Plant tissue class 9 class notes

Plant tissues

Tissues are a group of cells having a similar structure and performing a specific function.

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PlantsAnimals
Don’t move as they can prepare their own food.Move as they can’t prepare food
As they don't move so, they need less energyAs they move, they need more energy in search of food
Organ systems are root system and shoot system Complex organ systems like respiratory, digestive, circulatory, and excretory.
MERISTEMATIC TISSUEPERMANENT TISSUE
Cells of this tissue continuously divide and grow.Cells of this tissue stop dividing and hence have a permanent shape and function.
It is present in growing regions of plans like root and shoot tips.Present throughout the plant body.
Cells of this tissue have a fragile cell wall.Cells of this tissue may have thin or thick cell walls.
Cells of this tissue lack vacuole. (as they don’t need to store anything)They contain vacuoles.
Cells have a dense (thick) cytoplasm.The cytoplasm is not very dense.
Cells of this tissue are very active, and hence they are all living.Cells may be living or dead.
It helps to increase the length and girth (width) of plants.It is mainly supportive and gives structural and mechanical strength to plants.

MERISTEMATIC DIFFERENTIATION: 

When meristematic cells stop dividing, they acquire a permanent shape, size, and function, and this process is called differentiation. 

Type of Meristematic tissue

MERISTEMATIC TISSUE (MERISTEM) is of 3 types:-
  • Apical meristem 
  • Lateral (cambium) meristem
  • Intercalary meristem

Apical meristem 

  • Present at root and shoot tips. 
  • Helps to increase the length of stems and roots.

Lateral (cambium) meristem

  • The ring of cambium is present in stems and roots. 
  • Helps to increase the girth of stems and roots.

Intercalary meristem

  • Present at the base of leaves and internodes.
  • Helps in the growth of leaves and increases the length of the internode.

PERMANENT PLANT TISSUES 

There are of 2 types:- 
  • Simple permanent tissues 
  • Complex permanent tissues

Simple permanent tissues Complex permanent tissues
It is made up of only one type of cell.It is made up of more than one type of cell.
They are mainly supportive and protective in function.They are mainly used for conduction and transportation.
They can be divided into 3 types:-
Parenchyma
Collenchyma
Sclerenchyma
It can be divided into 2 types:-
Xylem
Phloem

Type of Simple permanent tissues:- There are three types of permanent tissues
  • Parenchyma 
  • Collenchyma 
  • Sclerenchyma

Structure of Parenchyma 

  • They have fragile cell walls. Cells are loosely packed. Hence they have large intercellular space.
  • Pits are absent Made up of living cells.
  • Located throughout plant body, i.e., in roots, stem, leaves, fruits
    etc.
  • It provides support to plants. It helps to store food. In some cases, parenchyma contains chlorophyll and can perform photosynthesis.

Structure of Collenchyma 

  • Have a thin cell wall with irregular thickenings in the corner.
  • Have very little intercellular space.
  • Pits are absent Made up of living cells.
  • Present in leaf stalks below the epidermis.
  • It provides flexibility to plants which helps various parts of plants.
Structure of Sclerenchyma
  • Cell walls are thickened throughout due to the deposition of lignin.
  • Intercellular spaces are totally absent.
  • Pits are present Made up of dead cells.
  • Present in stem around vascular bundles, roots, hard coverings of seeds and nuts (husk of the coconut is also made up of this tissue), and veins of leaves.
  • It provides support to plants and makes the plant hard and stiff.

EPIDERMAL TISSUE

 It is made up of a single layer of cells. Epidermal tissue is made up of a single layer of cells.

 FUNCTIONS OF EPIDERMIS

1. It protects various parts of plants as the epidermal cell is present on aerial parts of the plant often secrete a waxy resistant layer which protects these parts from) Excess loss of water) Mechanical injuries) Damage by parasites 2. In the leaves, the epidermis bears small pores called stomata enclosed by two kidney-shaped cells called guard cells.

FUNCTIONS OF STOMATA

*Exchange of gases Transpiration: The loss of water in water vapor from aerial surfaces of plants, especially leaves. 3. In roots, epidermal cells bear long hair-like parts, which greatly increases the surface area of roots for more absorption of water. 4. In some desert plants, the epidermis has a thick waxy coating of cutin, which is waterproof and helps plants prevent excess water loss due to transpiration.

CORK/BARK OF TREE
Location of meristematic tissue in plant body
Plant tissues


  • As the plant grows older, the outermost epidermis is replaced by secondary meristematic tissues, and these cells are cut off from the rest of the tissues.
  •  These cells form a several-layer thick cork are the bark of a tree.
  • Cells of a cork are dead.
  • Cells are compactly arranged with no intercellular space.
  • The walls of these cells deposition a chemical called suberin which makes these cells impervious to gases and water.

COMPLEX PERMANENT TISSUES

  • Xylem 
    • Tracheids
    • Vessels
    • Xylem Parenchyma
    • Xylem Fibres
  • Phloem
    • Sieve Tubes
    • Companions
    • Phloem Fibres 
    • Phloem Parenchyma
  • Tracheids and vessels: They are tubular structures and help in the transportation of water and minerals.
  • Xylem Parenchyma: They help to store food.
  • Xylem Fibres: They are mainly supportive in function.
  • Sieve Tubes structures: They are tubular with perforated cell walls, which help in the conduction of food.
  • Companion Cells: They help the sieve tubes in the conduction of food
  • Phloem Fibres and Parenchyma: they are supportive in function.

1. What is tissue? 

Ans: Tissue is a group of cells that are similar in structure and are organized together to perform a specific function. 

2. What is the utility of tissues in multicellular organisms? 

Ans: The different types of tissues perform different functions in multicellular organisms. Since a particular group of cells carry out only a particular function, they do it very efficiently. So, multicellular organisms exhibit a definite division of labor.

1. Name various types of simple tissues.

Ans: Various types of simple tissues are:
Parenchyma(chlorenchyma, aerenchyma)
  • Collenchyma
  • Sclerenchyma

2. Where is apical meristem found?

Ans: Apical meristem is present at the growing tips of the stem and roots.

3. Which tissue makes up the husk of coconut?

Ans: Sclerenchyma tissue makes up the husk of the coconut.

4. What are the constituents of phloem? 

Ans: The constituents of phloem are :
  • Sieve tubes 
  • Companion cells
  • Phloem parenchyma 

  • Phloem fibers

Location of meristematic tissue in plant body
Location of meristematic tissue in the plant body

Location of meristematic tissue in plant body
Location of meristematic tissue in the plant body.


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