Transport Systems in Plants

What Transport Systems in Plants covers

Transport Systems in Plants is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper. It covers the need for transport systems in plants, vascular tissue in roots, stems and leaves, water uptake and movement through the plant, transpiration and Its Measurement and translocation in the Phloem.

The 5 subtopics

Each one has its own page.

• The need for transport systems in plantsRecall questions on why large plants need transport systems, surface area to volume ratio and metabolic rate, why roots need sugars and leaves need water and mineral ions, what xylem and phloem carry, why mosses manage without vascular tissue, tall trees, support, and daily changes in water demand.Open →
• Vascular tissue in roots, stems and leavesRecall questions on xylem vessels and their lignin patterns, sieve tube elements and companion cells, the arrangement of vascular tissue in roots, stems and leaves of monocotyledonous and dicotyledonous crops, and preparing, staining with phloroglucinol and drawing plant sections.Open →
• Water uptake and movement through the plantRecall questions on root hair cells and water entry by osmosis, the apoplast, symplast and vacuolar pathways, the Casparian strip, root pressure, cohesion, adhesion and transpiration pull, the water potential gradient through the plant, and the evidence for the cohesion-tension theory.Open →
• Transpiration and Its MeasurementRecall questions on why transpiration is unavoidable, how light, temperature, humidity and air movement change its rate, what a potometer actually measures, and comparing shoots of different sizes.Open →
• Translocation in the PhloemRecall questions on sources and sinks, how sucrose is loaded at a source, what drives mass flow, why sucrose rather than glucose is carried, and the evidence from aphids.Open →

What you need to know

Answer each one before you reveal it.

Take Transport Systems in Plants further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Apoplast vs Symplast

  Apoplast: the route across the root cortex that runs through the cellulose cell walls and the spaces between them, crossing no membrane at all. Symplast: the route across the root cortex that runs through the cytoplasm, passing from one cell to the next through the plasmodesmata.

• Cohesion vs Adhesion

  Cohesion: the attraction of water molecules to one another by hydrogen bonds, which holds the column in the xylem together as one unbroken thread. Adhesion: the attraction of water molecules to the lignified walls of the xylem vessels, which helps support the column and draw it along.

• Root pressure vs Transpiration pull

  Root pressure: the push generated when ions are actively pumped into the xylem, lowering its water potential so that water follows by osmosis and forces the column upwards from below. Transpiration pull: the tension set up as water evaporates from the leaves, which draws the column upwards from above.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Explain why a large multicellular plant needs a transport system.

   Model answer

   Cells deep inside the plant are a long way from the soil and the air, and diffusion over such distances would be far too slow to supply them.

2. 2

   How does surface area to volume ratio relate to the need for transport in a plant?

   Model answer

   As a plant grows the surface area to volume ratio of the whole organism falls, so its exchange surfaces can no longer supply the interior by diffusion alone.

3. 3

   Name two parts of a plant that have a particularly high metabolic rate.

   Model answer

   The dividing meristem tissue at the root and shoot tips, and developing flowers, fruits and seeds.

4. 4

   Give one part of a plant with a low metabolic rate.

   Model answer

   The mature woody tissue of a stem, where much of the tissue is dead lignified xylem and little respiration occurs.

5. 5

   Explain why roots need substances to be transported to them.

   Model answer

   Roots are underground and contain no chloroplasts, so they cannot photosynthesise and must receive sugars made in the leaves.

6. 6

   Explain why leaves need substances to be transported to them.

   Model answer

   Water and mineral ions can only be absorbed from the soil by the roots, but they are needed in the leaves for photosynthesis and protein synthesis.

What is inside Levo

Six ways to work the same material.

Transport Systems in Plants revision questions

What does Transport Systems in Plants cover in OCR A-Level Biology B?

5 subtopics: the need for transport systems in plants, vascular tissue in roots, stems and leaves, water uptake and movement through the plant, transpiration and its measurement and translocation in the phloem. Each one has its own page with questions and model answers.

How is Transport Systems in Plants organised?

By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.