UPHESC Assistant Professor Botany 2025 PYQs

Concept: Verhulst–Pearl logistic model: $\frac{dN}{dt}=rN(1-\frac{N}{K})$ gives an S-shaped (sigmoid) curve.

1. a ✘ – at N = K the bracket is 0, so growth rate = 0; the maximum rate is at N = K/2 (inflection point).
2. b ✔ – as N → K, (1 − N/K) → 0, so growth slows.
3. c ✔ – if N > K, (1 − N/K) is negative → dN/dt < 0, population falls back to K.
4. d ✔ – K is the carrying capacity.

Short trick: Logistic: fastest at K/2, zero at K, negative above K.

Concept: Pathogen recognition (PAMP/effector) triggers an ion flux and, within minutes, an oxidative burst.

1. NADPH oxidase (RBOH) at the plasma membrane rapidly produces superoxide and H₂O₂ (ROS) – the earliest defence event.
2. ROS directly kill microbes, cross-link cell walls and act as signals for the later hypersensitive response (localized cell death, hours).
3. Hormonal (SA, JA, ET) signalling and chromatin remodelling for defence-gene expression follow later.

Short trick: Order: recognition → Ca²⁺/ion flux → ROS burst → HR → hormones/SAR.

Concept: SAR is long-lasting, broad-spectrum resistance that develops in uninfected parts after a local infection.

1. It needs salicylic acid (SA) accumulation; SA (with mobile signals like methyl salicylate, pipecolic acid) acts through NPR1 to induce PR (pathogenesis-related) proteins.
2. Plants unable to accumulate SA (NahG transgenics) cannot develop SAR.
3. Jasmonic acid + ethylene mediate ISR (induced systemic resistance by rhizobacteria); ABA and GA are not SAR inducers.

Short trick: SAR – SA; ISR – JA/ET.

Concept: Chloroplasts (and mitochondria) are double-membrane, semi-autonomous organelles.

1. They have their own circular DNA, 70S ribosomes and divide by fission – 'semi-autonomous' (printed 'semi-autosomal') because many proteins are still nuclear-encoded.
2. In most angiosperms plastids pass only through the egg cytoplasm → maternal (cytoplasmic) inheritance, e.g. leaf variegation in Mirabilis jalapa (Correns).
3. Lysosomes, peroxisomes and endosomes are single-membrane and lack DNA.

Short trick: Double membrane + own DNA + maternal = chloroplast/mitochondrion.

Concept: Micropropagation = rapid clonal multiplication of plants in vitro.

1. b ✔ – done in controlled culture rooms, so plantlets are produced all year, independent of season.
2. c ✔ – a very small explant (shoot tip, node, meristem) can give thousands of plants.
3. d ✔ – meristem-tip culture gives virus/disease-free propagules (e.g. potato, banana, sugarcane).
4. a ✘ – the aim is true-to-type clones; generating a range of variability (somaclonal variation) is a drawback for micropropagation.

Short trick: Micropropagation = Many, Uniform, Clean, All-year.

Concept: The statements are really the purposes/uses of producing haploids (anther/pollen culture, Guha & Maheshwari 1964).

1. a ✔ – a haploid has one allele per gene, so recessive mutants are seen and screened directly.
2. b ✔ – doubling haploids with colchicine gives completely homozygous (doubled-haploid) diploids in one generation.
3. c ✔ – these pure lines speed up breeding of disease-resistant, superior varieties.
4. d ✘ – haploids are not made to induce polyploidy; doubling only restores the diploid level.

Short trick: Haploids → see recessives → double → pure lines → new varieties.

Concept: A trichogyne is a receptive hair-like tip of the female sex organ.

1. (A) ✘ – it occurs on the ascogonium of Ascomycota (e.g. Neurospora, Pyronema, Ascobolus) and on the carpogonium of red algae (Polysiphonia, Batrachospermum) – not in Basidiomycota, which lack sex organs (somatogamy, spermatization in rusts on receptive hyphae).
2. (R) ✔ – its function is to receive the male nucleus/spermatium (or contact the antheridium) and conduct it to the female cell.

Short trick: Trichogyne → Ascomycetes & red algae; Basidiomycetes have no sex organs.

Concept: Downy mildews (Peronosporales, Oomycota) are obligate biotrophs.

1. (A) ✔ – Peronospora destructor causes downy mildew of onion (pale, elongated lesions with violet-grey sporulation).
2. (R) ✘ – like other downy mildews it cannot be grown on artificial culture media; it is maintained only on living host plants.

Short trick: Downy mildews, powdery mildews and rusts = obligate parasites – no lab culture.

Concept: Match botanical names with popular names.

1. Nigella damascena – love-in-a-mist (flower sits in a mist of feathery bracts) (a – ii).
2. Leucaena leucophloea (= Acacia leucophloea) – white-barked 'popinac' / safed babool (b – iii).
3. Helichrysum bracteatum – strawflower/paper flower (papery, everlasting bracts) (c – iv).
4. Cestrum nocturnum – night jasmine, raat-ki-rani (night-scented) (d – i).

Short trick: Nocturnum = night; bracteatum = papery bracts; Nigella = mist.

Concept: Locate each inhibitor on the mitochondrial ETC/ATP synthase.

1. Cyanide – binds Fe³⁺ of cytochrome a₃, inhibiting cytochrome oxidase (Complex IV) (a – IV).
2. Aurovertin (printed 'Auravertin') – binds the β-subunits of F₁ of ATP synthase (b – III).
3. Valinomycin – a K⁺ ionophore that dissipates the membrane potential (c – I).
4. Antimycin A – blocks Complex III (cyt b → cyt c₁/c, Q_i site) (d – II).

Short trick: CN – Complex IV; Antimycin – III; Aurovertin/Oligomycin – ATP synthase; Valinomycin – K⁺.