Plant Nutrition

6. Plant Nutrition — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 11 parts Lesson 1 of 4 Unit quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision

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Lesson summary

6. Plant Nutrition — IGCSE BIOLOGY notes: Explain photosynthesis, its products, limiting factors, leaf structure and mineral requirements, and describe the related practicals.Photosynthesis = the process by which plants manufacture carbohydrates from carbon dioxide and water usin…

Raw materials
Word equation
Balanced equation
Chlorophyll
Respiration
Amino acids

Part 1 of 9Photosynthesis and its equations

Photosynthesis

Photosynthesis the process by which plants manufacture carbohydrates from carbon dioxide and water using light energy absorbed by chlorophyll.

Raw materials

Raw materials carbon dioxide and water only; light is energy, not a substance.

Word equation

Word equation carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll.

Balanced equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Light energy is converted to chemical energy in the bonds of glucose;
- it is the reverse of aerobic respiration.

Chlorophyll

Chlorophyll a green pigment in chloroplasts that absorbs light energy and transfers it to chemical energy.
It reflects green light, so leaves look green; without chlorophyll there is no photosynthesis.

Part 2 of 9Uses of the products of photosynthesis

Respiration

Respiration glucose is used to release energy.

Starch

Starch insoluble, so it is an effective energy store in leaves, seeds and tubers.

Cellulose

Cellulose built into cell walls.

Sucrose

Sucrose transported in the phloem; sugars also form nectar to attract pollinating insects.

Lipids

Lipids made as an energy source in seeds.

Amino acids

Amino acids made when glucose is combined with nitrate and other mineral ions from the roots, then used for proteins.

Part 3 of 9Mineral ions in plants

Why they are needed

Why they are needed plants make proteins, lipids and DNA themselves and need elements such as nitrogen and magnesium to do so.
Chlorophyll contains magnesium and nitrogen.

Uptake

Uptake mineral ions are absorbed from the soil by active transport in root hair cells.

Mineral

Mineral any naturally occurring inorganic substance.

Part 4 of 9Testing a leaf for starch and investigating need for chlorophyll

Glucose cannot be tested for in the leaf because it is quickly converted or transported,
- so starch shows where photosynthesis has occurred.
  - (stored in chloroplasts)

Part 5 of 9Investigating need for light and carbon dioxide

Need for light

Need for light destarch the plant by keeping it in the dark for 24 hours.
Cover part of a leaf with aluminium foil and place the plant in light for a day, then test the leaf for starch.
The covered area stays orange-brown and the exposed area turns blue-black.

Need for carbon dioxide

Need for carbon dioxide destarch two plants and put each in a bell jar.
One jar contains sodium hydroxide, which absorbs carbon dioxide, and the control jar contains water.
After several hours in bright light the leaf with sodium hydroxide stays orange-brown and the control leaf turns blue-black.

Part 6 of 9Measuring the rate of photosynthesis

Place an aquatic plant such as Elodea (pondweed) in water in a beaker.

Count the bubbles of oxygen released from the cut end per minute,

or collect the gas in an inverted test tube, measuring cylinder or syringe and measure its volume.

Vary one factor only — move the lamp to different distances for light intensity, change the water temperature,

or dissolve different amounts of sodium hydrogencarbonate for carbon dioxide.

Keep every other variable constant, for example placing a glass tank between the lamp and beaker to absorb heat.

Part 7 of 9Limiting factors

Limiting factors

Limiting factor

Limiting factor something present in the environment in such short supply that it restricts a process.

Light intensity

Light intensity the rate rises as light increases until another factor becomes limiting.
On a graph the flat section means temperature or carbon dioxide is limiting.

Carbon dioxide concentration

Carbon dioxide concentration the rate rises with carbon dioxide until another factor limits.
On a graph the flat section means temperature or light is limiting.

Temperature

Temperature the rate rises as enzymes work faster, then falls at high temperature as enzymes denature.
This is why the graph peaks and then drops.

Water

Water necessary, but rarely limiting because the amount used is small compared with the amount transpired.

Graph reading

Graph reading on the rising section the limiting factor is the one on the x-axis;
- on the flat section it is a different factor.

Glasshouses

Glasshouses growers raise yield by adding light, heat and carbon dioxide, each useful only until another factor becomes limiting.

Part 8 of 9Leaf structure and adaptations

Structure	Adaptation and role
Wax cuticle	Waterproof layer that reduces water loss by evaporation
Upper epidermis	Thin and transparent, so light reaches the palisade layer
Palisade mesophyll	Column-shaped cells packed with chloroplasts to absorb as much light as possible
Spongy mesophyll	Large air spaces increase the surface area for gas exchange so carbon dioxide diffuses quickly
Lower epidermis with stomata and guard cells	Guard cells change shape to open or close stomata; stomata are usually open by day and closed at night and are the main site of water loss
Vascular bundle: xylem	Brings water and mineral ions to the mesophyll for photosynthesis and to replace water lost
Vascular bundle: phloem	Carries sucrose and amino acids away from the leaf

Part 9 of 9Gas exchange in plants

1In the light

In the light photosynthesis is faster than respiration in bright light, so there is a net intake of carbon dioxide and net output of oxygen.

2In the dark

In the dark plants respire but do not photosynthesise, so they take in oxygen and give out carbon dioxide.

3Respiration

Respiration plants respire all the time, day and night.

4Hydrogencarbonate indicator

Hydrogencarbonate indicator shows carbon dioxide concentration in solution because carbon dioxide is acidic.
Leaf in light turns the indicator purple (net carbon dioxide uptake);
- leaf in dark turns it yellow (net carbon dioxide release);
- a tube with no leaf is the red control.

Key terms

Term	Meaning
Photosynthesis	Making glucose from carbon dioxide and water using light energy absorbed by chlorophyll.
Chlorophyll	Green pigment in chloroplasts that absorbs light energy.
Limiting factor	The factor in shortest supply that restricts the rate of a process.
Stomata	Pores in the leaf epidermis for gas exchange.
Palisade mesophyll	Layer of tightly packed cells with many chloroplasts.
Chlorosis	Yellowing of leaves caused by lack of chlorophyll.
Destarching	Keeping a plant in the dark so that existing starch is used up.

Avoid these mistakes

Writing that plants take in oxygen for photosynthesis — they take in carbon dioxide and release oxygen.

Saying plants only respire at night — they respire all the time and photosynthesise in light.

Mixing up nitrate (for proteins) and magnesium (for chlorophyll).

Forgetting to remove chlorophyll before the iodine test — the colour change cannot be seen.

Listing light as a raw material — raw materials are carbon dioxide and water; light is energy.

Last updated: 13 October 2026