UPSC Botany 2026 — Paper I

(a) Discuss means marshal reasoned evidence: the answer must list and explain the cytological, biochemical, reproductive and molecular features that make blue-green algae (Cyanobacteria) prokaryotes comparable with bacteria. Only similarities are asked; differences may appear at most as a closing caveat. (b) Two parts with the printed split 2+8: first define and briefly describe bacteriophages (viruses that infect bacteria, with their structure and lytic / lysogenic cycles), then devote the bulk of the note to their applications in medical science - therapy, diagnosis, typing, and molecular medicine. (c) Printed split 6+4. First describe three distinct soil-nitrogen processes - mineralization (ammonification and nitrification), symbiotic nitrogen fixation and non-symbiotic (free-living and associative) nitrogen fixation, naming organisms; then explain how together they raise soil fertility and quality for agriculture. (d) Printed split 2+8. First define fossilization precisely as a process; then discuss the major categories of fossils found in nature, with plant examples for each, since this is a Botany paper. (e) Printed split 2+8. Define chemotaxonomy (chemosystematics) in 2 marks, then analyse - not merely list - how micromolecular, macromolecular and molecular chemical evidence has resolved specific taxonomic problems, which requires named compounds attached to named taxa.

• Prokaryotic cell: no nucleus or membrane-bound organelles, naked circular DNA, 70S ribosomes
• Peptidoglycan cell wall of Gram-negative type
• Binary fission or fragmentation, gene transfer by conjugation, transformation, transduction; plasmids
• Nitrogen fixation by nitrogenase (as in Azotobacter), sensitivity to lysozyme and penicillin
• Definition: bacteriophage, obligate parasite with nucleic acid in a capsid, lytic and lysogenic cycles (2 marks)
• Phage therapy against antibiotic-resistant bacteria, and lysins
• Phage typing and rapid detection (e.g. luciferase reporter phage for tuberculosis)
• Phage display, cloning vectors, and CRISPR-Cas origin from phage defence
• Mineralization: ammonification then nitrification (Nitrosomonas, Nitrobacter), C:N ratio control
• Symbiotic fixation: Rhizobium in legume nodules with leghaemoglobin, also Frankia and Azolla-Anabaena
• Non-symbiotic fixation: Azotobacter, Beijerinckia, Clostridium, cyanobacteria; Azospirillum associative
• Soil benefits: cheap nitrogen, less fertiliser use, humus, structure, rotations, green manure, biofertilisers
• Definition: preservation of remains, impressions or traces of ancient organisms in sedimentary rocks (2 marks)
• Petrifaction or permineralization and compression, each with an example
• Impression, mould and cast, incrustation
• Amber, coprolites, coal balls or microfossils; an Indian example
• Definition: use of chemical characters (secondary metabolites, proteins) in classification (2 marks)
• Betalains versus anthocyanins in Caryophyllales, including the exceptions
• Glucosinolates in Brassicales; flavonoid profiling of hybrids
• Chemotypes, seed proteins and serology; limitation from convergence and need to combine with morphology and molecular data

(a) Three parts with the printed split 8+6+6: (i) the major diagnostic characteristics of the class Anthocerotopsida (hornworts), (ii) the gametophytic generation of Anthoceros and (iii) its sporophytic generation. All three must be attempted separately. (b) Printed split 10+5. Describe the salient morphological, anatomical, reproductive and life-cycle features of Laminariales (the kelps, order of Phaeophyceae) in the larger part, then give their economic importance with named products and species. (c) Printed split 5+5+5. A comparison, with labelled diagrams, of the ovule-bearing structures of Cycas (loose megasporophylls bearing ovules) and Pinus (compact female cone with bract and ovuliferous scales): describe each, then set out the differences point by point, supported by labelled drawings.

• Class characters: dorsiventral thallus, one chloroplast with pyrenoid per cell, smooth rhizoids, Nostoc cavities, endogenous sex organs
• Sporophyte: horn-like capsule with basal meristem, foot, no seta, columella, stomata, pseudoelaters, dehiscence in two valves from the apex
• Gametophyte of Anthoceros: rosette thallus, slime pores, antheridia in chambers, sunken archegonia, vegetative propagation
• Sporophyte of Anthoceros: development from zygote, capsule anatomy (epidermis, assimilatory layer, columella, sporogenous tissue), spore release
• Large brown algae (kelps) with pigments chlorophyll a and c and fucoxanthin, laminarin and mannitol reserve, alginic acid in wall
• Sporophyte with holdfast, stipe, blade; intercalary meristem; stipe anatomy with trumpet hyphae
• Heteromorphic alternation: unilocular sporangia in sori, zoospores by meiosis, microscopic filamentous gametophytes, oogamy
• Economic use: alginates, food (kombu, wakame), iodine, mannitol, fodder and manure, kelp forests
• Cycas megasporophyll: loose rosette, leaf-like, stalk, fertile region with 2-6 marginal ovules, sterile pinnate tip; orthotropous ovule
• Pinus: compact female cone, bract scale and ovuliferous scale, two anatropous ovules on the upper surface with micropyles toward the axis
• Labelled diagrams of both structures
• Comparison on organisation, ovule number, position, orientation, seed and time to maturity

(a) Name the pathogen of stalk rot of maize and then give a full disease account - symptoms, disease cycle (survival, inoculum, infection, spread and predisposing conditions) and control and management. All four elements carry marks. (b) Three linked demands: (i) define what mycoplasmas are, (ii) distinguish them clearly from spheroplasts and from protoplasts - the crux is natural, permanent wall-lessness versus artificially induced, reversible wall removal, and (iii) describe their salient morphological, physiological and pathological features. All three sub-parts must be answered; a tabular comparison is welcome. (c) Two parts: first a note explaining what the geological time scale is (its hierarchy of eon, era, period and epoch, its basis in stratigraphy, fossils and radiometric dating), then a brief era-by-era account of plant life - Precambrian, Palaeozoic, Mesozoic and Cenozoic - with representative genera and approximate dates.

• Pathogen named: Fusarium verticillioides (Gibberella moniliformis), with the disease complex (Macrophomina, Stenocarpella, Pythium, Dickeya)
• Symptoms: post-flowering wilting, soft brown lower internodes, discoloured shredded pith, lodging, chaffy ears
• Disease cycle: survival in residue, soil and seed; root and wound infection (borer); favouring stress conditions; spread by conidia
• Control: resistant hybrids, rotation, residue destruction, balanced potassium and water management, seed treatment, borer control, drenching
• Definition: smallest free-living prokaryotes, class Mollicutes, no cell wall, unit membrane with sterols, pleomorphic, tiny genome
• Protoplast (wall completely removed) and spheroplast (partial wall) are artificial and can revert; mycoplasma naturally wall-less and never revert
• Features: binary fission and budding, fried-egg colonies, insensitive to penicillin but sensitive to tetracycline, pass through filters
• Diseases and vectors: phytoplasma yellows, little leaf, grassy shoot by leafhoppers; atypical pneumonia and CBPP in animals
• Time scale: basis (fossils, strata, radiometric), hierarchy of eons, eras, periods, epochs; ages of eras
• Palaeozoic, Mesozoic and Cenozoic with their periods and dates
• Palaeozoic plants: first land plants, Devonian forests and seed plants, Carboniferous coal forests, Permian Glossopteris flora
• Mesozoic age of gymnosperms and first angiosperms; Cenozoic age of angiosperms and grasslands

(a) Three explicit demands: explain what the APG IV system is and how it is built (molecular phylogeny, monophyly, its clade architecture), state briefly how it departs from earlier systems such as Bentham and Hooker, Engler and Prantl, Hutchinson, Takhtajan and Cronquist, and then discuss both merits and demerits. Omitting either merits or demerits forfeits a quarter of the marks. (b) Describe briefly the principal strategies of plant disease control and management. A good answer is organised around the classical principles (exclusion, eradication, protection, immunisation, therapy, avoidance) and then the operational categories - regulatory, cultural, physical, chemical, biological and host resistance - closing with integrated disease management. Named examples are expected throughout. (c) A strictly comparative question: contrast the sporophyte - and only the sporophyte - of Psilotum with that of Equisetum under external morphology, internal anatomy and reproductive (sporangial) structure. Gametophyte detail is outside the demand except as a brief closing remark.

• APG IV (2016): phylogenetic, cladistic, monophyletic groups, mainly DNA evidence (plastid rbcL, atpB, matK), consensus system; 64 orders and 416 families
• Informal clades above order (ANA grade, magnoliids, monocots, eudicots, superrosids, superasterids); five new orders over APG III
• Difference: earlier systems (Bentham-Hooker, Engler-Prantl, Cronquist) morphology-based with paraphyletic groups; dicots abandoned; families re-circumscribed (Malvaceae, Apocynaceae, Amaranthaceae)
• Merits (monophyly, objective evidence, stability, revision) and demerits (hard to key, lumping, gene dependence, angiosperms only, no ranks above order)
• Exclusion and avoidance: quarantine (Plant Quarantine Order 2003), certified seed, site and sowing time
• Eradication: rouging, rotation, residue destruction, alternate host removal, solarisation
• Protection: fungicides, bactericides, seed treatment; cultural methods
• Host resistance, biological control (Trichoderma, Pseudomonas, K84), therapy (hot water, meristem culture), integrated disease management
• Habit and underground parts: Psilotum rootless, rhizome with mycorrhiza; Equisetum rhizome with adventitious roots and tubers
• Stem and leaves: Psilotum forked ridged stem with enations; Equisetum jointed stem with ridges, furrows, silica, whorled scale leaves in sheaths
• Stele: Psilotum protostele to siphonostele; Equisetum siphonostele with carinal and vallecular canals
• Sporangia and spores: Psilotum trilocular synangia, no elaters; Equisetum sporangiophores in cone, four elaters

(a) Describe the androecium of Orchidaceae and of Asclepiadaceae separately and then highlight the differences. Both descriptions and an explicit set of contrasts are needed; a description without the contrast, or a contrast without the descriptions, is incomplete. (b) Two demands: classify and explain the types of polyembryony in plants with named examples, and then add a short note on its practical and biological importance. A list of types without examples, or types without the closing note on importance, is incomplete. (c) A purely factual recall question: give the correct binomial and the family for each of the five economically important plants named - pearl millet, flax, pomegranate, bottle gourd and chickpea. Each of the five sub-parts must be attempted; a list format with a one-line note on the economic use is the ideal answer. (d) A detailed account is asked, so both the technique - how a suspension is raised from friable callus, the types of suspension culture and how growth is measured - and its significance in research and industry must appear. An answer confined to the definition alone cannot pass. (e) An explanatory note, so the answer must not merely narrate dates: it must define domestication, explain the genetic changes of the domestication syndrome, and trace the history from the Neolithic centres of origin through Indian evidence and the theoretical contributions of de Candolle, Vavilov and Harlan to the modern era.

• Orchidaceae: one (or two) fertile stamen fused with style and stigma into gynostemium; pollen in pollinia with caudicle and viscidium; staminodes
• Asclepiadaceae: five stamens united into a staminal tube, gynostegium with the stigmatic head, corona of hoods
• Asclepiadaceae pollinia: waxy, one per anther lobe, joined in pairs by caudicles to a corpusculum (translator)
• Differences: stamen number, pollinia type and attachment, gynostemium versus gynostegium, corona
• Definition: more than one embryo in a seed
• Cleavage polyembryony and adventive (nucellar) embryony with examples (Pinus; Citrus, mango)
• Multiple embryo sacs and embryos from synergids or antipodals; simple polyembryony in gymnosperms
• Importance: true-to-type virus-free nucellar seedlings, rootstocks, haploid twins; problem for hybrid recovery
• Pearl millet: Pennisetum glaucum (Cenchrus americanus), Poaceae; flax: Linum usitatissimum, Linaceae
• Pomegranate: Punica granatum, Lythraceae (formerly Punicaceae)
• Bottle gourd: Lagenaria siceraria, Cucurbitaceae
• Chickpea: Cicer arietinum, Fabaceae (Leguminosae)
• Definition: cells and small aggregates dispersed in liquid medium
• Friable callus on MS medium with 2,4-D and cytokinin, transferred to liquid medium in flasks
• Rotary shaker (100-120 rpm, 25 °C), sieving, subculture every 1-2 weeks at 1:5 to 1:10 dilution
• Growth measurement and viability, batch and continuous culture; significance: secondary metabolites, protoplasts, somatic embryos, in vitro selection
• Definition of domestication by human selection; onset 10,000-12,000 years ago after the last Ice Age
• Centres of origin (Vavilov): Fertile Crescent, Mesoamerica, Andes, China, Indian region, with example crops; Mehrgarh evidence
• Domestication syndrome: loss of shattering, larger seeds, reduced dormancy, uniform ripening
• Spread, hybridisation and polyploidy (bread wheat), Columbian exchange, modern breeding and Green Revolution

(a) Four deliverables: the diagnostic (family-defining) characters of Apiaceae, the same for Solanaceae, and then five members of each family with correct botanical names and their uses. Diagnostic means the distinguishing characters, especially the floral and fruit characters and the floral formula, not a general description. (b) Substantiate means argue in support with evidence: establish, function by function and with named gardens and concrete instances, why a botanical garden serves botanists as a living out-of-doors laboratory. A definition-only answer, or a list of Indian gardens without their scientific functions, does not substantiate. (c) Two parts: describe the four structural components of xylem - tracheids, vessels, xylem fibres and xylem parenchyma - with their structure and function, and then explain the role of xylem in the survival and growth of the plant, namely conduction, mechanical support, storage and defence.

• Apiaceae: aromatic hollow-stemmed herbs, compound umbel, epigynous flowers, inferior bicarpellary ovary, cremocarp
• Solanaceae: bicollateral bundles, actinomorphic hypogynous flowers, five epipetalous stamens, superior bicarpellary ovary with oblique septum, berry or capsule
• Five correct botanical names with uses from Apiaceae (coriander, cumin, fennel, carrot, ajwain)
• Five correct botanical names with uses from Solanaceae (potato, tomato, brinjal, chilli, ashwagandha)
• Definition: labelled living collection used for study; taxonomy and reference to herbarium
• Ex situ conservation, seed banks and reintroduction, with examples (Kew, NBRI, Indian Botanic Garden, Howrah)
• Introduction and acclimatisation of economic plants (cinchona, tea, rubber); experimental research in physiology, genetics, ecology and phenology
• Education and training, medicinal and horticultural work; conclusion tying to laboratory functions
• Tracheids: dead, tapering, bordered pits, no perforation, main conducting cells in pteridophytes and gymnosperms
• Vessels: dead elements with perforated end walls, wide, in angiosperms; types of wall thickening
• Xylem fibres (support) and xylem parenchyma (storage, radial transport, tyloses)
• Role: water and mineral conduction (transpiration pull), mechanical support, storage; secondary xylem gives girth and timber

(a) Two parts weighted 15 and 5 as printed: describe the sequence of operations by which a herbarium specimen is prepared - collection, pressing, drying, poisoning, mounting, labelling, filing and maintenance - and then explain what herbaria contribute to modern taxonomic research, including types, molecular sampling, digitisation and phenological data. (b) Three named sub-parts of equal standing: the types (or levels and expressions) of totipotency, its regulation (hormonal, genetic, molecular and epigenetic), and its significance. An answer that only defines totipotency and narrates the history cannot score above half. (c) Two demands: give an account of the in vitro routes to haploid plants - androgenesis by anther and microspore culture, gynogenesis by unpollinated ovary and ovule culture, and chromosome elimination - including diploidisation; and then state the advantages of the resulting homozygous doubled-haploid lines for breeding and genetics.

• Collection with field notes (number, date, locality, habitat, colour, uses) and representative complete specimen
• Pressing between blotting paper and corrugated boards, changing driers, drying, poisoning or freezing against pests
• Mounting on 42 x 28 cm sheet, label at bottom right, filing in cabinets by a system and fumigation
• Role: reference and identification, type specimens, distribution data and floras, DNA and climate data, digital herbaria
• Definition of totipotency; zygote and embryonic cells; somatic cells after dedifferentiation; direct and indirect routes (organogenesis, somatic embryogenesis)
• Regulation by auxin:cytokinin ratio (Skoog and Miller) and genes such as WUS, BBM, LEC1, LEC2, SERK
• Epigenetic, stress and medium factors; explant and genotype
• Significance: micropropagation, synthetic seeds, transgenic regeneration, virus-free plants, cryopreservation, haploids, in vitro selection
• Androgenesis: anther or microspore culture at late uninucleate stage, cold pretreatment, medium, embryo or callus route, first in Datura (Guha and Maheshwari 1964)
• Gynogenesis (ovary or ovule culture) and chromosome elimination in wide crosses (Hordeum bulbosum)
• Chromosome doubling by colchicine to give doubled haploids; problems of albinism and low frequency
• Advantages: complete homozygosity in one generation, expression of recessives, fixed lines for hybrids, mapping and transformation

(a) Two clearly separated demands: first the role of the culture medium and of growth regulators at each stage of micropropagation, and second the practical control of two specific problems - exudation (phenolic browning) and microbial contamination. Both halves must be attempted; the second is a practical, remedy-oriented answer. (b) Describe the experimental techniques by which reproductive processes are studied and manipulated in vitro - anther and pollen culture, ovary and ovule culture, embryo culture and rescue, endosperm culture, test-tube fertilisation, isolated gamete fusion and the microscopic and molecular tools that accompany them - each with its purpose and a landmark example. (c) An outline of both the history and the progress of ethnobotanical research in India: the classical and colonial antecedents, the founding of the modern discipline by Janaki Ammal and S. K. Jain, the AICRPE phase, the institutional and legal framework, and current directions. Chronological organisation with names, dates and institutions is expected.

• Medium (MS): macro- and micronutrients, vitamins, sucrose, agar, pH 5.6-5.8, supplements
• Growth regulators by stage: cytokinin for multiplication, auxin for rooting, GA3, auxin:cytokinin ratio
• Exudation: phenolic oxidation to quinones; control by young explants, antioxidants, PVP or charcoal, frequent transfer, dark incubation
• Contamination: sources; autoclaving (121 °C, 15 psi), filter sterilisation, explant surface sterilisation, laminar flow, antibiotics
• Embryo culture (mature, immature) and embryo rescue of wide crosses
• Ovule and ovary culture; in vitro pollination and fertilisation (Kanta, Rangaswamy and Maheshwari 1962, Papaver)
• Pollen culture and pollen tube growth studies; endosperm culture
• Staining and microscopy (aniline blue fluorescence, clearing, autoradiography), anther and protoplast techniques; Indian contribution (Maheshwari school)
• Definition; Harshberger 1895; ancient records (Vedas, Charaka and Sushruta Samhitas, Ayurveda)
• Colonial works (Hortus Malabaricus, Roxburgh, Watt); pioneers E. K. Janaki Ammal and S. K. Jain
• Progress: AICRPE from 1982, BSI, NBRI, CSIR, journals, tribal surveys
• Drug leads (reserpine, Jeevani with Kani tribe), TKDL 2001, Biological Diversity Act 2002, National Medicinal Plants Board