9.9Chapter 9: Plants and Photosynthesis

Chapter 9 Review: Plants and Photosynthesis — Alhussan Biology - Stage 9 Revision Notes & Topical Questions

5 min read 7 parts Lesson 9 of 9 1 quiz

📚 Alhussan Biology - Stage 9 Hub / Topical Revision

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Lesson summary

9.9 Chapter 9 Review: Plants and Photosynthesis — Alhussan International Academy — Biology (Stages 7–9) notes: Revise plant organs, photosynthesis and its evidence, mineral requirements, fertilisers and transport in plants.Organs — roots absorb water and minerals, stems support a…

Reactants entering
Fair tests
Deficiency
NPK fertilisers
Water uptake
Rate of transpiration

Part 1 of 5Plant structure and photosynthesis

Plant structure and photosynthesis

Organs

Organs roots absorb water and minerals, stems support and transport, leaves photosynthesise and flowers reproduce.

Photosynthesis

Photosynthesis carbon dioxide and water form glucose and oxygen using light absorbed by chlorophyll in chloroplasts.
Equation6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Reactants entering

Reactants entering carbon dioxide diffuses in through the stomata and water is carried to the leaf in the xylem.

Leaves

Leaves they are thin and broad and contain palisade cells, air spaces and stomata.

Glucose

Glucose it is used in respiration, stored as starch or converted to cellulose, amino acids and lipids.
Surplus oxygen leaves through the stomata or is used in respiration.

Part 2 of 5Evidence and investigations

Oxygen bubbles from pondweed measure the rate, which rises with light, carbon dioxide and temperature until another factor limits it.

Starch tests with iodine on de-starched leaves show that light, chlorophyll and carbon dioxide are needed.

Fair tests

Fair tests always include a control and keep other variables constant.

Part 3 of 5Minerals and fertilisers

Nitrate

Nitrate it is needed for amino acids and proteins.

Magnesium

Magnesium it is needed for chlorophyll, so plants lacking it grow slowly and have yellow leaves.

Phosphate

Phosphate it is needed for DNA and membranes.

Potassium

Potassium it is needed for enzymes.

Deficiency

Deficiency it causes stunted growth or yellow leaves.

NPK fertilisers

NPK fertilisers they raise yields, but run-off causes eutrophication.
Algal bloom blocks light and plants die.
Decay by bacteria then depletes oxygen.

Part 4 of 5Transport in plants

Water uptake

Water uptake water enters root hairs by osmosis and rises in the xylem in the transpiration stream, driven by evaporation from leaves.

Rate of transpiration

Rate of transpiration it increases with temperature, light and wind, and decreases with humidity.

Phloem

Phloem it carries sucrose and amino acids by translocation from sources to sinks and needs energy.

Aphids

Aphids they feed on phloem sap.

Tissue	Carries	Direction
Xylem	Water, minerals	Up
Phloem	Sugars, amino acids	Up and down

Part 5 of 5Using key terms correctly

Water enters roots by osmosis, while minerals enter by active transport.

Limiting factor graphs

Limiting factor graphs the rate rises while that factor is limiting and plateaus when another factor limits.

Experiments need independent, dependent and control variables identified.

Key terms

Term	Meaning
Photosynthesis	Making glucose from carbon dioxide and water using light.
Transpiration	Loss of water vapour from leaves.
Xylem	Tissue that carries water and minerals up the plant.
Phloem	Tissue that carries sugars around the plant.
Eutrophication	Excess nutrients causing algal growth and oxygen loss in water.
Limiting factor	The factor in shortest supply that sets the rate.

Avoid these mistakes

Mixing osmosis and active transport in roots.

Forgetting oxygen is a product.

Saying fertilisers cause algae to die directly.

Mixing up the roles of xylem and phloem.

Last updated: 18 October 2026