K224 / K225 / 2027

Nutrition and transport in flowering plants

Try it without your notes

Choose an answer or explain your thinking. Then check what you understand.

Quick checks

0 answered / 0 correct. Your first try counts; you can try again any time.

Check your understanding

Which route correctly describes carbon dioxide entering a photosynthesising leaf?

  1. Cuticle -> sieve tube -> nucleus only
  2. Root hair -> xylem -> phloem -> mesophyll cell -> chloroplast in the leaf
  3. Stoma -> air space -> moist mesophyll cell wall -> cell -> chloroplast
Show the answer

Stoma -> air space -> moist mesophyll cell wall -> cell -> chloroplast

Carbon dioxide diffuses down its concentration gradient and dissolves at the moist cell surface before entering cells.

Check your understanding

Which identifies a typical herbaceous dicot stem bundle correctly?

  1. Phloem lies nearer the centre and carries water upwards.
  2. Xylem is on the inner side and phloem on the outer side.
  3. The bundles join in the centre to form a single tube.
Show the answer

Xylem is on the inner side and phloem on the outer side.

Name both the position within a bundle and the different transported materials.

Check your understanding

Which chain correctly explains a root-hair adaptation?

  1. Long extension -> more surface contacting soil water -> greater uptake capacity.
  2. More chloroplasts -> soil glucose absorbed by photosynthesis.
  3. Thicker cell wall -> longer entry route -> always faster uptake.
Show the answer

Long extension -> more surface contacting soil water -> greater uptake capacity.

This connects structure, immediate effect and absorption function.

Check your understanding

Which statement correctly follows photosynthesis into a food chain?

  1. Plants store absorbed light energy as chemical energy in organic food, which consumers can obtain.
  2. Mineral ions are the glucose molecules taken up from soil.
  3. Plants create new energy from sunlight, and consumers create more energy when they digest the plants.
Show the answer

Plants store absorbed light energy as chemical energy in organic food, which consumers can obtain.

Photosynthetic producers supply organic matter and chemical energy to most food chains.

Check your understanding

Why is oxygen volume usually a better measure than bubble count?

  1. Every bubble always contains a different gas.
  2. Bubbles can differ in size, so equal counts need not represent equal gas volumes.
  3. Measuring volume removes the need to time the experiment, so fewer readings can go wrong.
Show the answer

Bubbles can differ in size, so equal counts need not represent equal gas volumes.

Measuring volume accounts for size differences, although other practical limitations remain.

Check your understanding

Hydrogencarbonate indicator is red at normal carbon dioxide levels, yellow when carbon dioxide is higher and purple when it is lower. A leaf in bright light turns the indicator purple. Why?

  1. Light shining on the tube turns the indicator purple whatever the leaf does
  2. Photosynthesis takes in carbon dioxide faster than respiration releases it
  3. Respiration releases carbon dioxide faster than photosynthesis uses it
  4. The leaf has stopped respiring because light is shining on it
Show the answer

Photosynthesis takes in carbon dioxide faster than respiration releases it

In bright light the net uptake of carbon dioxide lowers its level, so the indicator turns purple.

Check your understanding

A light-response graph reaches a positive plateau. What can be concluded from that graph alone?

  1. Carbon dioxide is now the limiting factor, because light can no longer be limiting.
  2. Photosynthesis has completely stopped.
  3. More light is not increasing the rate there; another factor may be limiting.
Show the answer

More light is not increasing the rate there; another factor may be limiting.

More evidence is needed to identify which other factor limits the rate.

Check your understanding

Invented data: at 0.01% carbon dioxide, the rate of photosynthesis stops rising above light intensity 3 units. At 0.04%, it rises until 6 units. What limits the rate at 0.01% above 3 units?

  1. Carbon dioxide concentration
  2. Water lost by transpiration
  3. Light intensity
  4. The amount of chlorophyll
Show the answer

Carbon dioxide concentration

Raising carbon dioxide raised the plateau, so carbon dioxide was limiting at 0.01%.

Check your understanding

A leaf in a sealed tube of hydrogencarbonate indicator is kept in dim light. After an hour the indicator is still red, the same as a control tube without a leaf. What is the best explanation?

  1. The leaf has stopped both photosynthesis and respiration in dim light.
  2. The leaf is respiring but not photosynthesising.
  3. The leaf is photosynthesising faster than it respires.
  4. The rate of photosynthesis equals the rate of respiration.
Show the answer

The rate of photosynthesis equals the rate of respiration.

This is the compensation point: carbon dioxide used equals carbon dioxide released, so there is no net change.

Check your understanding

Which sequence correctly describes the final stages of transpiration?

  1. Water evaporates from mesophyll surfaces, then vapour diffuses through stomata.
  2. Water vapour enters phloem and turns into sucrose.
  3. Guard cells pump liquid water out through the open stomata, using energy from ATP.
Show the answer

Water evaporates from mesophyll surfaces, then vapour diffuses through stomata.

Keep the change of state and the subsequent movement through the pore as separate steps.

Check your understanding

Why does higher humidity usually reduce transpiration when other conditions are held constant?

  1. The water-vapour concentration difference between leaf air spaces and the outside air is smaller.
  2. The leaf loses all its stomata.
  3. Water vapour in humid air enters the leaf and refills the xylem, so less water needs to be drawn up.
Show the answer

The water-vapour concentration difference between leaf air spaces and the outside air is smaller.

A smaller gradient reduces outward diffusion of water vapour.

Check your understanding

In a potometer the air bubble moves 36 mm in 4 minutes. What is the rate of water uptake?

  1. 144 mm per minute
  2. 0.11 mm per minute
  3. 36 mm per minute
  4. 9 mm per minute
Show the answer

9 mm per minute

Rate = distance / time = 36 / 4 = 9 mm per minute.

Check your understanding

The largest bubble distance in a table is 45 mm and the grid has 10 large squares up the y-axis. Which y-axis scale is best?

  1. 7 mm per large square, so the axis reaches 70 mm.
  2. 5 mm per large square, so the axis reaches 50 mm.
  3. 20 mm per large square, so the axis reaches 200 mm.
  4. 1 mm per large square, so the axis reaches 10 mm.
Show the answer

5 mm per large square, so the axis reaches 50 mm.

It is an even step, it reaches 45 mm and the points fill most of the grid.

Check your understanding

Which chain best explains wilting?

  1. Loss exceeds uptake -> cells lose water -> turgor falls -> soft tissues droop.
  2. Stomata close at night, which stops respiration and so the cells stop taking up water.
  3. Water enters cells -> turgor rises -> all tissues become flaccid.
Show the answer

Loss exceeds uptake -> cells lose water -> turgor falls -> soft tissues droop.

This links the whole-plant imbalance to the cell-level mechanism and visible effect.

Check your understanding

Which correctly defines translocation?

  1. Transport of only mineral ions through xylem.
  2. Loss of water vapour through stomata.
  3. Transport of food, mainly sucrose, in phloem.
Show the answer

Transport of food, mainly sucrose, in phloem.

Include both the transported material and the tissue.

Explain your thinking

Write a short answer, then compare it with a sample and check for missing ideas.

Question 1 of 15

Follow water from soil to xylem

4 marks

Describe and explain how water moves from the soil into a root hair cell and then to the xylem in the centre of the root. Give one feature of the root hair cell that increases water uptake. [4]

Name the process, the gradient and every tissue on the route.

Loading saved work...

0 / 6000
Ctrl / Cmd + Enter

Use the checklist to compare your answer. This is a self-check, not an exam mark.

Keep one idea for tomorrow

Try a question again without looking at the answer. If you get stuck, revisit its lesson.

Open the chapter summary