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Testing
Plant Storage Organs for Starch and Sugar
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Information
: Plant Storage
Organs
|
Plant
Storage Organ |
Formed
from |
|
 |
Potatoes
are tubers. They are formed by the swelling of
sections of underground stems. |
|
 |
Carrots
are formed by swollen tap (main) roots. |
|
 |
Bulbs
are formed from the swollen bases of leaves. |
|
crocus
corm |
A corm is a short,
condensed, swollen stem. |
Method
1. Cut a quarter of a small
potato into small pieces.
2. Place the pieces of potato
into a mortar and cover them with distilled water.
3. Use a pestle to mash the
potato into a pulp.
4. Place about 1cm in height of
the potato pulp into two test tubes. Use one of these tubes
for each of the two tests detailed below:
| Test
for Starch
1. Add a few drops of
iodine solution and mix the contents of the tube.
2. Record your results. |
| Test
for Sugar
1. Add 1cm in height of
Fehling's solution to the potato pulp and mix the
contents of the tube.
2. Label this test tube
with your name and place the label near the mouth of
the tube. Place the test tube in a water bath at 90°C
for 3 minutes.
3. After 3 minutes
record the results. |
Repeat the method with each of
the other three storage organs in turn.
Results
Complete the following table:
|
Plant
Storage Organ |
Starch
Test with iodine solution |
Sugar
test with Fehling's solution |
| Potato |
|
|
| Tap Root |
|
|
| Bulb |
|
|
| Corm |
|
|
Conclusion
Iodine solution turns
blue/black in the presence of starch.
Fehling's solution (which is blue) will change colour when
heated in the presence of sugar. Green indicates a small
amount of sugar (+), yellow means that more sugar is present
(++) and orange indicates a lot of sugar (+++).
Complete the following table:
|
Food
Storage Organ |
Starch
(+ = present,
- = absent) |
Sugar
( - = absent, + = trace,
++ = some, +++ = a lot) |
| Potato |
|
|
| Tap Root |
|
|
| Bulb |
|
|
| Corm |
|
|
Study the diagrams below and answer the questions which
follow them:
 |
 |
 |
 |
|
The
potato tuber uses its stored energy to produce roots
and leaves |
The
old potato shrinks. The food made by the leaves is
stored in new potato tubers. |
The
leaves continue to make food. The new potatoes
increase in size. |
As
autumn approaches the parts of the plant above ground
wither and die. The new potatoes will be able to
develop new plants in the spring. |
A. Which types of food are
stored in the potato tuber?
B. Which parts of the potato plant make these high energy
foods?
C. What is the stored food used for?
Complete the following table:
|
Summary
of the conditions needed for the growth of a potato
plant |
|
Factors
needed above ground |
Factors
needed below ground |
Ways
of surviving winter |
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© Shirley Burchill
2008 |
The
Open Door Web Site