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.

1. Photosynthesis
Ms.Wong
BAMS(UG)
Lesson 02

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.

4. Diagrammatic Representation of
Photosynthesis

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.

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

9. Test to identify 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

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

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

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