Q6
(a) What are enzymes ? Describe "Key-lock theory" with respect to mode of enzyme action. 15 (b) What is plant physiological stress ? Describe morphological and physiochemical changes taking place in plants under drought condition. 15 (c) What do you understand by vernalization ? Describe its practical application in crops. 20
हिंदी में प्रश्न पढ़ें
(a) किण्वक क्या हैं ? किण्वक क्रियाविधि के संदर्भ में "की-लॉक थ्योरी" का वर्णन कीजिए । 15 (b) पादप दैहिकीय प्रतिबल (तनाव) क्या है ? सूखा होने की दशा में पौधों में होने वाले आकारिकीय तथा दैहिक-रासायनिक परिवर्तनों का वर्णन कीजिए । 15 (c) वसंतीकरण से आप क्या समझते हैं ? फसलों में इसके प्रयोगात्मक उपयोग का वर्णन कीजिए । 20
Directive word: Describe
This question asks you to describe. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.
See our UPSC directive words guide for a full breakdown of how to respond to each command word.
How this answer will be evaluated
Approach
The directive 'describe' demands detailed, structured exposition of processes and phenomena. Allocate approximately 25-30% time/words to part (a) on enzymes and Key-lock theory, 30-35% to part (b) on drought stress responses, and 35-40% to part (c) on vernalization given its higher marks. Structure as: brief introduction defining enzymes → detailed description of Key-lock theory with diagram → definition of plant physiological stress → morphological and physiochemical changes under drought with examples → definition of vernalization → mechanism → practical applications in Indian agriculture with crop-specific examples.
Key points expected
- Part (a): Definition of enzymes as proteinaceous biocatalysts; explanation of Key-lock theory (Fischer's template model) with specific reference to enzyme-substrate specificity; limitations and comparison with induced fit model
- Part (b): Clear definition of plant physiological stress as any external factor causing deviation from optimal metabolic functioning; morphological changes under drought (wilting, leaf rolling, reduced leaf area, increased root-shoot ratio, stomatal closure)
- Part (b): Physiochemical changes under drought (accumulation of proline and other compatible solutes, ABA synthesis, osmotic adjustment, ROS scavenging, photosynthetic rate decline, membrane lipid peroxidation)
- Part (c): Definition of vernalization as low temperature-induced transition from vegetative to reproductive phase; distinction between facultative and obligate vernalization requirements
- Part (c): Mechanism involving VIN3, FLC and FT gene expression; practical applications in Indian agriculture (winter wheat cultivation in Punjab/Haryana, temperate vegetable seed production in Nilgiris/Kashmir, double cropping systems, breeding for earliness)
- Integration: Linkage between stress physiology and vernalization as temperature-dependent phenomena; mention of climate change implications for vernalization-requiring crops in India
Evaluation rubric
| Dimension | Weight | Max marks | Excellent | Average | Poor |
|---|---|---|---|---|---|
| Concept correctness | 25% | 12.5 | Precise biochemical definitions: enzymes as globular proteins with active sites; accurate Key-lock theory explanation with substrate specificity; correct distinction between physiological stress categories; accurate drought response mechanisms (ABA biosynthesis, osmotic adjustment equations); precise vernalization definition distinguishing it from stratification; correct gene regulatory pathway (VIN3-FLC-FT) | Basic definitions correct but conflates Key-lock with induced fit; lists stress symptoms without mechanistic explanation; describes vernalization as mere 'cold treatment' without genetic basis; minor errors in biochemical pathways | Fundamental errors: describes enzymes as carbohydrates; confuses vernalization with photoperiodism; lists drought effects without physiological basis; incorrect gene names or pathways; conflates morphological with physiochemical changes |
| Quantitative reasoning | 15% | 7.5 | Includes quantitative parameters: enzyme kinetics (Km, Vmax concepts), optimal temperature ranges for vernalization (0-10°C for 30-60 days), critical thresholds for drought stress (soil moisture tension, relative water content percentages), proline accumulation values, yield reduction percentages under drought in Indian crops | Mentions temperature ranges or duration qualitatively without specific values; vague references to 'high' or 'low' stress levels without quantitative benchmarks; no kinetic parameters | No quantitative data; incorrect temperature ranges (e.g., vernalization at 20°C); confuses units or orders of magnitude; invents implausible numerical values |
| Indian context examples | 20% | 10 | Specific Indian applications: HD-2967 wheat variety vernalization in NWPZ; drought-resistant varieties (C306 wheat, ICCV-10 chickpea); seed production of temperate vegetables in Ooty/Munnar; impact of warming winters on rabi wheat in Indo-Gangetic plains; traditional cold storage methods for potato seed tuber vernalization | Generic references to 'Indian agriculture' or 'temperate regions' without specific crops or varieties; mentions wheat/rapeseed without varietal or regional specificity; standard drought examples without Indian data | No Indian examples; uses exclusively foreign crop varieties or regions; inappropriate examples (tropical crops for vernalization); factual errors about Indian agro-climatic zones |
| Diagram / process | 25% | 12.5 | Three quality diagrams: (a) Key-lock model with enzyme, substrate, active site, ES complex clearly labeled; (b) drought stress response pathway showing soil-plant-atmosphere continuum, ABA signaling, osmotic adjustment; (c) vernalization pathway with temperature perception → VIN3 induction → FLC repression → FT activation → flowering; all with proper arrows, labels, and integration with text | One or two diagrams present but incomplete labeling; hand-drawn quality acceptable but missing key components; text descriptions substitute for visual representation; diagrams not adequately referenced in explanation | No diagrams despite clear requirement; diagrams copied without understanding (e.g., photosynthesis diagram for enzyme action); illegible or irrelevant sketches; diagrams contradict textual description |
| Policy / extension angle | 15% | 7.5 | Extension relevance: ICAR recommendations for drought mitigation (mulching, antitranspirants); NMSA (National Mission on Sustainable Agriculture) for stress-tolerant varieties; seed village concept for vernalized seed production; climate-resilient agriculture under NAPCC; farmer advisories on vernalization timing under changing climate; precision agriculture applications for stress monitoring | Generic mention of 'government schemes' without specificity; standard extension recommendations without institutional backing; vague climate change references without policy linkage | No policy or extension perspective; irrelevant policy discussion; outdated or non-existent scheme names; purely academic treatment with no practical application context |
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