Photosynthesis Investigating Photosynthesis Objectives Controls and experimental Setups

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 • 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.

Destarching the Plants • • • This can be done by placing the plants in the dark for at least 48 hrs. 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.

Experiments for Photosynthesis Destarch the plants Investigation Testing for Starch Conclusion

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

Is light necessary for photosynthesis? 1. Take a destarched potted plant as shown in the diagram. 2. Leave in strong sunlight for a few hours. 3. Pluck out leaf X and test for starch. Leaf X (From: http: //faculty. ntcc. edu/mhearron/photosynthesis. htm)

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

Is carbon dioxide necessary for photosynthesis?

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

Experiments for Photosynthesis Destarch the plants Investigation Testing for Starch Conclusion

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

Name: ____________ ( Class: _____ 1. 2. 3. 4. 5. 6. ) Date: _______ 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.

Testing for Starch 1. Place leaf in boiling water Purpose : to kill the cell and tear open the cell membranes, break the open cells and make it soft. 2. 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. 3. Dip leaf into warm water to remove the alcohol so the iodine stain can penetrate the leaf. 4. Cover leaf with iodine solution to test for the presence of starch. 5. Those parts of the leaf that stain blue-black contain starch. 6. Those parts that are yellowish-brown (the colour of the iodine stain) do not have starch.

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

Test leaf for starch (From: http: //www. macleans. school. nz/students/science/F 4/plants/photosynthesis. Exptgif. gif)