Process
OCR A-Level Biology H420
Cell Structure
Biological Molecules
Nucleotides and Nucleic Acids
Enzymes
Biological Membranes
Cell Division, Cell Diversity and Cellular Organisation
Exchange Surfaces
Transport in Animals
Transport in Plants
Communicable Diseases, Disease Prevention and the Immune System
Biodiversity
Classification and Evolution
Communication and Homeostasis
Excretion as an Example of Homeostatic Control
Neuronal Communication
Hormonal Communication
Plant and Animal Responses
Topic overviewTropisms and plant responses to stress and herbivoryPlant hormones and their commercial usesThe nervous system and the brainReflex actions and the knee jerk reflexFight or flight and the control of heart rateThe structure of skeletal muscleThe neuromuscular junction and the sliding filament model
Photosynthesis
Respiration
Cellular Control
Patterns of Inheritance
Manipulating Genomes
Cloning and Biotechnology
Topic overviewNatural plant cloning and taking cuttingsMicropropagationAdvantages and disadvantages of plant cloningAnimal cloning: embryo twinning and nuclear transferAdvantages and disadvantages of animal cloningMicroorganisms in food productionAseptic techniqueFermentation and its conditionsThe microbial growth curveImmobilised enzymes
Ecosystems
Populations and Sustainability
Practical Skills and Mathematical Requirements
Transport in Plants
- 5 subtopics
- 8 things to know
- Components 01 and 03
What Transport in Plants covers
Transport in plants closes Module 3. It covers xylem and phloem and how they are arranged in root, stem and leaf, transpiration and the potometer, the pathways water takes from soil to leaf, the adaptations of xerophytes and hydrophytes, and translocation from source to sink.
Where it is assessed
Components 01 and 03
Module 3 is examined on Biological Processes, then the unified paper.
Check the OCR specification ↗The 5 subtopics
Each one has its own page.
- Xylem, phloem and vascular tissueXylem vessels and lignin, sieve tube elements, sieve plates and companion cells, and how the two tissues are arranged in root, stem and leaf.Open →
- Transpiration and the potometerWhy transpiration follows from gas exchange, how light, temperature, humidity and wind change the rate, and what a potometer actually measures.Open →
- Water uptake and movement up the xylemThe apoplast and symplast pathways, the Casparian strip, and how cohesion, adhesion and the transpiration stream pull water to the leaf.Open →
- Xerophytes and hydrophytesThe adaptations that cut water loss in cacti and marram grass, and the air spaces, surface stomata and reduced xylem of a water lily.Open →
- TranslocationSource and sink, the active loading of sucrose into companion cells and sieve tubes, and the water potential gradient that drives mass flow.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
Explain translocation from source to sink.
Key term
How do xerophytes reduce water loss?
Evaluation
What is the key limitation of a potometer?
Key term
What is adhesion and what role does it play in xylem transport?
Key term
What are companion cells and why are they important for phloem function?
Process
Define the apoplast pathway.
Process
Define the symplast pathway.
Take Transport in Plants further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Transpiration vs Translocation
Transpiration: loss of water vapour from aerial plant surfaces. Translocation: transport of assimilates through phloem from sources to sinks.
Questions from this topic
Each one with the model answer underneath.
- 1
Why do multicellular plants require specialised transport systems?
Model answer
Their large size means diffusion distances are too great for efficient exchange between cells and the external environment.
- 2
What happens to the surface area to volume ratio as organisms increase in size, and why does this matter for transport?
Model answer
The surface area to volume ratio decreases, making simple diffusion insufficient to meet metabolic demands.
- 3
Why do plants with higher metabolic rates require more developed transport systems?
Model answer
They have greater demands for nutrient supply and waste removal, necessitating specialised transport systems.
- 4
What are xylem vessels and what do they transport?
Model answer
Xylem vessels are dead, hollow, lignified cells that transport water and dissolved mineral ions from roots to leaves.
- 5
What two functions does lignin serve in xylem vessel walls?
Model answer
Lignin provides mechanical strength and waterproofs the vessels, preventing water loss to surrounding cells.
- 6
Why can water flow uninterrupted through xylem vessels?
Model answer
Xylem vessels have no end walls between adjacent cells, forming continuous tubes.
What is inside Levo
Six ways to work the same material.
Transport in Plants revision questions
- What does Transport in Plants cover in OCR A-Level Biology?
- 5 subtopics: xylem, phloem and vascular tissue, transpiration and the potometer, water uptake and movement up the xylem, xerophytes and hydrophytes and translocation. Each one has its own page with questions and model answers.
- How is Transport in Plants organised?
- By the OCR H420 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Transport in Plants, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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