Evolution of oxygen explanation:

• Demonstrates process of photosynthesis in water plants such as Elodea or Camboba (pondweed)
• Oxygen is a by-product of photosynthesis
• In water, oxygen released is observed as bubbles
• Confirm that the gas collected is oxygen
  • A splint previously put out can be inserted into the boiling tube
  • In the presence of oxygen, it will light on fire again.

Requirement of light practical:

Method 1:

1. Place a plant in the dark for 24 hours to use up the starch storage
2. Place another plant under light for 24 hours
3. Pluck a leaf from each plant
4. Test the leaves of both plants for starch by adding a drop of iodine

Results:

• Iodine solution for the plant in darkness should remain orange/brown
• • No sunlight could be absorbed
  • Photosynthesis could not occur
• Iodine solution for the plant in sunlight should turn blue/black
• Received enough sunlight to photosynthesize
• Creates glucose that can replace the starch storage

Requirement of CO2 practical:

1. Place 2 plants in the dark for 24 hours so that the starch storage gets used up
2. Post destarching, cover 1 plant with a plastic bag containing KOH
   • KOH absorbs the carbon dioxide in the surrounding environment
3. Cover another plant with a plastic bag not containing anything to use as a control
4. Place the plants in bright light for 8 hours
5. Remove the coverings and test both plants for starch in the following manner:
   1. Put leaves from the plant in water at 90OC
   2. Transfer the leaves into hot ethanol for 10 mins
   3. Dip the leaves in a 90OC water bath again
   4. Spread the leaves on a white tile
   5. Add iodine solution to the leaves
   6. Observe the colour change

Results:

• Leaf surrounded by potassium hydroxide will remain orange/brown
  • Photosynthesis should not occur due to the lack of carbon dioxide
• Leaf not surrounded by potassium hydroxide should turn blue/black
  • It has all the raw materials required to photosynthesise

Requirement of chlorophyll practical:

1. Put a variegated leaf (partially green and white) in water at 95oC
2. Transfer the leaf into hot ethanol for 10 mins
3. Dip the leaf in 95oC water
4. Spread the leaf on a white tile and cover it with iodine solution

Results:

• Areas of the leaf that are white:
  • Do not contain chlorophyll
  • Remain orange/brown as no photosynthesis can occur
  • No starch accumulated
• Areas of the leaf that are green:
  • Contain chlorophyll
  • Turn blue/black as photosynthesis would occur
  • Accumulates starch