11Plant tissue

📚
MERISTEMATIC TISSUE
▢ Definition of Meristematic Tissue:
  • •
    A group of young, immature, and undifferentiated cells that are actively dividing or retain the power of continuous cell division.
  • •
    These cells are responsible for the growth and development of the plant body.
  • •
    They are typically located at the growing regions of the plant, such as root and shoot apices.
▢ Features of Meristematic Tissue:
    Image 1
  1. Composed of immature, undifferentiated cells with continuous power of division
  2. Cells are small, isodiametric, spherical, oval, or polygonal in shape
  3. Cell wall is thin, elastic, and made up of cellulose
  4. Dense cytoplasm with a prominent, large nucleus
  5. Vacuoles are generally absent; if present, they are very small
  6. Intercellular spaces are absent; cells are compactly arranged
  7. High metabolic activity and rate of respiration
  8. Plastids are present in the form of proplastids
  9. Ergastic substances (non-living cell inclusions) are absent
▢ Types:
Image 1
Fig.Types of meristematic tissue based on position

Table 1: Types of meristematic tissue

Feature
Apical meristem
Intercalary meristem
Lateral / Radial meristem
Position
Apices of root + shoot
Between two permanent tissues; base of internode; base of leaves
Lateral sides
Function
Increase in length
Increase in length
Increase in girth / diameter
Consumption
Not consumed up
Consumed up
Examples / Notes
◉ Points:
  • •
    Leaf primordia → leaf
  • •
    Axillary bud + terminal bud derived from apical meristem activity
Grasses → growth by intercalary meristem
Cambium-like activity → radial growth
Special points
◉ Points:
  • •
    Pteridophytes → single cell
  • •
    Phanerogams → group of cells
▢ Apical Meristem Division by Haberlandt:
Image 1

Table 1: Haberlandt’s zones

Zone
Tissue system formed
Protoderm
Epidermal tissue system
Ground meristem
Ground tissue system
Procambium
Vascular tissue system
▢ Shoot Apex Organization:
❖ Apical Cell Theory:
Image 1

Table 1: Apical cell theory

Point
Data
Proposed by
Nageli
Concept
Single pyramidal cell → entire growth by division + redivision
Applicable to
Bryophytes, vascular cryptogams / pteridophytes, some higher algae
Not applicable to
Gymnosperms, angiosperms
❖ Histogen Theory:
Image 1

Table 1: Histogen theory of shoot apex

Histogen
Position
Gives rise to
Dermatogen
Outermost
Epidermis
Periblem
Middle
Cortex including endodermis
Pleurome
Innermost
Vascular bundle including pith
Proposed by Hanstein; 3 groups of initials in shoot apex
❖ Tunica-Corpus Theory:
Image 1

Table 1: Tunica-corpus theory

Region
Position
No. of layers
Division
Tissue formed
Tunica
Outer region
Generally 1
Anticlinal
Epidermis
Corpus
Inner mass
Several
Anticlinal + periclinal
Bulk of adult plant
Proposed by Schmidt; most accepted theory
◉ Anticlinal vs Periclinal Division:

Table 1: Division plane

Division
Plane
Effect
Anticlinal division
Perpendicular to surface
Surface area increases
Periclinal division
Parallel to surface / tangential cleavage
Layers increase → girth increases
▢ Root Apex Organization:
❖ Apical Cell Theory:

Table 1: Apical cell theory of root apex

Point
Data
Proposed by
Nageli
Concept
Single apical cell in root apex → entire growth
Applicable to
Pteridophytes, gymnosperms
Not applicable to
Angiosperms
❖ Histogen Concept:
Image 1

Table 1: Histogen concept of root apex

Histogen
Gives rise to
Dermatogen
Epiblema / piliferous layer / rhizodermis + root cap in dicot
Periblem
Cortex including endodermis
Pleurome
Vascular tissue including pith
Calyptrogen
Root cap in monocot
Proposed by Hanstein; 4 groups of initials in root apex
❖ Quiescent Centre Concept:
Image 1

Table 1: Quiescent centre

Point
Data
Given by
Clowes in maize
Meaning
Inactive centre in root apex
Biochemical status
Low DNA, RNA, protein
Cell cycle status
G₀ phase
Function
Reserve for replenishment of damaged meristem cells
Hormonal note
Some auxin synthesis
📚
PERMANENT TISSUE
▢ Definition:
  • •
    Formed by division + differentiation of meristematic tissue
  • •
    Fully mature + developed + differentiated cells
  • •
    Lost power of division
  • •
    May be living/dead
  • •
    May be thin-walled/thick-walled
  • •
    Generally thin-walled = living; thick-walled = dead
📖
Simple permanent tissue
▢ General Features:
  • •
    Made up of one type of cells
  • •
    Similar function
  • •
    Homogeneous group
📝
Parenchyma
Image 1
▢ Features:
  • •
    Isodiametric cells
  • •
    Thin-walled
  • •
    Living
  • •
    Abundant intercellular spaces
  • •
    Most abundant permanent tissue
  • •
    Evolved first
  • •
    Fundamental tissue → other tissues evolved from it
  • •
    Cell wall → cellulose + calcium pectate
  • •
    Main function → food storage
▢ Special Types:

Table 1: Special types of parenchyma

Type
Occurrence
Function / Note
Prosenchyma
Pericycle of some plants
Rigidity + strength
Aerenchyma
Hydrophytes
Floating + buoyancy
Chlorenchyma
Mesophyll of leaves
Photosynthesis
Palisade + spongy parenchyma
Dicot leaves only
Mesophyll differentiation
Idioblastic / storage parenchyma
Special storage cells
Contains enzymes, resin, ergastic substances
📝
Collenchyma
Image 1
▢ Features:
  • •
    Thick-walled but living cells
  • •
    Living mechanical tissue
  • •
    Cell wall thickening at corners/angles
  • •
    Thickening due to pectin + cellulose; mainly pectin
  • •
    Pectin → holds large amount of water
  • •
    Simple pits between adjacent collenchyma cells
  • •
    Absent in dicot roots + monocots
  • •
    Forms hypodermis in herbaceous dicot stem + woody climber / liana
▢ Types:
Image 1

Table 1: Types of collenchyma

Type
Angular collenchyma
Lacunar / tubular collenchyma
Lamellar collenchyma
Intercellular space
Absent
Present
Absent
Special point
Most common + most abundant
Thickening around intercellular spaces
Wall thickening in layers
📝
Sclerenchyma
Image 1
▢ Features:
  • •
    Dead cells
  • •
    No protoplasm
  • •
    Thick-walled
  • •
    Cell wall lignified
  • •
    Lignin → hardest plant tissue; maximum rigidity
  • •
    Bears compression, pull, bending, shearing forces
  • •
    Simple + bordered pits in sclerenchyma fibres
▢ Fibre Note:

Table 1: Commercial fibre composition

Fibre
Rich in
Cotton
Cellulose
Flax
Cellulose
Jute
Lignin
Coir
Lignin
▢ Common Occurrence:
  • •
    Hypodermis of monocot stem
  • •
    Pericycle
  • •
    Xylem
  • •
    Phloem
▢ Types:
  1. Sclerenchyma Fibres
  2. Sclereids / Stone Cells / Grit Cells
Image 1
📄
Sclerenchyma Fibres
  • •
    Elongated
  • •
    Tapering at both ends
  • •
    Spindle-shaped
  • •
    Commercial fibres = sclerenchyma fibres
  • •
    Directly derived from meristematic cells
📄
Sclereids / Stone Cells / Grit Cells
▢ Features:
  • •
    Derived by secondary thickening of parenchymal cells
  • •
    Shorter
  • •
    Highly thickened
  • •
    Narrow cavities
  • •
    Hard seed coat due to stone cells
  • •
    Stone cells in fruit pulp of Pyrus
▢ Occurrence:
    Image 1
  1. Endocarp of coconut
  2. Hard seed coats
  3. Fruit pulp of guava
  4. Fruit pulp of pear
▢ Types by Shape:

Table 1: Types of sclereids

Type
Shape
Occurrence
Brachysclereids / stone cells
Irregular
Pulp of pear, guava; endocarp of coconut fruit
Macrosclereids
Rod-shaped
Hard seed coat of Leguminosae
Osteosclereids
Bone-shaped
Subepidermis of legume seeds
Astrosclereids
Star-shaped
Tea leaves; petiole of lotus
📖
Complex permanent tissue
Secondary xylem = wood
📝
Xylem / Hadrome
Image 1
▢ Definition: Complex tissue made up of more than one type of cells/elements
▢ Elements:

Table 1: Xylem elements

Element
Special point
Vessels / trachea
Absent in pteridophytes + gymnosperms
Tracheids
Water conduction + support
Xylem parenchyma
Living storage element
Xylem fibres / wood fibres
Mechanical support
📝
Phloem / Leptome
Image 1
▢ Elements/ Cells:
❖ Sieve elements (Sieve cells/ Sieve tubes:
Sieve cells
Sieve tubes
Pteridophytes + gymnosperms
Angiosperms
❖ Albuminous cells/ Companion cells:
Albuminous cells
Companion cells
Pteridophytes + gymnosperms
Angiosperms
❖ Phloem parenchyma: Storage + lateral conduction
❖ Phloem fibres / bast fibres: Mechanical support
Living and Non-living structures of Xylem and Phloem (CEE 2025)
  1. In xylem every element are dead structures except xylem parenchyma.
  2. In phloem every elements are living structure except phloem fibres.
Q1.
Which cell is living and metabolically active?
📅CEE MBBS 2025
Q2.
Which sclerenchyma cell typically has a very narrow lumen because of thick secondary walls?
📅CEE MBBS 2024a
Q3.
Blocking of sieve pores in phloem occurs due to deposition of:
📅CEE MBBS 2024a
Q4.
Commercial jute fibres are obtained from bark. In the broad anatomical sense, bark includes:
📅CEE MBBS 2023
Q5.
Needle-shaped calcium oxalate crystals found in Colocasia are called:
📅CEE MBBS 2022
Q6.
Which is a living component of xylem?
📅CEE MBBS 2022
Q7.
Which of the following is generally considered the most advanced pattern of secondary wall thickening in xylem vessels?
📅CEE MBBS 2022
Q8.
Which pair consists of complex permanent tissues?
📅CEE BDS 2023
Q9.
Which plant tissue consists of thick-walled cells that are generally dead and lack protoplasm at maturity?
📅CEE Nursing 2024
Q10.
Intercalary meristem is generally derived from a portion of the:
📅IOM 1997
Q11.
Which is the living component of xylem?
📅IOM 1997
Q12.
Prepared food is transported through:
📅BPKIHS 2004
Q13.
Bidirectional translocation of organic solutes takes place through:
📅BPKIHS 2006
Q14.
The principal function of sclerenchyma is to:
📅MOE 2063
Q15.
Which of the following is a primary meristem?
📅MOE 2062
Q16.
Net-like secondary wall thickening in a xylem vessel is called:
📅MOE 2054
Q17.
Chlorenchyma and aerenchyma are modified forms of:
📅BPKIHS 1995
Q18.
An amyloplast is a plastid that stores:
📅BPKIHS 1990
Q19.
The pith develops from the:
📅BPKIHS 1997
Q20.
Jute is classified as a:
📅BPKIHS 1998, IOM 2059
Q21.
The most common simple ground tissue in plants is:
📅IE 2005
Q22.
Protoxylem commonly has vessel elements with:
📅IE 2009
Q23.
Primary growth is caused chiefly by activity of the:
📅IE 2009
Q24.
The chief transport function of phloem is:
📅BPKIHS 2015
Q25.
The histogen theory was proposed by:
📅BPKIHS 2014
Q26.
According to the histogen theory, the stele develops mainly from:
📅BPKIHS 2013
Q27.
Phloem is chiefly concerned with:
📅BPKIHS 2012
Q28.
The cohesion–tension theory of ascent of sap was proposed by:
📅BPKIHS 2011
Q29.
The wood commonly used to make cricket bats is obtained from:
📅BPKIHS 2011
Q30.
Protoderm occurs in the developing regions of the:
📅IOM 2014
Q31.
Jute fibres are derived from:
📅IOM 2016
Q32.
Which is a complex permanent tissue?
📅IOM 2012
Q33.
Tracheids, vessels, xylem fibres and wood parenchyma are components of:
📅IOM 2012
Q34.
Jute fibre is obtained from:
📅IOM 2012
Q35.
Which tissue is characteristically common in dicot stems but generally absent from typical monocot stems?
📅MOE 2010