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Nitrate deficiency causes stunted growth in plants, while magnesium deficiency causes chlorosis, the yellowing of leaves. Free notes and 10 questions answered.
Mineral Deficiencies in Plants is part of Plant disease (biology only) in GCSE AQA Higher Biology.
3 min
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GCSE AQA Higher
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Nitrate deficiency causes stunted growth in plants, while magnesium deficiency causes chlorosis, the yellowing of leaves. Free notes and 10 questions answered.
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Use this lesson to stay inside Plant disease (biology only) while connecting the detail back to the wider Infection and response topic.
Read the core explanations from Mineral Deficiencies in Plants before testing yourself from memory.
You've seen plants with yellow leaves or stunted growth. What's going wrong? Plants need more than water and sunlight - they need specific mineral ions to stay healthy. Without the right minerals, plants develop deficiency diseases that are more straightforward with practice to spot once you know what to look for.
Two key minerals cause the most obvious problems when missing: nitrates and magnesium. Each has a specific job, and when plants can't get enough, they show clear symptoms that gardeners and farmers recognise immediately.
Plants use nitrate ions to build proteins. Think of proteins as the building blocks - they make new cells, enzymes, and all the structures a plant needs to grow. Without enough nitrates, protein synthesis slows down dramatically.
The result? Stunted growth. The plant stays small because it can't make enough proteins to build new tissues. You'll see this as plants that look healthy but remain much smaller than they should be for their age.
Trap: Many students think nitrate deficiency makes leaves yellow. Actually, nitrate deficiency causes stunted growth - the yellowing comes from a different mineral problem.
Magnesium ions sit right at the centre of every chlorophyll molecule. Without magnesium, plants can't make chlorophyll - the green pigment that captures light energy for photosynthesis.
When magnesium runs low, chlorophyll production drops. The green colour fades from the leaves, leaving them yellow. This yellowing is called chlorosis, and it's the classic sign of magnesium deficiency.
Here's the key point: chlorosis affects photosynthesis. Less chlorophyll means less light energy captured, so the plant struggles to make glucose. Growth slows down, but the main symptom you'll see is the distinctive yellow leaves.
Both deficiencies harm plants, but in different ways. Nitrate deficiency hits growth directly - plants stay small but keep their green colour. Magnesium deficiency hits photosynthesis - leaves turn yellow but the plant might maintain normal size initially.
Worked example: Diagnosing Plant Mineral Deficiencies
A gardener has two unhealthy plants. Plant A is much smaller than normal but has green leaves. Plant B is normal size but has yellow leaves. Identify the likely deficiency in each case.
Answer: Plant A: Nitrate deficiency (stunted growth). Plant B: Magnesium deficiency (chlorosis).
The table below summarises the key differences:
Nitrate deficiency: Stunted growth, green leaves, reduced protein synthesisMagnesium deficiency: Yellow leaves (chlorosis), normal initial size, reduced photosynthesis
Examiners test mineral deficiencies through describe and explain questions. The key is linking the ion to its function, then to the visible symptom.
Exam depth extension: In mineral deficiencies in plants, connect why plants need minerals to nitrate deficiency - the growth problem using clear cause-and-effect statements. When you explain biological processes, include what changes, why it changes, and the consequence for cells, organisms, or populations. If calculations appear, show each step, include units, and end with a sentence that interprets the result in biological context.
Command word focus: 'Explain' questions want the mechanism. Don't just state that nitrate deficiency causes stunted growth - explain that nitrates are needed for protein synthesis, proteins are needed for new tissue growth, so without nitrates the plant cannot grow properly.
Watch out for questions that mix up the symptoms. Remember: small green plants need nitrates, yellow normal-sized plants need magnesium. This distinction wins marks in comparison questions.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-20.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Magnesium deficiency causes chlorosis, the yellowing of leaves. Magnesium ions sit at the centre of every chlorophyll molecule, so without magnesium plants cannot make chlorophyll, the green colour fades, and less light energy is captured for photosynthesis.
Nitrate deficiency causes stunted growth in plants. Plants use nitrate ions to make proteins, which build new cells, enzymes and structures, so without enough nitrates protein synthesis slows and the plant stays small, although its leaves stay green.
Chlorosis is the yellowing of plant leaves caused by insufficient chlorophyll production, most commonly due to magnesium deficiency. Less chlorophyll means less light energy captured, so the plant struggles to make glucose for growth.
Plants need nitrate ions (NO₃⁻), absorbed through their roots, to make proteins for growth. Proteins are needed for new tissue growth, so without nitrates the plant cannot grow properly.
Magnesium deficiency causes yellow leaves because magnesium ions sit at the centre of every chlorophyll molecule, so without magnesium plants cannot make chlorophyll. The green colour fades, leaving yellow leaves, which is called chlorosis.
Plants need mineral ions as well as water and sunlight, including nitrate ions to make proteins for growth and magnesium ions to make chlorophyll. Without them, plants develop deficiency diseases with clear symptoms.
A plant that is much smaller than normal but has green leaves likely has nitrate deficiency (stunted growth), while a normal-sized plant with yellow leaves likely has magnesium deficiency (chlorosis). Small green plants need nitrates; yellow normal-sized plants need magnesium.
Nitrate deficiency causes stunted growth because plants use nitrate ions to make proteins, which are needed to build new cells, enzymes and tissues. Without enough nitrates, protein synthesis slows down, so the plant stays small.
Nitrate deficiency causes stunted growth rather than yellow leaves; plants stay small but keep their green colour. The yellowing, called chlorosis, comes from a different mineral problem: magnesium deficiency.
Chlorosis reduces photosynthesis because less chlorophyll means less light energy is captured, so the plant struggles to make glucose. Growth then slows down, but the main visible symptom is the yellow leaves.