13 units. 78 of the 131 were 4-mark Part C questions.
| Paper | Part B | Part C | Total |
|---|---|---|---|
| June 2025 | 4 | 8 | 12 |
| December 2024, Shift 1 | 3 | 6 | 9 |
| December 2024, Shift 2 | 3 | 7 | 10 |
| June 2024, Shift 1 | 7 | 7 | 14 |
| June 2024, Shift 2 | 5 | 7 | 12 |
| December 2023, Shift 1 | 5 | 6 | 11 |
| December 2023, Shift 2 | 5 | 6 | 11 |
| June 2023, Shift 1 | 6 | 8 | 14 |
| June 2023, Shift 2 | 7 | 8 | 15 |
| February 2022, Shift 1 | 3 | 8 | 11 |
| February 2022, Shift 2 | 5 | 7 | 12 |
| All 11 papers | 53 | 78 | 131 |
Which Plant Physiology topics come up most
Stress Physiology & Plant–Pathogen Interactions and Photosynthesis together account for 43% of the unit’s questions.
16 solved Plant Physiology PYQs
One or two from each major subtopic, from different papers. Try each one before you open the solution.
Which one of the following statements represents correct sequence of events during electron transport chain from P680 to P700 in a light reaction of photosynthesis in a typical plant?
- 1Plastocyanin – Plastoquinone A – Plastoquinone B – Cytochrome b6f complex – Pheophytin
- 2Plastocyanin – Cytochrome b6f complex – Plastoquinone A – Plastoquinone B – Pheophytin
- 3Pheophytin – Plastoquinone A – Plastoquinone B – Cytochrome b6f complex – Plastocyanin
- 4Pheophytin – Cytochrome b6f complex – Plastoquinone A – Plastoquinone B – Plastocyanin
Show answer and solution
Electrons leave P680 for pheophytin, then pass to the bound plastoquinone QA and the mobile QB. Reduced plastoquinone hands them to the cytochrome b6f complex, and the soluble copper protein plastocyanin carries them across the lumen to P700. Only option 3 has that order.
Which one of the following is the strongest oxidizing agent produced during photosynthesis?
- 1NADPH
- 2P680+
- 3Ferredoxin
- 4P700+
Show answer and solution
When P680 gives up an electron it becomes P680+, with a redox potential of about +1.2 V. That is the strongest biological oxidant known, and the only one able to take electrons from water at the oxygen-evolving complex. NADPH and reduced ferredoxin are reductants. P700+ is a much weaker oxidant, at about +0.5 V.
Photochemically generated ATP is consumed in which one of the following phases of Calvin-Benson cycle?
- 1Only carboxylation
- 2Only regeneration
- 3Carboxylation and reduction
- 4Reduction and regeneration
Show answer and solution
Answer: (4) Reduction and regeneration
The Calvin–Benson cycle has three phases. Carboxylation (RuBisCO fixing CO2 onto RuBP) uses no ATP. Reduction uses ATP at phosphoglycerate kinase and NADPH at glyceraldehyde-3-phosphate dehydrogenase. Regeneration uses ATP at phosphoribulokinase to remake RuBP. So ATP is consumed in reduction and regeneration.
Which one of the following is a correct combination of four carbon intermediates formed during C4 photosynthesis in plants?
- 1Malate and Aspartate
- 2Aspartate and Alanine
- 3Phosphoenolpyruvate and Oxaloacetate
- 4Alanine and Pyruvate
Show answer and solution
Answer: (1) Malate and Aspartate
In C4 plants PEP carboxylase fixes HCO3− into oxaloacetate, which is quickly turned into malate (NADP-ME type) or aspartate (NAD-ME and PEPCK types) for transport to the bundle sheath. Both are four-carbon acids. Alanine, pyruvate and PEP are three-carbon compounds, so option 1 is the only pair of C4 intermediates.
In which one of the following organelles does glycine decarboxylase complex and serine hydroxymethyltransferase convert two molecules of glycine into one molecule of serine during photorespiration?
- 1Endoplasmic reticulum
- 2Chloroplast
- 3Mitochondria
- 4Peroxisome
Show answer and solution
Answer: (3) Mitochondria
Two glycines arriving from the peroxisome are handled in the mitochondrial matrix. Glycine decarboxylase releases CO2 and NH3 from one glycine, and serine hydroxymethyltransferase adds the remaining C1 unit to the second glycine, giving one serine. This is where photorespiration loses CO2.
Following are certain statements regarding photorespiration pathway in plants:
- A. The first two-carbon (2C) compound synthesized by the action of Rubisco in the chloroplast is glycolate.
- B. Glycolate exits the chloroplast and enters peroxisomes.
- C. Glycolate that is synthesized during C2 cycle enters the chloroplast from mitochondria.
- D. Glycine is transported from peroxisomes to mitochondria.
Which one of the following combinations is INCORRECT?
- 1A and B only
- 2A and C only
- 3B, C and D
- 4A, C and D
Show answer and solution
Answer: (2) A and C only
Statement A is wrong: RuBisCO’s oxygenase reaction makes 2-phosphoglycolate, which a phosphatase then converts to glycolate. Statement C is wrong too: the molecule that re-enters the chloroplast is glycerate, coming from the peroxisome, not glycolate from the mitochondrion. B and D are correct steps. The incorrect pair is A and C.
The following statements are made regarding the nitrogenase enzyme involved in the reduction of atmospheric nitrogen to ammonia:
- A. Nitrogenase enzyme is composed of two components: dinitrogenase and dinitrogenase reductase.
- B. MoFe protein component is a homodimer.
- C. Fe protein component is dinitrogenase.
- D. MoFe protein contains the active site metal cluster where N2 binds.
- E. Fe protein delivers electron to MoFe protein component in a reaction coupled to the hydrolysis of MgATP.
Which one of the following options represents the combination of all correct statements?
- 1A, B and D
- 2B and C only
- 3C, D and E
- 4A, D and E
Show answer and solution
Answer: (4) A, D and E
Nitrogenase has two parts. The Fe protein is dinitrogenase reductase (so C is wrong). It passes electrons to the MoFe protein, dinitrogenase, hydrolysing two MgATP per electron (E). The MoFe protein holds the FeMo cofactor where N2 binds (D). It is an α2β2 heterotetramer, not a homodimer (so B is wrong). A, D and E are correct.
The mobile signal, florigen, that controls the flowering status of the plants is encoded by which one of the following?
- 1Flowering locus C (FLC)
- 2Flowering locus D (FD)
- 3Flowering locus T (FT)
- 4CONSTANS (CO)
Show answer and solution
Answer: (3) Flowering locus T (FT)
FLOWERING LOCUS T encodes the FT protein. It is made in leaf phloem companion cells when CONSTANS builds up under inductive day lengths, and it travels through the phloem to the shoot apex. There it partners FD to switch on floral identity genes. CO and FD are needed for flowering, but they are not the mobile signal. FLC is a repressor.
The flowering repressor gene that is responsible for the vernalization requirement in Arabidopsis is:
- 1CONSTANS (CO)
- 2FLOWERING LOCUS D (FD)
- 3FLOWERING LOCUS T (FT)
- 4FLOWERING LOCUS C (FLC)
Show answer and solution
Answer: (4) FLOWERING LOCUS C (FLC)
FLOWERING LOCUS C is a MADS-box repressor that blocks FT and SOC1. Winter-annual Arabidopsis carries active FRIGIDA, which keeps FLC high, so the plant cannot flower until prolonged cold silences FLC epigenetically (Polycomb, H3K27me3). That silencing is vernalization. CO, FT and FD all promote flowering.
Which of the following phytohormone signaling pathways are evolutionarily related to bacterial two-component regulatory systems?
- 1Cytokinin and ethylene
- 2Brassinosteroid and auxin
- 3Auxin and cytokinin
- 4Brassinosteroid and strigolactone
Show answer and solution
Answer: (1) Cytokinin and ethylene
The cytokinin receptors (AHK2, AHK3, CRE1/AHK4) are histidine kinases that start a His–Asp phosphorelay through AHP proteins to type-B ARR response regulators. That is a bacterial two-component system. The ethylene receptors (ETR1, ERS1 and others) also descend from bacterial histidine kinases. Auxin, brassinosteroid and strigolactone signalling use unrelated receptors.
Given below are the list of plant hormones (Column X) and their biosynthesis precursors (Column Y).
| Column X | Column Y | ||
|---|---|---|---|
| A | Auxins | i. | Geranylgeranyl diphosphate |
| B | Cytokinins | ii. | Adenosine moiety |
| C | Ethylene | iii. | Tryptophan |
| D | Gibberellins | iv. | 1-aminocyclopropane 1-carboxylic acid |
Which one of the following options represents the correct match between column X and Y?
- 1A–i; B–ii; C–iii; D–iv
- 2A–iii; B–i; C–iv; D–ii
- 3A–iii; B–ii; C–iv; D–i
- 4A–iv; B–iii; C–ii; D–i
Show answer and solution
Answer: (3) A–iii; B–ii; C–iv; D–i
Auxin (IAA) is made from tryptophan. Cytokinins are adenine derivatives: isopentenyl transferase puts a prenyl side chain on an adenosine phosphate. Ethylene comes from methionine through ACC, by ACC oxidase. Gibberellins are diterpenoids built from geranylgeranyl diphosphate. That gives A–iii, B–ii, C–iv, D–i.
How many molecules of acetyl-CoA condense to produce isopentenyl diphosphate, the precursor for the formation of terpenoids by mevalonate pathway?
- 1Two
- 2Three
- 3Four
- 4Five
Show answer and solution
Answer: (2) Three
In the mevalonate pathway two acetyl-CoA form acetoacetyl-CoA, and a third adds on to give HMG-CoA. HMG-CoA reductase reduces it to mevalonate, which is phosphorylated twice and decarboxylated to give the C5 unit isopentenyl diphosphate. So three acetyl-CoA go into each IPP.
Which one of the following class of plant secondary metabolites is present specifically in the order Brassicales?
- 1Glucosinolates
- 2Alkaloids
- 3Phenolics
- 4Terpenoids
Show answer and solution
Answer: (1) Glucosinolates
Glucosinolates (mustard-oil glycosides) are sulfur- and nitrogen-containing compounds almost confined to the order Brassicales: cabbage, mustard, Arabidopsis, capers. When tissue is damaged, myrosinase hydrolyses them to isothiocyanates, the “mustard oil bomb”. Alkaloids, phenolics and terpenoids occur across many plant orders.
The following statements are made regarding materials transported through the phloem of a plant.
- A. Only reducing sugars are translocated.
- B. Non-reducing sugars are generally translocated.
- C. Sucrose and raffinose are generally translocated.
- D. Only D-glucose and D-fructose are translocated.
Which one of the following options represents the combination of all correct statements?
- 1A, C and D
- 2B and C only
- 3B and D only
- 4A and C only
Show answer and solution
Answer: (2) B and C only
Phloem carries non-reducing sugars, mainly sucrose and, in some families, raffinose-series oligosaccharides (raffinose, stachyose). Reducing sugars such as glucose and fructose have a free aldehyde or ketone group that would react on the long journey, so they are kept out of the sieve tubes. B and C are correct.
Which one of the following microbes is an obligate biotroph?
- 1Botrytis cinerea
- 2Phytophthora infestans
- 3Puccinia graminis
- 4Trichoderma harzianum
Show answer and solution
Answer: (3) Puccinia graminis
An obligate biotroph can grow only on living host tissue and cannot be cultured on its own. Puccinia graminis, the stem rust fungus, is the classic example. Botrytis cinerea is a necrotroph, Phytophthora infestans is a hemibiotroph, and Trichoderma harzianum is a free-living saprophyte used for biocontrol.
Which of the following ‘R’ gene products do not contain NBS-LRR domain?
- 1RPS2 protein of Arabidopsis
- 2Xa1 protein of rice
- 3N protein of tobacco
- 4Mlo protein of barley
Show answer and solution
Answer: (4) Mlo protein of barley
RPS2 (Arabidopsis), N (tobacco, with a TIR domain) and Xa1 (rice) are all NBS-LRR proteins, the usual class of resistance proteins. Barley Mlo is different: it is a seven-transmembrane, calmodulin-binding membrane protein, and powdery-mildew resistance comes from losing it (recessive mlo alleles). It has no NBS or LRR domain.
All 131 Plant Physiology questions, by subtopic
Each link opens the question on its full paper page. Press Show answer and solution there to see NTA’s final key and a worked solution.
Stress Physiology & Plant–Pathogen Interactions (29 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q56 | B | Which one of the following is NOT a microbe-associated molecular pattern (MAMP) of phytopathogens? |
| Jun 2025, Q80 | C | The table below lists genes (Column X) and their encoded proteins (Column Y) that play an important role in plant response to biotic… |
| Jun 2025, Q140 | C | The following statements are made regarding TAL effectors that play an important role during bacterial pathogenesis in plants. Which one of… |
| Dec 2024 S1, Q39 | B | Which one of the following microbes is an obligate biotroph? |
| Dec 2024 S1, Q95 | C | A researcher obtained a loss-of-function mutant of plasmodesmata protein synaptotagmin (SYTA) in Arabidopsis and infected the plants with… |
| Dec 2024 S2, Q85 | C | The following statements are made regarding root-knot nematode infection in plants. Which one of the following options represents the… |
| Dec 2024 S2, Q119 | C | The following statements are made about the involvement of the type III protein secretion system (T3SS) during bacterial pathogenesis in… |
| Jun 2024 S1, Q145 | C | The names of the plant pathogens and their taxonomic groups are given in the table. Choose the option with all the correct matches: |
| Jun 2024 S2, Q37 | B | Which one of the following statements regarding the invasion of blast fungus, Magnaporthe oryzae in rice is INCORRECT? |
| Jun 2024 S2, Q55 | B | Which one of the following is NOT an example of programmed cell death in plants? |
| Jun 2024 S2, Q81 | C | Salicylic acid (SA) regulates hypersensitive response and effector-triggered immunity at the primary infection site and systemic acquired… |
| Jun 2024 S2, Q125 | C | Plants perceive effector molecules of a pathogen and mount a series of events that lead to the activation of a defense response. Following… |
| Dec 2023 S1, Q105 | C | A researcher had inoculated the bottom leaves of a wild-type tobacco plant with tobacco ringspot virus (TRSV) and made the following… |
| Dec 2023 S2, Q42 | B | Which one of the following statements about the guardee protein, that plays an important role during plant-pathogen interactions is correct? |
| Dec 2023 S2, Q43 | B | Which one of the following statements regarding the production of various reactive oxygen species during oxidative burst is INCORRECT? |
| Dec 2023 S2, Q102 | C | The table below represents plant disease resistance genes, the protein type and race-specific nature: Choose the correct combination of… |
| Dec 2023 S2, Q103 | C | The following statements are made regarding diverse strategies adopted by fungal pathogens: Which one of the following options represents… |
| Dec 2023 S2, Q104 | C | The following statements are made regarding the defense signaling pathways locally activated following pathogen infection or pest attack… |
| Dec 2023 S2, Q106 | C | Following statements are given regarding cell toxicity due to heavy metals in plants: Which one of the following options represents all… |
| Jun 2023 S1, Q42 | B | Which one of the following statements is INCORRECT? |
| Jun 2023 S1, Q94 | C | The recognized family of PR proteins in plants and their activities are listed in columns X and Y, respectively. Which one of the following… |
| Jun 2023 S1, Q101 | C | Given below are the list of abiotic environmental factors (Column X) and their primary effects (Column Y) in plants: Which one of the… |
| Jun 2023 S2, Q36 | B | Which one of the following leads to the induction of defensin PDF1.2 in Arabidopsis? |
| Jun 2023 S2, Q94 | C | Below are some of the proposed roles of reactive oxygen species (ROS) in plant defense. Which one of the following options represents the… |
| Jun 2023 S2, Q104 | C | The following statements refer to the observations made by a student, upon using 2,6-dichloroisonicotinic acid (INA) to induce systemic… |
| Feb 2022 S1, Q42 | B | Which of the following ‘R’ gene products do not contain NBS-LRR domain? |
| Feb 2022 S1, Q102 | C | The phytohormones ethylene (ET), methyl jasmonate (MeJA) and salicylic acid (SA) play important roles in plant defense. The following… |
| Feb 2022 S2, Q102 | C | Plant pathogens produce effector molecules that aid in colonization of their host cells. Column X denotes the name of effector molecules… |
| Feb 2022 S2, Q105 | C | Glycophytes are salt-sensitive plants while halophytes are salt-tolerant plants. The following statements were made to explain the… |
Photosynthesis (27 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q25 | B | Which one of the following carotenoids is NOT involved in the nonphotochemical quenching of chlorophyll fluorescence in plants? |
| Jun 2025, Q33 | B | A student exposed a plant to a herbicide that blocks electron transport both in Photosystem II and Photosystem I. What is the likely outcome? |
| Jun 2025, Q143 | C | A researcher simultaneously disrupted the activities of “Ferrochelatase” and “Chlorophyllide a oxygenase” enzymes involved in the… |
| Dec 2024 S1, Q68 | B | Which one of the following events occurs during the light reaction of photosynthesis and directly contributes to the formation of ATP? |
| Dec 2024 S1, Q140 | C | RuBisCO enzyme catalyzes carboxylation or oxygenation of RuBP in five steps. Following are certain statements regarding the catalysis… |
| Dec 2024 S2, Q69 | B | Which one of the following statements represents correct sequence of events during electron transport chain from P680 to P700 in a light… |
| Dec 2024 S2, Q98 | C | Leaves can alter the intracellular distribution of their chloroplasts in response to changing light conditions. Shown below are schematic… |
| Dec 2024 S2, Q116 | C | Phosphoenolpyruvate carboxylase (PEPCase) is an important enzyme involved in both C4 and CAM photosynthesis. Given below are a few… |
| Jun 2024 S1, Q33 | B | Which one of the following is a correct combination of four carbon intermediates formed during C4 photosynthesis in plants? |
| Jun 2024 S1, Q81 | C | Following are certain statements regarding Crassulacean Acid Metabolism (CAM) plants: Which one of the following options represents the… |
| Jun 2024 S1, Q87 | C | Sucrose-phosphate synthase (SPS) is a key enzyme in the biosynthesis of sucrose in plants. Following are certain statements regarding SPS… |
| Jun 2024 S2, Q50 | B | Which one of the following is the strongest oxidizing agent produced during photosynthesis? |
| Jun 2024 S2, Q131 | C | Following are certain statements regarding NADP-malic enzyme type of C4 photosynthesis: Which one of the following options represents the… |
| Dec 2023 S1, Q101 | C | Given below are certain statements regarding the light absorption by chlorophyll pigment molecule in a green leaf. Which one of the… |
| Jun 2023 S1, Q44 | B | Which one of the following statements regarding PEPCase is INCORRECT? |
| Jun 2023 S1, Q60 | B | Given below are characteristic traits found in sun- or shade-acclimated leaves Select the option that has all correct characteristics for… |
| Jun 2023 S1, Q102 | C | The following are certain statements regarding the PSII electron carrier during the light reaction of photosynthesis: Which one of the… |
| Jun 2023 S1, Q104 | C | Sucrose-phosphate synthase (SPS) and sucrose-phosphate phosphatase (SPP) are two key enzymes involved in the biosynthesis of sucrose… |
| Jun 2023 S1, Q105 | C | Rubisco enzyme is involved in both reductive and oxidative carbon cycles in plants. Following are certain statements regarding them: Which… |
| Jun 2023 S2, Q44 | B | Which one of the following statements related to photosynthesis is NOT correct? |
| Jun 2023 S2, Q103 | C | The figure below depicts the absorption spectra of chlorophylls and carotenoid over a range of wavelengths. Which one of the following… |
| Feb 2022 S1, Q43 | B | Photochemically generated ATP is consumed in which one of the following phases of Calvin-Benson cycle? |
| Feb 2022 S1, Q104 | C | During light reaction in photosynthesis, electron is transported in electron transport chain (ETC) and produces ATP and NADPH in the… |
| Feb 2022 S1, Q123 | C | The following are a few statements on shade leaves vis-à-vis sun leaves in tree species Which one of the following combinations of above… |
| Feb 2022 S2, Q43 | B | Which one of the following are the correct encoding sites of large and small subunits of Rubisco enzyme in red and brown algae? |
| Feb 2022 S2, Q44 | B | Which one of the following correctly states the action of sucrose phosphate synthase enzyme? |
| Feb 2022 S2, Q100 | C | The following statements refer to photosystem structure and function involved in light-dependent reaction of photosynthesis: Which one of… |
Plant Hormones (18 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q145 | C | Following statements are made regarding the biosynthesis of phytohormones. Which one of the following combinations contains all correct statements? |
| Dec 2024 S1, Q105 | C | Shown in the table below are the enzymes (Column X) involved in the biosynthesis of listed phytohormones (Column Y). Which one of the… |
| Dec 2024 S2, Q64 | B | Which of the following phytohormone signaling pathways are evolutionarily related to bacterial two-component regulatory systems? |
| Dec 2024 S2, Q106 | C | Following statements are made with respect to polar auxin transport in plants. Which one of the following options represents the… |
| Jun 2024 S1, Q57 | B | Which one of the following statements correctly explains the function of a GTPase activating protein (GAP) in the regulation of… |
| Jun 2024 S1, Q84 | C | SLN1 receptor, a part of a two-component system, is required for osmoregulation in yeast. The yeast mutant (sln1) lacking the SLN1 receptor… |
| Jun 2024 S1, Q100 | C | ABA plays an important role in plant response to water stress. In the table below, column X represents some of the important enzymes in ABA… |
| Jun 2024 S1, Q122 | C | Following statements were made with respect to plant steroid hormones. Which one of the following options represents the combination of all… |
| Jun 2024 S2, Q140 | C | Given below is the list of F-box proteins of the SCF ubiquitin E3 ligase complex (Column X) and their associated regulatory proteins of… |
| Dec 2023 S1, Q42 | B | Which one of the following is referred to as tuberonic acid? |
| Dec 2023 S1, Q43 | B | The defect in a major semi-dwarfing gene of rice, sd-1, leads to cultivar with short, thick culms and improved lodging resistance. The gene… |
| Dec 2023 S1, Q106 | C | Given below are the list of plant hormones (Column X) and their biosynthesis precursors (Column Y). Which one of the following options… |
| Dec 2023 S2, Q105 | C | Following statements are made regarding the plant hormones, Gibberellins. Which one of the following options represents the combination of… |
| Jun 2023 S2, Q41 | B | Which one of the following statements about phytohormone ABA is correct? |
| Jun 2023 S2, Q102 | C | During water stress, ABA increases dramatically in leaves causing stomatal closure. Given below are the various events involved in this… |
| Jun 2023 S2, Q105 | C | The following statements are made regarding cytokinin (CK) biosynthesis in plants: Which one of the following options represents the… |
| Feb 2022 S1, Q103 | C | A researcher has obtained an Arabidopsis mutant defective in strigolactones (SLs), a novel plant hormone. The following statements were… |
| Feb 2022 S2, Q98 | C | Following are certain statements related to seed maturation: Which one of the following options has all correct statements? |
Secondary Metabolites (14 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q32 | B | The subclasses of terpenes that are generally volatile and often stored in glandular hairs or secretory cavities of leaves and fruits of… |
| Jun 2025, Q131 | C | Shown below is a hypothetical metabolic pathway leading to the production of lignin metabolite, and the three pathway enzymes (X, Y and Z)… |
| Dec 2024 S1, Q125 | C | Following statements are made regarding methyl erythritol phosphate (MEP) and mevalonate pathways for plant terpenoid biosynthesis. Which… |
| Jun 2024 S2, Q22 | B | Which of following is a likely consequence of a loss of function mutation in the gene encoding the enzyme phenylalanine ammonia-lyase (PAL)… |
| Jun 2024 S2, Q46 | B | How many molecules of acetyl-CoA condense to produce isopentenyl diphosphate, the precursor for the formation of terpenoids by mevalonate pathway? |
| Dec 2023 S1, Q44 | B | In the model plant Arabidopsis thaliana, methionine is a precursor amino acid in the biosynthesis of |
| Jun 2023 S1, Q41 | B | Which one of the following plant-derived molecules is widely used as an analgesic? |
| Jun 2023 S1, Q106 | C | Following statements are made regarding the plant natural product, terpenes. Which one of the following options represents the combination… |
| Jun 2023 S2, Q43 | B | Which one of the following class of plant secondary metabolites is present specifically in the order Brassicales? |
| Jun 2023 S2, Q101 | C | Given below are the list of plant derived alkaloids and their uses in modern medicine. Which one of the following options represents all… |
| Feb 2022 S1, Q44 | B | Dirigent proteins predominantly play an important role in biosynthesis of: |
| Feb 2022 S1, Q105 | C | Given below are various plant natural products and their basic structural unit: Which of the following options represents the correct match… |
| Feb 2022 S2, Q41 | B | β-thioglucosidases, also known as myrosinases, are the enzymes that are known to hydrolyse which one of the following plant natural products? |
| Feb 2022 S2, Q103 | C | Plants are known to synthesize more than 30,000 terpenoids, involving four stages of biosynthesis. Following are the list of biosynthetic… |
Sensory Photobiology (11 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q103 | C | Lettuce seed germination is a typical photo-reversible response controlled by phytochrome. Seeds in a petridish were exposed to Red light… |
| Dec 2024 S1, Q69 | B | Which of the following Vitamin B complex derivatives constitute the chromophore of the blue light photoreceptor cryptochrome in plants? |
| Jun 2024 S1, Q46 | B | Which one of the following correctly describes ‘Dark Reversion’ of phytochromes? |
| Jun 2024 S2, Q93 | C | DELLA proteins are known to interact with phytochrome interacting factors (PIFs) and regulate genes involved in etiolation in Arabidopsis… |
| Dec 2023 S1, Q41 | B | Which one of the following statements is INCORRECT regarding plant phytochrome (PHY), cyanobacterial phytochrome1 (Cph1) and bacterial… |
| Dec 2023 S1, Q103 | C | Stomata detached from the epidermis of common dayflower (Commelina communis) were treated with saturating photon fluxes of red light. After… |
| Dec 2023 S2, Q40 | B | The mobile signal, florigen, that controls the flowering status of the plants is encoded by which one of the following? |
| Dec 2023 S2, Q44 | B | A researcher, while studying vernalization in plants, has made the following statements. Choose the INCORRECT one. |
| Jun 2023 S2, Q40 | B | The flowering repressor gene that is responsible for the vernalization requirement in Arabidopsis is: |
| Jun 2023 S2, Q100 | C | Given below are the five experiments (A-E) showing effects of duration of the light and dark periods on flowering of the short-day plants… |
| Feb 2022 S1, Q101 | C | Following are certain statements regarding phytochrome interacting factors (PIFs), a family of proteins that regulates photomorphogenic… |
Solute Transport & Photoassimilate Translocation (11 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q84 | C | Sucrose transport in plant cells follows both active transport and diffusion mechanisms. The given figure shows the rate of sucrose uptake… |
| Dec 2024 S1, Q124 | C | A researcher simultaneously inhibited the activities of Triose-Phosphate Translocator (TPT) and Xylulose 5-Phosphate Translocator (XPT) in… |
| Jun 2024 S1, Q21 | B | A plant is NOT watered for seven days (day 1 – day 7). Leaf and root water potential are measured every two hours starting from day 1 till… |
| Jun 2024 S1, Q30 | B | Which of the following is LEAST suited for long-distance phloem transport of photo-assimilated carbon in plants? |
| Jun 2024 S1, Q47 | B | For maintaining hydraulic conductance, tree stems appear to trade-off vessel diameter with |
| Jun 2024 S1, Q68 | B | Which one of the following represents the predominant ‘source organ’ during phloem translocation in healthy plants? |
| Jun 2024 S2, Q139 | C | The steady state level of a plant metabolite ‘M’ is determined by the complex interplay of its biosynthesis, catabolism and transport… |
| Dec 2023 S1, Q104 | C | Apoplast phloem loading is determined by the cellular location and transport function of the membrane-bound proteins. Following are certain… |
| Dec 2023 S2, Q101 | C | Following are certain statements regarding the plant cell water potential (ψ): Which one of the following options represents all correct statements? |
| Jun 2023 S2, Q42 | B | Which one of the following statements is NOT a characteristic feature of aquaporins? |
| Jun 2023 S2, Q106 | C | The following statements are made regarding materials transported through the phloem of a plant. Which one of the following options… |
Nitrogen Metabolism (8 questions)
| Paper and question | Part | Question |
|---|---|---|
| Dec 2024 S1, Q84 | C | The figure below depicts the feedback regulation in the biosynthesis pathway of three branched-chain amino acids (BCAA) – Leu, Val, and… |
| Dec 2024 S2, Q54 | B | Acetohydroxy acid synthase (AHAS), an enzyme involved in branched-chain amino acid biosynthesis, is inhibited by all the following classes… |
| Dec 2024 S2, Q71 | C | The figure below depicts the allosteric regulation in the biosynthesis of three aromatic amino acids- Phe, Tyr and Trp, acting at four… |
| Jun 2024 S1, Q77 | C | Biosynthesis of glutamine and asparagine is sensitive to light and to the availability of reduced carbon. Following are a few statements… |
| Jun 2024 S2, Q96 | C | The feedback control of the branched amino acid biosynthesis pathway in Arabidopsis is given below. The activity of Acetohydroxyacid… |
| Jun 2023 S1, Q103 | C | The following statements are made regarding the nitrogenase enzyme involved in the reduction of atmospheric nitrogen to ammonia: Which one… |
| Feb 2022 S2, Q42 | B | The high affinity ammonium uptake system in plant’s roots involves transporters in the AMT/Rh family. Which of the following AMT genes is… |
| Feb 2022 S2, Q104 | C | Following statements are made about nitrate transporters in plant cells: Select the option that has the combination of all correct statements. |
Plant Anatomy & Development (7 questions)
| Paper and question | Part | Question |
|---|---|---|
| Dec 2023 S1, Q53 | B | Which one of the following statements is NOT correct about collenchyma? |
| Jun 2023 S1, Q40 | B | Which one of the following root initials gives rise to the root vascular system, including the pericycle? |
| Jun 2023 S1, Q100 | C | Genetic screens for mutants affecting development of leaf trichomes have led to the discovery of genes regulating trichome patterning -… |
| Jun 2023 S2, Q54 | B | Select the group of plants that are known to have an increase in the amount of vascular tissues by means of secondary growth from a vascular cambium. |
| Feb 2022 S1, Q97 | C | Following are certain statements regarding root growth and differentiation in plants: Which one of the following combination of statements is correct? |
| Feb 2022 S1, Q100 | C | Following are certain statements regarding tracheary elements of vascular plants Which one of the following options represents the… |
| Feb 2022 S2, Q38 | B | Which one of the following transcription factors is important for delimiting the meristematic and elongation zones of roots? |
Respiration & Photorespiration (6 questions)
| Paper and question | Part | Question |
|---|---|---|
| Jun 2025, Q76 | C | The operation of the photorespiratory (C2) pathway involves cooperative interaction among three separate subcellular organelles, namely… |
| Dec 2024 S2, Q120 | C | The interconversion of fructose 6-phosphate to fructose 1,6-bisphosphate is a critical step in central metabolism in plants. Followings are… |
| Dec 2023 S1, Q102 | C | Photorespiration or C2 cycle takes place in three distinct organelles in the plant cells. Following are certain statements related to the… |
| Dec 2023 S2, Q41 | B | In which one of the following organelles does glycine decarboxylase complex and serine hydroxymethyltransferase convert two molecules of… |
| Jun 2023 S1, Q43 | B | During glycolysis in plants, alanine and related amino acids are directly produced from which one of the following precursors? |
| Feb 2022 S2, Q101 | C | Following are certain statements regarding photorespiration pathway in plants: Which one of the following combinations is INCORRECT? |
PYQs for every CSIR-NET unit
How to revise Plant Physiology with these questions
- Start with the two biggest subtopicsStress Physiology & Plant–Pathogen Interactions and Photosynthesis are where most of the marks have been. Revise them first.
- Attempt before you readWork through a subtopic’s questions on paper, then check them against the answer keys.
- Find the repeatsThe same ideas keep coming back in new wording. When you get one wrong, look for its earlier version in the list above.
- Finish with a full paperTake a whole paper in live exam mode to practise choosing which Part C questions to attempt.
Keep going
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p class=”lbq-src”>Source: CSIR-NET Life Sciences question papers and final answer keys, National Testing Agency, February 2022 to June 2025. Subtopic tags, difficulty ratings and solutions: Lesson Basket.
