Plant Biology: Photosynthesis, Transport and Growth
What you must understand
Photosynthesis has light-dependent reactions in the thylakoid membranes (water split, oxygen released, ATP and NADPH made) and the Calvin cycle in the stroma (CO₂ fixed into sugar). Know the overall equation and that chlorophyll absorbs mainly red and blue light, reflecting green. Cellular respiration in plants mirrors animals, using mitochondria.
Transport: xylem carries water and dissolved minerals upward, driven largely by transpiration pull; phloem carries sugars (mainly sucrose) from source to sink, driven by pressure flow. Transpiration is regulated by stomata, which open to admit CO₂ and lose water - a trade-off. Growth: meristems are the sites of cell division (apical for length, lateral for girth); plant hormones include auxin (phototropism, apical dominance), gibberellin (stem elongation), cytokinin (cell division), abscisic acid (stress, stomatal closure) and ethylene (ripening). Reproduction: alternation of generations; in flowering plants, double fertilisation produces embryo and endosperm.
Traps
Xylem is dead at maturity and transports one way (up); phloem is living and transports both directions depending on source/sink. "Plants photosynthesise, so they don't respire" is false - they respire continuously. Oxygen released in photosynthesis comes from water, not CO₂. Auxin accumulating on the shaded side causes bending toward light, not away from it. Stomata close under drought via abscisic acid, which saves water but limits photosynthesis.
Rule of thumb
Ask "source or sink?" for any sugar-transport question, and "water potential gradient?" for any water-transport question.