PLANT TISSUE ANALYSIS

INRODUCTION:  Robert Hooke, an European scientist  in 1665 observed theoccurrence  of cell as a box-like apartment in a thin slice of bottle cork under his selfmade microscope and gave them the term cell.  In 1839  Matthias Schleiden  and  Theodor Schwann together proposed  the cell theory. They stated the organism some group of cells are performing exhalation and inhalation.  Some specialized cells are busy in doing intake of food while other group of cells are doing excretion. Another set of cells is responding to stimuli or sensation,  where other is specialized for reproduction.  These similar group of cells together perform a common factor.

DEFINITION: Tissue is defined as a group of cells having similar origin and structure and performing a common function as stated earlier.

CLASSIFICATION: Plant tissue is classified into

(i)Plant tissue: Present in plants

(ii)Animal tissue: Present in animal

Plant tissue is further divided into:

  • MERISTEMATIC TISSUE
  • PERMANENT TISSUE

 

OUTLINE STUDY OF PLANT TISSUE

TYPE OF TISSUE CONTENT SPECIALITY
MERISTEMATIC TISSUE Composed of undifferentiated cell It is always in the state of active cell division; cells can grow or regenerate new plant parts.
PERMANENT TISSUE Composed of cells that are differentiated and lost the power of division. They have various functions like photosynthesis; transportation of water and food; storage of food etc.

 

 

OCCURRENCE OF MERISTEMATIC TISSUE: Meristematic tissue are present in the growing region which is always dividing and bring about an increase in the length and width or girth and thickness.

CHARACTERISTICS OF MERISTEMATIC TISSUE: Structures of meristems are:

  • The shape of cells may be rounded, oval or polygonal .
  • Cells are having cell wall of cellulose which is thin in nature.
  • Cells are compactly arranged without intercellular space.
  • Each cell has large prominent nucleus.
  • Cytoplasm is abundant and dense.
  • Vacuoles are either small or absent.

 

 

 

TYPES OF MERISTEMATIC TISSUE

According to the occurrence,this is classified into three types:-

  • APICAL MERISTEM: Cells are present at the growing  region of the roots, stems and buds in axile helping in increase in length.
  • LATERAL MERISTEM:These cells are occurred below the bark, parallel to long axis of the stem. It helps in increase in thickness or girth of the plant in diameter.
  • INTERCALARY MERISTEM:These meristems are present at the base of nodes and internodes. It helps in secondary growth.

 

 

                                       PERMANENT TISSUE

DEFINITION:  Permanent tissues are types of tissues which has lost ability of division and formed by the differentiation of meristematic tissue.

CHARACTERISTICS OF PERMANENT TISSUE: (i) These are of various structures and thickening  are found.

(ii) These cells do not divide.

 

CLASSIFICATION: According to the type of cells present , permanent tissue is classified into: *Simple permanent tissue

          *Complex permanent tissue

 

ELABORATE AND COMPARATIVE STUDY OF SIMPLE PERMANENT TISSUE

 

TYPE OF TISSUE STRUCTURE LOCATION FUNCTION DIAGRAM
PARENCHYMA §   Isodiametric, round or rectangular cells

§  Cells are composed of living cells

§  Cells are large thin walled.

§  Cell walls are made up of cellulose.

§  Cells may be oval, spherical or polygonal.

§  Cells contain cytoplasm, distinct nucleus and a large central vacuole.

§  Intercellular spaces are often present between the cells.

ü   Cells are present in soft parts of  stem, root, leaf, flower and fruit.

ü   Also present in cortex of the stem and root.

ü  Present in mesophyll of leaves.

ü  It stores food.

ü  It provides temporary support to plant.

ü  Storage of starch mainly in potato.

ü   In leaf chlorophyll is present in parenchyma cells  called chlorenchyma.

ü  These cells carry out photosynthesis and manufacturing sugar and starch.

ü  In aquatic plant parenchyma cells have star like cavities in between the cells called aerenchyma; here air is trapped and makes the plant lighter in weight and helps to float in water.

COLLENCHYMA §  It consists of living cells.

§  Cells are elongated.

§  It appears circular, oval or polygonal.

§  Cell walls are thickened at the corners  due to deposition of cellulose or pectin.  

§  Intercellular spaces are absent.

§   Distinct nucleus and dense cytoplasm are present in the cells.

§  Cells often contain chloroplast.

ü  In lower level of epidermis of dicot stem.

ü   In dicot Leaf stalk or petiole

ü  Absent in monocot stems, roots and leaves.

ü  Plants get mechanical support and strength .

ü  Collenchyma with chlorophyll can do  photo synthesis.

SCLERENCHYMA §  Contains  matured and dead cell.

§  Lignin thickened cell wall makes the cell waterproof.

§  Intercellular spaces are generally absent.

§  Cells are connected through  non- lignified simple pits .

§  Sometimes in a plant some spherical or irregularly shaped highly lignified cells called stone cells.

ü  Found in stem, roots, veins of leaves.

ü  Present in the hard covering of seeds and nuts.

ü  Provides mechanical support and rigidity to the plant.

ü  It gives flexibility to the plant to withstand various strains like strong wind and jerk.

 

 

                                         USE OF SCLERENCHYMA

  • Fibres are strong and flexible so it is used to manufacture ropes and textile.
  • Sclereids impart toughness to seed coat. It provides grittiness to fruit pulp.

 

                             COMPLEX PERMANENT TISSUE

Cells of complex permanent tissue are having various types of cells with specific functions .

 

CLASSIFICATION:   According to their functions there are two types of tissues XYLEM  and PHLOEM . Together they constitute the vascular bundles of the of the plants and are called conducting tissue.

 

COMPLEX TISSUE TYPE STRUCTURE DIAGRAM
XYLEM TISSUE OR WOOD (i)                 Tracheids Elongated, tube like dead cells with lignified walls and tapering end.
(ii)Vessels It contains  elongated tube like dead cells with lignified thickening,   placed end to end with end walls dissolved.
(iii)Xylem parenchyma Only living cell associated with xylem. It has thin cell walls.
(iv)Xylem sclerenchyma Fibre-like elongated dead cells with tapering end and thickened lignified cell wall.
PHLOEM (i)Sieve tube Main component of phloem formed of living cells. These are long tubes like structure formed by end to end fusion of cells. Cells contain cytoplasm which is continuous with the sieve element above and below through the pores present at the end walls of the cells. End wall with pores is called sieve plate. On maturity sieve tubes  are living without nucleus.
(ii)Companion cells These are attached to each sieve tube. It is a thin-walled elongated cell. It is a living cell with large elongated nucleus. It helps sieve tube translocating of food material.
(iii)Phloem parenchyma Thin-walled living cells.
(iv)Phloem fibre Thick-walled but consists of dead sclerenchyma fibres called bast fibres.

 

 

                                                             LOCATION AND FUNCTION OF XYLEM AND PHLOEM

COMPLEX TISSUE LOCATION FUNCTION
XYLEM Vascular bundles of the plant in the root, stem and leaves. ü  Ascent of sap from root to stem and  stem to leaf.

ü  Tissues  give mechanical strength to the plant due to its thickness and lignified nature..

PHLOEM All parts of plant in stem, root and leaves. Found along with xylem in vascular bundle. ü  Conduction or translocation of the prepared food material from leaf to various parts of the plant for storage and growth.

 

                                                       PROTECTIVE TISSUE

 

INTRODUCTION: Entire outer surface of the plant body like stem, root and leaves is modified into a protective tissue. It protects the plant from mechanical injury, heat and cold and from undue loss of water. These cells are specialized into two types

EPIDERMIS  and CORK

STRUCTURE AND FUNCTION OF PROTECTIVE TISSUE

NAME OF THE TISSUE STRUCTURE FUNCTION
EPIDERMIS ·         Single layered

·         Covers all soft parts of plants like stem,root and leaf

·         Irregular cells without intercellular space.

·         Outer cell wall has a thin coat of water-proof layer called cuticle.

·         Cells are parenchymatous.

·         It contains colourless cell sap.

·         They bear unicellular or multicellular hair or glands.

·         Leaves and young green stems have minute pores for gaseous exchange called stomata.

§  Protection.

§  Cuticle reduces   excessive loss of water.

§  Epidermis  provides protection to  the plant from excessive heat, cold and attack of parasitic bacteria and fungi.

§  Stomata allows exchange of gases and transpiration.

CORK ·         Protective outer covering in the older stem and roots of dicot plants when growing older.

·         In dicot old plant, the single-layered epidermis is replaced by a multilayer cork cell.

·         Cells are composed of many layers of roughly rectangular shaped dead cells with suberin deposition.

·         Cells are compactly arranged without intercellular spaces.

§  Protects plants from mechanical injury and attack of micro-organisms.

§  It prevents water loss due to the presence of suberin.

§  Provides insulation from extreme hot and cold temperature.

§  Pores present on the outer surface allow exchange of gases (through lenticels).

§  Cells donot catch fire due to highly compressible cells.

 

 

 

 

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