BIOLOGY · Stage 9 · Chapter 9: Plants and Photosynthesis
Biology 9.9 Chapter 9 Review: Plants and Photosynthesis
5 min read 5 parts Lesson 9 of 9
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
Section 1 of 5Plant structure and photosynthesis
- Organs
- roots absorb water and minerals, stems support and transport, leaves photosynthesise and flowers reproduce.
- Photosynthesis
- carbon dioxide and water form glucose and oxygen using light absorbed by chlorophyll in chloroplasts.
- Equation: 6CO2 + 6H2O → C6H12O6 + 6O2.
- Reactants entering
- carbon dioxide diffuses in through the stomata and water is carried to the leaf in the xylem.
- Leaves
- they are thin and broad and contain palisade cells, air spaces and stomata.
- 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.
Section 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
- always include a control and keep other variables constant.
Section 3 of 5Minerals and fertilisers
- Nitrate
- it is needed for amino acids and proteins.
- Magnesium
- it is needed for chlorophyll, so plants lacking it grow slowly and have yellow leaves.
- Phosphate
- it is needed for DNA and membranes.
- Potassium
- it is needed for enzymes.
- Deficiency
- it causes stunted growth or yellow leaves.
- NPK fertilisers
- they raise yields, but run-off causes eutrophication.
- Algal bloom blocks light and plants die.
- Decay by bacteria then depletes oxygen.
Section 4 of 5Transport in plants
- 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
- it increases with temperature, light and wind, and decreases with humidity.
- Phloem
- it carries sucrose and amino acids by translocation from sources to sinks and needs energy.
- Aphids
- they feed on phloem sap.
| Tissue | Carries | Direction |
|---|---|---|
| Xylem | Water, minerals | Up |
| Phloem | Sugars, amino acids | Up and down |
Section 5 of 5Using key terms correctly
- Water enters roots by osmosis, while minerals enter by active transport.
- 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.
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