How can you prove that sunlight, carbon dioxide and chlorophyll is necessary for the process of photosynthesis?
Answers
Answer:
To prove the necessity of carbon dioxide in photosynthesis
following steps need to do
Insert a part of the leaf of a destarched plant into a conical flask containing potassium hydroxide.
Potassium hydroxide solution absorbs the carbon dioxide gas from the air present in the glass bottle.
Leave the plant sunlight.
After few hours, perform a starch test to this and another leaf of the same plant.
Observation-
Leaf exposed to the atmosphere are bluish black.
Leaf exposed to KOH does not change to blue-black colour
Result- Starch is present in the green part of the leaf.
Conclusion- Presence of starch proves that chlorophyll is necessary for photosynthesis as it traps sunlight.
Chlorophyll is necessary for photosynthesis
Process
Take a potted plant with variegated (green and white) leaves.
Destarch the plant by keeping it in complete darkness for about 48 hours.
Expose the plant to the sunlight for a few days.
Test one of the leaves for starch with iodine solution.
Observations
- Areas with previously green patches test positive (turn blue black).
- Areas with previously pale yellow patches test negative (remain brown).
Conclusion
- Photosynthesis takes place only in green patches because of the presence of chlorophyll.
- The pale yellow patches do not perform photosynthesis because of the absence of chlorophyll
To prove the necessity of sunlight in photosynthesis following steps need to do
Take a plant with destarched leaf.
Leaf is partially covered with black paper on which a design is cut.
Expose this plant to sunlight for few hours and perform a starch test with iodine solution.
Observation-
Covered leaf part shows brown colouration.
Exposed leaf shows blue-black colour.
Result- Starch is present in the exposed leaf.
Conclusion- Leaf exposed to sunlight give iodine test, proving that sunlight is necessary for photosynthesis.
Answer:
Steps of photosynthesis:-
- Absorphtion of light energy by chlorophyll.
- Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen .
- Reduction of carbon dioxide to carbohydrates.