Topic 3 of 8 · Form 3
Plant nutrition and transport in plants
carbon dioxide + water → (light, chlorophyll) → glucose + oxygen; 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Notes for this topic 1 file, in order
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Photosynthesis
carbon dioxide + water → (light, chlorophyll) → glucose + oxygen; 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Limiting factors: light intensity, carbon dioxide concentration and temperature. Uses of glucose: respiration, starch storage, cellulose, sucrose for transport, amino acids (with nitrate ions).
Leaf structure
Waxy cuticle, upper epidermis, palisade mesophyll (many chloroplasts), spongy mesophyll (air spaces), stomata and guard cells, vascular bundles (xylem and phloem).
Mineral ions
Nitrate ions for amino acids; magnesium ions for chlorophyll; deficiency symptoms.
Transport in plants
- Xylem: water and mineral ions from roots to leaves; dead, lignified cells.
- Phloem: translocation of sucrose and amino acids from sources to sinks.
- Water uptake by root hair cells (osmosis), movement through the root, and up the xylem by the transpiration pull.
- Transpiration: loss of water vapour from leaves; increased by higher temperature, light, wind and lower humidity; measured with a potometer. Wilting occurs when water loss exceeds uptake.
Check yourself
- Why are leaves destarched before photosynthesis experiments?
- What does phloem transport?
- Give two factors that increase transpiration.
Show answers
- So that any starch found must have been made during the experiment.
- Sucrose and amino acids.
- Any two: higher temperature, higher light intensity, more wind, lower humidity.
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