1. Name of Teacher-Dr. Brijesh Pathak
Designation- Assistant Professor
Address-University College, Dhilwan, Tapa
Subject Name- Botany (Tissues)
B.Sc.(Medical)-Semester IV
2. Definition of Tissues
A group of cells with similar origin, structure and function is
called tissue.
Classification of Plant Tissues-
•Meristematic tissue-Meristematic tissue may be defined as a
group of living cells which are located at specific location
• These divide continuously to add new cells to the plant body.
•Permanent tissues-Permanent tissue may be defined as a group of
living or dead cells formed by meristematic tissue
•They have lost their ability to divide and have permanently
placed at fixed position in plant body.
3. Characteristics of meristematic tissues
•Continuously dividing cells.
•Cells are small and isodiametric.
•The cell wall is thin and made up of cellulose.
•Cytoplasm is abundant.
•Nuclei are large.
•Vacuoles are absent
•Lack inter-cellular spaces.
•Metabolic activities are at high rate.
5. Classification of meristematic tissue
A)Based on Origin and development
(a) Promeristem-The meristem where foundation of new
organs is laid down is called promeristem.
•They occupy at the tips of stem and root.
•It differentiates into primary meristem.
(b) Primary meristematic tissue-It originate from
promeristem.
•Remains meristematic from the embryonic condition
throughout entire plant life at the growing apices of roots,
stems.
(c) Secondary meristematic tissue-It develops from primary
permanent tissue.
6. B)Based on location in plant body
1. Apical meristem
Position: At the root tip and shoot tip.
Function: To increase in length of the axis.
2. Lateral meristem
Position: On the lateral side of stem and root.
Function: To increase in diameter of plant.
3. Intercalary meristem
Position: At the base of the leaf/internodes/ leaf.
Function: To increase the length of the plant or its organs.
7. C)Based on function
•Protoderm- Developing into epidermis.
•Procambium- Developing into vascular tissue.
•Ground meristem- Developing into ground tissue and pith
I)Simple Tissues
9. TYPES OF SCLERENCHYMA
i)Fibres
•Fibres are long, thick and lignified cells usually with pointed or blunt
ends.
•Usually occur in bundles.
•Provide tensile strength, flexibility and elasticity to plant or plant's
parts.
• Originate from meristematic cells.
ii) Sclereids ( Also known as stone cells)
• Most common in fruits and seeds
• Cells are isodiametric, spherical, in shape, have thick lignified
secondary cell wall.
•Provide mechanical strength and rigidity.
•Formed by secondary thickening of parenchyma cells.
10. Complex permanent tissue
A) Xylem :
•Term introduce by Nageli(1858)
• Greek xylos meaning wood.
Elements of xylem:-
1)Tracheary elements:- These are nonliving cells, provide support
and conduct water.
Two types of Tracheary elements
(a)Tracheids: elongate, tube like cell, tapering, hard lignified walls.
(b)Vessels members: long, tube-like structures with lignified walls.
(2)Fibres: thick walls, evolve from tracheids and provide mechanical
strength.
11. Two types of Fibres
(a)Fibre-tracheids: medium thickness walls, have reduced boardered
pits.
(b)Libriform fibres: very thick walls, have reduced simple pits.
(3) Xylem Parenchyma: living cells, in woody plants, store of food in
starch form.
Two types:
(a)Axial parenchyma: derived from fusiform initials, have tracheary
elements and fibres.
(b)Ray parenchyma: derived from ray initials of cambium, xylem ray
cells.
12. b) Pholem :
•Term introduce by Nageli(1853)
•Greek word Meaning Bark
•Bark is a non technical term describing all tissues outside secondary
xylem
•Bark includes secondary pholem, primary pholem, cortex and
periderm
Elements of Pholem:-
•Sieve Elements
•Companion Cells
•Pholem Parenchyma
•Pholem Fibres
13. Sieve Elements:-
•Living cells in the pholem
•Presence of Protoplasm
•No Lignified Walls
•Two types namely sieve cells and sieve tubes
•Sieve cells occur in Pteridophytes and Gymnosperms and consists of
elongated cells with inclined end walls
•Sieve elemnets are characteristics of Angiosperms with longitudinal
arrangement of cells
Companion Cells:-
• Specialised Parenchyma cells are called as companion cells
14. • Companion cells are metabolically active and are connected to sieve
tubes by plasmodesmata
Pholem Parenchyma:-
• Thin Walled
• Living Cells
• Parenchymatous
• Act as storage tissue
Pholem Fibres:-
•Dead Cells
•Lignified
