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Playbook

Plant Biology

29 q · 3% HARD. Plant Tissues + Meristems (11 q · xylem-water-up / phloem-food-bidirectional / apical-vs-lateral meristem), Photosynthesis (10 · light/dark reactions, chloroplast site, 6CO₂+6H₂O→C₆H₁₂O₆+6O₂), Seed/Fruit/Embryo (4), Transpiration + Tropisms (3 · 33% HARD — chapter's HARD pool, vaseline-on-leaf experiment design). Apply strand because each subtopic demands mechanism-tracing, not just recall.

questions in the bank
29
tagged HARD
3%
subtopic(s)
5
worked examples
2

When you’ll see it

A plant-tissue function question (xylem vs phloem direction, meristem location), a photosynthesis-equation or site question, a seed/fruit/embryo development question, or a transpiration / tropism / plant-process experimental question.

How this chapter is tested

29 q in 10 years, 1 HARD. Plant Biology is the Apply strand workhorse — every subtopic requires tracing a plant process, not just naming a structure. Plant Tissues + Meristems (11 q) is the biggest subtopic: xylem carries water + minerals UP (root → leaves, one-direction, via transpiration pull + root pressure); phloem carries food (sugars from photosynthesis) BIDIRECTIONALLY (source → sink, via pressure-flow). Meristems are growth tissues: apical meristem (tips → length, primary growth), lateral meristem (sides → width, secondary growth, only in dicots).

Photosynthesis (10 q) — site = chloroplast (specifically thylakoid for light reactions, stroma for dark reactions). Equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂. Light-dependent reactions split water (H₂O → 2H⁺ + ½O₂ + 2e⁻), produce ATP + NADPH. Light-independent (Calvin cycle) uses ATP + NADPH to fix CO₂ into glucose. The pigment is chlorophyll (absorbs red + blue light, reflects green — that's why leaves look green).

Transpiration, Tropisms and Plant Processes (3 q, 33% HARD) is the chapter's Apply pocket. The HARD 2021 PYQ is the classic vaseline-on-leaf experiment: vaseline on upper surface vs vaseline on lower surface vs control. Stomata are MOSTLY on the LOWER surface in most dicots → vaseline-lower blocks most transpiration → that leaf loses LEAST mass. Tropisms: phototropism (toward light), geotropism (toward gravity for roots), hydrotropism (toward water), thigmotropism (toward touch — vine tendrils). All are auxin-mediated growth responses.

The sub-skills

The rules and habits that decide whether you get a question right.

  • Xylem vs phloem direction + function

    Xylem: dead cells (tracheids + vessels), carries WATER + dissolved minerals from roots UPWARD only (one-direction, via transpiration pull + root pressure). Phloem: living cells (sieve tubes + companion cells), carries FOOD (sugars from photosynthesis) BIDIRECTIONALLY from source (leaves) to sink (fruits, roots, growing parts).

  • Meristem location + growth type

    Apical meristem: at root tips + shoot tips → PRIMARY GROWTH (increases length). Lateral meristem (vascular cambium + cork cambium): along stem + root sides → SECONDARY GROWTH (increases width / girth) — only in dicots + gymnosperms; monocots lack lateral meristem (no secondary growth, that's why grass stems don't thicken).

  • Photosynthesis equation + site

    6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂. Site: chloroplast. Light reactions in THYLAKOID membranes (produce ATP + NADPH, split H₂O → O₂). Dark reactions / Calvin cycle in STROMA (fix CO₂ into glucose using ATP + NADPH). Pigment: chlorophyll a (primary), chlorophyll b, carotenoids — absorb red + blue, reflect green.

  • Transpiration physics

    Water loss from plant aerial parts (mostly leaves, mostly via STOMATA). Stomata mostly on LOWER leaf surface in dicots. Cohesion-tension theory: water column held together by cohesion (H-bonds) + adhesion to xylem walls → transpiration pull lifts water from root to leaf. Factors: temperature, humidity (low → more), wind, light (stomata open in light).

2 worked examples from the bank

Real past-year questions illustrating the playbook. Click to reveal options + solution.

Example 1Plant BiologyHARD
In a dicot pot herb, vaseline/vegetable oil was applied on the upper surface of one leaf (Experimental leaf 1) and on the lower surface of another leaf (Experimental leaf 2). Vaseline/Vegetable oil was not applied on the control leaf. The plant was deliberately not watered for several days. Which leaf will dry up last ?

[Q74 · Apr · 2021]

Example 2Plant BiologyMODERATE
Which part of the plant or flower contributes in the form of false fruit like apple?

[Q96 · Apr · 2026]

Traps to expect

Distractor shapes specific to this chapter. The page-wide Traps section covers the bank-level patterns.

  • Phloem one-direction (like xylem)

    Phloem is BIDIRECTIONAL — moves food from source (any photosynthesising leaf) to sink (any consuming tissue). Direction depends on time of year + plant part. Distractor says 'phloem moves food upward only' or 'phloem moves food downward only'. Only xylem is strictly one-direction (root→leaf, never reverse).

  • Photosynthesis happens at night

    Light-DEPENDENT reactions need light → only daytime. Light-INDEPENDENT (Calvin cycle / dark reactions) can technically run without direct light BUT depend on ATP + NADPH from the light reactions — so in practice photosynthesis stops without light. Plants RESPIRE 24/7 (release CO₂); photosynthesis is daytime only.

  • Vaseline-on-upper-surface = no effect

    In most dicots stomata are mostly on the LOWER surface, so vaseline on UPPER surface blocks fewer stomata + less transpiration. But it's NOT zero effect — some stomata + cuticular transpiration still occur upper. Distractor says 'upper-vaseline leaf transpires same as control'. Reality: upper-vaseline transpires slightly less than control; lower-vaseline transpires MUCH less than both.

Drill every plant biology question

29 questions from the bank, scoped to 5 bundled subtopics.

Drill the 29 questions

Related playbooks

Often paired with this one — drill these next if you found the worked examples above tractable.