We know that all the plants synthesize
their food by themselves. The plant
their food by themselves. The plant
synthesize their food by the process of
synthesize their food by the process of
photosynthesis. But they cannot utilize
photosynthesis. But they cannot utilize
all this food at once so they store it in
all this food at once so they store it in
the form of starch. So, if you want to see
the form of starch. So, if you want to see
that the plant has photosynthesized we
that the plant has photosynthesized we
can check this with the presence of
can check this with the presence of
starch. So, now let's do some experiments
starch. So now let's do some experiments
to see the presence of starch in the
to see the presence of starch in the
plants. So, in these experiments, we will use
plants. So in these experiments, we will use
iodine solution to confirm the presence
iodine solution to confirm the presence
of starch as this iodine solution turns
of starch as this iodine solution turns
blue-black in the presence of starch. Now
blue-black in the presence of starch. Now
let's start the experiment, pluck a leaf
let's start the experiment, pluck a leaf
from the plant with variegated leaves.
from the plant with variegated leaves.
Now, what are these variegated leaves?
Now, what are these variegated leaves?
The variegated leaves have green and non
The variegated leaves have green and non
green parts. The green parts contain
green parts. The green parts contain
chlorophyll and so they photosynthesize
chlorophyll and so they photosynthesize
and they have starch in them, while the non
and they have starch in them, while the non
green part do not have. Now boil this
green part do not have. Now boil this
variegated leaf in water for 40 to 60
variegated leaf in water for 40 to 60
seconds.
seconds.
This will stop all the ongoing chemical
This will stop all the ongoing chemical
reactions. Then dip this leaf in boiling
reactions. Then dip this leaf in boiling
ethanol for some time and this will
ethenol for some time and this will
remove all the color of the leaves. Then
remove all the color of the leaves. Then
wash the leaves with water and put
wash the leaves with water and put
iodine solution over it.
iodine solution over it.
What will you observe? You will see that all
What will you observe? You will see that all
the green parts of the plant are stained
the green parts of the plant are stained
blue black as they contain starch in
blue black as they contain starch in
them while the non green parts are left
them while the non green parts are left
unstained. In other words, we can say that
unstained. In other words, we can say that
the green parts of the plants
the green parts of the plants
photosynthesized and they could do so
photosynthesized and they could do so
because of the presence of chlorophyll
because of the presence of chlorophyll
pigments in them, while the non green
pigments in them, while the non green
plants, they do not have chlorophyll
plants, they do not have chlorophyll
pigment so they could not
pigment so they could not
photosynthesize. Let's do one more
photosynthesize. Let's do one more
experiment to
experiment to
see if you got the gist of photosynthesis.
see if you got the gist of photosynthesis.
In this experiment also,
In this experiment also,
we will use iodine solution to test the
we will use iodine solution to test the
presence of starch.We will take two potted
presence of starch.We will take two potted
plants and label them as plant one and
plants and label them as plant one and
plan two. Now keep these plants in dark
plan two. Now keep these plants in dark
for three days ,this will remove all the
for three days ,this will remove all the
starch present in the leaves. Then we will
starch present in the leaves. Then we will
invert the glass jars over these plants.
invert the glass jars over these plants.
We will keep potassium hydroxide in the jar
We will keep potassium hydroxide in the jar
which contains plant one, potassium
which contains plant one, potassium
hydroxide absorbs carbon dioxide. Now we
hydroxide absorbs carbon dioxide. Now we
will seal both the jars and make them
will seal both the jars and make them
airtight and will keep them in sunlight
airtight and will keep them in sunlight
for three hours. After three hours we will
for three hours. After three hours we will
test the presence of starch in the leaves
test the presence of starch in the leaves
of both of the plants.
of both of the plants.
Let's see what happens? Here, we can see
Let's see what happens? Here, we can see
that plant one does not contain starch
that plant one does not contain starch
while plant two confirms the presence of
while plant two confirms the presence of
starch in it. Can you tell me why?
starch in it. Can you tell me why?
Let me explain ,now the plant one which
Let me explain ,now the plant one which
contains potassium hydroxide in it could
contains potassium hydroxide in it could
not utilize carbon dioxide present
not utilize carbon dioxide present
inside the glass jar as pottasium
inside the glass jar as pottasium
hydroxide absorbs carbon dioxide and so
hydroxide absorbs carbon dioxide and so
the plant could not photosynthesize.
the plant could not photosynthesize.
While plant two as it does not have
While plant two as it does not have
potassium hydroxide in it, it utilized
potassium hydroxide in it it utilized
the whole carbon dioxide present inside
the whole carbon dioxide present inside
the glass jar and so it photosynthesized
the glass jar and so it photosynthesized
and confirmed the presence of starch in
and confirmed the presence of starch in
it. So, in these experiments we saw that
it. So in these experiments we saw that
chlorophyll and carbon dioxide are
chlorophyll and carbon dioxide are
essential for photosynthesis.
essential for photosynthesis.
