Extended
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Flashcards · 0610 · Topic 6
Plant nutrition flashcards
15 cards on Topic 6, subtopics 6.1 to 6.2. Pick a subtopic or study them all.
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6.1 Photosynthesis
- Photosynthesis
- The process by which plants synthesise carbohydrates from raw materials using energy from light.
- Word equation for photosynthesis
- carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll.
- Chlorophyll: where it is and what it does
- A green pigment in chloroplasts. It transfers energy from light into energy in chemicals, for the synthesis of carbohydrates.
- Uses of the carbohydrates made in photosynthesis
- Starch: energy store. Cellulose: cell walls. Glucose: respiration. Sucrose: transport in the phloem. Nectar: attracts insects for pollination.
- Why plants need nitrate ions and magnesium ions
- Nitrate: to make amino acids (then proteins); lack gives poor growth. Magnesium: to make chlorophyll; lack gives yellow leaves.
- Steps in testing a leaf for starch
- Destarch the plant (dark, about 2 days). After the experiment: boil the leaf in water, warm it in ethanol in a hot water bath (removes chlorophyll), rinse in warm water, add iodine on a white tile: blue-black = starch.
- Hydrogencarbonate indicator colours
- Purple: less CO₂ than air (bright light, photosynthesis faster than respiration). Orange-red: same as air. Yellow: more CO₂ than air (dark, respiration only).
- Balanced equation for photosynthesisExtended
- 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- Limiting factorExtended
- The factor in shortest supply, which stops the rate increasing. Raising it raises the rate; raising another factor does not. Light intensity, carbon dioxide concentration and temperature can all be limiting.
- On the flat part of a rate vs light intensity graph, what is limiting?Extended
- Not light intensity. Another factor, such as carbon dioxide concentration or temperature, is limiting.
6.2 Leaf structure
- Palisade mesophyll: position and adaptation
- Near the upper surface; tall, closely packed cells with many chloroplasts, so they absorb most of the light.
- Spongy mesophyll and air spaces
- Loosely packed cells with air spaces between them, so carbon dioxide can diffuse to the cells and oxygen out, over a large internal surface.
- Cuticle and upper epidermis
- The waxy cuticle reduces water loss and is transparent. The upper epidermis is transparent with no chloroplasts, so light passes through.
- Stomata and guard cells
- Stomata (mostly in the lower epidermis) let carbon dioxide in and oxygen out. Guard cells open and close them.
- Xylem and phloem in a leaf vein
- Xylem (upper side of the bundle) brings water and mineral ions. Phloem (lower side) carries sucrose away.