UPHESC Assistant Professor Agricultural Botany PYQs

Concept: Vesicles are small membrane-bound sacs that temporarily store and carry materials between ER, Golgi and plasma membrane (exo-/endocytosis).

1. Chloroplast – photosynthesis.
2. Lysosome – intracellular digestion.
3. Nucleus – genetic control.

Short trick: Vesicle = cellular courier bag.

Concept: Positively photoblastic seeds (e.g. lettuce cv. Grand Rapids) need red light, which acts via phytochrome to raise GA levels; applied GA₃ replaces this light requirement.

1. GA also substitutes cold (stratification) and long-day requirements in some plants.
2. Red light → Pfr → GA biosynthesis genes (GA3ox) ↑ → hydrolases → germination.

Short trick: Lettuce in the dark + GA = germination.

Concept: C₄ plants are grouped by the bundle-sheath decarboxylating enzyme.

1. NADP-ME type – maize, sugarcane, sorghum (malate shuttled; chloroplasts in bundle sheath).
2. NAD-ME type – Atriplex, Amaranthus, pearl millet (aspartate, mitochondrial).
3. PEP-CK type – Panicum maximum, Chloris.
4. Arabidopsis is a C₃ plant.

Short trick: Maize–Sugarcane–Sorghum = NADP-ME (the 'big three' crops).

Concept: Plant photoreceptors and their main roles.

1. Phytochromes – red/far-red receptors controlling germination, de-etiolation, flowering (a-3).
2. Cryptochromes – blue/UV-A receptors that entrain (reset) the circadian clock (b-2).
3. Phototropins – blue light: phototropism, chloroplast movement, stomatal opening (c-4).
4. Zeitlupe (ZTL) family – circadian period and day-length (photoperiodic) flowering (d-1).

Short trick: Phot = movement (chloroplasts, stomata); Phy = red; ZTL = 'slow motion' clock.

Concept: Photorespiration and carbon fixation take place in different organelles: Rubisco works in the chloroplast stroma; glycine → serine occurs in mitochondria.

1. (A) Glyoxylate → glycine (transamination) – peroxisome: correct.
2. (B) RuBP → 3-PGA (Rubisco carboxylation) – printed site 'Stomata': wrong; it occurs in the chloroplast stroma (stomata only admit CO₂).
3. (C) Glycine → serine – printed site 'Ribosome': wrong; it occurs in mitochondria (glycine decarboxylase + SHMT).
4. (D) Packaging of polysaccharides into vesicles – Golgi bodies: correct.
5. Two pairs (B and C) are not correctly matched, so the question has no single answer as printed.

Short trick: Photorespiration route: Chloroplast (stroma) → Peroxisome → Mitochondrion (Gly → Ser) → Peroxisome → Chloroplast.

Concept: Grey speck of oats (and other cereals) is a manganese-deficiency disorder, common on alkaline/over-limed soils.

1. Other Mn disorders: marsh spot of pea, speckled yellows of sugar beet, pahala blight of sugarcane.
2. Cu – reclamation disease/white tip; Mo – whiptail of cauliflower; B – hollow stem, internal cork.

Short trick: Grey speck & Marsh spot = Manganese (both 'spots').

Concept: Proline is the classic compatible solute accumulated under drought, salinity and cold for osmotic adjustment.

1. It also stabilises proteins/membranes and scavenges ROS.
2. Other osmolytes: glycine betaine, mannitol, trehalose, sugars.

Short trick: Stress → Proline (and glycine betaine).

Concept: The root-hair (maturation) zone has an enormous absorptive surface and is the main site of water and mineral uptake.

1. Root cap – protection, gravity perception.
2. Meristematic zone – cell division.
3. Elongation zone – cell enlargement (some uptake, but not the main site).

Short trick: Hairs = surface = absorption.

Concept: Loam (roughly 40% sand, 40% silt, 20% clay) combines good aeration and drainage with good water and nutrient retention – ideal for most crops.

1. Sandy soil – poor water/nutrient holding.
2. Clay – poor aeration, waterlogging, hard when dry.
3. Silt alone – crusting, poor structure.

Short trick: Loam = balanced = best.

Concept: Tilth is the physical condition of soil resulting from tillage – crumbly, well-aerated – suitable for a good seed bed.

1. Tillage is the operation (process); tilth is its result (condition).
2. Blade harrow – an implement; furrow – a trench made by a plough.

Short trick: Tillage = action, Tilth = condition.

Concept: India's NPK use is skewed towards N; the recommended ratio is 4 : 2 : 1.

1. In recent years the all-India ratio has hovered around 6–7 : 2.4–3 : 1 (e.g. about 6.7 : 2.4 : 1).
2. Ratios of 9 : 3 : 1 or 9 : 5 : 1 are not reported all-India figures (Punjab-type extremes are higher still in N).
3. The wide ratio reflects subsidised urea and costlier P and K.

Short trick: Ideal 4 : 2 : 1, actual ≈ 6.7 : 2.4 : 1.

Concept: Phloem-mobile nutrients (N, P, K, Mg) are remobilised from old to young leaves, so their deficiency shows first on older leaves.

1. Immobile: Ca, B (deficiency on young leaves/growing points).
2. S, Fe, Zn, Cu, Mn – low/intermediate mobility, symptoms on young leaves.

Short trick: Old leaves yellow first → mobile (N, P, K, Mg).

Concept: Microbes need about 24 : 1 C : N in their food; residues near or below this decompose quickly with net N release, while wide C : N residues decompose slowly and immobilise N.

1. Statement 1 is wrong: residues of 24–30 : 1 are close to the microbial optimum and decompose readily (net mineralisation begins below ~25–30 : 1).
2. Statement 2 is wrong: residues with 80 : 1 (e.g. straw) decompose slowly; microbes lock up soil N (immobilisation), causing temporary N deficiency.
3. Hence neither statement is correct.

Short trick: Narrow C : N = fast + release; wide C : N = slow + lock-up.

Concept: N. V. Kanitkar's ICAR monograph 'Dry Farming in India' (1944) first published the concept and practices of dry farming for Indian conditions.

1. Research began at Bombay-Deccan centres (Sholapur, Bijapur) in the 1930s.
2. Kanitkar is regarded as a pioneer of Indian dry-land agriculture.

Short trick: Kanitkar – 'Dry Farming in India' – 1944.

Concept: Water is a polar molecule (partial − on O, partial + on H) with high dielectric constant, so it hydrates ions and polar molecules – the 'universal solvent'.

1. Cohesion/adhesion and tensile strength explain ascent of sap.
2. High specific heat (thermal property) buffers temperature.

Short trick: Polar dissolves polar: 'like dissolves like'.

Concept: PCR amplifies a specific DNA segment in vitro, so it is a detection/diagnostic tool.

1. 1 ✔ – pathogen-specific primers detect viruses, bacteria, fungi, phytoplasma.
2. 3 ✔ – allele-specific PCR/sequencing diagnoses mutations.
3. 2 ✘ – monoclonal antibodies come from hybridoma technology (Köhler & Milstein).
4. 4 ✘ – rDNA is introduced by transformation (Agrobacterium, gene gun), not PCR.

Short trick: PCR copies and detects – it neither makes antibodies nor transforms cells.

Concept: Oligomycin blocks the F_o proton channel of ATP synthase – it is an inhibitor of phosphorylation, not an uncoupler.

1. Uncouplers dissipate the proton gradient: DNP, FCCP, CCCP.
2. Valinomycin, a K⁺ ionophore, collapses the membrane potential and acts as an uncoupler-type agent.
3. With oligomycin both ATP synthesis and electron flow stop; with uncouplers electron flow continues.

Short trick: Oligomycin – 'O' for F_O blocker.

Concept: Catalytic efficiency (specificity constant) = $k_{cat}/K_m$, units M⁻¹ s⁻¹.

1. $K_m$ – substrate concentration at half $V_{max}$ (affinity).
2. $k_{cat}$ – turnover number.
3. Upper limit of $k_{cat}/K_m$ ≈ 10⁸–10⁹ M⁻¹s⁻¹ (diffusion-limited, 'perfect' enzymes like catalase).

Short trick: Efficiency = speed ÷ Km: fast and high-affinity.

Concept: In Agrobacterium-mediated transformation the gene must be cloned first, then carried by the bacterium into plant cells.

1. Step 2: gene inserted into the (binary/Ti) plasmid with restriction enzyme and ligase.
2. Step 3: this plasmid is put into A. tumefaciens, which now carries the gene of interest.
3. Step 1: the bacterium is co-cultivated with plant cells/explants in culture (introduction).
4. Step 4: transformed cells are selected and regenerated into plants.
5. Correct order 2 → 3 → 1 → 4 is not among the codes; (B) puts 3 before 2 (the bacterium cannot carry the gene before it is cloned) and (C) puts 1 before 3. So no option is correct as printed.

Short trick: Clone → Carry → Co-cultivate → Regenerate (2-3-1-4).

Concept: Plant-specific RNA Pol IV and Pol V make non-coding RNAs for siRNA production and RNA-directed DNA methylation (RdDM), not snRNA.

1. Pol I – 28S/18S/5.8S rRNA.
2. Pol II – mRNA, most snRNAs, miRNA precursors.
3. Pol III – tRNA, 5S rRNA, U6 snRNA.
4. So pairing Pol IV/V with snRNA is wrong.

Short trick: Pol IV & V = plant silencing (siRNA, RdDM).