Plant Biology is a core part of IB Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.
XylemDead lignified vessels transporting water and minerals from roots upward via transpiration pull.
PhloemLiving sieve tubes with companion cells; translocate sucrose from source to sink (Munch 1930 pressure flow).
TranspirationEvaporative loss of water from leaves through stomata; creates tension drawing water column up.
StomataPores in epidermis flanked by guard cells; open when guard cells turgid via K+ uptake.
PhytochromePhotoreceptor pigment switching between Pr (red-absorbing) and Pfr (far-red) forms; controls flowering.
AuxinPlant hormone (IAA) promoting cell elongation and phototropism (Went 1926 oat coleoptile).
Cohesion-tensionWater column pulled up by H-bonds
StomaPore for gas exchange (guard cells)
Water potentialTendency of water to move
Apoplast / SymplastCell wall vs cytoplasm pathways
ChloroplastOrganelle with thylakoids and stroma
PhotosystemPigment-protein complex (PSII, PSI)
PhotolysisH₂O → 2H⁺ + 2e⁻ + ½O₂
NADPHReduced coenzyme from light reactions
Questions where students often pick the tempting wrong answer — make sure you know the right one: