Q8
(a) What factors affect in vitro stages of micropropagation? Discuss the applications and limitations of micropropagation. (20 marks) (b) Give an account of male gametophyte development in Gnetum. State the angiosperm characters shared by Gnetum. (15 marks) (c) Discuss the factors affecting the yield and viability of protoplasts isolated from leaves. How are isolated protoplasts purified? (15 marks)
हिंदी में प्रश्न पढ़ें
(a) कौन-से कारक पारे सूक्ष्मप्रवर्धन के चरणों को प्रभावित करते हैं? सूक्ष्मप्रवर्धन के अनुप्रयोगों और सीमाओं पर चर्चा कीजिए। (20 अंक) (b) नीटम के नर युग्मकोद्भिद के विकास का एक विवरण दीजिए। नीटम के द्वारा साझा किए गए आवृतबीजी गुणों का उल्लेख कीजिए। (15 अंक) (c) पत्तियों से विलगित प्रोटोप्लास्ट के उत्पाद और जीवनक्षमता को प्रभावित करने वाले कारकों पर चर्चा कीजिए। विलगित प्रोटोप्लास्टों को कैसे शोधित करते हैं? (15 अंक)
Directive word: Discuss
This question asks you to discuss. 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 'discuss' demands a comprehensive, analytical treatment with balanced coverage of all three sub-parts. Allocate approximately 40% of content to part (a) given its 20 marks, and roughly 30% each to parts (b) and (c). Structure with brief introductions for each sub-part, systematic development of factors/processes/applications, and conclude with forward-looking remarks on biotechnological significance. Use diagrams strategically for Gnetum male gametophyte stages and protoplast isolation workflow.
Key points expected
- Part (a): Factors affecting in vitro stages—explant selection, media composition (MS medium, growth regulators), culture conditions (light, temperature, photoperiod), and stage-specific requirements (initiation, multiplication, rooting, hardening); applications in clonal propagation, virus elimination, germplasm conservation; limitations including somaclonal variation, high cost, and species recalcitrance
- Part (b): Gnetum male gametophyte development—microsporangiate strobilus structure, microspore formation, prothallial cell formation, tube cell and generative cell differentiation, spermatogenous cell production, multiflagellate sperm development; angiosperm-like features including vessel elements in wood, absence of archegonia, pollen tube growth, and double fertilization tendencies
- Part (c): Factors affecting protoplast yield and viability—leaf age and physiological state, osmoticum type and concentration, enzyme composition (cellulase, macerozyme, pectinase), incubation conditions, and genotype effects; purification methods—filtering, centrifugation, floatation on sucrose or Percoll gradients, and viability assessment via FDA or Evans blue staining
Evaluation rubric
| Dimension | Weight | Max marks | Excellent | Average | Poor |
|---|---|---|---|---|---|
| Concept correctness | 22% | 11 | Demonstrates precise understanding of tissue culture stages (dedifferentiation, redifferentiation), accurately describes Gnetum's unique progymnosperm-angiosperm intermediate status with correct terminology (prothallial cells, spermatogenous cells), and correctly explains protoplast isolation mechanics including plasmolysis and enzymatic cell wall digestion | Covers basic concepts with minor errors in terminology or stage sequences; may confuse Gnetum features with other gymnosperms or oversimplify protoplast factors | Fundamental misconceptions about in vitro stages, incorrect description of Gnetum gametophyte development, or confusion between protoplast and cell suspension culture |
| Diagram / labelling | 18% | 9 | Includes well-drawn, properly labelled diagrams: micropropagation stages flowchart, detailed Gnetum male gametophyte development stages (microspore to sperm), and protoplast isolation-purification workflow; labels use standard botanical terminology | Provides at least one relevant diagram with partial labelling; diagrams may lack clarity or miss critical stages | No diagrams or poorly executed sketches without labels; diagrams that misrepresent structural relationships |
| Examples & nomenclature | 18% | 9 | Cites specific examples: Indian micropropagation success stories (banana varieties from NRCB, cardamom from IISR, sandalwood from IFGTB); names Gnetum species (G. gnemon, G. ula); references specific enzymes (Onozuka cellulase, Macerozyme R-10) and media formulations; mentions Indian research institutions and their contributions | Provides generic examples without specificity; mentions common crop species but lacks Indian context or precise nomenclature | No concrete examples; incorrect scientific names; confusion between common names and botanical nomenclature |
| Process explanation | 22% | 11 | Explains sequential processes with mechanistic clarity: stage-specific hormonal shifts in micropropagation (auxin-cytokinin ratios), stepwise male gametophyte ontogeny in Gnetum with cellular transformations, and systematic protoplast isolation protocol with critical control points; explains 'why' behind each step | Describes processes in linear fashion without explaining underlying mechanisms or interconnections between steps | Disorganized process description; missing critical steps; inability to explain causal relationships in protocols |
| Application / ecology | 20% | 10 | Critically evaluates applications: micropropagation for conservation of endemic/endangered Indian species (Nepenthes khasiana, Paphiopedilum spp.), commercial floriculture and forestry; discusses Gnetum's evolutionary significance as living fossil bridging gymnosperms-angiosperms; protoplast applications in somatic hybridization for crop improvement (asymmetric hybrids, cybrids) and limitations honestly assessed | Lists applications without critical evaluation; superficial treatment of evolutionary or biotechnological significance | No discussion of practical applications or ecological/evolutionary relevance; purely descriptive without synthesis |
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