IGCSE›Oxford AQA IGCSE Biology›Mind mapsExchange and transport in plantsOxford AQA IGCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsXylemCarries water and minerals upwardsCells dead, hollow tubesWalls thickened with ligninFlow is one way onlyPhloemCarries sucrose and amino acidsSieve tubes are living cellsCompanion cells have many mitochondriaFlows both directionsTranspiration streamWater evaporates from mesophyll, leaves via stomataWater molecules cohesive, form a columnTension pulls water up the xylemPassive once water is in the xylemPlant transportxylem, phloem, waterRate factorsHigher temperature, fasterLow humidity, steeper gradient, fasterMore wind, fasterMore light, stomata open widerTranslocationSource makes sugars, sink uses themActive loading uses ATPWater enters by osmosis, builds pressureMass flow pushes sugars to the sinkExam tipsHigh humidity means slow transpirationExplain the water potential gradientXylem dead so water can flow through