Introduction. We know that the cell is the structural and functional unit of life. Do you know what does it actually mean?
It means a single cell can perform all basic functions of life. Example, movement, intake of food and respiratory gases, respiration, excretion. Ok, it is true for a single cell. or unicellular organisms. But what happens when there are so many similar cells as in multicellular organisms?
In multicellular organisms, these cells are specialized to carry out a few functions efficiently. Each specialized function is done by a group of cells. Yes, I remember that nerve cells carry message from the brain to every part of the body.
Muscle cells contract and relax so that movements are caused. Blood flows to transport oxygen, food, hormones and waste materials. Plants are also living organisms and xylem and phloem cells conduct food and water from one part to another. It is said that in multicellular organisms there is division of labor. I do not understand what does it exactly mean?
Division of labor means that a particular function is carried out by a group of cells at a definite place in the body. This group of cells is called tissue which are arranged and designed to provide the efficient specialized function. So we can define tissues as a group of cells similar in structure that work together to perform a particular function. Example, nerve tissue. Objectives At the end of this lesson, you will be able to Define tissue Identify types of tissues Understand the difference between plant and animal tissues Understand plant tissues Understand types of plant tissues Find the characters of meristematic tissues Understand types of meristematic tissues.
Understand functions of meristematic tissues. Find the characters of permanent tissues. Understand types of permanent tissues. Understand functions of permanent tissues.
Plant and animal tissue. Plants and animals both are living organisms. But their internal structures are entirely different. Can you tell me why?
I know one major difference is that plants are autotrophic. That is, they can make their own food in presence of sunlight, carbon dioxide and water with help of chloroplasts. They are fixed at one place. So the tissues in plants are mainly of such types. which give them strength.
Some of them are also dead tissues which give mechanical strength. Yes, I know that animals are heterotrophic and have to move around in search of food, mate and shelter. So they need more energy in comparison of plants. That is why most of the tissue in animals are living.
One more big difference between plants and animals is pattern growth. The growth in plants is limited to some regions. There are some tissues in plants that divide. Yes, Madhuri. But in animals, the growth is not restricted to some places.
It is uniform growth. In animals, structural organization of organ system is more specified and localized. Types of Plant Tissues Ankita Do you know that on the basis of their dividing capacity, plant tissues are of two types, meristematic and permanent.
Those tissues which divide continuously and help in increasing in length and girth of plants are known as meristematic tissues. These are found only in growth regions of plants. While those tissues which are derived from meristematic tissues but have lost the power of division and have attained their definite forms are permanent tissues.
Activity We can prove that meristematic tissues are found by doing an activity. I will take a glass jar and Ankita you will also take a similar glass jar filled with water. Then we will place same sized onion bulb on each jar for 3 days to observe the growth of roots.
Yes, we will measure length of roots on day 1, 2 and 3. Then on the fourth day, you will have to cut roots of onion bulb. Then again, place it on the jar. On the fifth day, we will again measure the root length.
On the fifth day, we find that the growth of roots of my jar has stopped. Yes, this activity proves that growth of plants occurs only in certain specific regions because the dividing tissue also known as meristematic tissue is located only at these points. Characters of Meristematic Tissues Meristematic tissues are very active, thin-walled, isodiometric living cells. Their cell wall is formed of cellulose.
They are oval, rounded or polygonal in shape. Their cytoplasm is dense, vacuoles are small-sized. Nuclei are prominent.
They divide throughout life, so they help in growth. Types of meristematic tissues Depending on the region where they are present, meristematic tissues are classified as apical, lateral and intercalary. The tissues present in the growing tips of stems and roots are known as apical meristem. The tissues present on the lateral side of roots and stems are lateral meristem. The tissues which lie on the base of internodes of stem are called intercalary meristem.
Functions of Meristematic Tissues The main function of meristematic tissue is formation of new cells continuously. Apical meristem increases the height of the plant due to elongation of the root and stem. It is also called primary growth. Lateral meristem increases diameter of the plant.
It is also called secondary growth. Intercalary meristem increases the length of organ. Permanent tissues After some duration, meristematic tissues lose their ability to divide and take up a specific role and form a permanent tissue.
This process is called differentiation. Differentiated meristematic tissues form different types of permanent tissues. Characters of permanent tissues In permanent tissues cells are thin or thick walled, living or dead and mature. The shape of permanent tissues may be oval, rounded, polygonal or elongated, fiber-like. They have intercellular spaces.
Cytoplasm is vacuolated. Because they have lost the power of division, so they do not help in growth. Activity We can see by an activity that there are different types of cells in plants.
Take a plant stem and cut its thin section. Then stain it with saffron and keep it on a slide with a drop of glycerin and cover it with cover slip. Observe it under microscope. We can see various types of cells and their arrangement. Types of Permanent Tissues Permanent tissues are of two types.
On the basis of nature of cell, simple permanent tissues, complex permanent tissues. Simple permanent tissues are composed of cells which are functionally and structurally similar. Types of simple permanent tissues On the basis of nature of cells, simple permanent tissues are of three types.
Parenchyma, colonchyma, and sclerenchyma. Parenchyma is made up of cells with thin primary walls that retain their protoplasm. Collenchyma is made up of the cells with thick primary walls that retain their protoplasm. Sclerenchyma is made up of cells with lignified secondary walls that have lost their protoplasm at maturity i.e. are dead.
Activity With the help of another activity, we can find out various layers of cells in leaf. Ankita Take a leaf of royo. Yes, I have taken a leaf of royo. What should I do next?
Then, stretch and break it by applying a little pressure on it. When you stretch it, some peel or skin projects out from the cut. I have removed this peel and kept it in water in a petri dish.
Yes, now add few drops of saffron in. and wait for 2 to 3 minutes. I have now transferred it on a slide with a drop of glycerine and covered it with cover slip. When you will observe it under microscope, you will find different layers of cells. Outermost layer of cells is known as epidermis.
It is usually made of single layers of cells. Outer and side walls of epidermis are thicker than inner walls. The entire surface of all plants has epidermis. It protects all the parts of the plants from water loss, mechanical injury and invasion by parasitic fungi. Small pores are there in the epidermis of the leaf.
These pores are known as stomata. Stomata are covered by two kidney shaped cells known as guard cells. They help in exchange of gases with the atmosphere and transpiration functions of simple permanent tissues parent key myself as a packaging tissue to fill the spaces between other tissues and maintain the shape of the plant do to its turgid cells it also stores and assimilates the food transport of material occurs through cells or cell walls of parent keema Their intercellular spaces allow gaseous exchange. They also store waste products of plants like tannin, gum, raisins, etc.
Collenchyma is a mechanical tissue so it provides mechanical support and elasticity. Sclerenchyma is mainly mechanical and protective in function. It gives strength, rigidity, flexibility and elasticity to the plant body. and thus enables it to withstand various strains. Types of Complex Permanent Tissues Complex tissues are made of more than one type of cells.
All these cells coordinate to perform a common function. On the basis of nature of cells, complex permanent tissues are of two types, xylem and phloem. The supporting and water conducting tissue of vascular plants consisting primarily of tracheids and vessels, woody tissue. The food conducting tissue of vascular plants consisting of sieve tubes, fibers, parenchyma and scleroids, also called BAST. Functions of complex permanent tissues.
The main function of xylem is to carry water and mineral salts upwards from root to different parts of shoots. Phloem transports photosynthetically prepared food materials from the leaves to storage organs and later from storage organs to the growing regions of the plant body. Did you know? Chewing gum is the latex of the plant Acrar sapota.
Sclerenchyma is the longest cell in plant kingdom. Commercial cork is obtained from the oak plant. In monocotyledonous plants like grasses, the guard cells are dump shaped. Summary Let us summarize what we have learnt. Tissue is a group of cells similar in structure and function.
Plant tissues are of two main types. Meristematic and Permanent Meristematic tissue is the dividing tissue present in the growing regions of the plant. Permanent tissues are derived from meristematic tissue once they lose the ability to divide.
They are classified as simple and complex tissues. Parenchyma, colonchyma and sclerenchyma are three types of simple tissues. Xylem and phloem are types of complex tissues.