Botany 2025 Paper I 50 marks Explain

Q8

(a) What is micropropagation and how does it differ from traditional plant propagation methods ? Give an account of the applications of micropropagation in crop improvement and conservation of endangered plants. Add a brief note on the challenges of this technique. 5+10+5=20 (b) Distinguish between polyembryony and parthenocarpy. Classify parthenocarpy and add a note on its significance. 5+5+5=15 (c) Give an outline on the process of producing cybrids. How do cybrids differ from hybrids in terms of their genetic composition ? Comment on the potential applications of cybrid technology. 5+5+5=15

हिंदी में प्रश्न पढ़ें

(a) सूक्ष्मप्रवर्धन क्या है तथा यह पारंपरिक पादप प्रवर्धन विधियों से कैसे भिन्न है ? सूक्ष्मप्रवर्धन के फसल सुधार और लुप्तप्राय पौधों के संरक्षण में उपयोगों पर विवरण दीजिए। इस तकनीक की चुनौतियों पर एक संक्षिप्त टिप्पणी लिखिए। 5+10+5=20 (b) बहुभ्रूणता एवं अनिषेकफलन में अंतर स्पष्ट कीजिए। अनिषेकफलन का वर्गीकरण कीजिए और इसके महत्व पर टिप्पणी दीजिए। 5+5+5=15 (c) साइब्रिड्स के उत्पादन की प्रक्रिया की एक रूपरेखा दीजिए। साइब्रिड वर्ण-संकर से आनुवंशिक संरचना के रूप में कैसे भिन्न हैं ? साइब्रिड तकनीक के संभावित अनुप्रयोगों पर टिप्पणी कीजिए। 5+5+5=15

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Directive word: Explain

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How this answer will be evaluated

Approach

Explain requires systematic exposition with cause-effect relationships. Structure: (a) Define micropropagation, contrast with traditional methods (seed/vegetative), detail applications in crop improvement (virus-free stocks, rapid multiplication) and conservation (endangered species like Red Sanders), note challenges (somaclonal variation, cost); (b) Distinguish polyembryony (multiple embryos, genetic) from parthenocarpy (seedless fruit, hormonal), classify parthenocarpy (genetic, environmental, artificial), note significance; (c) Outline cybrid production (protoplast fusion with selective elimination), contrast cybrid (nuclear genome of one parent + cytoplasmic genome of both) vs hybrid (complete nuclear fusion), cite applications (cytoplasmic male sterility, Brassica). Allocate ~40% time to (a), ~30% each to (b) and (c).

Key points expected

  • (a) Micropropagation definition: in vitro clonal propagation via tissue culture; contrast with traditional methods (sexual reproduction, grafting, cutting) emphasizing speed, disease-free status, year-round operation
  • (a) Applications: rapid multiplication of elite genotypes (banana, potato), virus elimination through meristem culture, germplasm conservation (cryopreservation of endangered species like Nepenthes khasiana, Madhuca insignis)
  • (a) Challenges: somaclonal variation, high capital/technical costs, phenotypic abnormalities, acclimatization problems, contamination risks
  • (b) Polyembryony vs parthenocarpy: genetic basis (zygotic cleavage/adventitious embryos vs auxin/GA-induced fruit development without fertilization); examples (Citrus nucellar embryos vs seedless grapes/oranges)
  • (b) Parthenocarpy classification: genetic (parthenocarpic tomato cultivars), environmental (low temperature-induced), artificial (2,4-D, NAA application); significance: commercial seedless fruit production, consumer preference, parthenocarpic varieties in horticulture
  • (c) Cybrid production: protoplast isolation, fusion (PEG/electrofusion), selective elimination of one parental nucleus (irradiation/chemical), regeneration of cytoplasmic hybrids
  • (c) Genetic composition: cybrids contain nuclear genome of one parent + mitochondrial/chloroplast DNA of both; hybrids contain complete nuclear genome combination
  • (c) Applications: transfer of cytoplasmic male sterility (CMS) in Brassica, Nicotiana; disease resistance through cytoplasmic genes; bypassing nuclear incompatibility barriers

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness20%10Precise definitions of micropropagation, polyembryony, parthenocarpy, cybrids; accurate distinction between cytoplasmic vs nuclear inheritance; correct understanding of somaclonal variation; no conflation of apomixis with polyembryonyGenerally correct definitions with minor errors (e.g., confusing parthenocarpy with parthenogenesis); incomplete distinction between cybrid and hybrid genetic compositionFundamental errors: treating micropropagation as genetic modification, confusing polyembryony with polymbryony, equating cybrids with somatic hybrids, or misidentifying CMS as nuclear trait
Diagram / labelling15%7.5Clear diagram of protoplast fusion showing cybrid formation with labelled nuclei (irradiated/non-functional vs active), mitochondria/chloroplasts; OR tissue culture stages (callus → shoot → root); OR parthenocarpy induction pathway; proper labels and arrowsBasic diagram present but incomplete labelling, missing organelle detail in cybrid diagram, or generic tissue culture flow without specific technique illustrationNo diagram, or irrelevant sketch; diagram with major errors (showing complete nuclear fusion in cybrid, incorrect pathway arrows)
Examples & nomenclature20%10Specific Indian/endemic examples: Red Sanders (Pterocarpus santalinus), Nepenthes khasiana for conservation; Citrus for nucellar polyembryony; seedless varieties (Pusa Seedless, Thompson Seedless); Brassica napus CMS (ogura system); correct hormone names (2,4-D, NAA, BAP, kinetin)Generic examples (banana, potato for micropropagation; grapes for parthenocarpy) without Indian specificity; some hormone names correct but incompleteNo specific examples, invented variety names, or incorrect examples (e.g., mango for parthenocarpy which is not naturally parthenocarpic); wrong hormone identification
Process explanation25%12.5Stepwise clarity: for micropropagation (explant → sterilization → culture initiation → multiplication → rooting → hardening); for cybrid production (protoplast isolation → fusion → selective elimination → heterokaryon selection → regeneration); for parthenocarpy (hormonal mechanism: auxin/GA role in ovary development without fertilization)Process mentioned but sequence unclear or steps missing (e.g., omitting hardening in micropropagation, or irradiation step in cybrid production); hormonal mechanism vaguely statedNo logical process flow; jumbled steps; fundamental misunderstanding of in vitro vs in vivo processes; missing critical steps entirely
Application / ecology20%10Comprehensive coverage: crop improvement (virus indexing, germplasm exchange, synthetic seed production); conservation (in situ/ex situ link, cryobanks at NBPGR); cybrid applications (CMS for hybrid seed production, overcoming sexual incompatibility); challenges balanced with solutions (bioreactors for cost reduction)Applications listed superficially without elaboration; generic conservation mention without institutional/species context; challenges stated without mitigation strategiesApplications confused (e.g., claiming micropropagation creates transgenics); no conservation relevance; missing challenges entirely or listing irrelevant problems

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