osmosis and guard cells class 9 Biology in Urdu / in Hindi | Lec #23 | cells and tissues

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Transcript

00:00Assalamu alaikum today our topic of discussion is osmosis and guard cell.

00:08What is osmosis? Water molecules always move from low solute concentration to high solute

00:17concentration. This is called osmosis. Then what is guard cell? To understand guard cell,

00:27it is important to know the structure of the leaf. For example, we have taken a leaf,

00:32we have cut a small section of it and shown it by enlarging it. So, the uppermost part of the leaf

00:40is called epidermis. Epi means outer, dermis comes from derma which means skin. That is,

00:51the uppermost layer is called epidermis and there are two epidermis present in the plant.

00:57The uppermost layer is called upper epidermis and the lowest layer is called lower epidermis.

01:03And in epidermis, guard cells are present. And it is always in the form of a pear,

01:12a beam-shaped structure is present in epidermis. This is called a guard cell. And between two guard

01:21cells, there is a small pore, a small opening. This is called stromata as shown here. So,

01:30guard cells are present in the upper epidermis and lower epidermis. And the upper epidermis

01:37and lower epidermis are the upper layers of the plant leaf.

01:42Here, the guard cell is shown by enlarging it. During the day, when the stromata opens,

01:52the structure of the guard cell is like this. These are two guard cells. It is always in the

01:57form of a pear. This is a guard cell and this is a guard cell. And between these two,

02:02the structure of the guard cell is like this. This is a guard cell and this is a guard cell.

02:13So, the guard cell is green in color and chloroplasts are present in it.

02:20We read about chloroplasts in detail at the back. Chloroplasts have a green pigment present

02:28in it, which is called chlorophyll. And chlorophyll are responsible for photosynthesis. The photosynthesis

02:35process is taking place in chlorophyll. So, plants in the presence of sunlight make their

02:43food. This process is called photosynthesis. So, in the presence of sunlight, carbon dioxide

02:52plus water react in the presence of sunlight. And after this, glucose is made. Glucose is

03:02a solute. And with this, oxygen is made. As a by-product, plants are made. Because oxygen

03:12is not needed in the plant, plants extract it through stromata. When photosynthesis is

03:24taking place during the day, glucose is being made in the guard cell. So, glucose is a solute.

03:33And here, the concentration of solute will increase as compared to the surrounding.

03:38So, water always moves from low solute concentration to high solute concentration. So, as more as possible, water will enter the guard cell.

03:45Because of this, guard cells will expand. And this way, its stromata remains open during the day.

03:53Through this stromata, plants exchange gaseous, which is CO2. So, this is the process of exchanging

04:00carbon dioxide. So, plants take carbon dioxide from their environment. And where do they

04:07take water from? So, the roots of the plants are in the guard cell. So, the plants take

04:14water from the guard cell. So, this is the process of exchanging gaseous. So, this is

04:21the process of exchanging gaseous. So, this is the process of exchanging gaseous. So,

04:28this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

04:35So, this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

04:42So, this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

04:49So, this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

04:56So, this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

05:03So, this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

05:10So, this is the process of exchanging gaseous. So, this is the process of exchanging gaseous.

05:17So, when photosynthesis is not happening, glucose is also not formed.

05:24So, water will move out of the guard cell.

05:30So, here is an isotonic condition.

05:34So, as much solute is inside the guard cell, so much is in its surrounding.

05:39So, as much water is entering inside the guard cell, so much is coming out.

05:47Because of this, these cells become flaccid.

05:51Because of this, stomata also become closed.

05:55As shown in this diagram.

05:57As shown in this diagram.

05:59As shown in this diagram.

06:01As shown in this diagram.

osmosis and guard cells class 9 Biology in Urdu / in Hindi | Lec #23 | cells and tissues | chp # 4

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