2.1 Nutrition

• Types of nutrition in plants
• Structure of the chloroplast and its function
• The light stage of photosynthesis
• The dark stage of photosynthesis
• Significance of photosynthesis in nature

• describe types of nutrition in plants
• relate the structure of the chloroplast to its function in plant cells
• illustrate the light and dark stages of photosynthesis in plants
• appreciate the significance of photosynthesis in nature

“Where does the mass of a tree actually come from?”

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1. How plants feed
   40 min · 2 practice tasks · quiz
   Making food from air and water, and the structure that does it.
2. The light and dark stages
   40 min · 2 practice tasks · quiz
   What happens in each stage, and why photosynthesis matters beyond the plant.
3. Leaf structure for photosynthesis
   40 min · 1 practice tasks · quiz
   The leaf is the organ of photosynthesis: lamina, epidermis, palisade, spongy mesophyll, stomata and veins.
4. How the leaf is adapted
   40 min · 1 practice tasks · quiz
   Each leaf feature - thin blade, palisade packing, air spaces, stomata, veins - is a solution to a photosynthetic problem.
5. Destarching and the starch test
   40 min · 1 practice tasks · quiz
   Remove existing starch, then use iodine to show whether a leaf has photosynthesised.
6. Showing that light is necessary
   40 min · 1 practice tasks · quiz
   A destarched leaf, partly covered, then tested for starch: only the uncovered parts go blue-black.
7. Showing that chlorophyll and carbon dioxide are necessary
   40 min · 1 practice tasks · quiz
   A variegated leaf tests chlorophyll. A destarched plant with soda lime tests carbon dioxide.
8. Limiting factors of photosynthesis
   40 min · 1 practice tasks · quiz
   The rate is held down by whichever factor - light, carbon dioxide or temperature - is in shortest supply.
9. Light intensity and pondweed
   40 min · 1 practice tasks · quiz
   Count oxygen bubbles from pondweed at different lamp distances to plot rate against light intensity.
10. Temperature, carbon dioxide and the compensation point
    40 min · 1 practice tasks · quiz
    Dark-stage enzymes set the temperature curve. Extra carbon dioxide raises the plateau. The compensation point is where photosynthesis equals respiration.
11. Mineral nutrition in plants
    40 min · 1 practice tasks · quiz
    Photosynthesis makes carbohydrate. Nitrogen, phosphorus, potassium, magnesium and other ions turn that carbohydrate into chlorophyll, proteins, ATP and structure.
12. Kenyan crops, minerals and photosynthesis
    40 min · 1 practice tasks · quiz
    Apply light, carbon dioxide, temperature and mineral ions to maize, tea, greenhouse crops and beans, and return to why photosynthesis matters.