Ask learners to join the new class WhatsApp group. Tell them to check the rubric for assessment.
please click on the link to watch the introduction
To complete this task you need adult guidance for safety.
In this experiment, we’re going to investigate the role of light in the process of photosynthesis and find out if the light is necessary for photosynthesis to occur in a plant. For this experiment, we’ll need the following:
• A potted plant preferably with broad leaves
. • Water bath
• A large test tube
• Ethanol, or Isopropanol or Methylated spirit
• Aqueous Iodine solution
• Petri dish
• A piece of black paper
• A pair of scissors and sticky tape
• Paper clips
You will complete a scientific report, explaining the process in your own words upon completing this investigation. This experiment is simply about understanding and following experimental instructions.
Begin the experiment by placing the potted plant in the dark for about 2-3days. This step is essential in order to rid the plant of any starch that was formed in the leaves prior to the start of the experiment. At the end of this time period, remove the potted plant from the dark. Cut a piece of black paper like so, and secure the cut end of the paper using sticky tape. To make this experiment a bit more interesting and fun, I’ve carved out my initial which is the letter “T” as well on the black paper covering the leaf. Cover both surfaces of one of the leaves using this piece of black paper like so, and secure the paper on the leaf using some paper clips.
Now what we can see here is that the parts of the leaf-covered by the black paper will continue to remain in the dark. Leave the potted plant in sunlight for several hours Then, detach the leaf from the plant and remove the black paper from the leaf Now, introduce the leaf into the test tube containing the alcohol solution.
Place the tube in the boiling water bath to decolorize the chlorophyll pigments. Once bleaching of the leaf has been accomplished, remove the leaf from the alcohol using forceps. Briefly place the leaf for a few seconds in the hot water bath in order to soften the leaf. Transfer the leaf to a Petri dish containing iodine solution. After a couple of minutes, you’ll see that the exposed parts of the leaf not covered by the black paper turn blue-black in color in the iodine solution. The part which was covered by the black paper, however, do not show any significant change in color except for a faint brown iodine color. This is a negative test for starch and thereby photosynthesis.
This simple experiment clearly demonstrates that light is an essential external component for photosynthesis to take place in a plant. Every learner will have to demonstrate or prove this in their reports. I will expect this task to be handed over on the 29th of September 2022. I will decide if you will present the reports depending on academic time. I will release marks before the term ends. Thank you.