GCSE · Biology · AQA · Spec 8461

Plant ion deficiencies (biology only)

One plant is small and weedy. Another's leaves are fading to yellow. Each symptom is a clue to what's missing, and you're about to learn to read it.

Be the plant doctor

What is this plant short of?

Pick a patient, then decide which ion it's short of. Use the job under each heading to reason it out.

Still to sort

Short of nitrate (0)

Nitrate ions are needed for protein synthesis, and so for growth.

Where the line is: Think growth. A plant that hasn't grown as it should points here.

Short of magnesium (0)

Magnesium ions are needed to make chlorophyll, the green pigment.

Where the line is: Think colour. Leaves losing their green point here.

6 of 6 still to sort.

A deficiency is simply a shortage: the plant isn't getting enough of an ion it needs. Work out which job has failed, match it to the ion that job needs, and you've found what's missing.

The nitrate chain

?

Reason it through

Why does a plant that's short of nitrate end up stunted?

Link 1 of 4

First link · your turn

A plant takes in nitrate ions. What does it need them for?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Predict, then check

You know one fact: magnesium ions are needed to make chlorophyll, the pigment that makes leaves green.

So what will the leaves of a plant that's short of magnesium look like?

Your turn to write it

Diagnose the tomato plants

A gardener notices that the leaves of some tomato plants are turning yellow, although the plants have grown to a normal height. Suggest which ion the plants are most likely short of, and explain how this shortage causes the symptom. [3 marks]

0 words · your answer stays on this page and is not sent anywhere.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Two missing ions, two tell-tale symptoms, and how to work out which is which

What you need to know

  • A deficiency is a shortage: the plant isn't getting enough of an ion it needs, and that can damage it.
  • Nitrate ions are needed for protein synthesis, and therefore for growth.
  • Magnesium ions are needed to make chlorophyll, the green pigment in leaves.
  • Nitrate deficiency causes stunted growth. Magnesium deficiency causes chlorosis: yellowing leaves.

The big picture

Plants can be damaged when they're short of an ion they need: an ion deficiency. Nitrate ions are needed for protein synthesis and therefore for growth, so a plant short of nitrate shows stunted growth. Magnesium ions are needed to make chlorophyll, so a plant short of magnesium shows chlorosis, a yellowing of the leaves.

Key points

1Start from the sick plant: read the symptom, ask which job has failed, and the missing ion follows.
2Too little nitrate means too little protein synthesis, so the plant can't grow properly and is stunted.
3Too little magnesium means too little chlorophyll, so the leaves lose their green and turn yellow (chlorosis).
4The ions come in from the soil. Protein and chlorophyll are made by the plant itself, using those ions.
5Stunted growth and chlorosis are symptoms, the things you can see. The ion deficiency is the cause.

Worked example

Problem

A farmer notices that the wheat in one field is much shorter and smaller than the wheat in the next field. Suggest which ion the wheat is most likely short of, and explain how this causes the symptom.

⚠ Watch out

Crossing the wires: linking magnesium to growth, or nitrate to leaf colour. Don't lean on memorised labels. Reason from the job: protein synthesis needs nitrate, so nitrate is about growth; chlorophyll needs magnesium, so magnesium is about green.

🧠

Memory hook

Nitrate: Not growing. Magnesium: Missing green. Then say the reason: nitrate for protein, so growth; magnesium for chlorophyll, so green.

✓

Check yourself

Cover the page. A plant's leaves are turning yellow: name the symptom, the missing ion and that ion's job. Now do the same for a plant that's far too small.

Flashcards

(9)
What does it mean when a plant has an ion deficiency?
It isn't getting enough of an ion it needs, and this can damage the plant.
What are magnesium ions needed for in a plant?
Making chlorophyll.
Which symptom does nitrate deficiency cause?
Stunted growth.
What is chlorosis?
Yellowing of the leaves.
Which ion deficiency causes chlorosis?
Magnesium deficiency.
Why do the leaves of a magnesium-deficient plant turn yellow?
It can't make enough chlorophyll, the pigment that makes leaves green, so the green fades.
Why is a nitrate-deficient plant stunted?
Without enough nitrate it can't carry out enough protein synthesis, and growth depends on that.
Does a plant take in chlorophyll from the soil?
No. The plant makes its own chlorophyll; magnesium ions are what it needs in order to make it.
What does stunted growth look like?
A plant that is smaller than it should be: still alive, but it hasn't grown properly.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

Learning with Lightbulb is opening soon

You can use this lesson now. Join the waitlist and we'll let you know when the full Lightbulb experience is ready.

Keep me posted

More AQA GCSE Biology topics

See the full AQA Biology curriculum →

How this lesson was checked. This AQA GCSE Biology (specification 8461)lesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 29 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.