Botany 2021 Paper I 50 marks Describe

Q7

(a) Describe the economic botany of fibre and gum yielding plants (five species each). (20 marks) (b) Discuss the factors affecting somatic embryogenesis. (20 marks) (c) Describe the method of isolation of protoplast from leaf tissue. (10 marks)

हिंदी में प्रश्न पढ़ें

(a) रेशा व गोंद उत्पादक पादपों (प्रत्येक के पाँच) के आर्थिक वनस्पति-विज्ञान का वर्णन कीजिए। (20 अंक) (b) कायिक भ्रूणजनन को प्रभावित करने वाले घटकों की विवेचना कीजिए। (20 अंक) (c) पर्ण उत्तक से जीवद्रव्यक के अलगाव की विधि का वर्णन कीजिए। (10 अंक)

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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 systematic, factual exposition with adequate detail. For part (a) (20 marks), allocate ~40% effort covering five fibre species (Cotton, Jute, Flax, Hemp, Sisal) and five gum species (Acacia senegal/Arabic gum, Sterculia urens/Karaya gum, Astragalus/Tragacanth, Anogeissus latifolia/Ghatti, Bauhinia variegata) with botanical names, plant parts, extraction methods and economic uses. For part (b) (20 marks), allocate ~35% discussing genotype, explant source, growth regulators (2,4-D, NAA, BAP), nitrogen source, and culture conditions. For part (c) (10 marks), allocate ~25% detailing enzymatic maceration using cellulase, pectinase, hemicellulase, osmoticum (mannitol/sorbitol), filtration, and purification. Structure: brief introduction → systematic treatment of each sub-part → concluding synthesis on plant biotechnology applications.

Key points expected

  • Part (a): Five fibre plants with botanical names (Gossypium spp., Corchorus spp., Linum usitatissimum, Cannabis sativa, Agave sisalana), fibre type (lint, bast, leaf), extraction process (retting, decortication) and industrial applications (textiles, cordage, paper)
  • Part (a): Five gum plants with botanical names (Acacia senegal, Sterculia urens, Astragalus gummifer, Anogeissus latifolia, Bauhinia variegata), gum chemistry (arabinogalactan, rhamnogalacturonan), tapping methods and commercial uses (food, pharmaceuticals, adhesives)
  • Part (b): Genotypic and explant factors affecting embryogenic competence; role of auxin-cytokinin ratios (especially 2,4-D induction and subsequent reduction); nitrogen source (NH4+ vs NO3-) and somatic embryo maturation
  • Part (b): Physical factors: light, temperature, osmotic stress; biochemical markers (SERK gene expression); conversion efficiency and synthetic seed technology relevance
  • Part (c): Pre-plasmolysis treatment; enzyme cocktail composition (Cellulase Onozuka R-10, Macerozyme R-10, Driselase); osmotic stabilizers (0.4-0.6 M mannitol); incubation conditions (25°C, 4-16h); filtration through nylon mesh; purification by floatation or washing
  • Part (c): Viability assessment (FDA staining, Evans blue exclusion) and yield calculation; significance for somatic hybridization and genetic transformation

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11Accurate botanical classification for all ten species in (a); precise hormonal mechanisms and gene regulation in (b); correct enzyme action and osmotic principles in (c); no taxonomic or physiological errorsMinor errors in botanical names (e.g., Gossypium herbaceum vs hirsutum); oversimplified hormone explanation; basic enzyme list without specificityMajor taxonomic confusion (e.g., calling jute a leaf fibre); incorrect hormone roles (cytokinin for induction); fundamental errors in protoplast isolation steps
Diagram / labelling18%9Clear diagram of somatic embryo stages (globular, heart, torpedo, cotyledonary) for (b); labelled protoplast isolation flowchart or enzymatic digestion schematic for (c); fibre cross-section or gum exudation diagram for (a)One relevant diagram with partial labelling; OR three parts covered textually without visual aidNo diagrams where essential; OR diagrams present but completely unlabelled or biologically inaccurate
Examples & nomenclature20%10All ten species with correct binomials and families; Indian examples emphasized (Corchorus capsularis, Anogeissus latifolia); mentions specific cultivars or varieties where relevant; standard trade names for gumsMost species identified correctly; common names substituted for some binomials; limited Indian contextRepeated species across fibre/gum categories; incorrect binomials; no family mention; entirely generic examples
Process explanation22%11Detailed sequential steps for fibre extraction (retting biochemistry by pectinolytic bacteria), gum tapping (wound response, yield optimization), somatic embryo induction-to-maturation protocol, and protoplast isolation with critical parameters (pH, temperature, duration)Process mentioned but lacking critical parameters; OR one part detailed while others superficialVague, non-sequential description; missing critical steps (e.g., no osmoticum in protoplast isolation); confused chronology
Application / ecology18%9Links fibre cultivation to jute geotextiles and soil conservation; gum trade to Indian economy (Rajasthan gum belt); somatic embryogenesis to clonal propagation, cryopreservation and synthetic seeds; protoplasts to somatic hybridization (e.g., Brassica + Sinapis) and CRISPR applicationsGeneric mention of economic importance without specific applications; limited biotechnology relevanceNo application context; purely descriptive with no linkage to agriculture, industry or research

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