The
Effect of Light Toward Amylum Synthesis in Geranium
1.1.
Goal
f To know and understand the
effect of light toward amylum synthesis in Geranium
f
1.2.
Basic Theories.
Photosynthesis, process by which green
plants and certain other organisms use the energy of light to convert carbon
dioxide and water into the simple sugar glucose. In so doing, photosynthesis
provides the basic energy source for virtually all organisms. An extremely
important byproduct of photosynthesis is oxygen, on which most organisms depend.
Green
Plants and Photosynthesis
All
of our food ultimately results from the process of photosynthesis in green
plants and algae. The pigment chlorophyll is responsible for the green color of
plants as well as their ability to photosynthesize. In common terrestrial
plants photosynthesis is usually carried out in the leaves, although it can
also occur in the stem or other parts of the plant.
Encarta Encyclopedia
Dr. C.E. Jeffree/Oxford Scientific Films
1.3.
Tools and Materials
a.
Tools
j Tongs for test tube
j Tripods and wire gauze
j Beaker glasses
j Petri dishes
j Bunsen burner
j Paper clips
j Tweezers
b.
Materials
b
Ethanol
b
Black
paper or aluminum foil
b
Water
b
Iodine
solution
b A pot of geranium plant or
other decorative plant (whose leaves have motifs and not ‘fleshy’)
1.4.
Working Procedure
1.
Geranium plant or other is kept for 2-3 days in
dark place so it will not undergo photosynthesis. To ensure that photosynthesis
is stopped, the leaf can be tested with iodine test as follows.
2.
Boil water in beaker glass using Bunsen burner.
Pick a piece of leaf and soak in the boiling water for 10 seconds. The soaking
is to kill plant cells and soften leaf tissues.
3.
Then, roll the leaf and put inside ethanol in test
tube. Ethanol is a solvent for the leaf chlorophylls. Test tube along with leaf
in it is boiled in beaker glass for 10 minutes. Turn off the Bunsen burner.
4.
Rinse the leaf by holding it with tweezers and
shaking it inside the hot water in the beaker glass. Rinsing is to dissolve
ethanol.
5. Rinse the
leaf by holding it with tweezers and shaking it inside the hot water in the
beaker glass. Rinsing is to dissolve ethanol.
6. Put the
leaf turns mostly black / dark, keep the plant for a few more days in the dark.
After that, retest it with iodine test. If the blackening is less, it does not
synthesize amylum anymore.
7. Afterwards,
cover some part of the geranium’s leaves with black paper. You can make V
symbol or others. Sandwich it with two object glasses and tie with rubber
bands. Look at the photos.
8. Put the
geranium plant in bright place. After a few days (1-2 days), pick the covered
leaves. Test it for the presence of starch as in steps no. 2-5.
Write down
the working procedure explained by your teacher in the column below !
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1.5.
Observation Result
1.6.
Questions
1. What is the
function of the iodine solution?
2. What is the
function of hot etanol?
3. What is the
difference between putting the plant the plant in dark and bright place?
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