3.Chlorophyll and carbon dioxide are necessary conditions for plants to photosynthesis. How can prove this? Explain each with the help of a diagram.
Answers
Answer:EXPERIMENT TO PROVE THE NECESSITY OF CARBON DIOXIDE IN PHOTOSYNTHESIS - DEFINITION
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.
How will you prove that chlorophyll is essential for photosynthesis?
The following activity can prove that chlorophyll is essential for photosynthesis.
Activity:
1. Take a potted plant with variegated leaves (leaves partly green and partly non-green), for example colens, croton, money plant.
2. Keep the plant in a dark place for 3 days. So that all the starch of leaves gets used
up.
3. Place the plant for 6 hours in sunlight.
4. Pluck a leaf from the plant. Mark the green areas of the leaf and trace them on a sheet of paper.
5. Boil the leaf first in water for a few minutes and then replace the leaf in a beaker containing alcohol. Place this beaker in a bigger beaker containing enough water. Heat till the alcohol begins to boil on a burner.
(Note: If you use a hot plate to heat the leaf in alcohol, there is no need to use water bath. Boil the leaf directly in alcohol on a hot plate. In case, you use burner, vapour of alcohol can catch fire from flame of the burner).
6. Boiling of the leaf in alcohol decolourizes the leaf.
7. Place decolourlized leaf in a petridish and pour .iodine solution on it.
To show that chlorophyll is necessary for photosynthesis
8. Take out the leaf and rinse off the iodine solution. Observe the colour of the leaf and compare this with the tracing of the leaf done in the beginning iodine solution on it. The portion of the leaf which was previously green has turned into dark blue colour while the non-green portion turns yellow (colour of iodine solution). The dark blue colour indicates the presence of starch (starch with idone turns blue black) while the yellow portion does not show any starch.
This proves that only chlorophyll containing cells synthesize starch. Hence chlorophyll is necessary for photosynthesis.
Explanation:
Hope it was helpful