Реферат: Finding About Photosynthes Essay Research Paper

(g) Spread the leaf on a petri dish.

(h) Pour iodine over the whole leaf.

(i) Iodine changes to a blue-black colour in the presence of starch. Note whether this occurs.

Part A: Setting up your experiment

You will investigate the three conditions necessary for photosynthesis:

h Chlorophyll

h Light

h Carbon dioxide

You can use different leaves on one plant to test all three conditions. Use figure 2.5A as a guide to setting up the experiment.

Is chlorophyll necessary for photosynthesis?

2. (a) Select a leaf, but leave it attached to the plant. Sketch it, showing the arrangement of the green and non-green areas.

(b) Record all your sketches for this exercise in a copy of table 2.5A

( c) Remember the leaf s position on the plant so that you can locate it again later. Sketch a section of the plant to show its location.

Is light necessary for photosynthesis?

3. Select another leaf and sketch it to show the arrangement of green and non-green areas. Take a piece of aluminium foil and cover a strip of the leaf. Hold the foil in position with a paperclip.

Is carbon dioxide necessary for photosynthesis?

Carbon dioxide is present in air. One way to test if carbon dioxide is required for photosynthesis is to remove carbon dioxide from the air surrounding the plant and observe the consequences. Potassium hydroxide absorbs carbon dioxide and therefore can be used to remove the carbon dioxide from the air around the plant.

4. Use a funnel to pour potassium hydroxide into a flask so that it covers the bottom of the flask.

5. Select a small branch of the plant. Leave it on the plant. Carefully insert this branch into the flask. Do not allow the leaves to touch the potassium hydroxide solution. You may have the support the flask with a clamp and stand depending on the plant s height and shape.

6. Seal the opening of the flask with cotton wool.

7. Set up another branch in a flask as described above, but do not add the potassium hydroxide.

8. Leave the plant under the Grolux lamp or bight light for 24 hours.

Day 2 (24 hours later)

Part B: Testing for the presence of starch.

In the introduction it was mentioned that the carbohydrate produced during photosynthesis is converted to starch. The presence of starch can be used as evidence to show that photosynthesis has occurred.

9. After the plant has been in bright light for 24 hours, locate the leaf described in step 2.

10. Test the leaf for the presence of starch.

11. Draw the leaf for the presence of starch.

12. Repeat steps 10 and 11 for a leaf selected from each of the experimental procedures: