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Photosynthesis

Photosynthesis. Investigating Photosynthesis. Objectives. Controls and experimental Set-ups Destarching Plants. Experiments for Photosynthesis. Destarch the plants. Investigation. Testing for Starch. Conclusion. Destarching the Plants.

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Photosynthesis

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  1. Photosynthesis Investigating Photosynthesis

  2. Objectives • Controls and experimental Set-ups • Destarching Plants

  3. Experiments for Photosynthesis Destarch the plants Investigation Testing for Starch Conclusion

  4. Destarching the Plants • Before carrying out investigation, we have to ensure that the leaves of the plants do not contain any starch. • This can be done by destarching the plants.

  5. Destarching the Plants • This can be done by placing the plants in the dark for at least 48hrs. • In this way, any starch will be converted to glucose for growth and energy production (respiration). • The plants will not contain any starch and are ready for investigation. Any starch that is detected in the leaves during the investigation shows that photosynthesis has taken place.

  6. Experiments for Photosynthesis Destarch the plants Investigation Testing for Starch Conclusion

  7. Control and Experimental Setups • To investigate photosynthesis, we need to have to have control and experimental set-ups. • Control: Everything is given to the setup. • Experimental: Everything is given except for the condition that is to be tested.

  8. Is light necessary for photosynthesis? • Take a destarched potted plant as shown in the diagram. • Leave in strong sunlight for a few hours. • Pluck out leaf X and test for starch. Leaf X (From: http://faculty.ntcc.edu/mhearron/photosynthesis.htm)

  9. Observation Blue-black colour on parts of leaf exposed to light  showing presence of starch Yellowish-brown on part not exposed to light  showing absence of starch (Diagram from: http://faculty.ntcc.edu/mhearron/photosynthesis.htm)

  10. Is carbon dioxide necessary for photosynthesis?

  11. Is chlorophyll necessary for photosynthesis? (From: http://faculty.ntcc.edu/mhearron/photosynthesis.htm)

  12. Experiments for Photosynthesis Destarch the plants Investigation Testing for Starch Conclusion

  13. Testing for Starch • After carrying out investigation, we need to test the leaves for starch in order for us to observe the results.

  14. Name: _______________________ ( ) Date: _____________ Class: __________ Testing for Starch • Place leaf in boiling water Purpose : ___________________________________ ___________________________________________ • Put the leaf in a boiling tube and cover with ethanol Purpose: ____________________________________ ___________________________________________ • Dip leaf into warm water to remove the alcohol so the iodine stain can penetrate the leaf. • Cover leaf with iodine solution to test for the presence of starch. • Those parts of the leaf that stain _______________ contain starch. • Those parts that are ________________ (the colour of the iodine stain) do not have starch.

  15. Testing for Starch • Place leaf in boiling water Purpose : to kill the cell and tear open the cell membranes, break the open cells and make it soft . • Put the leaf in a boiling tube and cover with ethanol Purpose: to remove the green chlorophyll so the final results can be clearly seen. • Dip leaf into warm water to remove the alcohol so the iodine stain can penetrate the leaf. • Cover leaf with iodine solution to test for the presence of starch. • Those parts of the leaf that stain blue-black contain starch. • Those parts that are yellowish-brown (the colour of the iodine stain) do not have starch.

  16. Yellowish-brown; this part does not contain any starch Blue-black; this part contains starch (From: faculty.ntcc.edu/mhearron/photosynthesis.htm)

  17. Test leaf for starch (From: http://www.macleans.school.nz/students/science/F4/plants/photosynthesisExptgif.gif)

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