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Nutrition
Activity 5.1: Experiment to prove (d) Detach the covered leaf and remove
the importance of light during the black paper covering it.
photosynthesis (e) Place the detached leaf in the beaker
containing water. Boil it for about 10
Materials minutes, as shown in Figure 5.4(b)
A healthy potted plant, petri dish or (f) Take out the leaf and place the test
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white tile, a beaker containing water, tube containing the boiled leaf and
forceps, hot water bath, a piece of wire alcohol into the beaker containing
gauze, tripod stand, burner, match box,
alcohol (90% ethanol), strip of black boiling water for 10 minutes, as
paper (carbon paper), Iodine solution, shown in Figure 5.4(c).
and clips Caution
Procedure Do not heat ethanol directly because
(a) Take a potted plant and keep it in a it is highly flammable
dark place for 2-3 days so that the (g) Take out the leaf and wash it under
leaves get destarched. running water to remove traces of
(b) Cover part of one of its leaves with ethanol and to soften the tissues as
a strip of black paper. Make sure that shown in Figure 5.4(d).
you cover both the lower and the upper (h) Spread the leaf on a petri dish or white
sides of the leaf to prevent the entry of tile and put a few drops of Iodine
light as shown in Figure 5.4(a). solution on it. Observe the changes
(c) Place the plant in sunlight for 3 to 4 in colour as shown in Figure 5.4(e).
hours.
Black paper
Green leaf
Leaf boiling
in water Alcohol
Beaker
Bunsen burner Decolorised Decolorised Petri dish
leaf in water
leaf
Iodine solution
(a) (b) (c) (d) (e)
Figure 5.4: Experiment to show the importance of light during photosynthesis
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