Experiments of photosynthesis

Conditions necessary for photosynthesis:

• Sunlight
• Chlorophyll
• Carbon Dioxide
• Water

Basis of Experiments:

• Plants make starch as their food.
• Starch gives a blue black colour with iodine
• We destarch the leaves by keeping it in a dark room for about 3 days.

Sunlight necessity experiment

• 
• Destarch the leaf.
• Cover the centre part of leaf with aluminium foil or black paper. (seal tightly so that sunlight can not enter)
• Keep for 3 - 4 days then pluck out the leaf and remove the foil.
• Boil the leaf in water to break the cell membrane and make it permeable.
• Keep it in alcohol and give a water bath. (since alcohol is flammable and can not be heated directly.)
• Wash with warm water and keep in a petri dish.
• Pour iodine solution.

Observation & Conclusion

• Observation
• The uncovered part of leaf turns blue black but the covered part remains the same.
• Result
• Sunlight is necessary for photosynthesis.
• Leaves make starch as a food by photosynthesis

VARIEGATED LEAVES

• 
• A variegated leaf is a leaf which has both green and non-green parts.

croton(left) & coleus(right)

Chlorophyll necessity experiment

• 
• Destarch a plant with variegated leaves (like croton) .
• Keep in bright sunshine for 3 - 4 days.
• Mark the boundries of non green parts (so as to differentiate between green and non green parts after leaf loses its colour)
• Boil the leaf in water.
• Keep in alcohol and give a water bath.
• Wash it in hot water.
• Dip in iodine solution.
• Observation: Only the area which was earlier green, turned blue black in colour.
• Result: Chlorophyll is important for photosynthesis.

CO2 Necessity experiment

• 
• Take two healthy potted pots of nearly same size.
• Destarch them and place each of them on glass plates.
• Keep a watch glass containing potassium hydroxide (KOH) near one plant.
• KOH will absorb the CO2
• Cover each plant with separate bell jars and seal them using vaseline.
• Keep in sunlight for around 2 hours and then pluck a leaf from both plants.
• Pour iodine to do the starch test.
• Observation: The leaf which had no CO2 around it didn't turn blue-black while the other did
• Result: Carbon Dioxide is necessary for photosynthesis.