a) Carbon (iv) oxide:
i) Aim : to show that Carbon (IV) oxide is necessary for photosynthesis
ii) Material /apparatus
Potted plant, dark cupboards, potassium/sodium hydroxide pellets, iodine solution, water, methylated spirit, white tile, petroleum jelly, corks and source of heat
iii) Procedure
-destarch the potted plant by keeping it in a dark cupboard for 48hrs
-put pellets of NaOH/KOH into a conical flask A and distilled water in flask B
-fit the petioles of two different leaves of the potted plant in the grooves of corks and fit them as shown below;-
-seal the mouth of the conical flasks with petroleum jelly to make them air tight
-expose the apparatus to sunlight for about 3hrs
-remove the leaves from flask A and B and test each for the presence of starch using available reagents and materials
iv) Expected observation
leaf from flask A would retain iodine colour ; while leaf from flask B would turn blue.-black with iodine solutions.
iv) Conclusion
Starch is absent in leaf from flask A but present in leaf from flask B
KOH/NaOH pellets absorbed all CO2 hence no photosynthesis
b) Chlorophyll
i) Aim: to show chlorophyll is necessary for photosynthesis
ii) Materials and apparatus
Potted plant with variegated leaves, iodine solution, white tiles, water, methylated spirit and source of heat
iii) Procedure
-destarch the potted plant
-expose the plant to light for a period of 3 hrs
-pluck one or more variegated leaves from the plant and test for the presence of starch using the available materials and reagents
iv) Expected observation
green parts of the leaves would turn blue-black with iodine solution
while white or non-green parts would retain brown colour of iodine solution
iv) Conclusion
-photosynthesis took place in green plants but not in non-green parts
-chlorophyll is necessary for photosynthesis
c) Sunlight
i) Aim; to show that sunlight is necessary for photosynthesis
ii) Materials and apparatus
potted plant , clips or pins, black carbon paper, white tile, source of heat, water, iodine solution and methylated spirit
iii) Procedure
-destarch a potted plant
-using clips or pins , attach a piece of carbon paper on the upper surface of
one of the leaves to cover part of it as shown by the diagram below
-expose the setup to sunlight for a period of 3hrs
- pluck the experimental leaf, remove the carbon paper and test it for the
presence of starch using the available materials and reagents
iv) Expected observation
part which had been covered by black paper would turn brown while the
part exposed to sunlight would turn black
v) Conclusion
Starch is absent in part of the leaf which had been covered by black paper, indicating that no photosynthesis took place. Light is therefore necessary for photosynthesis
marto answered the question on September 25, 2019 at 09:10
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