This document discusses photosynthesis, including the factors that affect it (chlorophyll, light, water, carbon dioxide), its products (glucose and oxygen), and importance. It describes experiments to test for the presence of starch as evidence that photosynthesis occurred under different conditions by changing one factor at a time, such as blocking light or carbon dioxide. The key conclusion is that photosynthesis requires chlorophyll, light, water, and carbon dioxide to produce glucose and oxygen.
2. Lesson Overview:
2.1Factors that affect photosynthesis
◦ Testing Factors essential for photosynthesis
2.2 Products of photosynthesis
◦ Testing products of photosynthesis
2.3 Importance of photosynthesis
3. What is Photosynthesis?
Production of glucose in the plant cells of
green leaves of plants by using water and
carbon dioxide in the presence of sunlight
and chlorophyl pigment.
5. Factors that affect photosynthesis
Accordingly, the factors that affect photosynthesis are,
Chlorophyll -Present in the palnt leaves in chloroplast
Light energy - from the sunlight
Water -Taken from the soil via root hairs
Carbon dioxide -taken through stomata from the
atmosphere
6. Products of photosynthesis
The glucose (C6 H12O6 ) produced during
photosynthesis will be temporarily stored in leaves as
starch
Later, part of that starch is converted into sucrose
(C12H22O11) and transport into other tissues, via
phloem
The sucrose that is transported to storing organs are
again stored as starch
E.g :-Fruits,Vegetables,Yams, Leaves, Roots
The byproduct of photosynthesis is O2 and it is diffused
into the atmosphere through stomata.
7.
8. Test for starch
Glucose produced during photosynthesis is stored
temporarily in leaves as starch
Therefore it could be tested whether the
photosynthesis has taken place or not by doing a test
for starch
10. As chlorophyll dissolve in alcohol, the leaf
is boiled in an alcohol solution
Then the solution becomes green in
colour and leaf turns to pale colour
As alcohol is highly inflammable, it is
boiled in a water bath
If the leaf turns to blue or dark purple,
once iodine is added, we can conclude
that starch is present in the leaf
11.
12. The covered area of leaf A has not received light energy
Therefore photosynthesis has not taken place
Hence, there was no colour change with iodine solution
The covered area of leaf B with colourless polythene has received
light energy
Therefore photosynthesis has taken place and showed a colour
change to dark purple or blue indicating starch has been produced
Accordingly, we can conclude that light energy is necessary for
photosynthesis
13.
14. KOH present in bag D absorbs CO2
Therefore leaf D does not do photosynthesis as it does not receive CO2
Therefore there is no colour change
Leaf C receives CO2, so it photosynthesises
Therefore a colour change can be observed
Leaf D has not produced starch but leaf C has produced starch
Accordingly it can be concluded that CO2 is necessary for photosynthesis
15. The white colour regions lack chlorophyll, so
photosynthesis has not taken place
Therefore starch has not been produced
So it can be concluded that chlorophyll is
essential for photosynthesis
16.
17. Gas bubbles release from the aquatic plant and
that gas gets collected at the top of the boiling
tube
After the accumulation of gas about 3/4 th of
its volume, the tube will be taken out and a
glowing splinter is inserted to test whether the
gas is oxygen
The splinter will burn with a bright flame
So we can conclude that the gas given out in
photosynthesis is oxygen
18. 2.3 Importance of photosynthesis
Light energy is converted to chemical energy during
photosynthesis
Plants produce food and all organisms live on earth
depend directly or indirectly on that food
Photosynthesis cannot be done artificially
Therefore this process carried out by green plants is
essential for the maintenance of life on earth
The oxygen gas which is required for the survival of
aerobic organisms and combustion of materials is
released mainly by photosynthesis
Carbondioxide that is accumulated due to respiration
and combustion is removed from the environment by
photosynthesis
Thereby it helps to maintain O2 and CO2 balance in the
atmosphere
Photosynthesis helps to maintain the carbon cycle