UPSC Mains Answer PYQ 2024: Agriculture Paper 2 (Section- B) | Agriculture Optional for UPSC PDF Download

​​Q1:Answer the following questions in about 150 words each: (10 × 5 = 50 marks)
(a) Explain the properties and functions of enzymes in plants.
Ans: Enzymes are biological catalysts made up of proteins that accelerate chemical reactions in plants without undergoing any permanent changes themselves. They are essential for regulating physiological and biochemical processes necessary for plant growth and development.
Properties of Enzymes in Plants

1. Catalytic Nature: Enzymes accelerate the rate of biochemical reactions without being consumed.
   

2. Specificity: Each enzyme acts on a specific substrate (lock and key model).
   

3. Proteinaceous Nature: Most enzymes are proteins and sensitive to heat and pH changes.
   

4. Optimum Conditions: Enzymes require specific temperature (usually 25–40°C) and pH to function effectively.
   

5. Reversibility: Some enzymatic reactions are reversible depending on cellular needs.
   

6. Coenzymes and Cofactors: Some enzymes require additional molecules (e.g., metal ions or vitamins) to function properly.
   

7. Regulated Activity: Enzyme activity can be activated or inhibited by various internal signals and environmental factors.
   

Functions of Enzymes in Plants

1. Photosynthesis: Enzymes like RuBisCO catalyze carbon fixation during the Calvin cycle.
   

2. Respiration: Enzymes like dehydrogenases are involved in glycolysis and Krebs cycle.
   

3. Growth and Development: Enzymes regulate hormone biosynthesis, cell division, and elongation.
   

4. Defense Mechanisms: Enzymes such as peroxidases and polyphenol oxidases help plants defend against pathogens.
   

5. Nutrient Assimilation: Nitrate reductase assists in nitrogen assimilation.
   

6. Fruit Ripening: Enzymes like pectinase and cellulase help soften fruits.
   

Example: Catalase enzyme decomposes hydrogen peroxide into water and oxygen, protecting cells from oxidative damage.
Conclusion:
Enzymes play a vital role in almost every aspect of plant life, from energy production to defense. Their high specificity and efficiency are fundamental to plant physiology and adaptation.

(b) Write the methods of production of seed tubers from true potato seeds (TPS) under protected cultivation.
Ans: True Potato Seeds (TPS) are botanical seeds produced by potato flowers, unlike traditional tubers. Producing seed tubers from TPS under protected conditions helps reduce disease transmission and maintain high-quality planting material.
Methods of Production under Protected Cultivation

1. Selection of TPS: Use genetically pure, disease-free, and high-germination TPS varieties.
   

2. Raising Seedlings:

   • Sow TPS in nursery trays or seedbeds under polyhouse conditions.

   • Use sterile media like cocopeat, vermiculite, or sand for germination.

3. Transplanting: Healthy seedlings (4–5 weeks old) are transplanted into protected fields or net houses.
   

4. Spacing: Maintain plant spacing of 20–25 cm between plants and 60 cm between rows.
   

5. Crop Management:

   • Proper irrigation, fertilization, and pest management to ensure healthy growth.

   • Mulching with straw or plastic helps retain moisture.

6. Harvesting Seed Tubers: Harvest when foliage turns yellow, indicating tuber maturity (about 90–120 days).
   

7. Post-Harvest Handling:

   • Cure tubers for 10–15 days under shade before storage.

   • Store seed tubers in cool, dry conditions.

Advantages:

• Reduces dependency on bulky seed tubers.
• Minimizes disease transmission.
• Produces healthy, virus-free planting material.

Conclusion:
TPS technology under protected cultivation ensures the production of high-quality seed tubers. It is a cost-effective and sustainable alternative to conventional potato seed tuber propagation.

(c) Discuss the systematic position, nature of damage and management of insect and mite pests of brinjal.
Ans: Brinjal (Solanum melongena) is susceptible to various insect and mite pests, causing significant yield losses. Effective pest management requires understanding their classification, damage pattern, and control strategies.
Systematic Position

• Kingdom: Animalia
• Phylum: Arthropoda
• Class: Insecta / Arachnida (mites)
• Order: Lepidoptera, Hemiptera, Acarina
• Families: Noctuidae, Aphididae, Tetranychidae

Major Pests and Nature of Damage

1. Brinjal Shoot and Fruit Borer (Leucinodes orbonalis):

   • Larvae bore into shoots and fruits.

   • Causes wilting and rotting of fruits.

2. Aphids (Aphis gossypii):

   • Suck sap from tender shoots and leaves.

   • Cause leaf curling and stunted growth.

3. Red Spider Mites (Tetranychus urticae):

   • Feed on leaf sap, leading to yellowing and leaf drop.

   • Fine webbing on the underside of leaves.

4. Whiteflies (Bemisia tabaci): Sap feeders and vectors of viral diseases.
   

Management Strategies

1. Cultural Control: Crop rotation, removal of infested plants, and timely sowing.
   

2. Mechanical Control: Hand-picking of infested shoots and fruits.
   

3. Biological Control: Release of predators like ladybird beetles and parasitoids like Trichogramma.
   

4. Chemical Control:

   • Spraying with neem-based insecticides.

   • Use of recommended insecticides like spinosad or imidacloprid.

5. Resistance Varieties: Cultivation of borer-resistant brinjal varieties.
   

Conclusion:
Integrated Pest Management (IPM) combining cultural, mechanical, biological, and chemical methods ensures effective and sustainable
control of brinjal pests, safeguarding crop yield and quality.

(d) What is the scenario of hunger and malnutrition in the country? Discuss the initiatives taken by the government for their mitigation.
Ans: Despite economic progress, India continues to face severe hunger and malnutrition challenges, particularly among children and women. Addressing these issues is essential for national development.
Scenario of Hunger and Malnutrition

1. Global Hunger Index (2023):

   • India ranked 111th among 125 countries.

   • Classified under “serious” hunger level.

2. Malnutrition Statistics:

   • High rates of child stunting (35%) and wasting (19%).

   • High levels of anemia among women (57%) and children (67%).

3. Causes:Poverty, inadequate dietary intake, poor healthcare, and sanitation issues.
   

Government Initiatives

1. POSHAN Abhiyaan: National Nutrition Mission launched to reduce stunting, undernutrition, and anemia.
   

2. Mid-Day Meal Scheme: Provides free lunches to school children to improve nutrition.
   

3. Integrated Child Development Services (ICDS): Focuses on nutrition, health, and education services for children under six and pregnant women.
   

4. Pradhan Mantri Matru Vandana Yojana (PMMVY): Provides financial incentives to pregnant and lactating mothers for better nutrition.
   

5. Anemia Mukt Bharat: Focused program to combat anemia across age groups.
   

6. Food Security Act (2013): Legal right to subsidized food grains to two-thirds of India’s population.

Conclusion:
While India has made progress, the fight against hunger and malnutrition requires stronger implementation of schemes, intersectoral coordination, and community participation to ensure a healthier future.

(e) Illustrate how technology is improving the efficiency of public distribution system in the country.
Ans: The Public Distribution System (PDS) plays a crucial role in ensuring food security for millions of Indians. Technological advancements have made PDS more transparent, efficient, and accessible.
How Technology is Improving PDS

1. Digitization of Beneficiary Data:

   • Ration cards are digitized, creating a real-time database.

   • Elimination of fake and duplicate beneficiaries.

2. Aadhaar Seeding: Linking ration cards with Aadhaar ensures targeted delivery.
   

3. Electronic Point of Sale (e-PoS) Machines: Biometric authentication ensures genuine beneficiaries receive food grains.
   

4. Online Portals and Dashboards: Real-time monitoring of stock availability and distribution at Fair Price Shops (FPS).
   

5. Supply Chain Management: GPS tracking of food grain movement ensures transparency.
   

6. One Nation, One Ration Card (ONORC) Scheme: Enables beneficiaries to access their entitlements anywhere in the country.
   

Example: States like Andhra Pradesh and Chhattisgarh have successfully implemented end-to-end computerization of PDS operations.
Conclusion: 
Technology has significantly improved the efficiency, transparency, and accountability of the PDS, ensuring better service delivery and minimizing leakages. Continued technological innovation can further strengthen India's food security system.

Q2:
(a) Describe the process of anaerobic respiration and explain the factors affecting respiration. (20 marks)
Ans: Respiration is the process by which living cells break down glucose molecules to release energy. When this breakdown occurs in the absence of oxygen, it is known as anaerobic respiration. Anaerobic respiration is important for certain plants, microorganisms, and also occurs under stressed conditions in higher plants.
Process of Anaerobic Respiration

1. Glycolysis: The first step is glycolysis, where glucose (C₆H₁₂O₆) is broken down into pyruvate in the cytoplasm, producing a small amount of ATP.
   

2. Formation of End Products: In the absence of oxygen, pyruvate is further converted into:
   

3. Ethanol and Carbon Dioxide: In yeast and some plant cells.

4. Lactic Acid: In some plants and animal muscles under oxygen-deficient conditions.

5. Overall Reaction (in Yeast): Glucose → Ethanol + CO₂ + Energy (ATP)
   

6. Energy Yield: Anaerobic respiration yields only 2 ATP molecules per glucose molecule compared to 36–38 ATP in aerobic respiration.

Factors Affecting Respiration

1. Temperature: Respiration rate increases with temperature up to an optimum point, beyond which enzyme denaturation reduces the rate.
   

2. Oxygen Availability: Although anaerobic respiration occurs without oxygen, limited oxygen availability can still affect glycolytic activity.
   

3. Sugar Concentration: Higher glucose availability increases the respiration rate, providing more substrate for energy production.
   

4. Water Content: Water is essential for enzyme activity; dehydration slows down respiration.
   

5. Plant Type and Tissue: Respiration rates vary among different species and tissues. Actively growing tissues like root tips respire more.
   

6. Presence of Inhibitors: Chemicals like cyanide and azide inhibit respiratory enzymes and block energy production.

Example:In waterlogged conditions, paddy plants resort to anaerobic respiration for survival.
Conclusion:
Anaerobic respiration allows plants and microorganisms to survive in oxygen-deprived environments, although it is less efficient than aerobic respiration. Various environmental and internal factors regulate the rate of respiration, impacting plant growth and productivity.

(b) Discuss banana crop in respect of its varieties, nutrient management, plant protection and post-harvest handling. (20 marks)
Ans: Banana (Musa spp.) is a major fruit crop grown in tropical and subtropical regions. It plays an important role in food security, nutrition, and income generation for farmers.
Varieties of Banana

1. Dwarf Cavendish: Popular table variety with short stature.

2. Robusta: High-yielding variety for commercial production.

3. Rasthali: Known for its excellent flavor.

4. Nendran: Used for chips and processing in Kerala.

5. Grand Naine: Widely cultivated export-quality variety.

Nutrient Management

1. Macronutrients:

   • High nitrogen, phosphorus, and potassium requirements.

   • Typical recommendation: 150–200g N, 100–150g P₂O₅, 200–300g K₂O per plant per year.

2. Micronutrients: Zinc, boron, and magnesium sprays help in improving fruit quality.
   

3. Organic Manures: Application of FYM (Farmyard Manure) 20–25 kg per plant enhances soil fertility.
   

4. Fertigation: In drip irrigation systems, soluble fertilizers are applied efficiently through fertigation.

Plant Protection

1. Diseases:

   • Panama Wilt (Fusarium wilt): Managed by using resistant varieties and soil treatment.

   • Sigatoka Leaf Spot: Controlled by fungicide sprays and good field sanitation.

2. Pests: Banana Weevil and Nematodes: Managed by pseudostem trapping and application of nematicides.
   

3. Integrated Pest Management (IPM): Combining chemical, biological, and cultural practices ensures effective control.
   

Post-Harvest Handling

1. Harvesting: Harvest at the mature green stage.
   

2. Post-Harvest Practices: Washing with clean water, grading based on size and ripeness, and careful packaging to avoid bruising.
   

3. Ripening: Controlled ripening using ethylene chambers ensures uniform ripening.
   

4. Storage: Ideal temperature: 13–15°C to prolong shelf life.

Conclusion:
Banana cultivation demands proper nutrient management, pest and disease control, and scientific post-harvest practices to achieve high productivity, better quality, and increased profits for farmers.

(c) Discuss the factors which contribute to food insecurity in the country despite of significant improvement in food production and distribution. (10 marks)
Ans: Even though India has achieved remarkable growth in food production, food insecurity remains a persistent problem. Several socio-economic, infrastructural, and administrative factors contribute to this paradox.
Factors Contributing to Food Insecurity

1. Poverty and Inequality: Poor purchasing power restricts access to nutritious food, despite availability.
   

2. Regional Disparities: Food production is concentrated in certain states, causing shortages in others.
   

3. Post-Harvest Losses: Poor storage and transportation facilities lead to significant food wastage.
   

4. Unemployment and Underemployment: Lack of stable income sources makes regular food purchase difficult for many families.
   

5. Inflation and Price Volatility: Rising food prices make essential commodities unaffordable for vulnerable populations.
   

6. Malnutrition and Lack of Dietary Diversity: Dependence on cereals with insufficient intake of fruits, vegetables, and proteins.
   

7. Natural Disasters and Climate Change: Droughts, floods, and erratic weather patterns affect agricultural productivity.
   

8. Inefficient Public Distribution System (PDS): Leakages, corruption, and targeting errors weaken food security initiatives.
   

Example: During COVID-19 pandemic lockdowns, many migrant workers faced acute food shortages despite food grain stocks being sufficient.

Conclusion:
Food insecurity is not just about production but also about access, affordability, and proper distribution. Strengthening livelihoods, minimizing wastage, and improving the efficiency of welfare schemes are essential to achieve true food security in India.

Q3:
(a) Define water stress. Discuss the effects of water stress on anatomical and physiological changes in plant growth. Also discuss soil and weather based plant water stress indicators. (20 marks)
Ans: Water stress refers to a condition where the water available to plants is insufficient to meet their physiological needs. It can occur due to drought, high temperature, low soil moisture, or high evapotranspiration demand, leading to adverse effects on plant growth and productivity.
Effects of Water Stress
Anatomical Changes:

1. Reduced Leaf Area: Leaves become smaller to minimize water loss.
   

2. Thicker Cuticle: Cuticle becomes thicker to reduce transpiration.
   

3. Increased Root Growth: Roots grow deeper and spread wider to access more water.
   

4. Reduced Stomatal Number and Size: Some plants produce fewer and smaller stomata under water stress.
   

5. Formation of Sclerenchyma Tissues: Strengthens the plant structure and reduces water loss.
   

Physiological Changes:

1. Stomatal Closure: Stomata close to reduce water loss, but this limits CO₂ intake, affecting photosynthesis.
   

2. Reduced Photosynthesis: Decrease in chlorophyll content and enzyme activity affects carbon fixation.
   

3. Decreased Cell Expansion: Leads to reduced plant growth and wilting.
   

4. Osmotic Adjustment: Accumulation of solutes like proline, glycine betaine to maintain cell turgor.
   

5. Hormonal Changes: Increase in abscisic acid (ABA) levels that induce stomatal closure.
   

Soil and Weather-Based Plant Water Stress Indicators
Soil-Based Indicators:

1. Soil Moisture Content: Measured by tensiometers or soil moisture sensors.
   

2. Soil Cracking: Visible cracks in clay soils indicate severe water stress.
   

3. Color and Hardness: Dry soil appears lighter and becomes hard.
   

Weather-Based Indicators:

1. High Temperature and Low Humidity: Increases evapotranspiration, leading to water stress.
   

2. Prolonged Dry Periods: Lack of rainfall over extended periods.
   

3. High Wind Speeds: Accelerate water loss from plants and soil.
   

Conclusion:
Water stress significantly impacts the anatomical and physiological traits of plants, affecting their survival and productivity. Early detection using soil and weather indicators can help farmers take timely interventions to minimize yield loss.

(b) Discuss the causal organism, symptoms and management of tungro disease in rice. (20 marks)
Ans: Tungro disease is a major viral disease in rice, particularly affecting crops in South and Southeast Asia. It severely reduces rice yields if not properly managed.
Causal Organism

• Rice Tungro Bacilliform Virus (RTBV) and Rice Tungro Spherical Virus (RTSV)
• Both viruses are transmitted by green leafhopper (Nephotettix virescens).

Symptoms of Tungro Disease

1. Stunted Growth: Plants appear shorter and bushier.
   

2. Leaf Discoloration: Yellow to orange-yellow discoloration starting from leaf tips.
   

3. Reduced Tillering: Fewer tillers and delayed flowering.
   

4. Partial Sterility: Poor grain filling and low yield.
   

5. Twisted and Crinkled Leaves: Infected leaves may become brittle and twisted.
   

6. Root System: Roots appear underdeveloped and fewer in number.
   

Management of Tungro Disease

1. Cultural Practices:

   • Avoid early planting when leafhopper populations are high.

   • Maintain field sanitation by removing weed hosts.

2. Resistant Varieties: Plant tungro-resistant rice varieties like IR64 and IR36.
   

3. Vector Control: Spray insecticides like imidacloprid and thiamethoxam to control green leafhoppers.
   

4. Seed Treatment: Treat seeds with insecticides to protect seedlings.
   

5. Synchronize Planting: Community-based synchronized planting reduces virus spread.
   

6. Use of Trap Crops: Early maturing varieties act as a trap to reduce leafhopper population.

Conclusion:
Effective management of tungro disease requires an integrated approach focusing on vector control, use of resistant varieties, and adopting cultural practices. Timely interventions can prevent large-scale yield losses.

(c) What are the reasons behind food inflation? Discuss how it can be mitigated. (10 marks)
Ans: Food inflation refers to the persistent rise in food prices, affecting affordability and nutrition, especially among lower-income groups. Although India has achieved self-sufficiency in food production, food inflation remains a recurring problem.
Reasons Behind Food Inflation

1. Supply Chain Disruptions: Inefficient logistics, storage issues, and hoarding lead to price rises.
   

2. Climatic Factors: Droughts, floods, and unseasonal rains impact agricultural output.
   

3. High Input Costs: Increases in fertilizer, diesel, and transportation costs push up food prices.
   

4. Government Policies: Export bans, minimum support price (MSP) hikes, and procurement inefficiencies.
   

5. Demand-Supply Mismatch: Rising income levels increase demand for high-value foods (fruits, vegetables, dairy).
   

6. Global Factors: International commodity price volatility affects domestic food prices.
   

Mitigation Measures

1. Strengthening Supply Chains: Improve storage facilities and transportation networks.
   

2. Promoting Climate-Resilient Agriculture: Develop drought- and flood-tolerant crop varieties.
   

3. Market Reforms: Implement e-NAM (electronic National Agriculture Market) for better price discovery.
   

4. Buffer Stock Management: Maintain adequate reserves of essential commodities to stabilize prices.
   

5. Reducing Post-Harvest Losses: Investing in cold storage and processing industries.
   

6. Controlling Hoarding: Strict enforcement of the Essential Commodities Act.

Conclusion:
Managing food inflation requires a holistic strategy combining agricultural reforms, better market linkages, improved storage, and timely policy interventions. Ensuring affordable food for all is crucial for national stability and welfare.

Q4:
(a) Explain the mode of action of organophosphate and Bacillus thuringiensis which are used in pest management. (20 marks)
Ans: Pest management relies on different chemical and biological agents to protect crops. Organophosphates (chemical pesticides) and Bacillus thuringiensis (biopesticide) are widely used because of their effectiveness against various pests while having different modes of action.
Mode of Action of Organophosphates

1. Acetylcholinesterase Inhibition:  Organophosphates inhibit the enzyme acetylcholinesterase (AChE), which breaks down acetylcholine (ACh) in nerve synapses.
   

2. Accumulation of Acetylcholine: Excess ACh leads to continuous nerve signal transmission causing paralysis and death of the insect.
   

3. Examples of Organophosphates: Chlorpyrifos, Malathion, Dimethoate.
   

4. Target Pests: Effective against sucking pests (aphids, whiteflies), chewing insects (caterpillars), and soil insects.
   

5. Characteristics: Quick knock-down effect but relatively short environmental persistence compared to older chemicals like organochlorines.
   

Mode of Action of Bacillus thuringiensis (Bt)

1. Toxin Production: Bacillus thuringiensis produces crystalline (Cry) proteins during sporulation.

2. Ingestion by Insects: Target larvae (mostly Lepidoptera) ingest Bt spores and crystals.
   

3. Activation in Gut: In the alkaline midgut environment of insects, Cry proteins are activated and bind to gut wall receptors.

4. Pore Formation: Cry toxins create pores in the gut membrane, causing cell lysis, gut paralysis, and death.
   

5. Examples of Bt Strains: Bt kurstaki (effective against caterpillars), Bt israelensis (effective against mosquito larvae).

6. Target Pests:Caterpillars (e.g., cotton bollworm, corn borer), mosquito larvae.
   

Conclusion:
Organophosphates and Bacillus thuringiensis play vital roles in integrated pest management. While organophosphates act chemically by disrupting nerve functions, Bt acts biologically by damaging insect gut cells. Their combined use ensures effective and sustainable pest control.

(b) What is phytochrome? Discuss its two forms and differentiate them. (20 marks)
Ans: Phytochrome is a photoreceptor pigment found in plants that regulates various developmental processes in response to light, especially red and far-red wavelengths. It plays a key role in seed germination, flowering, stem elongation, and shade avoidance.
What is Phytochrome?

• It is a blue-green protein pigment that detects red (660 nm) and far-red (730 nm) light.

• Acts as a molecular switch that controls light-dependent physiological processes.

Two Forms of Phytochrome

1. Pr (Phytochrome red):

   • Absorbs red light (~660 nm).

   • Biologically inactive form.

   • Converts to Pfr upon exposure to red light.

2. Pfr (Phytochrome far-red):

   • Absorbs far-red light (~730 nm).

   • Biologically active form.

   • Triggers developmental responses like seed germination and flowering.

Interconversion Between Forms

• Exposure to red light converts Pr → Pfr (activation).
• Exposure to far-red light converts Pfr → Pr (deactivation).
• This photoreversibility allows plants to respond dynamically to changing light environments.

Differences Between Pr and Pfr Forms
Example: In lettuce seeds, red light exposure (Pr → Pfr) promotes germination, while far-red light reverses it.

Conclusion:
Phytochrome, through its two interconvertible forms, acts as a master regulator of light-mediated plant development. Understanding its role helps in manipulating crop growth for better yield and adaptability.

(c) Discuss the reasons for gap between production and consumption of cereals in the country. How can it be rectified? (10 marks)
Ans: Despite considerable cereal production in India, gaps persist between production and actual consumption. This mismatch affects food security, rural livelihoods, and nutritional outcomes.
Reasons for Gap Between Production and Consumption

1. Post-Harvest Losses: Poor storage, handling, and transportation cause significant cereal losses.

2. Crop Diversification: Farmers are shifting from cereals to cash crops like vegetables, fruits, and cotton for better profits.
   

3. Regional Imbalances: High production in certain states (Punjab, Haryana) but low production in others (eastern and northeastern states).

4. Climate Change: Erratic rainfall, droughts, and floods adversely affect cereal yields.
   

5. Changing Consumption Patterns: Urban consumers prefer processed foods and protein-rich diets over traditional cereals.

6. Policy Focus: Greater emphasis on rice and wheat under MSP, leading to neglect of coarse cereals (millets).
   

7. Low Profitability:High input costs and low returns discourage farmers from growing cereals.

Rectification Measures

1. Improved Post-Harvest Management: Strengthen cold chains, warehouses, and transport infrastructure.

2. Promotion of Climate-Resilient Crops: Encourage cultivation of millets and drought-tolerant cereals.
   

3. Balanced Policy Support:Expand MSP and procurement operations to include coarse cereals.

4. Awareness Campaigns: Promote the nutritional value of traditional cereals to boost consumption.
   

5. Support for Small Farmers: Provide input subsidies, crop insurance, and assured markets.

6. Research and Development: Develop high-yield, stress-tolerant cereal varieties.
   

Conclusion:
Bridging the production-consumption gap in cereals requires a multi-pronged approach involving better policies, infrastructure improvement, and promoting dietary shifts towards nutritious cereals. Strengthening rural production systems will ensure food and nutritional security for the country.