TISSUE CLASS 9
Ch-6 Tissues
✤ Tissue → A group of cells having a common origin similar in structure
and/or work together to achieve a particular function is known
as tissue.
→ Plant tissue are primarily classified into two groups
Plant tissue
Meristematic Permanent
Tissue Tissue
✤ Meristematic tissue = The growth of plants occurs only in certain
specific regions. This is because the dividing tissue is known as
meristematic tissue.
→ Cells of meristematic tissue are capable of dividing continuously to
produce new cells. The meristematic tissue are present only at the
growing regions such as shoot tip, root tip, and at the basic of
internodes and leaves.
→ Depending on the region where they are present, meristematic tissue
are classified as apical, lateral and the intercalary.
PARENCHYMA
COLLENCHYMA SCLERENCHYMA
TRACHEID VESSEL XYLEM PARENCHYMA
✤ The cells of meristematic tissue are very active, have dense cytoplasm, thin cellulose walls and prominent nuclei. They lack vacuoles.
✤ Cells of permanent tissue do not have power of division. They have
differentiated and attained a permanent shape suitable for their
function.
PERMANENT TISSUE
SIMPLE COMPLEX
Parenchyma Collenchyma Sclerenchyma Xylem Phloem
✤ Simple plant tissues: Tissues which are made up of only one type
cells are called simple plant tissue. Parenchyma,
collenchyma and sclerenchyma are examples of Simple
tissue.
✤ Parenchyma tissue consists of relatively unspecialized living cells
with thin cell wall. Large intercellular spaces are found between
Parenchymatous cells.
✤ Aerenchyma and chlorenchyma are modification of parenchyma
Tissue
( NERVE CELL )
✤ A collenchyma tissue which provides mechanical support to plants
also consists of living cells. These tissue are elongated and slightly
thickened at corners.
✤ Sclerenchyma tissue which makes the plant hard and stiff consists of
dead cells. These cells are long, narrow and Their cell walls are
thickened due to deposition of lignin.
✤ This tissue provide support to plants and also stores food. In sume
situation, it contain chlorophy II and I performs Photosynthesis, and
then it is called collenchyma.
✤ In aquatic plants, large and air cavities are present in parenchyma to
give buoyancy to the plants to help them float. Such a parenchyma
type is called aerenchyma.
✤ The parenchyma of stem and roots also stores nutrient and water. The flexibility in plants due to another permanent tissue, collenchyma.
✤ The epidermis of leaves have small pores, called stomata.
Stomata are enclosed by two kidney shaped cells called guard cells.
stomata are useful for exchange of gases and transpiration.
✤ In older plants, epidermis is replaced by secondary meristem which
produces the cork on the bank of tree. Cells of cork are dead,
compactly arranged without intercellular spaces. cork cells have
deposition of suberin on the walls that makes them impervious to
gases and water.
✤ We have seen the turk of a cocount- it is made of sclerenchymatous
tissue. the cells of this tissue are dead. They are long and narrow as
the walls are thickened due to lignin a chemical substance which acts
as cement and hardens them.
✤ The outermost layer of cells called epidermis: the epidermis is
usually made of a single layer of cells. Epidermis cells of the roots
whose function is those absorption. commonly bear long hair-like
parts that greatly increase the total absorptive surface area.
✤ They also have a chemical called suberin in their walls that makes them impervious to gases and water.
✤ Complex plant tissue :- These tissue are made up of more than one
type of cells which coordinate to perform a common
function: they are mainly conducting tissues are of two
types:
1) Xylem 2) Phloem
(a) Xylem :- Consists of tracheids, vessels, xylem parenchyma and xylem
fibres. Xylem conduct water and dissolve minerals from
roots to all parts of the plant Except xylem parenchyma,
xylem cells are dead cells.
(b) Phloem:- It conducts food from the green/parts to other parts of the
plant. It is composed of four elements - sieve tubes,
companion cells, Phloem parenchyma and Phloem Fibres.
Except Phloem fibres, Phloem cells are living cells.
# Animal tissues are of four types in higher animals including human being:
Animal
↓ ↓ ↓ ↓
Epithelial connective Muscular Nervous
tissue tissue tissue tissue
(a) Epithelial tissues:- They are the covering tissue. They also from
barrier to keep different body systems separate. On the
basis of their shape and function they are classified as
given below:-
Epithelial tissues
(i) Squamous (flattered cells)
(ii) Cuboidal (cubical cells)
(iii) Columnar (tall or pillar like cells)
(iv) Ciliated (cells having cilia)
(v) Glandular (with secretary function)
(b) Muscular tissue : So they are made up of muscle cells called muscle
fibres. There are three types of muscle fibres:
(i) Straited muscle (Skeletal muscle or voluntary muscle) are long,
cylindrical, unbranched and multinucleated
(ii) unstriated muscle (Smooth muscle or involuntary muscle) are
long, pointed at ends and uninucleated.
(iii) cardiac muscle cells are cylindrical, branched and uninucleated.
(c) Connective Tissue : They are connect different tissues and organs.
They provide support to different parts of the body by
forming packaging around different organs of the
body. The different types of connective tissue in our
body are bone, cartilage, tendon, ligament and blood.
(d) Nervous tissue : This tissue compose of specialized cells nerve cells
or neurons which conduct nerve impulses (i.e.,
stimulus and its response for from nervous tissue)
Brain, spinal cord and nerves are composed of nervous
tissue.
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