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Photosynthesis

Photosynthesis. Describe, using a word equation, how plants make their own food through photosynthesis. “photosynthesis”. “photo” means light… “synthesis” means to make … …so what do you think the word photosynthesis could mean?. oxygen. Carbon dioxide. glucose. water.

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Photosynthesis

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  1. Photosynthesis Describe, using a word equation, how plants make their own food through photosynthesis

  2. “photosynthesis” “photo” means light… “synthesis” means to make… …so what do you think the word photosynthesis could mean?

  3. oxygen Carbon dioxide glucose water how plants make their food Energy from sunlight, with chlorophyll as a catalyst, is used to combine CO2 and H2O to form glucose and release O2 chlorophyll

  4. Photosynthesis word equation Watch the animation again… Can you write what is happening as a word equation?

  5. oxygen chlorophyll Carbon dioxide glucose water

  6. Photosynthesis word equation Carbon dioxide plus water, with light and chlorophyll, gives glucose and oxygen

  7. Sugar is transported to all other parts of the plant

  8. Experiment To show that starch is made by a plant in photosynthesis

  9. MethodTo show that starch is made by a plant in photosynthesis • Leave a pot plant in the dark for two days. • To destarch the leaves, i.e. the starch moves out of the leaves.

  10. Aluminium foil Light Place tinfoil over some of the leaves of the plant. • To prevent light reaching the leaves and, therefore, to prevent photosynthesis. These leaves act as a control or comparison in the experiment.

  11. Aluminium foil Light Leave the plant in strong light for a few hours. • To allow photosynthesis to take place.

  12. Aluminium foil Light Test some of the covered and uncovered leaves for starch. • To show whether or not photosynthesis took place.

  13. Experiment To test leaves for starch

  14. Leaves Water Tripod Bunsen burner MethodTo test leaves for starch • Boil the leaves in water for a few minutes. This kills and softens the leaves.

  15. Boiling water Alcohol Leaves Method cont.To test leaves for starch • Soak the leaves in hot alcohol for ten minutes. This removes the chlorophyll from the leaves. Removing the green colour allows any later colour changes to be seen.

  16. Leaves Water Method cont.To test leaves for starch • Rinse the leaves briefly in boiling water. Alcohol makes the leaves stiff and brittle. Rinsing off the alcohol will soften the leaves.

  17. Iodine solution Leaf Tile Method cont.To test leaves for starch • Add iodine solution to the leaves. Iodine turns from a red-yellow colour to blue-black if starch is present. 3 2 1

  18. 1 3 2 30 seconds 3 minutes green leaf white leaf boiling water in beaker hot alcohol in tube 4 30 seconds leaf turns black warm water yellow iodine solution

  19. ResultsTo test leaves for starch • The leaves that were uncovered turn blue-black. • This shows that starch is present. • The leaves that were covered remain red-yellow. • This shows that starch is not present.

  20. ConclusionTo test leaves for starch Starch is made by leavesin the presence of light.

  21. Plant responses • The ability to respond is one of the characteristics of life. • A tropism is the change in growth of a plant in response to an outside stimulus.

  22. Phototropism Phototropism is the change in growthof a plant in response to light. • The shoots (aerial parts) of a plant grow towards light due to phototropism. • Phototropism allows shoots to get more light and make more food.

  23. Experiment To investigate phototropism

  24. Light Light MethodTo investigate phototropism Set up the apparatus as shown in the diagram. Petri dish containing wet cotton wool sprinkled with seedlings

  25. ResultsTo investigate phototropism Section A: the seedlings grow towards the light and bend. Section B: the seedlings grow straight up towards the light. Section C: the seedlings turn yellow and do not grow.

  26. ConclusionTo investigate phototropism Seedlings grow towards the light.

  27. Geotropism Geotropism is the change in growth of aplant in response to gravity. • The shoots of a plant grow away from gravity. • This means they grow upwards towards the light. • The roots grow towards gravity. • This means they grow into the soil to get a better grip and to absorb more water.

  28. Experiment To investigate geotropism

  29. Damp compost Blotting paper Soaked seeds Beaker MethodTo investigate geotropism • Soak some large seeds in water for a day or two. • Set up the apparatus as shown in the diagram. • Leave the apparatus in a warm dark place for a few days.

  30. The shoots grow up away from gravity The roots grow down towards gravity ResultTo investigate geotropism As the diagram shows:

  31. ConclusionTo investigate geotropism Shoots grow away from gravity and roots grow towards gravity.

  32. Summary Sunlight Describe, using a word equation, how plants make their own food through photosynthesis Water + Carbon Dioxide  Glucose(energy) + Oxygen Chlorophyll Tropism – plants response to a stimulus e.g. Phototropism

  33. H/W • P105-107 • Q 1,3,5,6,7.

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